ARCHIVED - Organized Breast Cancer Screening Programs in Canada - Report on Program Performance in 2005 and 2006

 

2005 AND 2006 RESULTS

This report presents statistics for the 2005 and 2006 calendar years using data submitted up to March 2010. Further, the outcomes presented in this report are based on the 2007 report by the Evaluation Indicators Working Group except where otherwise indicated.[Note 5] (4) Data submission is staggered and may impact the completeness of cancer-related data for some programs. Unless otherwise noted, the summary statistics include data from all 10 provinces and the Northwest Territories and apply to women aged 50 to 69. These results are based on the experiences of Canadian organized breast cancer screening programs (Appendix A) and not on opportunistic breast cancer screening.

Participation in Organized Breast Cancer Screening Programs

Participation Rate

Adequate participation in breast cancer screening is essential for reductions in mortality to occur in the target population. Based on principles of screening and extrapolation from randomized controlled trials, Canadian programs have established 70% as the target participation rate.(4) The participation rate presented is calculated over a 30 month time period, which is similar to international reporting but results for the traditional 24 months are reported for comparison to previous reports.

Participation rates include all 10 provinces and the Northwest Territories. Overall, 1,588,699 Canadian women between 50 and 69 (Table 6. pg29 ), and 2,031,754 women of all ages (40+) [Note 4] , received a screening mammogram through a Canadian organized screening program in 2005 and 2006 (Table 3. pg15 ). Since the inception of the first Canadian organized screening program in British Columbia, over 8 million screening mammograms have been performed.

Although these numbers appear high, the targeted program participation rate of 70% among women 50 to 69 years for biennial screening is far from being reached through organized programs. In 2005 and 2006, 43.9% of the target population received a screening mammogram through an organized program over 30 months and 40.0% over 24 months. The participation rate varies among organized programs from 10.4% to 59.2% over 30 months
(Figure 3a. below ) and 9.1% to 53.3% over 24 months (Figure 3b. pg13 ).

Figure 3a. Participation in organized breast cancer screening programs: within 30 months, women aged 50-69
Figure 3a - Text Equivalent

The participation rate varies among organized programs from 10.4% to 59.2% over 30 months and 9.1% to 53.3% over 24 months.

Figure 3b. Participation in organized breast cancer screening programs: within 24 months, women aged 50-69, 2005 and 2006 screen years 10-12
Figure 3b - Text Equivalent

The participation rate varies among organized programs from 10.4% to 59.2% over 30 months and 9.1% to 53.3% over 24 months.

Participation among women 50 to 69 years is influenced by the proportion of women outside of this age group who are screened. Although there is relative consistency among programs on acceptance of women outside of the 50 to 69 year age group (Table 1. pg5 ), the proportion of screening occurring in the target age group (50 to 69) varies considerably from 36.7% to 100% (Figure 4. pg14 ).

Figure 4. Age distribution of program screens by province
Figure 4 - Text Equivalent

Participation among women 50 to 69 years is influenced by the proportion of women outside of this age group who are screened. Although there is relative consistency among programs on acceptance of women outside of the 50 to 69 year age group, the proportion of screening occurring in the target age group (50 to 69) varies considerably from 36.7% to 100%.

Table 3. Annual screening volume by program, age 40+, 1988 to 2006 screen years
Year Program
NT BC AB SK MB ON QCa NB NS PE NL Canada

a Although Québec accepts women aged 35-49 and 70+ with physician referral, they are not officially considered within the program and are not included in this table.

Notes:

  1. Nunavut does not have an organized screening program.
  2. Data unavailable for Yukon.
  3. Data include all screens; figures have been updated and may vary slightly from previous reports.
  4. This value is underestimated because volume counts are not provided to the CBCSD by some programs for women under 50 years or over 69 years of age.
1988 --- 4,370 --- --- --- --- --- --- --- --- --- 4,370
1989 --- 9,155 --- --- --- --- --- --- --- --- --- 9,155
1990 --- 22,271 616 6,355 --- 590 --- --- --- --- --- 29,832
1991 --- 54,185 5,871 14,305 --- 15,380 --- --- 1,876 --- --- 91,617
1992 --- 80,295 15,441 15,778 --- 40,294 --- --- 4,346 --- --- 156,154
1993 --- 99,806 16,146 26,057 --- 45,541 --- --- 4,885 --- --- 192,435
1994 --- 118,505 15,370 25,540 --- 55,480 --- --- 8,457 --- --- 223,352
1995 --- 143,003 14,169 29,603 2,671 58,287 --- 5,648 12,474 --- --- 265,855
1996 --- 166,304 14,679 28,901 13,594 67,729 --- 17,956 15,529 --- 3,120 327,812
1997 --- 173,516 23,333 33,915 19,163 80,132 --- 17,769 19,458 --- 4,694 371,980
1998 --- 189,612 18,887 34,093 23,454 98,597 43,987 25,716 25,423 --- 5,521 465,290
1999 --- 217,137 22,408 35,049 28,201 114,059 145,107 30,454 29,253 5,549 6,087 633,304
2000 --- 223,156 21,714 35,264 28,563 138,308 152,989 32,106 35,228 6,258 6,790 680,376
2001 --- 224,174 23,745 36,286 28,728 163,862 172,062 33,190 35,224 6,685 8,054 732,010
2002 --- 234,510 23,342 34,461 29,261 192,233 194,437 36,798 38,567 6,256 8,859 798,724
2003 --- 220,662 21,809 35,643 31,636 211,925 207,862 37,242 44,934 6,092 11,038 828,843
2004 1,103 230,550 23,106 36,125 32,301 248,548 220,893 37,150 48,576 6,050 9,819 894,221
2005 1,137 256,669 22,225 35,742 33,698 280,123 237,733 39,714 50,809 7,242 14,812 979,904
2006 1,268 266,490 22,109 34,994 36,585 318,421 253,290 37,614 58,137 7,693 15,249 1,051,850
total 3,508 2,934,370 304,970 498,111 307,855 2,129,509 1,628,360 351,357 433,176 51,825 94,043 8,737,084

Importantly, these rates do not include women who receive their breast cancer screening outside of an organized program. Results from population health surveys suggest that close to 63% of women between 50 and 69 years received a screening mammogram within the past two years (Figure 5a. below ). This figure is self-reported and may be slightly inflated as survey respondents tend to overestimate desirable behaviours, however, it is more closely aligned with the target of 70% set by the Evaluation Indicators Working Group Report. When attendance to mammography through opportunistic screening [Note 6] , in addition to organized screening, is considered screening mammography utilization substantively increases and becomes very similar to self-reported screening mammography from the same period (Figure 5b. below ). Data for mammography utilization includes women 50-69 years old with bilateral mammography (including screening mammography in organized programs, screening mammography outside of organized programs, and bilateral diagnostic mammography in provinces that included this in their mammography billing code). The range of screening mammography utilization shows little variation among provinces (60.0%-64.6%), but large variation in the proportion of utilization attributable to organized screening (14.5%-85.2%).

Figure 5a. Proportion of women aged 50-69 with a self-reported screening mammogram
Figure 5a - Text Equivalent

Results from population health surveys suggest that close to 63% of women between 50 and 69 years received a screening mammogram within the past two years.

Figure 5b. Mammography utilization among women 50-69 within: 24 months by province in 2005-2006
Figure 5b - Text Equivalent

When attendance to mammography through opportunistic screening, in addition to organized screening, is considered screening mammography utilization substantively increases and becomes very similar to self-reported screening mammography from the same period. The range of screening mammography utilization shows little variation among provinces (60.0%-64.6%), but large variation in the proportion of utilization attributable to organized screening (14.5%-85.2%).

Retention Rate

Optimal benefits from screening programs are achieved when regular participation in screening occurs. Two targets have been set based on an understanding of participation rates, sojourn time, screening interval studies and randomized controlled trials.(5,6,7) The first, for women undergoing their initial screening mammogram, states that ≥75% of women should return within 30 months. The second states that ≥90% of women undergoing a subsequent screen should return within 30 months. The retention rate for women aged 50 to 67 excludes women who did not return because of death, breast cancer, or age limit (greater than 67 years). This indicator differs from that reported in the Evaluation Indicators Report and has been updated to censor women greater than 67 years to allow more accurate comparison of provinces where screening is strictly limited to between ages 50 and 69.

Overall, most women aged 50 to 67 who received a screening mammogram between 2002 and 2003 were rescreened within 30 months up to 2006. Among women who received their first screening mammogram in the 2002 and 2003 calendar years, 68.9% returned for a subsequent mammogram within 30 months. Among women aged 50 to 67 who received a subsequent screening mammogram in the 2002 and 2003 calendar years, 81.3% returned for a subsequent mammogram within 30 months. (Tables 6-8. pg29-35 )

In general, younger women (40 to 49 years) were more likely to return for subsequent screening within 30 months compared to older women (70+ years) regardless of whether it was an initial (65.2% and 45.5% respectively) or subsequent screen (83.6% and 63.6% respectively) (Table 7. pg32 ). Women aged 40 to 49, who choose to have a screening mammogram, are usually recommended for annual screens. Most women, aged 50 to 67, returned for subsequent screening between 21 and 27 months after their 2002 to 2003 screen but women between age 40 and 49 were more likely than older women to return between 12 and 15 months (Figure 6. pg19 ).

Figure 6. Cumulative probability of returning for a subsequent program: screen by age group, 2002 and 2003 screen years
Figure 6 - Text Equivalent

Organized Breast Cancer Screening Programs in Canada - Report on Program Performance in 2005 and 2006

Results of Organized Breast Cancer Screening Programs

The goal of organized screening programs is to identify disease in asymptomatic women and at the same time minimize the number of healthy women who receive abnormal screening results and associated follow-up tests. Both the abnormal call rate and the positive predictive value offer insight into the process of accurately identifying asymptomatic women with breast cancer.

Abnormal Call Rate

The abnormal call rate refers to the percentage of all women screened who are referred for further testing because of abnormalities found during the screening mammogram and is one way to measure the quality of a screening program. The Canadian target is <10% for women undergoing their first screen and <5% of women undergoing their subsequent timely screens.

Figure 7. Abnormal call ratea by age group, 2005 and 2006 screen years
Figure 7 - Text Equivalent

For all age groups, the abnormal call rate rises after a screening interval of 30 months indicating the importance of regular screening Intervals.

Among women 50 to 69 years, the abnormal call rate for women receiving their first screening mammogram is 12.2% and for a subsequent screening mammogram is 6.0% (Table 6. pg29 ). Radiologist inexperience and/or low reading volumes can contribute to unnecessarily high abnormal call rates, as can delays in rescreening. For all age groups, the abnormal call rate rises after a screening interval of 30 months indicating the importance of regular screening intervals (Figure 7. above).

Positive Predictive Value

The positive predictive value is determined by the proportion of women with an abnormal call who go on to be diagnosed with invasive or in situ cancer. A high positive predictive value reflects the minimization of unnecessary follow-up procedures. The Canadian target is ≥5% for first screens and ≥6% for subsequent timely screens.

Among women aged 50 to 69 years, and based on detection by mammography alone, the positive predictive value meets these targets for subsequent screening (7.8%) and is close to meeting the target for initial mammograms (4.7%). It is worth noting that positive predictive value is sensitive to the age distribution of the screened population, which is among the reasons why the Canadian targets are only intended for women age 50 to 69. The positive predictive value increases dramatically with age: it is as low as 2.0% for women between 40 and 49 years undergoing their initial screening mammogram and as high as 13.9% in women over 70 years (Tables 6-8. pg29-35 ).

Figure 8. Combinations of diagnostic procedures after an abnormal screen,: women aged 50-69, 2005 and 2006 screen years
Figure 8 - Text Equivalent

In 2005 and 2006, 75.3% of women who received an abnormal screen were followed-up with additional breast imaging only. Breast imaging includes diagnostic mammography, ultrasound, or magnetic resonance imaging (MRI). A further 13.6% received breast imaging combined with core biopsy or fine needle aspiration; similar to the 13.0% in the previous reported interval (2003 and 2004).

Diagnostic Process Used by Organized Breast Cancer Screening Programs

As suggested by the positive predictive value, most women who receive abnormal screening results do not actually have breast cancer; however, additional assessment is required to determine the definitive diagnosis. The provision of timely, well coordinated, and minimized follow-up assessment has been shown to reduce fear and anxiety associated with abnormal results.(8) Women who receive abnormal screening results require additional radiological or surgical assessment including diagnostic mammography, ultrasonography, core or open biopsy, and/or fine needle aspiration.

Table 4. Diagnostic procedures after an abnormal screen, by mode of referral, women aged 50-69, 2005 and 2006 screen years
  Modes of referral
All modes of referral Referred by
mammography alone
Referred by clinical breast examination alone Referred by both mammography and clinical breast examination

a All provinces combined excluding Prince Edward Island (data unavailable).

b Proportion of all abnormal screens that had this diagnostic procedure by mode of referral.

c Range among provinces.

d Ultrasound may be underestimated in Québec as tests performed outside the program are not included.

Notes:

  1. Proportions will not add up to 100% since a woman is likely to have a combination of procedures performed during her work-up.
  2. Resolution of an abnormal screen is set at a maximum of 6 months post screen.
Diagnostic procedure Numbera
(%b) c
(Range % )
Numbera (%b) Numbera (%b) Numbera (%b)
Diagnostic mammogram 91,798
(52.6 - 92.1)
(75.1) 90,252 (80.1) 331 (4.4) 1,215 (58.6)
Ultrasoundd 67,461
(30.6 - 75.8)
(55.2) 60,608 (53.8) 5,031 (66.3) 1,822 (87.9)
Fine-needle aspiration 3,595
(0.0 - 5.3)
(2.9) 3,160 (2.8) 277 (3.7) 158 (7.6)
Core biopsy 16,513
(6.4 - 30.6)
(13.5) 15,757 (14.0) 233 (3.1) 523 (25.2)
Open biopsy with or without fine wire localization 5,303
(2.6 - 13.2)
(4.3) 4,888 (4.3) 267 (3.5) 148 (7.1)

In 2005 and 2006, 75.3% of women who received an abnormal screen were followed-up with additional breast imaging only. Breast imaging includes diagnostic mammography, ultrasound, or magnetic resonance imaging (MRI). A further 13.6% received breast imaging combined with core biopsy or fine needle aspiration; similar to the 13.0% in the previous reported interval (2003 and 2004) (Figure 8. pg21 ). Lastly, there was a shift from the use of open biopsy to core biopsy in 2005 and 2006 compared to the previous reported interval (2003 and 2004) . Core biopsy increased from 12.3% (13,648 women) to 13.5% (16,513 women) and open biopsy decreased from 5.6% (6,188 women) to 4.3 % (5,303 women) (Table 4. pg22 ).

Diagnostic Interval

The diagnostic interval is defined as the duration of time from the abnormal screen to its resolution. Excessively long diagnostic intervals can have negative psychological impact and potentially worsen prognosis.(8) The Canadian target is ≥90% of abnormal screens will be resolved with 5 weeks if no tissue biopsy is required and ≥90% within 7 weeks if a tissue biopsy is ever required during diagnostic follow-up. This methodology differs from that reported in the Evaluation Indicators Report and has been updated to close the diagnostic interval after 6 months of benign test results.

Nationally, 75.0% of women not requiring a tissue biopsy received resolution within five weeks and 46.7% of women requiring tissue biopsy received resolution within seven weeks. The proportion of women who did not require tissue biopsy and received resolution within five weeks has been showing gradual improvement, and has now stabilized at approximately 75%. The proportion of women requiring at least one tissue biopsy who received resolution within seven weeks has been relatively stable over time (Tables 6-8. pg29-35 ).

Benign Open Surgical Biopsy Rate

The rate of open surgical biopsy can provide an indication of the quality of pre-surgical assessment but no target has been set for this indicator.

In 2005 and 2006, the benign open surgical biopsy rate was 3.4 and 2.1 per 1,000 screens (initial and subsequent screens respectively). The biopsy rate is lower among older women (70+ years) undergoing their first screening mammogram compared to younger women. The rates among women undergoing subsequent screening mammograms shows little variation by age group. Since 2002, the rate has decreased for both initial and subsequent screening mammograms suggesting a shift away from the use of open surgical biopsy (Tables 6-8. pg29-35 ).

Benign to Malignant Open Surgical Biopsy Ratio

This indicator has been removed due to the small number of open biopsies performed on a provincial basis. This has occurred because there has been a shift to the use of core biopsy as a means to achieve definitive diagnosis resulting in less stable ratios that are sensitive to small changes and have become difficult to interpret.

Benign Core Biopsy Rate

The rate of benign core biopsy can provide an indication of the quality of pre-surgical assessment but no target has been set for this indicator.

In 2005 and 2006, the benign core biopsy rate was 13.0 and 4.8 per 1,000 screens (initial and subsequent screens respectively). The biopsy rate is lowest among older women (70+ years) undergoing subsequent screens. Since 2002, the rate has increased for both initial and subsequent screening mammograms suggesting a shift toward the use of core biopsy (Tables 6-8. pg29-35 ).

Benign to Malignant Core Biopsy Ratio

The ratio of benign to malignant core biopsies, can provide an indication of the quality of pre-surgical assessment but no target as yet has been set for this indicator. As with the open surgical biopsy rate this indicator has been updated to close the diagnostic interval after 6 months of benign test results.

In 2005 and 2006, the benign to malignant core biopsy ratio was 2.9:1 for initial screens and 1.4:1 for subsequent screens, and is lowest in older women (70+ years). For women, 50 to 69 years, undergoing subsequent screens the ratio has remained stable at approximately 1.4:1 since 2002. For women undergoing their first screen, the value has been relatively stable since 2002 at approximately 2.8:1 (Tables 6-8. pg29-35 ).

Cancer Detection by Organized Breast Cancer Screening Programs

In total, organized screening programs detected 7,872 cancers (invasive, in situ and unclassified types combined) among women aged 50 to 69 during 2005 and 2006 (Table 6. pg29 ). In order to ensure consistency between provinces this report identifies screen-detected cancers as those diagnosed within 6 months from the screen date. Other breast cancers among Canadian women were detected by opportunistic screening (outside of an organized program) or when a woman became symptomatic of disease.

Table 5. Characteristics of screen-detected cancers by age group, 2005 and 2006 screen years
  Age group

a Unclassified cancers are not included in this analysis.

b Québec and Prince Edward Island do not provide TNM staging and account for 78.3% and 1.9 % of all cases in the 'Invasive TNM stage missing' category respectively.

c This analysis includes invasive cancers only.

d Québec and Prince Edward Island do not provide tumour size and account for 90.3% and 2.2 % of all cases in the 'Tumour size unknown' category respectively.

e Includes pathologically positive nodes only.

f Includes missing values (94.9%) and cases in which dissection was not done (5.1%).

g New Brunswick has 22.0% positive nodes but number of positive nodes is not provided. New Brunswick accounts for 8.8% of all cases in this category.

h Québec and Prince Edward Island do not provide number of positive nodes and account for 81.5% and 2.0% of all cases in this category respectively.

Note:

Alberta is not included in this analysis as data was unavailable.

  40-49 50-59 60-69 70+ All ages
  n  % n  % n  % n  % n  %
Number of cancersa
Invasive 347 71.0 3,005 77.1 3,144 83.0 1,223 85.5 7,719 80.4
DCIS 142 29.0 894 22.9 643 17.0 207 14.5 1,886 19.6
TNM staging                    
0 (in situ) 142 30.6 894 34.3 643 25.5 207 16.9 1,886 27.6
I 200 43.1 1,027 39.3 1,257 49.8 717 58.4 3,201 46.9
II 111 23.9 579 22.2 535 21.2 251 20.5 1,476 21.6
III / IV 11 2.4 110 4.2 91 3.6 52 4.2 264 3.9
Invasive (TNM stage missing)b 25   1,289   1,261   203   2,778  
Tumour sizec
> 0 to < 2 mm 6 1.8 35 1.9 36 1.8 15 1.3 92 1.7
2 to 5 mm 29 8.6 116 6.4 150 7.5 81 6.8 376 7.0
6 to 10 mm 77 22.7 412 22.6 560 28.0 347 29.0 1,396 26.1
11 to 15 mm 90 26.6 482 26.5 573 28.7 357 29.9 1,502 28.0
16 to 20 mm 52 15.3 311 17.1 282 14.1 188 15.7 833 15.6
≥ 21 mm 85 25.1 465 25.5 399 20.0 208 17.4 1,157 21.6
Size unknownd 8   1,184   1,144   27   2,363  
Median tumour size (mm) 15.0   15.0   13.0   13.0   13.0  
Positive nodesce
0 225 71.7 1,261 71.8 1,515 77.5 864 80.5 3,865 75.8
1 to 3 69 22.0 372 21.2 335 17.1 166 15.5 942 18.5
4+ 20 6.4 123 7.0 106 5.4 43 4.0 292 5.7
Nodal status unknownfgh 33   1,249   1,188   150   2,620  

Among all women diagnosed with cancer through an organized screening program (≥40 years) 80.4% (7,719 women) were diagnosed with invasive and 19.6% (1,886 women) were diagnosed with in situ cancers. The proportion of cancers considered invasive increased with age; 71.0% of women aged 40 to 49 were diagnosed with invasive cancers compared to 85.5% of women 70 or more years. Women aged 50 to 59 and 60 to 69 were diagnosed with 77.1% and 83.0% invasive respectively (Table 5. above ).

In Situ Cancer Detection Rate

Ductal carcinoma in situ (DCIS) is a form of cancer detected through mammography screening, but, there is limited evidence supporting the transition of all forms of DCIS to invasive cancer. Because of this, no target has been set for in situ cancer detection rates in Canada. Despite this, it is important to monitor rates of detection until appropriate targets can be set.

In Canada, women (50 to 69 years) undergoing their first screen had a DCIS detection rate of 1.2 cases per 1,000 screens. Women undergoing subsequent screens had a DCIS detection rate of 0.9 case per 1,000 screens [Note 7] (Table 6. pg29 ).

Figure 9. Cancer detection (Invasive and In situ) rate per 1,000 screens: by age group, 2005 and 2006 screen years
Figure 9 - Text Equivalent

In Canada, women (50 to 69 years) undergoing their first screen had a DCIS detection rate of 1.2 cases per 1,000 screens. Women undergoing subsequent screens had a DCIS detection rate of 0.9 case per 1,000 screens. In Canada, women undergoing their first screen had an invasive cancer detection rate of 4.6 cases per 1,000 screens. Women undergoing subsequent screens had an invasive cancer detection rate of 3.7 cases per 1,000 screens. As anticipated, the invasive cancer detection rates were highest among initial screens and also increased in older women and when subsequent screening was not timely.

Among women aged ≥40 years, diagnosed with breast cancer in 2005 and 2006, 46.9% of tumours were classified as stage I and 3.9% were classified as stage III/IV (Table 5. pg25 ). Among women aged 50 to 69, the proportion of invasive tumours less than 10 mm was 34.1% and almost 75% of women had negative lymph nodes at diagnosis (Table 6. pg29 ). A larger proportion of older women had tumours smaller than 10 mm at diagnosis (range: 30.7% to 37.2%) and negative lymph nodes at diagnosis (range: 72.0% to 80.8%) compared to younger women (Table 7. pg32 ).

Invasive Cancer Detection Rate

The targets for invasive cancer detection rates established in Canada are >5 per 1,000 first screens and >3 per 1,000 subsequent timely screens.

In Canada, women undergoing their first screen had an invasive cancer detection rate of 4.6 cases per 1,000 screens. Women undergoing subsequent screens had an invasive cancer detection rate of 3.7 cases per 1,000 screens [Note 7] (Table 6. pg29 ). As anticipated, the invasive cancer detection rates were highest among initial screens and also increased in older women and when subsequent screening was not timely (Figure 9. pg27 ).

Invasive Tumour Size and Negative Node Rate

Cancer detected at earlier stages has more treatment options, less recurrence, and improved survival. Research in Canada has shown that among women diagnosed with breast cancer, participants of organized breast cancer screening programs have more breast conserving surgery and less chemotherapy compared to non-participants.(9) In addition, 97.9% of women with stage I breast cancer survive at least five years while only 27.9% of women diagnosed in stage IV survive for five years.(10) Early stage cancer has smaller tumours and no lymph node involvement. The Canadian target is for greater than 25% of invasive tumours to be ≤10mm and greater than 50% of invasive tumours to be ≤15mm. The second target is for >70% of women with invasive cancer to have no lymph node involvement.

Post-Screen Invasive Cancers

Post-screen invasive cancers are those cancers that develop after a normal screening mammogram but before the next screen, and the post-screen invasive cancer rate serves as an indicator of the sensitivity of the screening program. Post-screen invasive cancers include two types of cancers: those that occur after the recommended 12 or 24 months among women who do not return for their regular annual or biennial screen respectively (non-compliant cancers), or among women who become symptomatic before their next regular screen (interval cancers). This methodology differs from that reported in the Evaluation Indicators Report and has been updated include cases referred for diagnostic follow-up with a benign result that later developed breast cancer.(4) Post-screen invasive cancer rates were calculated based on all women screened from 2002 to 2003 who developed an interval cancer during 2004 to 2005.[Note 7] In order to ensure consistency between provinces this report also considers interval cancers to include those detected by a screening mammogram that have taken longer than 6 months to diagnosis. Due to the changes in the method of calculation, it is anticipated that the rate reported in this report should be higher than in previous reports assuming stability in the true incidence.

The target is for less than 6 women per 10,000 person years to be diagnosed with a post screen cancer within 12 months of screening and less than 12 women per 10,000 person years within 24 months.

Nationally, the post-screen invasive cancer rate was 6.5 per 10,000 person years within 12 months and 8.0 per 10,000 person years within 24 months (Table 6. pg29 ).

Table 6. Performance measures by program, women aged 50-69, 2005 and 2006 screen years
Indicator Targeta Program
NT BC AB SK MB ONb QC NB NSc PEd NLb Canada

a Targets apply to women aged 50-69 years.

b Screening visit includes mammography and complete clinical breast examination (CBE).

c Screening visit includes mammography and modified CBE by technician.

d Information for Prince Edward Island was based on data external to the CBCSD and may differ from previous reports.

e Surveillance and monitoring purposes only.

f Includes invasive, in situ, and unclassified cancers. Does not include bilateral cancers (Cases of bilateral cancer = Ontario (36), Saskatchewan (2), British Columbia (19).

g Data for 2002 and 2003 screen years are used.

h Retention rate for women aged 50-67. This calculation method has been updated from previous reports.

i Northwest Territories is excluded from this measure as data is not available for 2002-2003 (program began in 2004).

j Total abnormal screens by mammography (Initial + Rescreen) for Prince Edward Island = 1,122.

k Independent of CBE or its findings.

l Tissue biopsy does not include fine needle aspiration (FNA). Time to diagnosis is based on the date of the first pathological biopsy result of breast cancer (excludes FNA and all inconclusive or incorrect procedures) or the date of the last benign test or pathological biopsy.

m Excludes tests beyond 6 months post screen. This calculation method has been updated from previous reports.

n Includes all final biopsy test results (may include bilateral tests).

o Includes direct to open surgical biopsy diagnosis and cases who underwent an inconclusive or incorrect core biopsy prior to a definitive diagnosis by open surgical biopsy.

p Québec calculates the benign to malignant open biopsy ratio using a different method. Canada total excludes Québec data.

q Missing values are excluded from calculations. Expressed as a proportion of screen-detected invasive cancers with complete data on tumour size or number of positive nodes.

r New Brunswick does not provide the number of pathologically positive nodes; rate is calculated based on N stage of disease data.

s Calculated based on all women screened from 2002-2003 who developed a post-screen cancer during 2002-2005. Non-compliant cancers were not included in this calculation. Post-screen cancers include all invasive cancers diagnosed after a normal program screen (not referred) or screen detected cancers (referred) that took >6 months to diagnosis (beyond the 'normal screening episode'). Post-screen cancers also include cases referred for diagnostic follow-up with a benign result (missed at diagnosis). This calculation method has been updated from previous reports.

t Rates in Newfoundland and Labrador may be underestimated due to incomplete cancer registry incidence data.

Notes:

* Province/territory is excluded from this measure (information unavailable). Canadian total excludes indicated province(s)/territory. x Province/territory is excluded from this measure due to small values. Canadian total excludes indicated province(s)/territory.

Number of screens N/Ae 882 275,838 31,384 55,171 68,854 513,388 491,023 53,821 60,625 9,734 27,979 1,588,699
Number of first screens N/Ae 422 22,533 6,993 9,193 13,875 159,901 121,356 5,202 11,181 * 9,688 360,344
Number of cancersf N/Ae x 1,288 141 282 373 2,368 2,752 196 300 47 125 7,872
Participation rate within 30 months ( %) 70 29.4 55.5 10.4 54.3 56.8 35.1 57.7 59.2 50.8 * 37.9 43.9
Participation rate within 24 months ( %) N/Ae 26.3 51.1 9.1 48.3 52.5 32.4 51.7 53.0 45.8 53.3 35.4 40.0
Retention rate ( % initial rescreen within 30 months)gh 75 N/Ai 54.9 53.0 68.1 67.8 78.5 65.0 55.5 68.6 * 73.7 68.9
Retention rate ( % subsequent rescreen within 30 months)gh 90 N/Ai 80.2 74.9 84.6 81.7 88.1 77.6 77.5 79.8 * 84.8 81.3
Abnormal call rate ( %)j
Abnormal by mammographyk
Initial screen <10 8.1 15.9 6.9 13.7 9.2 10.5 15.0 15.3 8.3 * 7.4 12.2
Rescreen <5 9.6 5.7 3.1 5.3 4.6 5.5 7.3 6.9 4.3 * 4.9 6.0
Abnormal by any mode of detection
Initial screen <10 8.1 15.9 6.9 13.7 9.5 11.9 15.0 15.3 8.4 * 11.1 13.0
Rescreen <5 9.6 5.7 3.1 5.3 4.7 6.8 7.3 6.9 4.5 * 8.3 6.4
Invasive cancer detection rate (per 1,000 screens)
Detected by mammographyk
Initial screen >5 x 5.8 * 4.2 5.5 4.1 4.9 4.2 5.1 * 3.8 4.6
Rescreen >3 x 3.4 * 4.2 4.2 3.4 4.2 2.8 3.9 * 3.2 3.7
Detected by any mode of detection
Initial screen >5 x 5.8 * 4.2 5.5 4.3 4.9 4.2 5.2 * 4.0 4.7
Rescreen >3 x 3.4 * 4.2 4.2 3.6 4.2 2.8 3.9 * 3.5 3.7
In situ cancer detection rate (per 1,000 screens)
Initial screen N/Ae x 1.4 * 1.1 1.1 1.0 1.5 1.0 1.0 * 0.5 1.2
Rescreen N/Ae x 1.1 * 0.9 0.9 0.7 1.1 0.7 0.8 * 0.6 0.9
Diagnostic interval ( %)lm
Completed with no tissue biopsy, within 5 weeks 90 72.4 66.5 51.5 67.0 73.4 83.4 70.4 87.7 75.3 * 63.9 75.0
Completed with tissue biopsy, within 7 weeks 90 40.0 39.9 50.6 33.6 39.3 57.4 41.6 43.8 57.8 * 40.1 46.7
Positive predictive value ( %)f
Detected by mammographyk
Initial screen 5 x 4.5 5.0 3.9 7.2 4.9 4.3 3.6 7.3 * 5.9 4.7
Rescreen 6 x 7.8 15.5 9.7 11.2 7.5 7.3 5.3 10.8 * 8.3 7.8
Detected by any mode of detection
Initial screen 5 x 4.5 5.2 3.9 6.9 4.4 4.3 3.6 7.3 * 4.2 4.5
Rescreen 6 x 7.8 15.5 9.7 10.8 6.3 7.3 5.3 10.4 * 5.3 7.3
Benign open surgical biopsy rate (per 1,000 screens)mnop
Initial screen N/Ae x 7.9 0.9 6.3 3.2 2.6 N/Ap 10.6 1.5 * 5.0 3.4
Rescreen N/Ae x 2.8 0.4 3.1 1.1 1.6 N/Ap 3.4 0.8 * 4.2 2.1
Benign core biopsy rate (per 1,000 screens)mn
Initial screen N/Ae x 11.1 8.0 6.1 10.7 9.9 18.3 8.7 21.7 * 7.3 13.0
Rescreen N/Ae x 2.6 2.5 1.2 3.3 4.3 7.5 3.6 8.3 * 3.3 4.8
Benign to malignant core biopsy ratiomn
Initial screen N/Ae x 2.7 : 1 2.9 : 1 3.1 : 1 1.8 : 1 2.4 : 1 3.3 : 1 3.5 : 1 4.1 : 1 * 2.4 : 1 2.9 : 1
Rescreen N/Ae x 1.1 : 1 0.6 : 1 0.6 : 1 0.7 : 1 1.3 : 1 1.7 : 1 2.0 : 1 2.0 : 1 * 1.6 : 1 1.4 : 1
≤10 mm >25 x 35.1 * 35.2 39.1 34.2 * 30.6 30.5 * 28.2 34.1
≤15 mm >50 x 64.8 * 68.1 65.9 60.0 * 58.6 58.9 * 57.3 61.8
Node negative rate in cases of invasive cancer ( %)qr >70 x 75.0 * 78.3 78.2 74.0 * 75.5 74.6 * 70.9 74.8
Post-screen invasive cancer rate (per 10,000 person-years)gs
Within 12 months <6 x 6.1 6.8 6.5 6.8 6.4 * 10.2 5.8 * 3.2t 6.5
Within 24 months <12 x 8.5 6.6 8.0 8.7 7.9 * 9.4 6.3 * 4.0t 8.0
Table 7. Performance measures by age group, 2005 and 2006 screen years
Indicator Targeta Age groupb
40-49 50-59 60-69 70+ All ages
Number of screensc N/Ad 247,710 952,390 636,309 195,345 2,031,754

a Targets apply to women aged 50-69 years.

b Prince Edward Island is excluded for all age groups unless otherwise indicated (information unavailable).

c Prince Edward Island is included in this indicator.

d Surveillance and monitoring purposes only.

e Includes invasive, in situ, and unclassified cancers. Does not include bilateral cancers (Cases of bilateral cancer) = 40-49 (9), 50-59 (21), 60-69 (36), 70+ (20).

f Northwest Territories is excluded from this measure due to small values.

g In the case of multiple screens, the first screen within the target population is used (40-49, 50-69 and 70+).

h Data for 2002 and 2003 screen years are used.

i Retention rate for women aged 50-67. This calculation method has been updated from previous reports.

j Northwest Territories is excluded from this measure as data is not available for 2002-2003 (program began in 2004).

k Total abnormal screens by mammography (Initial + Rescreen) for Prince Edward Island: 40-49 =577, 50-59 =697, 60-69 =425, 70+ =247.

l Independent of clinical breast examination or its findings.

m Alberta is excluded from this measure as data was unavailable.

n Tissue biopsy does not include fine needle aspiration (FNA). Time to diagnosis is based on the date of the first pathological biopsy result of breast cancer (excludes FNA and all inconclusive or incorrect procedures) or the date of the last benign test or pathological biopsy.

o Excludes tests beyond 6 months post screen. This calculation method has been updated from previous reports.

p Includes all final biopsy test results (may include bilateral tests).

q Includes direct to open surgical biopsy diagnosis and cases who underwent an inconclusive or incorrect core biopsy prior to a definitive diagnosis by open surgical biopsy.

r Québec calculates the benign to malignant open biopsy ratio using a different method. Canada total excludes Québec data.

s Québec, Alberta, and Prince Edward Island were excluded from this measure as data was unavailable.

t Missing values are excluded from calculations; Expressed as a proportion of screen-detected invasive cancers with complete data on tumour size or number of positive nodes.

u New Brunswick does not provide the number of pathologically positive nodes; rate is calculated based on N stage of disease data.

v Post-screen detected cancer rates are calculated with 2002 and 2003 data and include the following provinces: British Columbia, Alberta, Saskatchewan, Manitoba, Ontario, New Brunswick, Nova Scotia and Newfoundland and Labrador.

w Calculated based on all women screened from 2002-2003 who developed a post-screen cancer during 2002-2005. Non-compliant cancers were not included in this calculation. Post-screen cancers also include all invasive cancers diagnosed after a normal program screen (not referred) or screen detected cancers (referred) that took >6 months to diagnosis (beyond the 'normal screening episode'). Post-screen cancers alsot include cases referred for diagnostic follow-up with a benign result (missed at diagnosis). This calculation method has been updated from previous reports.

Number of first screens N/Ad 78,239 284,932 75,412 19,142 457,725
Number of cancerscef N/Ad 498 3,998 3,874 1,483 9,853
Participation rate within 30 months ( %)g 70 7.7 44.4 43.2 10.9 24.6
Participation rate within 24 months ( %)cg N/Ad 7.0 39.7 40.4 9.8 22.4
Retention rate ( % initial rescreen within 30 months)ghij 75 65.2 69.2 67.7 45.5 66.4
Retention rate ( % subsequent rescreen within 30 months)ghij 90 83.6 80.8 81.7 63.6 78.0
Abnormal call rate (%)k
Abnormal by mammographyl
Initial screen <10 13.7 12.7 10.3 9.3 12.3
Rescreen <5 6.6 6.2 5.7 5.1 6.0
Abnormal by any mode of detection
Initial screen <10 13.7 13.5 11.1 10.2 13.0
Rescreen <5 6.7 6.7 6.2 5.6 6.4
Invasive cancer detection rate (per 1,000 screens)fm
Detected by mammographyl
Initial screen >5 2.0 3.9 6.9 11.7 4.4
Rescreen >3 1.2 2.8 4.7 5.8 3.7
Detected by any mode of detection
Initial screen >5 2.0 4.0 7.1 11.8 4.5
Rescreen >3 1.2 2.9 4.8 5.9 3.7
In situ cancer detection rate (per 1,000 screens)fm
Initial screen N/Ad 0.8 1.2 1.2 1.2 1.1
Rescreen N/Ad 0.5 0.9 1.0 1.1 0.9
Diagnostic interval (%)no
Completed with no tissue biopsy, within 5 weeks 90 70.9 74.7 75.6 75.6 74.4
Completed with tissue biopsy, within 7 weeks 90 41.7 45.3 48.8 49.3 47.5
Positive predictive value (%)ef
Detected by mammographyl
Initial screen 5 2.0 4.0 7.9 13.9 4.5
Rescreen 6 2.6 6.0 10.1 13.8 7.7
Detected by any mode of detection
Initial screen 5 2.0 3.9 7.5 12.8 4.3
Rescreen 6 2.6 5.7 9.4 12.7 7.3
Benign open surgical biopsy rate (per 1,000 screens)fopqr
Initial screen N/Ad 5.6 3.8 2.5 2.1 3.9
Rescreen N/Ad 2.1 2.1 2.1 2.0 2.1
Benign core biopsy rate (per 1,000 screens)fop
Initial screen N/Ad 13.0 13.6 10.5 8.1 12.8
Rescreen N/Ad 3.6 4.9 4.8 3.1 4.5
Benign to malignant core biopsy ratiofop
Initial screen N/Ad 8.5 : 1 3.4 : 1 1.7 : 1 0.8 : 1 3.0 : 1
Rescreen N/Ad 3.7 : 1 1.7 : 1 1.1 : 1 0.7 : 1 1.4 : 1
Invasive cancer tumour size (%)fst
≤10 mm >25 33.3 30.7 37.2 37.0 34.7
≤15 mm >50 60.1 57.2 65.9 66.9 62.8
Node negative rate in cases of invasive cancer ( %)fstu >70 72.4 72.0 77.4 80.8 75.9
Post-screen invasive cancer rate (per 10,000 person-years)hvw
Within 12 months <6 5.0 6.2 6.9 7.4 6.3
Within 24 months <12 3.9 7.8 8.3 8.3 7.4
Table 8. Performance measures by year, women aged 50-69
Indicator Targeta Screen year
2002 2003 2004 2005b 2006b

a Targets apply to women aged 50-69 years.

b Prince Edward Island is excluded for 2005-2006 unless otherwise indicated (information unavailable).

c Prince Edward Island is included in this indicator for all screen years.

d Surveillance and monitoring purposes only.

e Includes invasive, in situ, and unclassified cancers. Does not include bilateral cancers (Cases of bilateral cancer) = 2002 (12) , 2003 (22), 2004 (22), 2005 (30), 2006 (27)

f Northwest Territories is excluded from this measure due to small values and where data is not available (program began in 2004).

g Participation rate was calculated in two year intervals due to biennial recall (Screen Years: 2001-2002, 2002-2003, 2003-2004, 2004-2005, 2005-2006).

h Retention rate for women aged 50-67. This calculation method has been updated from previous reports.

i Northwest Territories is excluded as data is not available for 2002-2003 (program began in 2004).

j Insufficient time for follow-up to ensure data completeness.

k Excludes Prince Edward Island in 2005-2006; Total abnormal screens by mammography (Initial + Rescreen): 2005 = 604, 2006 = 518.

l Independent of clinical breast examination or its findings.

m Ablerta is excluded from this measure for 2005-2006 as data was unavailable for this time period.

n Tissue biopsy does not include fine needle aspiration (FNA). Time to diagnosis is based on the date of the first pathological biopsy result of breast cancer (excludes FNA and all inconclusive or incorrect procedures) or the date of the last benign test or pathological biopsy.

o Excludes tests beyond 6 months post screen. This calculation method has been updated from previous reports.

p Includes all final biopsy test results (may include bilateral tests).

q Includes direct to open surgical biopsy diagnosis and cases who underwent an inconclusive or incorrect core biopsy prior to a definitive diagnosis by open surgical biopsy.

r Québec calculates open biopsies using a different method. Canada total excludes Québec data.

s Excludes Alberta and Québec (2005-2006) and Prince Edward Island (2002-2006) as data was unavailable.

t Missing values are excluded from calculations. Expressed as a proportion of invasive cancers with complete data on tumour size or number of positive nodes.

u New Brunswick does not provide the number of pathologically positive nodes; rate is calculated based on N stage of disease data.

v Post-screen detected cancer rates are calculated with 2002 and 2003 data and include the following provinces: British Columbia, Alberta, Saskatchewan,

Manitoba, Ontario, New Brunswick, Nova Scotia and Newfoundland and Labrador.

w Calculated based on all women screened from 2002-2003 who developed a post-screen cancer during 2002-2005. Non-compliant cancers were not included in this calculation. Post-screen cancers also include all invasive cancers diagnosed after a normal program screen (not referred) or screen detected (referred) cancers that took >6 months to diagnosis (beyond the 'normal screening episode'). Post-screen cancers do not include cases referred for diagnostic follow-up with a benign result (calculation includes those missed at screening and excludes those missed at diagnosis). This calculation method has been updated from previous reports.

Note:

Figures have been updated and may vary slightly from previous reports.

Number of screensc N/Ad 609,202 646,605 699,610 765,517 823,182
Number of first screens N/Ad 169,633 159,136 162,636 172,737 187,607
Number of cancerscef N/Ad 3,205 3,327 3,487 3,818 4,054
Participation rate within 30 months ( %)g 70 37.3 38.8 40.1 41.9 43.9
Participation rate within 24 months ( %)cg N/Af 33.9 35.3 36.5 38.1 40.0
Retention rate ( % initial rescreen within 30 months)hi 75 68.6 69.2 N/Aj N/Aj N/Aj
Retention rate ( % subsequent rescreen within 30 months)hi 90 81.7 80.8 N/Aj N/Aj N/Aj
Abnormal call rate ( %)k
Abnormal by mammographyl
Initial screen <10 11.7 12.0 12.2 12.2 12.2
Rescreen <5 6.6 6.6 6.4 6.0 6.0
Abnormal by any mode of detection
Initial screen <10 12.7 12.8 13.0 13.0 13.0
Rescreen <5 7.3 7.1 6.9 6.5 6.4
Invasive cancer detection rate (per 1,000 screens)fm
Detected by mammographyl
Initial screen >5 4.9 4.9 4.6 4.4 4.7
Rescreen >3 3.9 3.8 3.6 3.7 3.7
Detected by any mode of detection
Initial screen >5 5.0 5.0 4.7 4.5 4.8
Rescreen >3 3.9 3.8 3.7 3.8 3.7
In situ cancer detection rate (per 1,000 screens)fm
Initial screen N/Ad 1.1 1.2 1.3 1.2 1.2
Rescreen N/Ad 1.0 0.9 1.0 1.0 0.9
Diagnostic interval ( %)no
Completed with no tissue biopsy, within 5 weeks 90 73.6 75.3 74.8 75.1 74.9
Completed with tissue biopsy, within 7 weeks 90 48.7 48.4 48.8 47.3 46.0
Positive predictive value ( %)ef
Detected by mammographyl
Initial screen 5 5.1 5.1 4.8 4.6 4.8
Rescreen 6 7.3 7.2 7.3 7.8 7.7
Detected by any mode of detection
Initial screen 5 4.8 4.9 4.6 4.4 4.6
Rescreen 6 6.8 6.7 6.8 7.4 7.3
Benign open surgical biopsy rate (per 1,000 screens)fopqr
Initial screen N/Ad 5.6 4.9 4.3 3.6 3.3
Rescreen N/Ad 3.0 3.0 2.6 2.2 1.9
Benign core biopsy rate (per 1,000 screens)fop
Initial screen N/Ad 10.6 11.6 12.2 12.5 13.4
Rescreen N/Ad 4.1 4.7 5.0 4.8 4.9
Benign to malignant core biopsy ratiofop
Initial screen N/Ad 2.9 : 1 2.8 : 1 2.9 : 1 2.9 : 1 2.8 : 1
Rescreen N/Ad 1.4 : 1 1.5 : 1 1.6 : 1 1.4 : 1 1.4 : 1
Invasive cancer tumour size ( %)fst
≤15 mm >50 66.1 65.0 63.8 61.7 61.8
Node negative rate in cases of invasive cancer ( %)fstu >70 75.7 75.6 73.9 75.3 74.4
Post-screen invasive cancer rate (per 10,000 person-years)vw
Within 12 months <6 7.1 5.9 N/Aj N/Aj N/Aj
Within 24 months <12 8.4 7.7 N/Aj N/Aj N/Aj

 

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