Organized Breast Cancer Screening Programs in Canada - Report on Program Performance in 2003 and 2004

2003 and 2004 Results

This report presents statistics for the 2003 and 2004 calendar years using data submitted up to August 2007. Further, the outcomes presented in this report are based on the 2007 report by the Evaluation Indicators Working Group (6). Some outcomes are based on a relatively small number of events but are included to accurately reflect the work of the Evaluation Indicators Working Group (for example: benign to malignant open surgical biopsy ratio). In these cases, sample size is presented. 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 apply to women aged 50 to 69. Importantly, the data from the Northwest Territories is only available for the 2004 reporting year and therefore tables requiring at least two years of data exclude this region.

Participation and Retention in Organized Screening Programs

Participation

Adequate participation in breast cancer screening is essential for reductions in mortality to occur in the target population. Based on extrapolation from randomized controlled trials, Canadian programs have established 70% as the target participation rate.

Participation rates include all 10 provinces and data from the Northwest Territories for screening exams in the year 2004 only. Overall, 1,345,382 Canadian women between 50 and 69, and 1,723,690 women of all ages, received a screening mammogram through a Canadian organized screening program in 2003 and 2004 (Table 2). Since the inception of the first Canadian organized screening program in British Columbia, over 6.5 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 2003 and 2004, only 36.5% of the target population received a screening mammogram through an organized program. This represents a small improvement from 2001 and 2002 when only 33.9% of eligible women attended. The participation rate varies between programs from 10.4% in Alberta to 52.9% in New Brunswick (Figure 3).

Overall, many well-established programs have seen participation rates stabilize since 1997 and 1998; British Columbia (46-51%), Alberta (10-15%), and Saskatchewan (52-55%). While programs in Nova Scotia (27-41%) and Ontario (13-27%) have continued to see participation rates increase. Newer programs in Québec (12-48%), New Brunswick (36-53%), and Newfoundland and Labrador (18-26%) have also seen increases in participation rates.

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 62% of women between 50 and 69 years received a screening mammogram within the past two years (Figure 4). This figure is selfreported 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.

Figure 3 – Participation in organized breast cancer screening programs, women aged 50-69, 2003 and 2004 screen years

Source: Statistics Canada data for 2003 and 2004 are used for denominator values.

Notes: Population estimates are averaged.
The national participation rate of 36.5% is indicated by the horizontal bar.

^a Northwest Territories (NT) rate is based on 2004 data only.

Retention

Optimal benefits from screening programs are achieved when regular participation in screening occurs. Two targets were set based on participation rates, sojourn time, screening interval studies and randomized controlled trials (7-9). 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. Retention rate for women aged 50 to 69 excludes women who returned at age 70 years or older.

Overall, 74.3% of women aged 50 to 68 who received a screening mammogram between 2001 and 2002 were rescreened within 30 months during 2003 to 2004. Among women who received their first screening mammogram in the 2001 and 2002 calendar years, 64.9% returned for a subsequent mammogram within 30 months. Among women aged 50 to 68 who received a subsequent screening mammogram in the 2001 and 2002 calendar years, 76.8% returned for a subsequent mammogram within 30 months. (Table 6)

Figure 4 - Proportion of women aged 50-69 with a self-reported mammogram^a in the past two years by province, 2005 Canadian Community Health Survey

^a Diagnostic mammography excluded.

^b The CCHS sampling frame covers 71% of the private households in Nunavut.

Source: Health Canada. 2005 Canadian Community Health Survey: share file.

Figure 5 – Cumulative probability of returning for a subsequent program screen by age group, 2000 and 2001 screen years

Note: Northwest Territories data are not included in this analysis.

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 (63.9% and 53.5% respectively) or subsequent screen (86.7% and 68.4% respectively) (Table 7). Most women returned for subsequent screening between 21 and 27 months after their 2001 to 2002 screen, however, women between age 40 and 49 were more likely than older women to return between 12 and 15 months (Figure 5).

Results of Screening

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. Both the abnormal call rate and the positive predictive value offer insight into the process of accurately identifying asymptomatic women with breast cancer.

Figure 6 – Age distribution of program screens by province, 2003 and 2004 screen years

^a Although Québec accepts women aged 35-49 and 70+ with physician referral if done at a program screening centre, they are not officially considered within the program.

^b Data for Northwest Territories available only for year 2004.

Abnormal Call Rates

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 of 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.

Among women 50 to 69 years, the abnormal call rate for women receiving their first screening mammogram is 12.1% and for a subsequent screening mammogram is 6.5% (Table 6). These rates have been relatively stable since 2001 and 2002. 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).

Positive Predictive Value

The positive predictive value (PPV) 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 PPV 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 PPV meets these targets (5.0% and 7.3% for initial and subsequent screening mammograms respectively) and has been relatively stable since 2001. It is worth noting that PPV 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 PPV improves dramatically with age for it is as low as 2.3% for women between 40 and 49 years undergoing their initial screening mammogram and as high as 13.8% in the 70+ age group (Table 6-8).

Figure 7 - Abnormal call rate^a by age group, 2003 and 2004 screen years

^a Includes mammography and clinical breast examination as screening modalities.
Northwest Territories data are not included in this analysis.

Notes: The median time for women to return for screening is as follows:
Rescreen (>9 months, ≤18 months) by 12.5 months;
Rescreen (>18 months, ≤30 months) by 24.4 months;
Rescreen (>30 months) by 35.7 months.

Diagnostic Interventions

As suggested by the PPV, most women who receive abnormal screening results do not actually have breast cancer, however, additional assessment is required to determine the defi nitive diagnosis. The provision of timely, well coordinated, and minimized follow-up assessment has been shown to reduce fear and anxiety associated with abnormal results (10). Women who receive abnormal results require additional radiological or surgical assessment including diagnostic mammography, ultrasonography, core or open biopsy, and/or fine needle aspiration.

Analysis of diagnostic test type (Figure 8) includes all 10 provinces and data from the Northwest Territories for screening exams in the year 2004 only. In 2003 and 2004, approximately three quarters of women who received an abnormal screen were followed-up with additional breast imaging only. A further 13% received breast imaging combined with core biopsy or fine needle aspiration; an increase from 9.3% in 2001 and 2002 (Figure 8). Lastly, there was a shift from the use of the more invasive open biopsy to the less invasive core biopsy from 2001 and 2002 to 2003 and 2004. Core biopsy increased from 9.6% (9,187 women) to 12.3% (13,648 women) and open biopsy decreased from 7.2% (6,874 women) to 5.6% (6,188 women) (Table 4).

Diagnostic Interval

The diagnostic interval is the duration of time from the abnormal screen to its resolution. Excessively long diagnostic intervals can have negative psychological impact and potentially worsen prognosis (10). 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 tissue biopsy is required.

Nationally, 74.3% of women not requiring a tissue biopsy received resolution within five weeks and 46.3% of women requiring tissue biopsy received resolution within seven weeks. The proportion of women who did not require tissue biopsy and received resolution within fi ve weeks has been showing gradual annual improvement, however, the proportion of women requiring tissue biopsy who received resolution within seven weeks has been relatively stable over time (Table 6-8).

Table 4 – Diagnostic procedures after an abnormal screen, women aged 50-69, 2003 and 2004 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
Diagnostic procedure	Numbera (%b) (Range%c)		Numbera (%b)		Numbera (%b)		Numbera (%b)
Diagnostic mammogram	82,019 (74.1) (50.8 - 90.7)		79,639 (79.3)		401 (5.5)		1,979 (65.0)
Ultrasound	59,651 (53.9) (32.4 - 71.4)		53,207 (53.0)		4,235 (58.3)		2,209 (72.6)
Fine-needle aspiration	4,232 (3.8) (0.4 - 6.7)		3,633 (3.6)		356 (4.9)		243 (8.0)
Core biopsy	13,648 (12.3) (4.8 - 29.0)		12,759 (12.7)		184 (2.5)		705 (23.2)
Open biopsy with or without fine wire localization	6,188 (5.6) (0.0 - 13.1)		5,659 (5.6)		294 (4.1)		235 (7.7)

^a All provinces combined. Northwest Territories data not included due to small numbers.
^b Proportion of all abnormal screens that had this diagnostic procedure performed.
^c Range among provinces.

Note: Proportions will not add up to 100% since a woman is likely to have a combination of procedures performed during her work-up.

Benign to Malignant Open Surgical Biopsy Ratio³

High quality pre-surgical assessment reduces the number of women requiring invasive follow-up who ultimately have a normal or benign result. The ratio of benign results compared to malignant results after an open surgical biopsy is one way to assess the quality of the pre-surgical assessment. This includes women who went directly to an open surgical biopsy as their primary assessment and those who underwent an inconclusive core biopsy prior to a definitive diagnosis by open surgical biopsy. The target for this indicator is ≤1:1; for every malignant cancer detected there should be one or fewer benign results.

In 2003 and 2004, the ratio was 1.8:1, meaning that close to two benign results for every malignant cancer case were detected by open surgical biopsy. The ratio among women undergoing their initial mammogram was 2.6:1 while women undergoing a subsequent mammogram had a ratio of 1.6:1 (Table 6). This result varies by the age of the women. Women 70 years and older undergoing a subsequent mammogram had the best ratio (0.9:1) while women between 40 and 49 years undergoing their first mammogram had the poorest ratio (5.6:1) (Table 7).

Figure 8 – Combinations of diagnostic procedures after an abnormal screen, women aged 50-69, 2003 and 2004 screen years

^a For women who had none of the above procedures, 93.8% were referred based on an abnormal clinical breast examination (CBE) and may have had their final diagnosis established by their primary care provider. Québec data included for all procedures but not calculated for CBE referral status.

Northwest Territories data are for 2004 only.

The benign to malignant open surgical biopsy ratio reflects the experience of very few women because there has been a substantial shift to core biopsy, and away from open surgical biopsy, as a means to achieve definitive diagnosis. As a result, the indicator is nearing the end of its usefulness as the declining numbers of procedures result in ratios that are difficult to interpret. The number of women undergoing this procedure is included in Table 6 to illustrate this point.

Benign Open Surgical Biopsy Rate

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

In 2003 and 2004, the benign open surgical biopsy rate was 4.5 and 2.6 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, however, rates among women undergoing subsequent screening mammograms shows little variation by age group. Since 2000, the rate has decreased for both initial and subsequent screening mammograms suggesting a shift away from the use of open surgical biopsy (Table 6-8).

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, however, no target as yet has been set for this indicator.

In 2003 and 2004, the benign to malignant core biopsy ratio was 2.8:1 for initial screens and 1.5:1 for subsequent screens, and is lowest in older women (70+ years). For women undergoing their first screen the ratio has decreased to 2.8:1 from 3.3:1 since 2000, however, for women undergoing subsequent screens the value has been relatively stable between 1.4 and 1.6:1 (Table 6-8).

Benign Core Biopsy Rate

The rate of benign core biopsy can provide an indication of the quality of presurgical assessment, however, no target has been set for this indicator.

In 2003 and 2004, the benign core biopsy rate was 11.6 and 4.7 per 1,000 screens (initial and subsequent screens respectively). The biopsy rate is lowest among older women (70+ years) undergoing subsequent screens. Since 2000, the rate has increased for both initial and subsequent screening mammograms suggesting a shift toward the use of core biopsy (Table 6-8).

Cancer Detection

In total, 6,900 cancers (invasive, in situ and unclassified types combined) were detected among women aged 50 to 69 during 2003 and 2004 by organized screening programs (Table 6). Other breast cancers among Canadian women were detected by opportunistic screening (outside of an organized program) or when a woman became symptomatic of disease.

Among women ≥40 years, 79.7% (6,851 women) were diagnosed with invasive and 20.3% (1,747 women) with in situ cancers. This includes data from women diagnosed in the Northwest Territories during 2004. The proportion of cancers considered invasive increased with age; 70.8% of women aged 40 to 49 were diagnosed with invasive cancers compared to 85.3% of women 70 or more years (Table 5).

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 4.7 cases per 1,000 screens. Women undergoing subsequent screens had an invasive cancer detection rate of 3.7 cases per 1,000 screens⁴ (Table 6). As anticipated, the invasive cancer detection rate increased in older women and when subsequent screening was not timely (Figure 9).

In Situ Cancer Detection Rate

Ductal carcinoma in situ (DCIS) is a form of cancer detected through mammography screening, however, 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 undergoing their first screen had a DCIS detection rate of 1.3 cases per 1,000 screens. Women undergoing subsequent screens had a DCIS detection rate of 1.0 case per 1,000 screens⁴ (Table 6).

Table 5 - Characteristics of screen-detected cancers by age group, 2003 and 2004 screen years

	Age group
	40-49		50-59		60-69		70+		All ages
	n	%	n	%	n	%	n	%	n	%
Number of cancersa
Invasive	312	70.8	2,758	77.7	2,673	80.8	1,108	85.3	6,851	79.7
DCIS	129	29.3	790	22.3	637	19.2	191	14.7	1,747	20.3
TNM staging
0 (in situ)	129	29.9	790	33.5	637	28.7	191	16.4	1,747	28.3
I	172	39.9	970	41.2	1,034	46.6	713	61.4	2,889	46.8
II	119	27.6	544	23.1	502	22.6	218	18.8	1,383	22.4
III / IV	11	2.6	52	2.2	45	2.0	40	3.4	148	2.4
Invasive (TNM stage missing)b	11		1,215		1,105		134		2,465
Tumour sizec
> 0 to < 2 mm	9	3.0	69	2.7	61	2.5	24	2.4	163	2.6
2 to 5 mm	21	7.0	215	8.6	191	7.8	74	7.5	501	8.0
6 to 10 mm	60	19.9	619	24.7	647	26.5	303	30.8	1,629	26.1
11 to 15 mm	87	28.9	684	27.3	724	29.6	260	26.4	1,755	28.1
16 to 20 mm	45	15.0	388	15.5	398	16.3	157	16.0	988	15.8
≥ 21 mm	79	26.2	535	21.3	422	17.3	166	16.9	1,202	19.3
Size unknownd	11		248		230		124		613
Median tumour size (mm)	14.0		14.0		13.0		12.0		13.0
Positive nodesc
0	194	70.5	1,819	74.6	1,751	75.3	750	83.6	4,514	76.1
1 to 3	61	22.2	441	18.1	451	19.4	110	12.3	1,063	17.9
4+	20	7.3	177	7.3	122	5.2	37	4.1	356	6.0
Number unknownefg	37		321		349		211		918

^a Unclassified cancers are not included in this analysis.
^b Quebec and Prince Edward Island do not provide TNM staging and account for 80.1% and 2.6% of all cases in this category respectively.
^c Saskatchewan and Prince Edward Island do not provide tumour size and account for 51.3% and 10.3% of all cases in this category respectively.
^d This analysis includes invasive cancers only.
^e Includes missing values (5.9%) and cases in which dissection was not done (1.6%) .
^f New Brunswick has 27.5% pathologically positive nodes but nodal distribution is not provided. New Brunswick accounts for 28.1% of all cases in this category.
^g Prince Edward Island does not provide number of positive nodes and accounts for 6.9% of all cases in this category.

Note: Northwest Territories data are for 2004 only.

Invasive Tumour Size and Node Negative Rate

Cancer detected at earlier stages has more treatment options, less recurrence, and improved survival. Research in Canada has shown that 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 (11). Early stage cancer has smaller tumours and no lymph node involvement. Based on size of tumour, 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.

Analysis of cancer stage (Table 5) includes all 10 provinces and data from 2004 screening exams in the Northwest Territories. Among women aged ≥40 years, diagnosed with breast cancer in 2003 and 2004, 46.8% of tumours were classified as stage I and fewer than three percent were classified as stage III/IV (Table 5). The proportion of women with DCIS (stage 0) detected decreased with age while the proportion with stage I invasive cancer increased with age. Stage II - IV invasive cancer stayed relatively stable across age groups.

Accordingly, the proportion of invasive tumours less than 10 mm was 36.4% and almost three quarters of women had negative lymph nodes at diagnosis (Table 6). A larger proportion of older women had smaller tumours at diagnosis and negative lymph nodes at diagnosis compared to younger women (Table 7).

Figure 9 – Cancer detection (Invasive and In situ) rate per 1,000 screens by age group, 2003 and 2004 screen years

Notes: The shaded area indicates the rate of invasive cancers detected, while the non-shaded area indicates the rate of DCIS cancers detected.
Northwest Territories data are not included in this analysis.

The median time for women to return for screening is as follows:
Rescreen (>9 months, ≤18 months) by 12.5 months;
Rescreen (>18 months, ≤30 months) by 24.4 months;
Rescreen (>30 months) by 35.7 months.

Post-screen Cancers

Post-screen cancers are those cancers that develop after a normal screening mammogram but before the next screen and serve as an indicator of the sensitivity of the screening program. Post-screen cancers can include cancers that occur after the recommended 12 or 24 months in women who do not return for their regular annual or biennial screen respectively (non-compliant cancers) or women who become symptomatic before their next regular screen (interval cancers). These cancers do not include cases referred for diagnostic follow-up with a benign result. Post-screen cancers were calculated based on all women screened from 2000 to 2001 who developed an interval cancer during 2000 to 2003. Non-compliant cancers were not included in this calculation. 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 six months to diagnosis. The target is for less than 6 women per 10,000 person years 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 cancer detection rate was 5.4 per 10,000 person years within 12 months and 7.9 per 10,000 person years within 24 months (Table 6).

Table 6 - Performance measures by program, women aged 50-69, 2003 and 2004 screen years

Indicator	Targeta	Program
		BC	AB	SK	MBb	ONb
Number of screens	N/Ae	242,835	32,319	55,722	62,648	393,415
Number of first screens	N/Ae	18,648	7,323	8,725	13,484	122,309
Number of cancersf	N/Ae	1,094	168	280	328	1,914
Participation rate (%)	≥70	48.8	10.4	52.1	51.1	26.8
Retention rate (% initial rescreen within 30 months)gh	≥75	55.9	51.9	68.0	63.3	74.3
Retention rate (% subsequent rescreen within 30 months)gh	≥90	76.4	69.5	77.2	75.6	80.6
Abnormal call rate (%)
Abnormal by mammographyi
Initial screen	<10	15.4	6.3	16.5	9.4	10.2
Rescreen	<5	5.8	3.3	6.5	4.8	6.0
Abnormal by any mode of detection
Initial screen	<10	15.4	6.3	16.5	10.5	11.9
Rescreen	<5	5.8	3.3	6.5	5.6	7.6
Invasive cancer detection rate (per 1,000 screens)
Detected by mammographyi
Initial screen	>5	5.4	4.2	2.3	5.3	4.5
Rescreen	>3	3.2	4.6	4.2	3.7	3.5
Detected by any mode of detection
Initial screen	>5	5.4	4.2	2.3	5.5	4.7
Rescreen	>3	3.2	4.6	4.2	3.8	3.7
In situ cancer detection rate (per 1,000 screens)
Initial screen	N/Ae	1.8	0.4	2.2	0.7	1.1
Rescreen	N/Ae	1.1	0.8	0.9	1.1	0.7
Diagnostic interval (%)j
Completed with no tissue biopsy, within 5 weeks	≥90	71.1	60.8	62.4	76.8	81.0
Completed with tissue biopsy, within 7 weeks	≥90	43.6	59.1	24.9	39.6	52.2
Positive predictive value (%)f
Detected by mammographyi
Initial screen	≥5	5.0	7.3	2.8	6.4	5.5
Rescreen	≥6	7.5	16.1	7.9	10.0	7.1
Detected by any mode of detection
Initial screen	≥5	5.0	7.3	2.8	5.9	4.8
Rescreen	≥6	7.5	16.1	7.9	8.8	5.9
Benign open surgical biopsy (per 1,000 screens)k
Initial screen	N/Ae	9.0	1.8	13.2	4.7	3.8
Rescreen	N/Ae	3.7	0.6	4.8	1.7	2.3
Benign to malignant open surgical biopsy ratiokl
Initial screen	≤1:1	2.3 : 1	13.0 : 1	3.5 : 1	4.5 : 1	2.6 : 1
Total open biopsies (benign + malignant)		n = 240	n = 14	n = 148	n = 77	n = 641
Rescreen	≤1:1	1.6 : 1	0.9 : 1	1.5 : 1	1.8 : 1	1.7 : 1
Total open biopsies (benign + malignant)		n = 1,360	n = 29	n = 372	n = 127	n = 989
Benign core biopsy rate (per 1,000 screens)
Initial screen	N/Ae	7.8	9.6	4.6	10.6	7.7
Rescreen	N/Ae	2.0	3.0	0.8	4.0	4.1
Benign to malignant core biopsy ratio
Initial screen	N/Ae	2.5 : 1	2.1 : 1	2.7 : 1	2.1 : 1	1.9 : 1
Rescreen	N/Ae	1.0 : 1	0.6 : 1	0.4 : 1	1.0 : 1	1.4 : 1
Invasive cancer tumour size (%)no
≤10 mm	>25	37.3	28.5	N/Ao	28.4	35.0
≤15 mm	>50	64.9	59.7	N/Ao	63.2	61.4
Node negative rate in cases of invasive cancer (%)npq	>70	75.6	73.3	80.2	75.7	75.1
Post-screen detected invasive cancer rate (per 10,000 person-years)grs
Within 12 months	<6	6.2	6.6	N/Ar	3.3	4.8
Within 24 months	<12	8.6	8.9	N/Ar	6.9	7.1

Table 6 - Performance measures by program, women aged 50-69, 2003 and 2004 screen years (con't)

Indicator	Targeta	Program
		QC	NB	NSc	PEd	NLb	Canada
Number of screens	N/Ae	428,637	50,169	52,966	7,266	19,405	1,345,382
Number of first screens	N/Ae	127,756	6,165	11,950	622	4,324	321,306
Number of cancersf	N/Ae	2,510	231	233	37	105	6,900
Participation rate (%)	≥70	47.9	52.9	41.4	40.4	25.5	36.5
Retention rate (% initial rescreen within 30 months)gh	≥75	62.7	56.5	62.4	71.2	71.9	64.9
Retention rate (% subsequent rescreen within 30 months)gh	≥90	74.3	73.2	77.6	83.7	82.3	76.8
Abnormal call rate (%)
Abnormal by mammographyi
Initial screen	<10	14.2	13.3	7.5	16.7	11.6	12.1
Rescreen	<5	8.1	7.2	4.2	11.0	6.2	6.5
Abnormal by any mode of detection
Initial screen	<10	14.2	13.3	7.7	16.7	16.8	12.9
Rescreen	<5	8.1	7.2	4.3	11.0	10.6	7.0
Invasive cancer detection rate (per 1,000 screens)
Detected by mammographyi
Initial screen	>5	5.0	4.7	4.7	9.6	4.9	4.7
Rescreen	>3	4.3	3.5	3.0	4.4	3.6	3.7
Detected by any mode of detection
Initial screen	>5	5.0	4.7	4.7	9.6	5.1	4.8
Rescreen	>3	4.3	3.5	3.0	4.4	3.6	3.8
In situ cancer detection rate (per 1,000 screens)
Initial screen	N/Ae	1.4	0.6	1.3	1.6	1.9	1.3
Rescreen	N/Ae	1.2	1.0	1.0	0.2	1.3	1.0
Diagnostic interval (%)j
Completed with no tissue biopsy, within 5 weeks	≥90	71.5	78.0	78.4	56.2	58.2	74.3
Completed with tissue biopsy, within 7 weeks	≥90	45.7	39.9	63.4	46.3	24.8	46.3
Positive predictive value (%)f
Detected by mammographyi
Initial screen	≥5	4.7	4.0	7.9	7.1	5.6	5.0
Rescreen	≥6	6.9	6.3	9.3	4.4	8.0	7.3
Detected by any mode of detection
Initial screen	≥5	4.7	4.0	7.7	7.1	4.1	4.8
Rescreen	≥6	6.9	6.3	9.2	4.4	4.7	6.9
Benign open surgical biopsy (per 1,000 screens)k
Initial screen	N/Ae	4.2	7.3	1.8	0.0	9.3	4.5
Rescreen	N/Ae	2.0	3.1	0.7	0.0	6.2	2.6
Benign to malignant open surgical biopsy ratiokl
Initial screen	≤1:1	N/Al	2.0 : 1	1.4 : 1	N/Am	2.0 : 1	2.6 : 1
Total open biopsies (benign + malignant)		N/Al	n = 67	n = 36	n = 0	n = 60	n = 1,283
Rescreen	≤1:1	N/Al	1.1 : 1	2.0 : 1	N/Am	2.2 : 1	1.6 : 1
Total open biopsies (benign + malignant)		N/Al	n = 253	n = 45	n = 0	n = 136	n = 3,311
Benign core biopsy rate (per 1,000 screens)
Initial screen	N/Ae	16.6	7.1	16.1	14.5	4.9	11.6
Rescreen	N/Ae	8.0	3.2	7.6	8.7	3.1	4.7
Benign to malignant core biopsy ratio
Initial screen	N/Ae	3.5 : 1	4.9 : 1	3.5 : 1	1.5 : 1	2.3 : 1	2.8 : 1
Rescreen	N/Ae	1.8 : 1	1.8 : 1	2.1 : 1	4.8 : 1	1.6 : 1	1.5 : 1
Invasive cancer tumour size (%)no
≤10 mm	>25	39.0	28.4	35.0	N/Ao	34.2	36.4
≤15 mm	>50	68.8	56.3	65.5	N/Ao	63.2	64.8
Node negative rate in cases of invasive cancer (%)npq	>70	74.0	69.4	77.1	N/Aq	77.9	74.8
Post-screen detected invasive cancer rate (per 10,000 person-years)grs
Within 12 months	<6	N/Ar	7.4	N/Ar	N/Ar	3.0	5.4
Within 24 months	<12	N/Ar	10.3	N/Ar	N/Ar	5.3	7.9

^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 Screening visit includes modified CBE by technician, with all referrals based on mammography.
^e Surveillance and monitoring purposes only.
^f Includes invasive, in situ, and unclassified cancers.
^g Data for 2000 and 2001 screen years are used.
^h Retention rate for women aged 50-69 excludes women who returned at age 70 years or older.
ⁱ Independent of CBE or its findings.
^j 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.
^k 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.
^l Québec calculates the benign to malignant open biopsy ratio using a different method. Canada total excludes Québec data.
^m Ratio not applicable due to null values.
ⁿ 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.
^o Saskatchewan and Prince Edward Island do not provide tumour size. Canada total excludes Saskatchewan and Prince Edward Island data.
^p New Brunswick does not provide the number of pathologically positive nodes; rate is calculated based on N stage of disease data.
^q Prince Edward Island does not provide number of pathologically positive nodes. Canada total excludes Prince Edward Island data.
^r Data on out of program cancers are not available for analysis in the national database.
^s Calculated based on all women screened from 2000-2001 who developed a post-screen cancer during 2000-2003. 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 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: Northwest Territories data not included due to small numbers (463 first screens among women aged 50-69 in 2004).

Table 7 - Performance measures by age group, 2003 and 2004 screen years

Indicator	Targeta	Age group
		40-49	50-59	60-69	70+	All ages
Number of screens	N/Ab	207,262	810,367	535,015	168,701	1,721,345
Number of first screens	N/Ab	62,239	245,424	75,882	18,351	401,896
Number of cancersc	N/Ab	439	3,572	3,328	1,299	8,638
Participation rate (%)	≥70	6.2	36.1	36.7	8.7	19.9
Retention rate (% initial rescreen within 30 months)de	≥75	63.9	67.7	60.8	53.5	65.1
Retention rate (% subsequent rescreen within 30 months)de	≥90	86.7	81.4	72.7	68.4	79.2
Abnormal call rate (%)
Abnormal by mammographyf
Initial screen	<10	13.4	12.6	10.5	9.0	12.2
Rescreen	<5	6.6	6.7	6.2	5.3	6.4
Abnormal by any mode of detection
Initial screen	<10	13.5	13.4	11.2	9.9	12.9
Rescreen	<5	6.6	7.3	6.7	5.8	6.8
Invasive cancer detection rate (per 1,000 screens)
Detected by mammographyf
Initial screen	>5	2.1	3.9	7.4	10.8	4.6
Rescreen	>3	1.2	3.1	4.5	5.9	3.7
Detected by any mode of detection
Initial screen	>5	2.1	4.0	7.4	11.2	4.7
Rescreen	>3	1.2	3.1	4.6	6.0	3.8
In situ cancer detection rate (per 1,000 screens)
Initial screen	N/Ab	1.0	1.1	1.8	1.5	1.2
Rescreen	N/Ab	0.5	0.9	1.1	1.1	0.9
Diagnostic interval (%)g
Completed with no tissue biopsy, within 5 weeks	≥90	73.0	74.1	74.7	75.1	74.2
Completed with tissue biopsy, within 7 weeks	≥90	41.0	45.4	47.8	49.9	46.1
Positive predictive value (%)c
Detected by mammographyf
Initial screen	≥5	2.3	4.0	8.9	13.8	4.9
Rescreen	≥6	2.6	6.0	9.1	13.4	7.4
Detected by any mode of detection
Initial screen	≥5	2.3	3.9	8.4	13.0	4.7
Rescreen	≥6	2.6	5.6	8.5	12.3	6.9
Benign open surgical biopsy (per 1,000 screens)h
Initial screen	N/Ab	7.3	4.9	3.4	3.3	4.9
Rescreen	N/Ab	2.7	2.6	2.6	2.6	2.6
Benign to malignant open biopsy ratiohi
Initial screen	≤ 1:1	5.6 : 1	3.2 : 1	1.5 : 1	1.3 : 1	3.0 : 1
Rescreen	≤ 1:1	3.5 : 1	1.9 : 1	1.3 : 1	0.9 : 1	1.6 : 1
Benign core biopsy rate (per 1,000 screens)
Initial screen	N/Ab	10.1	12.3	9.3	5.9	11.1
Rescreen	N/Ab	3.0	4.7	4.7	2.6	4.3
Benign to malignant core biopsy ratio
Initial screen	N/Ab	6.2 : 1	3.6 : 1	1.4 : 1	0.7 : 1	2.8 : 1
Rescreen	N/Ab	3.4 : 1	1.7 : 1	1.3 : 1	0.7 : 1	1.4 : 1
Invasive cancer tumour size (%)jk
≥10 mm	>25	30.0	35.9	36.8	40.6	36.7
≥15 mm	>50	59.0	63.2	66.4	67.1	64.9
Node negative rate in cases of invasive cancer (%)jlm	>70	69.9	74.5	75.0	83.8	75.9
Post-screen detected invasive cancer rate (per 10,000 person-years)dno
Within 12 months	<6	4.7	5.9	4.7	5.0	5.2
Within 24 months	<12	6.6	8.1	7.7	8.6	7.9

^a Targets apply to women aged 50-69 years.
^b Surveillance and monitoring purposes only.
^c Includes invasive, in situ, and unclassified cancers.
^d Data for 2000 and 2001 screen years are used.
^e Retention rate for women aged 50-69 excludes women who returned at age 70 years or older.
^f Independent of clinical breast examination or its findings.
^g 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.
^h 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.
ⁱ Quebec calculates the benign to malignant open biopsy ratio using a different method. Canada total excludes Quebec data.
^j 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.
^k Saskatchewan and Prince Edward Island do not provide tumour size. Canada total excludes Saskatchewan and Prince Edward Island data.
^l New Brunswick does not provide the number of pathologically positive nodes; rate is calculated based on N stage of disease data.
^m Prince Edward Island does not provide number of pathologically positive nodes. Canada total excludes Prince Edward Island data.
ⁿ Post-screen detected cancer rates are calculated with 2000 and 2001 data and include the following provinces: British Columbia, Alberta, Manitoba, Ontario, New Brunswick and Newfoundland.
^o Calculated based on all women screened from 2000-2001 who developed a post-screen cancer during 2000-2003. 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 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: Northwest Territories data not included due to small numbers (1103 first screens among women ≥40 years in 2004).

Table 8 - Performance measures by year, women aged 50-69

Indicator	Targeta	Screen year
		2000	2001	2002	2003	2004
Number of screens	N/Ab	503,946	550,463	608,979	646,386	698,996
Number of first screens	N/Ab	229,120	173,251	169,523	159,062	162,244
Number of cancerscd	N/Ab	2,648	2,853	3,268	3,373	3,527
Participation ratee	≥70	30.3	31.9	33.9	35.4	36.5
Retention rate (% initial rescreen within 30 months)f	≥75	64.5	65.5	N/Ag	N/Ag	N/Ag
Retention rate (% subsequent rescreen within 30 months)f	≥90	77.7	75.9	N/Ag	N/Ag	N/Ag
Abnormal call rate (%)
Abnormal by mammographyh
Initial screen	<10	11.4	12.3	11.8	12.0	12.3
Rescreen	<5	5.9	6.6	6.7	6.6	6.4
Abnormal by any mode of detection
Initial screen	<10	12.1	13.4	12.7	12.8	13.0
Rescreen	<5	7.0	7.5	7.3	7.1	6.9
Invasive cancer detection rate (per 1,000 screens)d
Detected by mammographyh
Initial screen	>5	4.8	4.7	5.0	5.0	4.5
Rescreen	>3	3.5	3.7	3.9	3.8	3.7
Detected by any mode of detection
Initial screen	>5	4.9	4.8	5.1	5.0	4.6
Rescreen	>3	3.6	3.7	4.0	3.9	3.7
In situ cancer detection rate (per 1,000 screens)
Initial screen	N/Ab	1.2	1.3	1.1	1.2	1.3
Rescreen	N/Ab	1.0	0.9	1.0	1.0	1.0
Diagnostic interval (%)i
Completed with no tissue biopsy, within 5 weeks	≥90	70.3	69.7	73.0	74.7	74.0
Completed with tissue biopsy, within 7 weeks	≥90	47.0	45.8	47.1	46.1	46.5
Positive predictive value (%)cd
Detected by mammographyh
Initial screen	≥5	5.3	5.0	5.2	5.2	4.8
Rescreen	≥6	7.5	7.1	7.5	7.3	7.4
Detected by any mode of detection
Initial screen	≥5	5.1	4.6	4.9	5.0	4.6
Rescreen	≥6	6.5	6.3	6.9	6.8	6.9
Benign open surgical biopsy rate (per 1,000 screens)dj
Initial screen	N/Ab	4.9	4.7	4.6	4.6	4.5
Rescreen	N/Ab	3.7	3.1	2.8	2.7	2.5
Benign to malignant open biopsy ratiodjk
Initial screen	≤1:1	2.2 : 1	2.3 : 1	2.3 : 1	2.6 : 1	2.7 : 1
Rescreen	≤1:1	1.5 : 1	1.5 : 1	1.4 : 1	1.6 : 1	1.6 : 1
Benign core biopsy rate (per 1,000 screens)d
Initial screen	N/Ab	10.3	11.3	10.4	11.3	11.9
Rescreen	N/Ab	2.5	3.8	4.0	4.6	4.8
Benign to malignant core biopsy ratiod
Initial screen	N/Ab	3.3 : 1	3.2 : 1	2.8 : 1	2.8 : 1	2.8 : 1
Rescreen	N/Ab	1.4 : 1	1.6 : 1	1.4 : 1	1.5 : 1	1.5 : 1
Invasive cancer tumour size (%)dlm
≥10 mm	>25	38.8	35.9	37.4	37.7	35.0
≥15 mm	>50	67.5	63.2	66.0	65.5	64.0
Node negative rate in cases of invasive cancer (%)dlno	>70	75.1	75.1	75.7	75.7	73.8
Post-screen detected invasive cancer rate (per 10,000 person-years)dpq
Within 12 months	<6	5.7	5.1	N/Ag	N/Ag	N/Ag
Within 24 months	<12	7.9	8.0	N/Ag	N/Ag	N/Ag

^a Targets apply to women aged 50-69 years
^b Surveillance and monitoring purposes only.
^c Includes invasive, in situ, and unclassified cancers.
^d Screen detected invasive cancers have been updated for women screened in 2000 and 2001, to reflect the total exclusive of post-screen detected cancers.
^e Participation rate was calculated in 2 year intervals due to biennial recall (Screen Years: 1999-2000, 2000-2001, 2001-2002, 2002-2003, 2003-2004).
^f Retention rate for women aged 50-69 excludes women who returned at age 70 years or older.
^g Insufficient time for follow-up to ensure data completeness.
^h Independent of clinical breast examination or its findings.
ⁱ 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.
^j 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.
^k Québec calculates the benign to malignant open biopsy ratio using a different method. Canada total excludes Québec data.
^l Missing values are excluded from calculations. Expressed as a proportion of invasive cancers with complete data on tumour size or number of positive nodes.
^m Saskatchewan and Prince Edward Island do not provide tumour size. Canada total excludes Saskatchewan and Prince Edward Island data.
ⁿ New Brunswick does not provide the number of pathologically positive nodes; rate is calculated based on N stage of disease data.
^o Prince Edward Island does not provide number of pathologically positive nodes. Canada total excludes Prince Edward Island data.
^p Post-screen detected cancer rates are calculated with 2000 and 2001 data and include the following provinces: British Columbia, Alberta, Manitoba, Ontario, New Brunswick and Newfoundland.
^q Calculated based on all women screened from 2000-2001 who developed a post-screen cancer during 2000-2003. 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 (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.

Notes: Data include all screens; figures have been updated and may vary slightly from previous reports.
Northwest Territories data not included due to small numbers (463 first screens among women aged 50-69 in 2004)

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3. Quebec calculates the benign to malignant open biopsy ratio using a different method. Canada total excludes Quebec data.
4. Refers to all women, including those who may have returned late (≥ 30 months) from their previous mammogram.