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

Background

Introduction

An estimated 22,400 women will be diagnosed with breast cancer and 5,300 women will die from the disease in 2008 (1). This makes breast cancer the most common form of cancer¹ and the second leading cancer cause of death in Canadian women (1). Although breast cancer incidence has risen over the past decades, it has levelled off and is showing statistically non-significant declines since 1999. In addition, deaths attributed to breast cancer continue to decline and are approximately 25% lower than the peak in the mid-1980’s (2) (Figure 1a and 1b).

Figure 1a – Age-standardized incidence rates (ASIR) per 100,000 women for breast cancer in Canada, 1982-2008

Source: National Cancer Institute of Canada. Canadian Cancer Statistics 2008. Toronto, Canada, 2008.

Notes: Incidence rates are estimated for 2006-2008 and in 2005 for Québec, Manitoba and Alberta. Projected estimates for breast cancer beyond 2004 reflect the long-term increasing trend in breast cancer incidence and are not sensitive to recent decline.
The national rate is an estimate computed from observed case counts for all provinces and territories.
Rates are standardized to the age distribution of the 1991 population.

Figure 1b — Age-standardized mortality rates (ASMR) per 100,000 women for breast cancer in Canada, 1982-2008

Source: National Cancer Institute of Canada. Canadian Cancer Statistics 2008. Toronto, Canada, 2008.

Notes: Mortality rates are estimated for 2005-2008.
The national rate is an estimate computed from the death counts estimated for each province and territory.
Rates are standardized to the age distribution of the 1991 population.

Early detection of breast cancer, through organized mammography screening programs, is an effective method to reduce death and morbidity associated with breast cancer. This is partially because primary prevention of breast cancer has been limited: most known risk factors are not easily modifiable, however, changes in some of the more modifiable risk factors at the population level such as physical activity holds future promise. Of known risk factors, age has the strongest influence on breast cancer incidence; roughly, half of all new cases are among women between 50 and 69 years of age. Modelling exercises have shown that the delivery of high quality breast screening programs to this age group has the potential to reduce breast cancer deaths by as much as one third (4). Among other considerations, this scientific information influences Canadian provinces and territories to provide breast cancer screening services to this age group. Many provinces and territories also provide screening services to other age groups but in a less targeted fashion.

Breast Cancer Screening in Canada

In December 1992, the federal government launched the first phase of the Canadian Breast Cancer Initiative (CBCI) with $25 million over five years including the Canadian Breast Cancer Screening Initiative among its priorities. In June 1998, ongoing funding for the CBCI was put in place at $7 million per year. The Public Health Agency of Canada was created in September 2004 and at that time was given responsibility for overseeing the CBCI.

Organized Breast Cancer Screening Programs

Canada’s first organized breast cancer screening program began in British Columbia in 1988 and was followed quickly by most provinces (Table 1). Organized breast cancer screening programs now exist in all provinces, and the Northwest and Yukon Territories. Nunavut has not developed an organized mammography screening program.

All organized programs provide women between 50 and 69, without a prior diagnosis of breast cancer, with a bilateral, 2-view screening mammogram biennially. Some programs also include women outside of this age group and some provide screening at more frequent intervals (Table 1). In 2003 and 2004, several programs provided clinical breast examination by a nurse or technologist but most programs had phased out this service based on scientific evidence (5). Lastly, some programs include breast cancer survivors; however, survivors within five years of their diagnosis are excluded from this report.

The Screening Process

Organized breast cancer screening programs offer screening to women who are asymptomatic for breast cancer. Organized programs in Canada typically involved three steps:

• Identification and invitation of the target population
• Provision of a screening examination
• Follow-up of any abnormalities detected at screening

A number of methods are used to invite women to a screening examination and include media campaigns targeting women, population-based invitations, physician education to increase referrals, and personal invitations. Women may enter into organized programs through their personal letter of invitation, physician referral or self referral.

Table 1 – Breast cancer screening programs in Canada^a – usual practices, 2003 and 2004 screen years

Province/territory	Program start date	Clinical breast examination on site	Program practices for women outside the 50-69 year age group
			Age group	Accept	Recall
Northwest Territories	2003	No	40-49	Yes	Annual
			70+	Yes	Biennial
Yukon Territory	1990	No	40-49	Yes	None
			70+	Yes	None
British Columbia	1988	No	<40	Yesb	None
			40-49	Yes	Annual
			70-79	Yes	Biennial
			80+	Yesb	None
Alberta	1990	No	40-49	Yes	Annual
			70-74	Yes	Biennial
			75+	Yes	None
Saskatchewan	1990	No	40-49	No	N/A
			70-74	Yes	Biennial
			75+	Yes	None
Manitoba	1995	Yesf	40-49	Yesc	Biennial
			70+	Yesc	None
Ontario	1990	Yesg	40-49	No	N/A
			70-74	Yes	Biennial
			75+	Yes	None
Québec	1998	No	35-49	Yesd	Biennial
			70+	Yesd	None
New Brunswick	1995	No	40-49	Yesb	None
			70+	Yesb	None
Nova Scotia	1991	Yesh	40-49	Yes	Annual
			70+	Yes	None
Prince Edward Island	1998	Yesh	40-49	Yes	Annual
			70-74	Yes	Biennial
Newfoundland and Labrador	1996	Yesi	40-49	No	N/A
			70+	Yese	None

^a Nunavut has not developed an organized breast cancer screening program.

^b Accept with physician referral.

^c Accept to mobile unit with a physician referral.

^d Accept with physician referral if done at a program screening centre, but is not officially considered within the program.

^e Accept if previously enrolled in program

^f Nurse or Technologist.

^g Nurse provides clinical breast examination at 69% of sites.

^h Modified examination only, performed by technologist at time of mammography.

ⁱ Nurse.

Screening mammograms are provided at both fixed and mobile sites. Fixed sites are located in larger urban areas while mobile sites are used to provide service to rural and distant communities.

Results of a screening mammogram are provided to both the woman and her physician. In general, women who have normal screening results are invited back for subsequent screening through a letter of invitation. The interval is generally 24 months; however, some women are invited back after 12 months based on their age, breast density, family history, and results of their screening. After receipt of normal results, women are encouraged to follow-up with their family physicians if they become symptomatic prior to their next scheduled screening visit.

In the case of abnormal results, both the woman and her family physician are informed. The family physician or the screening program then provides coordination of follow-up. This process varies by region. The follow-up process is resolved when a final diagnosis of cancer or normal / benign is concluded (Figure 2).

Figure 2 – Pathway of a breast cancer screening program

^a Breast screening programs obtain final diagnoses from sources such as physicians, pathology reports, and cancer registries.

Canadian Breast Cancer Screening Database

Monitoring and evaluation of organized breast cancer screening programs through the systematic collection, analysis, and interpretation of health data, allows for the enhancement of programming across Canada. The Canadian Breast Cancer Screening Database (CBCSD) provides a method to examine and assess Canadian organized breast cancer screening programs. The CBCSD was established in 1993 and is operated and maintained by the Public Health Agency of Canada on behalf of the Canadian Breast Cancer Screening Initiative. Participating provincial and territorial screening programs contribute to the national database while retaining ownership over their data.

The CBCSD contains screening information from the inception of each organized screening program up to December 2004. At the present time Yukon does not keep electronic records and Nunavut does not have an organized program so they are excluded from the database. At every screening event, data including demographic characteristics, risk factors, the screen event, screening results and subsequent referral, diagnostic tests, outcomes, and cancer information is collected.

Table 2 – Annual screening volume by program, all ages, 1988 to 2004 screen years

Year	Program
	NT	BC	AB	SK	MB	ON
1988	---	4,395	---	---	---	---
1989	---	9,188	---	---	---	---
1990	---	22,482	616	6,355	---	590
1991	---	54,564	5,873	14,305	---	15,380
1992	---	80,893	15,442	15,778	---	40,295
1993	---	100,276	16,146	26,057	---	45,541
1994	---	118,878	15,372	25,540	---	55,480
1995	---	143,412	14,170	29,603	2,671	58,287
1996	---	166,738	14,679	28,901	13,594	67,729
1997	---	173,908	23,336	33,915	19,163	80,132
1998	---	189,963	18,887	34,094	23,457	98,597
1999	---	217,551	22,408	35,050	28,204	114,059
2000	---	223,610	21,714	35,265	28,566	138,308
2001	---	224,566	23,745	36,133	28,728	163,862
2002	---	234,873	23,338	34,344	29,263	192,237
2003	---	220,933	21,806	35,477	31,637	211,926
2004	1,103	230,830	23,098	35,950	32,301	248,551
Total	1,103	2,417,060	260,630	426,767	237,584	1,530,974

Table 2 – Annual screening volume by program, all ages, 1988 to 2004 screen years (con’t)

Year	Program
	QCa	NB	NS	PE	NL	Canada
1988	---	---	---	---	---	4,395
1989	---	---	---	---	---	9,188
1990	---	---	---	---	---	30,043
1991	---	---	1,877	---	---	91,999
1992	---	---	4,354	---	---	156,762
1993	---	---	4,891	---	---	192,911
1994	---	---	8,461	---	---	223,731
1995	---	5,853	12,491	---	---	266,487
1996	---	18,441	15,547	---	3,120	328,749
1997	---	18,247	19,477	---	4,694	372,872
1998	43,987	26,044	25,459	---	5,521	466,009
1999	145,107	30,623	29,285	5,578	6,087	633,952
2000	152,989	32,620	35,260	6,268	6,790	681,390
2001	172,062	33,681	35,260	6,700	8,054	732,791
2002	194,368	37,196	38,612	6,267	8,859	799,357
2003	207,816	37,433	44,998	6,094	11,038	829,158
2004	220,821	37,344	48,655	6,060	9,819	894,532
Total	1,137,150	277,482	324,627	36,967	63,982	6,714,326

^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.

Notes: Yukon Territory and Nunavut programs are still in development.
Data include all screens; figures have been updated and may vary slightly from previous reports.

The database is currently used for monitoring, evaluation, and applied screening research. Research priorities are identified on an ongoing basis and the CBCSD is made available to researchers external to the Canadian Breast Cancer Screening Initiative.

Monitoring and Evaluation Using the CBCSD

Monitoring and evaluation of organized screening programs is essential to ensure Canadian women are receiving high quality services that result in the reduction of morbidity and mortality from breast cancer while minimizing the unwanted effects of screening. The results of monitoring and evaluation stemming from the CBCSD are used to enhance the performance of organized screening programs in Canada.

In order to provide fair evaluation for Canadian organized breast screening programs, standardized methods of evaluation have been developed. For detailed information please refer to the most recent Evaluation Indicators Working Group Report². In general, agreed upon performance indicators for women aged 50 to 69 include those related to recruitment and retention (participation rate, retention rate), timeliness (diagnostic interval), mammography interpretation (abnormal call rate, positive predictive value), diagnosis (invasive and in situ cancer detection rate, benign:malignant open surgical biopsy ratio, benign:malignant core biopsy ratio, benign open surgical biopsy rate, benign core biopsy rate), and cancers (tumour size, node negative rate in invasive cancers, post-screen invasive cancer rate) (Table 3).

Table 3 – Performance measures for organized breast cancer screening programs in Canada, women aged 50-69

Indicator	Definition	Target
1. Participation rate	Percentage of women who have a screening mammogram (calculated biennially) as a proportion of the eligible population.	≥70% of the eligible population.
2. Retention rate	The estimated percentage of women who are re-screened within 30 months of their previous screen.	≥75% initial re-screen within 30 months; ≥90% subsequent re-screens within 30 months.
3. Abnormal call	rate Percentage of women screened who are referred for further testing because of abnormalities found with a program screen.	<10% (initial screen); <5% (subsequent screens).
4. Invasive cancer detection rate	Number of invasive cancers detected per 1,000 screens.	>5 per 1,000 (initial screen) >3 per 1,000 (subsequent screens).
5. In situ cancer detection rate	Number of ductal carcinoma in situ cancers (rather than invasive cancer) during a screening episode per 1,000 screens.	Surveillance and monitoring purposes only.
6. Diagnostic interval	Total duration from abnormal screen to resolution of abnormal screen.	≥90% within 5 weeks if no tissue biopsya performed; ≥90% within 7 weeks if tissue biopsya performed.
7. Positive predictive value	Proportion of abnormal cases with completed follow-up found to have breast cancer (invasive or in situ) after diagnostic work-up.	≥5% (initial screen); ≥6% (subsequent screens).
8. Benign open surgical biopsyb rate	The number of benign open surgical biopsies per 1,000 screens.	Surveillance and monitoring purposes only.
9. Benign to malignant open surgical biopsyb ratio	Among open surgical biopsies, the ratio of the number of benign cases to the number of malignant cancer cases.	≤1:1 (initial screen); ≤1:1 (subsequent screens).
10. Benign core biopsy rate	The number of benign core biopsies per 1,000 screens.	Surveillance and monitoring purposes only.
11. Benign to malignant core biopsy ratio	Among core biopsies, the ratio of number of benign cases to the number of malignant cancer cases.	Surveillance and monitoring purposes only.
12. Invasive cancer tumour size	Percentage of invasive cancers with tumour size of .10mm and .15mm in greatest diameter as determined by the best available evidence: 1) pathological, 2) radiological, and 3) clinical.	>25% ≤10mm; >50% ≤15mm.
13. Node negative rate in cases of invasive cancer	Proportion of invasive cancers in which the cancer has not invaded the lymph nodes.	>70% (initial and subsequent screens).
14. Post-screen invasive cancer ratec	Number of women with a diagnosis of invasive breast cancer after a normal screening within 12 AND 24 months of the screen date.	<6 per 10,000 person-years (within 12 months); <12 per 10,000 person-years (within 24 months).

Source: Public Health Agency of Canada. Report from the Evaluation Indicators Working Group: Guidelines for Monitoring Breast Cancer Screening Program Performance: Second edition. Ottawa: Minister of Health, 2007.

Note: Table adapted from the Program Performance Measures.

^a Tissue biopsy does not include fine needle aspiration (FNA).

^b Open surgical biopsy includes cases that went directly to an open surgical biopsy as their primary diagnostic assessment and those who underwent an inconclusive or incorrect core biopsy prior to a definitive diagnosis by open surgical biopsy.

^c 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).

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1. Incidence of non-melanoma skin cancer exceeds that of breast cancer in Canada, however, rates are typically not reported due to difficulty estimating true incidence.
2. The Evaluation Indicators Working Group Report: Guidelines for Monitoring Breast Screening Program Performance: 2nd Edition.