Breast Cancer Screening Outside of Guidelines

Key message

A considerable proportion of screening mammograms were performed in women outside of the target age range recommended in the CTFPHC guidelines (age 50–74).

Indicator definition

The percentage of self-reported screening mammograms performed on women within and outside of the target age range recommended in the Canadian Task Force on Preventive Health Care (CTFPHC) guidelines (ages 50–74)^†. The indicator includes mammograms performed in the previous two years on asymptomatic women. Results are presented by province/territory using data from the 2012 Canadian Community Health Survey.

Measured since

The 2014 Cancer System Performance Report.

The indicator definition was changed in 2015 to include women younger than 50 or older than 75 (rather than women aged 75 or older only), thus looking at all breast cancer screening outside of the guideline-recommended age range.

Why measure this?

Screening mammography has been shown to reduce breast cancer mortality and morbidity associated with advanced cancer, but the evidence of benefit is strongest for women between the ages of 50 and 74.¹ While there is evidence of the benefit of screening on breast cancer mortality, it is essential to balance this benefit with potential harms, namely false positive results, over-diagnosis, over-treatment and financial costs to both the system and the patient.^2,1,3 Guidelines from the CTFPHC recommend that women aged 50–74 years at average risk for breast cancer be routinely screened using mammography every two to three years.² Adherence to evidence-informed screening guidelines maximizes the benefits of screening while offsetting the harms caused by unnecessary interventions.

What are the key findings?

• The percentage of self-reported screening mammograms performed in the previous two years on women outside the guideline-recommended age range (ages 50–74) varied widely, from 13.5% in Yukon to 37.7% in the Northwest Territories (2012 data) (Figure 7.1).
• More screening mammograms were performed in women aged 35–49 than in women aged 75 or older (from 11.5% in Quebec to 26.3% in Prince Edward Island and from 3.6% in New Brunswick to 8.6% in Saskatchewan, respectively) (Figure 7.1).

Why do these findings matter?

A considerable proportion of screening mammograms were performed on women outside the guideline-recommended age range of 50–74 years in some provinces/territories, though there is large variability across the country. While organized breast cancer screening programs, which exist in all Canadian provinces and territories except Nunavut, invite women of average risk aged 50–69 years to undergo breast cancer screening by mammography every two years, program guidelines vary in their acceptance and screening of women who are in their 40s or over age 75.⁴ Women may also access mammographic screening without going through a provincial program (also known as opportunistic screening), which means that they may not be subject to the same guidelines and eligibility that govern provincial programs and may differ in their characteristics. This practice may contribute to some variability.

The goal is not to eliminate all screening outside of the 50–74 age group, particularly in women aged 40–49, but to ensure that mammography resources are being targeted to those who truly need them–that is, women at high risk of developing breast cancer. Understanding interprovincial/territorial differences in the use of screening mammography outside guideline-recommended age groups may identify ways to streamline screening practices across the country to better align with guidelines and provide opportunities for balancing resource allocation in some provinces, while also reducing unnecessary and potentially harmful interventions that could cause women emotional distress.

While adherence to guidelines is important from a population health and systems planning perspective, it is important that individual women have the appropriate information to enable them to decide whether or not to undergo screening mammography, particularly if they are outside the age range where benefits are clear and are judged to outweigh the potential harms of screening. Women can be given this information through an informed decision-making approach, wherein women and their doctors discuss the harms and benefits of screening, as well as patient preferences.²

Notes

^† This indicator does not distinguish between women at higher-than-average risk and women of average risk. Because of this, for some women captured in these results, screening may be appropriate.

References

1. Lauby-Secretan B, Scoccianti C, Loomis D, Benbrahim-Tallaa L, Bouvard V, Bianchini F, et al. Breast-cancer screening-viewpoint of the IARC Working Group. N Engl J Med. 2015 Jun 11;372(24):2353-8.
2. Canadian Task Force on Preventive Health Care, Tonelli M, Gorber SC, Joffres M, Dickinson J, Singh H, et al. Recommendations on screening for breast cancer in average-risk women aged 40-74 years. CMAJ. 2011 Nov 22;183(17):1991-2001.
3. World Health Organization. WHO Position Paper on Mammography Screening. Geneva (CH): World Health Organization; 2014. 55 p.
4. Cancerview.ca. Breast Cancer Screening Guidelines Across Canada: Environmental Scan. Toronto (ON): Canadian Partnership Against Cancer; 2015 Jul.