Organized Breast Cancer Screening Programs in Canada

1999 and 2000 Report

Special Topic: Retention of Screened Women

Reductions in breast cancer mortality require a high level of ongoing and timely participation in screening among target-aged women, as evidenced in randomized controlled trials. The benefit of a single screen is time limited, as cancers may develop even after several normal screens have been achieved. Maintaining ongoing participation of women in a program is not only important for screening success at a population level but is also an indicator of the acceptability of screening to women. Performance targets for retention in Canadian programs aim to screen at least 75% of women screened in the previous round. 

Although programs consistently meet or exceed performance targets for overall retention, Figure 12 indicates that in Canadian organized breast cancer screening programs, women are most likely to discontinue screening after their initial screen: 64% retention at 30 months between first and second screen as compared with 85% to 99% at later rounds. This pattern holds across all programs and suggests that efforts to encourage women to return should focus on those first entering the program. Here, the contribution of four factors to a woman's likelihood of returning for a second screen by 30 months was evaluated in women aged 50 to 69 screened in 1996 and 1997. The four factors were family history of breast cancer, false positive mammography at first screen, recommendation for one-year follow-up and age. 

Women with a family history of breast cancer were generally more likely to return for a second screen. Depending on the program, the probability of returning by 30 months was 2% to 48% higher among women with a family history than among women without such a history. Other research has found that family history of breast cancer is a commonly cited factor associated with an increased likelihood of reattendance and long-term compliance with a program^21-24. 

Women who were referred for follow-up after their first screen but who did not have a diagnosis of breast cancer (false positives) were 8% to 56% less likely to return for a second screen by 30 months, depending on the program. This is contrary to the results of most studies, which show that women are either equally or more likely to return or intend to return for screening if they experienced previous false-positive mammography results^23,25-32. However, two studies have noted a decreased likelihood of returning to screening among women with false-positive findings^33,34. It is uncertain whether the decision not to return to the program is a result of a negative experience with screening, continued clinical follow-up, or absorption of clients into the fee-for-service sector. This finding underlines the need for a well- coordinated follow-up to minimize anxiety and unnecessary referral. A recent study from the Ontario Breast Screening Program indicated that screening program facilities with an integrated assessment service improved reattendance by women with false-positive screen results³⁵. 

No consistent pattern of retention by 30 months was seen across programs for women who were given a recommendation to return within one year rather than two years. In Saskatchewan and Alberta, women with a one-year recommendation were less likely to return; in Newfoundland and Ontario they were more likely to return; in Manitoba, there was no difference. Similarly, the impact of age differed by program. Older women (aged 65+) were most likely to return for a second screen by 30 months in Newfoundland, Nova Scotia, New Brunswick, Ontario, Manitoba and Alberta, and younger women (aged 50 to 54) were most likely to return in Saskatchewan. In British Columbia, women aged 55 to 64 were most likely to return. 

Although the factors examined give some indication of where efforts can be directed to improve retention, more in-depth study at the program level is needed. Furthermore, retention differed widely across programs. This emphasizes the need to consider the different environments in which screening programs operate. For example, the three most long- standing screening programs had the lowest retention rates by 30 months between first and second screen (54.0%-60.0%), whereas the two newest programs had the highest retention rates (72.8%-74.1%). This suggests that issues of capacity may be contributing to reduced retention in mature programs. Alternatively, efforts to promote screening may be greater in settings where screening programs have been recently initiated. Some programs also face the ongoing challenge of competition from the fee-for-service sector. 

[Previous] [Table of Contents] [Next]