Recruitment and Retention

Organized breast cancer screening programs promote participation through a variety of recruitment methods. All Canadian organized breast cancer screening programs use letters of invitation to reach at least part of their target population. However, not all programs have access to population-based lists, which may contribute to lower participation rates. Other means of recruitment include physician referrals for screening, media campaigns and referrals from women themselves.

Consistent with the national recommendation, all programs currently actively encourage 50 to 69 year old women to attend a biennial screening examination. Some programs also screen women aged 40 to 49 and aged 70 and over. In 1997 and 1998, the percentage of total screens that were delivered to women aged 50 to 69 ranged by province from 52.3% to 99.1% (Figure 6). Programs still in their expansion phase, such as the newly initiated organized breast cancer screening program in Quebec, predominantly recruit women for their first-ever program screen. By contrast, for mature programs, women returning for subsequent screens can comprise more than 80% of the screened population (Figure 7).

Figure 6 Age distribution of program screens by province, 1997 and 1998

Note: Data for the New Brunswick program are incomplete and therefore do not comprehensively reflect program activity.

Figure 7 Distribution of first and subsequent program screens by province, women aged 40 and older, 1997 and 1998

Notes: Number in brackets indicates program start date; programs with earlier start dates can be expected to have more rescreens. Data for the New Brunswick program are incomplete and therefore do not comprehensively reflect program activity.

Retention rates are indicators of the acceptability of screening to women. When it is time to return for another routine screening, eligible women are sent a reminder letter asking them to contact the program to set up an appointment. To determine the proportion of women returning to the screening program, those screened in 1994 and 1995 who were eligible for a subsequent screen were followed up until the end of 1998 and the probability of their returning for a subsequent screen were followed up until the end of 1998 (Figure 8). Among women aged 50 to 69, approximately 80% returned for their next screen by 2.5 years. This compares favourably with the target of a 75% retention rate in the Australian program (Appendix 1). Although they were more likely to return just beyond one year, overall, women aged 40 to 49 were less likely to return to screening programs, which may reflect less intensive targeting through promotional material, mixed policies regarding screening and weaker scientific evidence of the benefits of screening for women in this age group. Some women who were screened in their forties may decide to wait until they reach 50 before obtaining further screening.

Figure 8 Cumulative probability of returning for a subsequent program screen by age group, women screened in 1994 and 1995

Notes: In 1994 and 1995 annual screening frequencies were recommended by B.C. for women aged 40-49. Evaluated with data from B.C., Alta., Sask., Man., Ont., N.B., and N.S. Data for the New Brunswick program are incomplete and therefore do not comprehensively reflect program activity.

A further consideration regarding returning for a subsequent screen is the tendency to stretch out the intervals between screening, a phenomenon labelled 'slippage'¹⁶. Many women returning to organized programs in Canada did so 3 to 6 months later than the recommended biennial interval, possibly reflecting the time it takes to act on their reminder letters, or to schedule an appointment given a waiting list. Suggestions to improve compliance with the screening schedule have been outlined by the Quality Determinants Working Group of the CBCSI's National Committee¹⁷.

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