Risk of breast cancer in women who attend the NHS breast screening programme: cohort study.

Not all women invited to participate in the NHS breast screening programme will do so; those who do not may differ in their risk of breast cancer from those who do. This “self selection” for screening can result in women at either high or low risk being overrepresented in those screened. A screening programme in which those who attend have a high risk of breast cancer is likely to detect more cancers and be of more benefit to the women screened than a programme with a similar participation rate but no self selection of women at high risk. In the Health Insurance Plan of Greater New York (HIP) and Stockholm trials, the incidence of breast cancer in non-attenders was lower than in the control group but no difference was observed in the Edinburgh trial. 2 We report, for the first time, the incidence of breast cancer in women who declined to participate in the NHS breast screening programme.