Survival in interval breast cancer in the DOM screening programme

The study describes breast cancer survival of 75 interval cancer cases (cancer occurring within 2 years of a negative screen) detected in women who participated in the DOM screening programme. After mammographic revision, this group was divided into 17 so-called 'missed' cases and 58 'true' interval cases. Ten year survival of these 58 'true' interval cases was 58%, which was not significantly different from that of 219 cancers detected in a non-screened, control group of women, diagnosed with breast cancer before the start of screening (63%; log rank chi 2 test, P = 0.98). Results remained essentially the same after correction for age at diagnosis, tumour size, axillary status and year of diagnosis. Ten year survival of 'true' interval cancers (58%) was slightly worse than that of 'missed' cases (67%; log rank chi 2 test: P = 0.38). This difference could largely be explained by differences in tumour size and axillary status. We conclude that there was no important difference in survival between 'true' interval cancers and non-screened historical controls. This could mean that either this subgroup of interval cancers does not constitute an excess of rapidly growing tumours, or if it does, that a fast growth rate is not associated with an exceptionally poor prognosis.