Abstract
BACKGROUND: Cancers not detected by breast screening are commonly assumed to have poorer prognosis. METHODS: We examined the survival experience of all women aged 50-74 years diagnosed with a first breast cancer between 1998 and 2006 in British Columbia, Canada and determined their screening experience. Disease-specific survival rates were calculated and, for cases diagnosed in 2002, prognostic factors (size, nodal involvement, grade ER status and stage) were examined by time since screening. RESULTS: Breast cancers diagnosed at screening had the best survival (P<0.001). Cancers detected within 12 months of a negative screen had similar survival rates (P=0.98) to those diagnosed within 12-23 and 24-47 months, with other non-screen-detected cancers having poorer survival (P<0.001). The prognostic profile of cancers diagnosed in 2002 followed a similar pattern. INTERPRETATION: There was no evidence that cancers diagnosed within 12 months had poorer prognosis than those diagnosed up to 48 months following screening.