Prognosis, treatment, and recurrence of breast cancer for women attending or not attending the Screening Mammography Program of British Columbia

Breast cancer screening programs have been initiated in many countries in t he past decade. To determine the impact of the Screening Mammography Progra m of British Columbia (SMPBC), disease and treatment outcomes for women wit h breast cancer diagnosed in BC between 1989 and 1996 were compared on the basis of attendance at the SMPBC. An SMPBC attender was a women diagnosed w ith breast cancer within three years of an SMPBC screen, regardless whether the cancer was detected as a result of that screen. Of the 13,636 women ag ed 40-89 years diagnosed with breast cancer in BC during the study period, 2,647 (19.4%) were SMPBC attenders. 73.5% of SMPBC attenders (N = 1,946) an d 74.2% of non-attenders (N = 8,149) were referred to the BC Cancer Agency and had pathology, staging, treatment, and outcome information available. S MPBC attenders compared with non-attenders were more likely to have in situ disease alone, and those with invasive cancers had smaller tumors which we re less likely to have grade III histology and less likely to have spread t o axillary lymph nodes (all P < 0.001). SMPBC attenders were more likely to be treated with breast conservation and less likely to receive adjuvant ch emotherapy or tamoxifen (P < 0.001). Log-rank tests showed local (P = 0.017 ), distant (P < 0.001), and overall (P < 0.001) disease-free survival were better for SMPBC attenders. These favorable surrogate endpoints suggest tha t the benefits of breast screening as demonstrated by randomized trials can be translated into community practice by an organized breast screening pro gram.