Background: There is ongoing debate about the role of screening mammography and its impact on overall survival in breast cancer. We hypothesized that women with screen-detected breast cancers (SDBC) receive less surgery, regional radiotherapy (RRT), and chemotherapy (CH) than women with non-screen-detected breast cancers (NSDBC). Less therapy equates to less personal and societal burden, including less time away from work, fewer side effects, lower health care and disability costs, and reduced psychosocial distress. These may be adequate justification for screening programs even in the absence of an overall survival benefit. Methods: Women aged 40-79 years with stage 0-III breast cancers diagnosed between 2007-2012 and referred to the British Columbia Cancer Agency were identified using the Breast Cancer Outcomes Unit database. Clinical and tumor characteristics and type/extent of treatment were extracted. Linkage with the Screening Mammography Program of British Columbia segregated cases into SDBCs and NSDBCs. Interval breast cancers arising in regularly screened women (minimum 2-year interval) were excluded. Results: We identified 12,393 women; 7807 with SDBC and 4586 with NSDBC. Compared with NSDBCs, SDBCs were lower stage, less often treated with mastectomy and CH, and occurred in slightly older women (Table 1). SDBC received more radiation than NSDBC. Conclusions: Women with NSDBC are more likely to present with higher stage breast cancer. Rates of mastectomy and CH were 20% higher in NSDBC whereas SDBC had a modest 5% higher rate of RRT. These findings suggest that screening mammography decreases the extent of local and systemic treatment for breast cancer.