Abstract PD2-13: Benefits to breast screening beyond mortality reduction

Background The value of population-based mammographic screening has been questioned by those who believe that the reduction in mortality from earlier diagnosis is outweighed by harms including overdiagnosis and overtreatment. Much of these commentaries assume that all Early-Stage Breast Cancer (ESBC) is treated the same way after diagnosis; with extensive therapies including surgery, radiotherapy and chemotherapy being standard. Intensity of treatment received is rarely mentioned in the debate. We hypothesised that those diagnosed through a screening program (Active Screeners (AS)) would receive less extensive surgical treatment and less intense adjuvant therapies than those not recently screened (NRS). If demonstrated, these differences would form an important component of the debate over the role of mammographic screening. Methods Retrospective analysis of a consecutive cohort of female patients aged 50-69 and managed for ESBC (invasive or DCIS) during 2007-2013 within a large metropolitan Breast Service, diagnosed either via a population screening program (AS) or outside of the program (NRS). Data on patient characteristics, symptoms, mode of detection, tumour pathology, surgical intervention and adjuvant treatment recommendations were derived from prospectively collected Multi-Disciplinary Meeting (MDM) records. Patients with metastatic disease or prior treatment for breast cancer were excluded. Results 791 cases were identified (569 with screen-detected cancer, 53 with interval cancers and 169 cancers diagnosed in women not recently screened). Invasive cancers in the AS group were much smaller than in the NRS group – mean 17mm versus 26mm. The AS group had lower grade invasive cancer – grade 1, 2 and 3 were 27%, 42%, 31% - compared with 10%, 39% and 52% in the NRS group. The AS group were more likely to have ER+ve cancers (88% vs 80%) and less likely to have nodal involvement (26% vs 48%). For invasive breast cancer, the NRS group were more than twice as likely to undergo mastectomy than cancers in the AS group (35% vs 16%). Axillary dissections were more common in the NRS than the AS group (43% vs 19%). Adjuvant chemotherapy was recommended more frequently for the NRS group compared to the AS group (65% vs 37%), as was post mastectomy radiotherapy (58% vs 39%). Endocrine therapy was less often recommended to the NRS group (86% versus 77%). Conclusion Women diagnosed with early stage breast cancer who are participating in a population based screening program are less likely to receive mastectomy and/or axillary dissection, less likely to receive adjuvant chemotherapy and less likely to receive post-mastectomy radiotherapy. These differences in treatment intensity should be considered in the debate surrounding mammographic screening. Citation Format: Elder KJ, Nickson C, Cooke S, Machalek D, Rose A, Mou A, Collins JP, Park A, De Boer R, Phillips C, Pridmore V, Farrugia H, Mann GB. Benefits to breast screening beyond mortality reduction [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr PD2-13.