Abstract PS3-02-01: Trends in the uptake of nipple-sparing mastectomy in BRCA1/2, PALB2 and other pathogenic variant carriers undergoing risk reducing mastectomy

Abstract Introduction: Risk-reducing mastectomy (RRM) a well-established preventive intervention in germline pathogenic variants (GPVs) carriers. Historically, RRMs were performed as total mastectomy (TM) or skin-sparing mastectomy (SSM), although nipple-sparing mastectomy (NSM) has recently emerged as a RRM option. In this study, we assessed temporal trends in NSM uptake. Methods: This retrospective cohort study included all female patients with confirmed BRCA1, BRCA2, PALB2, or other GPVs carriers at two academic institutions in Montreal, Canada, between 2003 and 2024. The primary outcome was the proportion of GPV carriers NSM compared to SSM and TM over time as evaluated by Mantel Haenszel test for trend. Results: After exclusions, 441 GPV carriers were included in the cohort, 260 (59%) affected carriers and 181 (41%) unaffected carriers. The median age at RRM was 44 years old (range 22-76). Most were BRCA1 carriers (45.5%) or BRCA2 carriers (44.8%) while the remaining 9.8% were PALB2 and other GPV carriers. Overall, 269 (61%) underwent NSM, 118 (26.8%) underwent SSM, and 54 (12.2%) underwent TM. NSM uptake was highest among patients aged 40-49 years (68.6%) and lowest in those ≥60 years (45.8%, p=0.04). Relative to affected carriers, unaffected carriers were more likely to undergo NSM (72.4%, Vs.53.1% p