Impact of Ethnicity on the Uptake of Risk Reducing Mastectomy in Unaffected BRCA1/2 and PALB2 Carriers in Canada.

While several studies have reported on factors influencing the uptake of risk-reducing mastectomy (RRM) in patients with germline pathogenic variants (gPV) in BRCA1/2, there remains a paucity of data regarding variations in uptake by ethnicity. We conducted a retrospective cohort study of unaffected female patients with a confirmed gPV in BRCA1/2 or PALB2 between March 2000 to March 2023 at two academic institutions in Montreal, Canada. Ethnicity was self-reported as: White/European, Black/African/Caribbean, Asian/Southeast Asian, Hispanic/South/Central American, Middle Eastern/North African, Indigenous/First Nations, or mixed. Fisher's exact test and multivariable logistic regression were used to evaluate predictors of RRM uptake. Of 476 unaffected female carriers, 205 (43.1%) had a gPV in BRCA1, 250 (52.5%) in BRCA2, and 21 (4.4%) in PALB2. The median age at genetic testing was 37 years (interquartile range [IQR], 29-47) and 365 (76.7%) patients were of White ethnicity. At a median follow-up of 49 months (IQR, 17-87), 182 (38.2%) women underwent RRM. Univariate analysis showed highest RRM uptake in Hispanic/South/Central American carriers (58.8%) and White carriers (40.3%) and lowest uptake in Black/African/Caribbean carriers (11.1%; p = 0.047). In adjusted analyses, ethnicity did not remain independently associated with RRM (p = 0.21), although age and family history of ovarian cancer did. In this study of unaffected BRCA1/2 and PALB2 carriers, RRM uptake was lowest among Black/African/Caribbean carriers. However, ethnicity was not significantly associated with uptake of RRM in adjusted analyses. Further studies are needed to understand disparities in risk-reduction uptake and the complex decision-making process.