Decisional regret following risk-reducing mastectomy versus surveillance among Japanese women with breast cancer carrying BRCA1/2 pathogenic variants

Abstract Background Women with germline BRCA1/2 variants have a high lifetime risk of breast cancer, but the psychological impact and decisional regret associated with intensified surveillance versus risk-reducing mastectomy (RRM) remain unclear in Japan. Methods We conducted a cross-sectional study of 29 Japanese women with unilateral breast cancer carrying BRCA1/2 variants between April 2020 and August 2024. All participants completed questionnaires at least one year after genetic test disclosure; 15 chose RRM and 14 opted for surveillance. Decisional regret and psychological outcomes were assessed using the Decision Regret Scale (DRS), Impact of Event Scale–Revised (IES-R), and Hospital Anxiety and Depression Scale (HADS); high regret was defined as DRS ≥ 26. Results The RRM group had a lower median DRS score than the surveillance group (10 vs 25). High decisional regret occurred in 1 of 15 RRM patients versus 6 of 14 surveillance patients ( p = 0.035). Adjusted analysis showed that RRM was independently associated with lower odds of high regret (odds ratio 0.07, 95% CI 0.005–0.857). IES-R scores tended to be lower among RRM patients, whereas HADS scores were similar; DRS correlated positively with IES-R but not with HADS. Conclusions In a Japanese cohort of women with breast cancer carrying pathogenic BRCA1/2 variants, lower decisional regret was observed among those who chose risk-reducing mastectomy compared with surveillance.