What question did this study set out to answer?

This study aims to compare the effectiveness of bilateral risk-reducing mastectomy (BRRM) to imaging surveillance in women identified as carriers of pvBRCA1/2.

May 24, 2026Open Access

366P Mismatch repair deficiency in breast cancer: Clinical features and genetic implications beyond the traditional homologous recombination repair pathway

Puntos clave

This study aims to compare the effectiveness of bilateral risk-reducing mastectomy (BRRM) to imaging surveillance in women identified as carriers of pvBRCA1/2.
Utilized a prospective cohort design with 331 women referred for pvBRCA1/2 testing from 2001-2023.
Confirmed carriers opted for either BRRM or imaging surveillance following national guidelines.
Cumulative follow-up of women tracked breast cancer incidence and mortality.
Among 103 confirmed carriers, 10.7% opted for BRRM; BC incidence was 9.7% during surveillance and 1.9% at BRRM.
No significant difference was found in the cumulative incidence of BC between surveillance and post-BRRM groups (p=0.3).
Annual all-cause mortality rates were not significantly different (BRRM: 2.2%; surveillance: 4.7%; p=0.72).

Resumen

Background: Greater availability of, and indications for, genetic testing for germline pvBRCA1/2 have led to increasing numbers of older women being diagnosed as carriers.Evidence for optimum treatment strategies in these women is limited.This study evaluates uptake and effectiveness of BRRM compared to imaging surveillance in presymptomatic women identified as carriers when aged 60y. Methods:We used a prospective cohort design to study presymptomatic women aged 60y referred for pvBRCA1/2 testing at our institution between 2001-23.Confirmed carriers elected to undergo either BRRM or imaging surveillance in line with UK national guidance and were followed from pvBRCA1/2 reporting to breast cancer (BC) or mortality.Women in either group with no event were censored on 01/ 10/25.All-cause mortality and BC incidence were compared between both groups.Data was verified by individual case note review.Results: Of 331 women tested, pvBRCA1 prevalence (30 of 151 tested (20%)) was lower than pvBRCA2 (73/180 (41%); P<0.001).Of these 103 confirmed carriers, 11 women (10.7%) underwent BRRM (4 pvBRCA1, 7 pvBRCA2), some having undergone a prior period of imaging surveillance, whereas 92 (89.3%) underwent imaging surveillance only.Cumulative follow up totalled 381.8 women-years for surveillance and 45.0 women-years post BRRM.Women choosing BRRM were younger at mutation reporting compared to women electing surveillance only (median 63y IQR 60-66 vs 65y IQR 63-71 respectively; p=0.02).During surveillance 9.7% (n = 10) developed BC (2 pvBRCA1; 8 pvBRCA2); 1.9% (n = 2) had occult BC at BRRM (1 pvBRCA1; 1 pvBRCA2) but no BC developed following BRRM.We did not find a significant difference in cumulative incidence of BC during surveillance compared to post BRRM (log-rank 2 =1.1, p=0.3) nor a significant difference in all-cause mortality rate per annum (BRRM: 2.2% n = 1; surveillance: 4.7% n = 18; p = 0.72).Conclusions: Among 103 women aged 60 years at the time of pvBRCA1/2 reporting, no significant difference was observed in cumulative BC risk or all-cause mortality rate per annum between women undergoing surveillance or electing for BRRM.Future research should explore these findings in larger cohorts.

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