Defining Lifetime Risk Thresholds for Breast Cancer Surgical Prevention.

Importance Expanding access to genetic testing and availability of validated breast cancer (BC) risk prediction models are increasingly identifying women at elevated BC risk who do not carry high-penetrance BRCA1/BRCA2/PALB2 pathogenic variants. The precise BC risk threshold for offering risk-reducing mastectomy (RRM) for BC prevention is unknown. Objective To define the lifetime BC risk thresholds for RRM to be cost-effective compared with nonsurgical alternatives for BC prevention. Design, Setting, and Participants This economic evaluation used a decision-analytic Markov model to compare the cost-effectiveness of RRM with BC screening and medical prevention in a simulated cohort. Extensive sensitivity analyses were performed. The study setting was from a UK payer perspective over a lifetime horizon until age 80 years. The simulated cohort included women aged 30 to 60 years at varying lifetime BC risks from 17% to 50%. The study was conducted between September 2022 and September 2024. Exposures Undergoing RRM or receiving risk-stratified BC screening with medical prevention (tamoxifen or anastrozole). Main Outcomes and Measures The incremental cost-effectiveness ratio was calculated as incremental cost per quality-adjusted life-year (QALY) gained and compared with the UK willingness-to-pay (WTP) threshold of £20 000 (US $27 037) to £30 000 (US $40 555) per QALY. BC cases prevented were estimated at the population level. Results In the simulated cohort of 100 000 thirty-year-old women in the UK, undergoing RRM became cost-effective at a 34% lifetime BC risk using the £30 000 (US $40 555) per QALY WTP threshold. This increased to a 42% lifetime BC risk using the £20 000 (US $27 037) per QALY WTP threshold. The identified lifetime BC risk thresholds for RRM to be cost-effective among women aged 35, 40, 45, 50, 55, and 60 years were 31%, 29%, 29%, 32%, 36%, and 42%, respectively, using the £30 000 (US $40 555) per QALY WTP threshold. Overall, undergoing RRM was deemed cost-effective for women aged 30 to 55 years with a lifetime BC risk of at least 35%, with more than 50% of simulations being cost-effective in probabilistic sensitivity analysis. Offering RRM for women with a lifetime BC risk of 35% or higher could potentially prevent approximately 6538 (95% CI, 4454-7041), or approximately 11% (95% CI, 8%-12%), of the 58 756 BC cases occurring annually in women in the UK. In the probabilistic sensitivity analysis, 20.71% to 59.96%, 44.04% to 81.29%, and 97.26% to 99.35% of simulations were cost-effective for women with 35%, 40%, and 50% lifetime BC-risk undergoing RRM at age 30 under the £20 000 to £30 000 per QALY WTP threshold, respectively. Conclusions and Relevance In this economic evaluation, undergoing RRM appears cost-effective for women aged 30 to 55 years with a lifetime BC risk of 35% or higher. These results could have significant clinical implications to expand access to RRM beyond BRCA1/BRCA2/PALB2 pathogenic variant carriers. Future studies evaluating the acceptability, uptake, and long-term outcomes of RRM among these women are warranted.