Significant Improvement in Overall Survival with Adjuvant Olaparib in High-Risk Early Breast Cancer Patients with BRCA1/2 Mutations

Background

The OlympiA trial, a randomized, double-blind study, compared the efficacy and safety of 1 year of adjuvant olaparib, a poly(adenosine diphosphate-ribose) polymerase (PARP) inhibitor, versus placebo in patients with germline BRCA1/2 pathogenic variants (gBRCA1/2pv) and high-risk, early breast cancer (EBC). The trial aimed to address the unmet need for effective adjuvant therapies in this patient population, who remain at high risk for recurrence despite standard treatments.

Patients and Methods

A total of 1,836 patients were randomized to receive either olaparib or placebo following (neo)adjuvant chemotherapy, surgery, and radiation therapy if indicated. The study's primary endpoint was invasive disease-free survival (IDFS), with secondary endpoints including distant disease-free survival (DDFS) and overall survival (OS). Statistical significance for OS at the second interim analysis (IA2) required a P value of <0.015.

Results

With a median follow-up of 3.5 years, the second interim analysis of OS demonstrated a significant improvement in the olaparib group relative to the placebo group, with a hazard ratio (HR) of 0.68 (98.5% CI 0.47–0.97; P = 0.009). The 4-year OS rates were 89.8% in the olaparib group and 86.4% in the placebo group, indicating a 3.4% absolute improvement. Additionally, the trial showed sustained improvements in IDFS and DDFS, with 4-year IDFS rates of 82.7% versus 75.4% and 4-year DDFS rates of 86.5% versus 79.1% in the olaparib and placebo groups, respectively.

Subgroup analyses revealed consistent benefits across major subgroups, including hormone receptor status, prior platinum use, and the context of adjuvant versus neoadjuvant chemotherapy. The safety profile of olaparib remained consistent with previous studies, with no new safety signals identified. Notably, the incidence of acute myeloid leukemia or myelodysplastic syndrome (AML/MDS) was low, with only two cases reported in the olaparib group.

Conclusion

The OlympiA trial confirms the significant benefit of adjuvant olaparib in improving overall survival, invasive disease-free survival, and distant disease-free survival in patients with gBRCA1/2pv-associated high-risk early breast cancer. The findings underscore the importance of genetic testing for BRCA1/2 mutations in newly diagnosed high-risk EBC patients and support the use of olaparib as an effective adjuvant therapy in this population. Continued follow-up is essential to assess long-term outcomes and safety, including the risk of AML/MDS.