Background
Phase III, open-label RCT. 302 patients with germline BRCA1 or BRCA2-mutated HER2-negative (HR+ or TNBC) metastatic breast cancer who had received ≤2 prior lines of chemotherapy for advanced disease (not more). Prior platinum allowed but not required; ≤2 prior chemotherapy lines in advanced setting. Olaparib exploits BRCA1/2 synthetic lethality to block DNA damage repair in tumor cells.
Interventions and follow up
Arm A: Olaparib 300mg BID (tablets) continuously
Arm B: Standard single-agent chemotherapy (capecitabine, eribulin, or vinorelbine — physician's choice)
Primary endpoint: Progression-free survival (PFS)
mFollow up: 14.5 month
Arm B: Standard single-agent chemotherapy (capecitabine, eribulin, or vinorelbine — physician's choice)
Primary endpoint: Progression-free survival (PFS)
mFollow up: 14.5 month
Results
PFS: 7.0 vs 4.2mo, HR 0.58, 95% CI 0.43–0.80, P<.001
OS: 19.3 vs 17.1mo, HR 0.90, 95% CI 0.66–1.23 — not significant
ORR: 59.9% vs 28.8%
OS: 19.3 vs 17.1mo, HR 0.90, 95% CI 0.66–1.23 — not significant
ORR: 59.9% vs 28.8%
Adverse events
Hematologic: Grade ≥3 anemia 16.1% vs 4.3%
Gastrointestinal: Grade ≥3 nausea 0.0% vs 1.4%
Constitutional: Grade ≥3 fatigue 2.0% vs 2.4%
Secondary malignancy: MDS/AML 0.7% vs 0.0%
Overall: Generally well-tolerated, oral once-daily dosing; dose reduction 25.8%; discontinuation 4.7%
Gastrointestinal: Grade ≥3 nausea 0.0% vs 1.4%
Constitutional: Grade ≥3 fatigue 2.0% vs 2.4%
Secondary malignancy: MDS/AML 0.7% vs 0.0%
Overall: Generally well-tolerated, oral once-daily dosing; dose reduction 25.8%; discontinuation 4.7%
Conclusions
Olaparib significantly improved PFS and ORR vs chemotherapy in gBRCA1/2-mutated HER2-negative mBC. OS was not significantly improved, though crossover and post-progression therapy effects may have diluted the OS signal. OlympiAD established the first PARP inhibitor approval in metastatic breast cancer.
Key Limitations
Key Limitations: OS non-significant despite strong PFS benefit — likely due to ~22% crossover and extensive post-progression therapies. The maximum of 2 prior chemotherapy lines limits applicability in later-line settings where PARP inhibitors might also be active. Germline BRCA1/2 testing required (somatic BRCA mutations confer uncertain benefit). Not established in the post-CDK4/6i setting in HR+/BRCA-mutated disease. EMBRACA (talazoparib) showed similar PFS results in a larger trial but also no OS benefit.
Clinical Context
OlympiAD established olaparib monotherapy for gBRCA1/2-mutated HER2-negative mBC (FDA approved 2018). ESMO-MCBS score: 3. Germline BRCA testing is essential for eligibility. PARP inhibitors are also being tested in combination with CDK4/6i (in HR+ disease) and in maintenance settings. The adjuvant benefit of olaparib (OlympiA) has strengthened the clinical rationale for BRCA testing across all high-risk BC presentations.
References
References: Robson M et al, NEJM 2017