Author(s): Amit M Oza, David Cibula, Ana Oaknin, Christopher John Poole, Ron HJ Mathijssen
Background: The oral PARP inhibitor olaparib has shown antitumor activity in pts with SOC. Our multicenter study compared the efficacy of (Arm A) olaparib capsules plus P/C for 6 cycles then maintenance olaparib monotherapy vs (Arm B) P/C alone for 6 cycles and no further therapy in pts with PSR SOC (NCT01081951 ). Methods: Pts received 6 x 21-day(d) cycles of olaparib (200 mg bid, d1–10/21) + P (175 mg/m2 iv, d1) + C (AUC4 iv, d1), then olaparib monotherapy as maintenance (400 mg bid, continuous) (Arm A), or 6 x 21d cycles of P (175 mg/m2 iv, d1) + C (AUC6 iv, d1) then no further therapy (Arm B), until progression. Randomization (1:1) was stratified by number of platinum treatments and platinum-free interval. Primary endpoint: progression-free survival (PFS) by central review (RECIST 1.1). Secondary endpoints: overall survival (OS), objective response rate (ORR), safety. Archival tissue was collected where available for analysis of biomarker correlation. Results: Of 162 pts randomized (n=81 per arm), 156 received treatment (Arm A, n=81; Arm B, n=75) and 121 began the maintenance/no further therapy phase (Arm A, n=66; Arm B, n=55). Olaparib + P/C (AUC4) followed by maintenance olaparib showed a significant improvement in PFS vs P/C (AUC6) alone (HR = 0.51, 95% CI 0.34, 0.77; P=0.0012; median = 12.2 vs 9.6 months). OS data are immature (total events: 14%). ORR was similar for Arm A and Arm B (64 vs 58%). Most common AEs during the combination phase were alopecia (74 vs 59%), nausea (69 vs 57%) and fatigue (64 vs 57%) for Arm A vs Arm B, respectively. Pts with grade ≥3 AEs (65 vs 57%), serious AEs (SAEs: 15 vs 21%) and AEs leading to treatment discontinuation (19 vs 16%) were similar for Arm A vs Arm B. Most common AEs during maintenance/no further therapy were nausea (50 vs 6%) and vomiting (29 vs 7%). 29 vs 16% of pts had grade ≥3 AEs, 9 vs 7% had SAEs and 8% vs N/A discontinued due to AEs in the olaparib vs no treatment arms, respectively. There were no fatal AEs. Conclusions: In pts with PSR SOC, olaparib plus P/C (AUC4) followed by olaparib 400 mg bid monotherapy maintenance treatment resulted in a significant improvement in PFS vs P/C (AUC6) alone.