Three-year overall survival update from the PACIFIC trial

Abstract

Background: In the phase 3 PACIFIC study of patients with unresectable, Stage III NSCLC without progression after chemoradiotherapy (CRT), durvalumab demonstrated significant improvements versus placebo in the primary endpoints of progression-free survival (HR, 0.52; 95% CI, 0.42-0.65; P < 0.0001) and overall survival (OS; HR, 0.68; 95% CI, 0.53-0.87; P = 0.00251). Safety was similar and durvalumab had no detrimental effect on patient-reported outcomes. Here, we report 3-year OS rates for all patients randomized in the PACIFIC study. Methods: Patients with WHO PS 0/1 (any tumor PD-L1 status) who received >2 cycles of platinum-based CRT were randomized (2:1), 1-42 days following CRT, to receive durvalumab 10 mg/kg intravenously every 2 weeks or placebo, up to 12 months, and stratified by age, sex, and smoking history. OS was analyzed using a stratified log-rank test in the ITT population. Medians and OS rates at 12,24 and 36 months were estimated by Kaplan-Meier method. Results: In total, 713 patients were randomized of whom 709 received treatment (durvalumab, n = 473; placebo, n = 236). The last patient had completed the protocol-defined 12 months of study treatment in May 2017. As of January 31, 2019 (data cutoff), 48.2% of patients had died (44.1% and 56.5% in the durvalumab and placebo groups, respectively). The median duration of follow-up was 33.3 months (range, 0.2-51.3). Updated OS remained consistent with that previously reported (stratified HR 0.69,95% CI, 0.55-0.86), with the median not reached (NR; 95% CI, 38.4 months-NR) with durvalumab versus 29.1 months (95% CI, 22.1-35.1) with placebo. The 12-, 24-and 36-month OS rates with durvalumab and placebo were 83.1% versus 74.6%, 66.3% versus 55.3%, and 57.0% versus 43.5%, respectively. After discontinuation, 43.3% and 57.8% in the durvalumab and placebo groups, respectively, received subsequent anticancer therapy (9.7% and 26.6% subsequently received immunotherapy). OS subgroup results will be presented. Conclusions: Updated OS data from PACIFIC, including 3-year survival rates, underscore the long-term clinical benefit with durvalumab following CRT and further establish the PACIFIC regimen as the standard of care in this population.