Pembrolizumab monotherapy has demonstrated durable antitumor activity in advanced programmed death ligand 1 (PD-L1)-expressing nonsmall-cell lung cancer (NSCLC). We report 5-year outcomes from the phase Ib KEYNOTE-001 study. These data provide the longest efficacy and safety follow-up for patients with NSCLC treated with pembrolizumab monotherapy.

Eligible patients had confirmed locally advanced/metastatic NSCLC and provided a contemporaneous tumor sample for PD-L1 evaluation by immunohistochemistry using the 22C3 antibody. Patients received intravenous pembrolizumab 2 mg/kg every 3 weeks or 10 mg/kg every 2 or 3 weeks. Investigators assessed response per immune-related response criteria. The primary efficacy end point was objective response rate. Overall survival (OS) and duration of response were secondary end points.

We enrolled 101 treatment-naive and 449 previously treated patients. Median follow-up was 60.6 months (range, 51.8 to 77.9 months). At data cutoff-November 5, 2018-450 patients (82%) had died. Median OS was 22.3 months (95% CI, 17.1 to 32.3 months) in treatment-naive patients and 10.5 months (95% CI, 8.6 to 13.2 months) in previously treated patients. Estimated 5-year OS was 23.2% for treatment-naive patients and 15.5% for previously treated patients. In patients with a PD-L1 tumor proportion score of 50% or greater, 5-year OS was 29.6% and 25.0% in treatment-naive and previously treated patients, respectively. Compared with analysis at 3 years, only three new-onset treatment-related grade 3 adverse events occurred (hypertension, glucose intolerance, and hypersensitivity reaction, all resolved). No late-onset grade 4 or 5 treatment-related adverse events occurred.

Pembrolizumab monotherapy provided durable antitumor activity and high 5-year OS rates in patients with treatment-naive or previously treated advanced NSCLC. Of note, the 5-year OS rate exceeded 25% among patients with a PD-L1 tumor proportion score of 50% or greater. Pembrolizumab had a tolerable long-term safety profile with little evidence of late-onset or new toxicity.