The overall response rate now was 21.1% with pembrolizumab and 11.0% with chemotherapy. In the former group, the rate of complete response had increased from 7.0% to 9.3% with the longer follow-up. Median time to response was identical, at 2.1 months, but duration of response was longer with pembrolizumab (not reached vs. 4.4 months).
“We haven’t seen any signals of cumulative toxicity with subsequent follow-up,” Dr. Bellmunt reported. Similar to findings of the initial analysis, the most common grade 3-5 treatment-related adverse events were pruritus, fatigue, and diarrhea with pembrolizumab, and neutropenia, anemia, and fatigue with chemotherapy. As expected, the pembrolizumab group had higher rates of hypothyroidism, pneumonitis, hyperthyroidism, and colitis.
“The overall survival benefit and superior safety of pembrolizumab versus chemotherapy in this second-line patient population is maintained after 2 years of follow-up. At 24 months, 27% of patients are alive, and this is similar to what we are seeing with other immune-sensitive diseases like melanoma,” he concluded. “Results in patients with PD-L1–positive or –negative tumors were consistent with the intent-to-treat population. We have seen some hints with this biomarker, but they are not very striking.”