Impact of Radiotherapy on the Efficacy and Toxicity of anti-PD-1 Inhibitors in Metastatic NSCLC.

ABSTRACT

BACKGROUND: The impact of radiotherapy (RT) on the efficacy and toxicity of immune checkpoint inhibitors (ICIs) in patients with metastatic non-small-cell lung cancer (NSCLC) is unclear. MATERIALS AND METHODS: We identified patients with metastatic NSCLC treated with the anti-programmed death 1 antibodies nivolumab or pembrolizumab between January 2016 and May 2019 at 3 tertiary centers, who were also treated with palliative RT either during or within 3 months of starting anti-programmed death 1 treatment. Patient demographics, tumor characteristics, and treatment history were collected. Response rates, progression-free survival (PFS), and overall survival (OS) were analyzed and correlated with RT use. RESULTS: A total of 269 patients were identified, with a median follow-up of 19.4 months. The median age was 70 years (range, 35-90 years), and they were 63% male, 60% smokers, and 65% had adenocarcinoma histology. At the commencement of ICI treatment, the majority (86%) had ≥ 1 line of prior therapy and 34% had brain metastases. A total of 102 (38%) patients received RT within 3 months of starting ICI or subsequently during ICI treatment. Of patients that received RT, 86 (84%) received conventional hypofractionated RT, and, in the majority, 81 (79%) the intent of RT was symptom control. The use of RT did not increase grade 3/4 immune-related adverse events. The overall median PFS was 2.0 months (95% confidence interval, 1.3-2.6 months) and the median OS was 9.0 months (95% confidence interval, 6.4-9.5 months). There were no significant differences in median PFS (3.0 vs. 2.0 months; P = .515) and median OS (9.0 vs. 9.0 months; P = .917) in the patients who received RT versus those that did not. CONCLUSIONS: In patients with metastatic NSCLC, the addition of RT to ICI was not associated with increased toxicity or improved survival.