Immunotherapy After Chemotherapy and Radiation for Clinical Stage III Lung Cancer.

Importance: The 2017 international PACIFIC trial established a role for immunotherapy after chemoradiation for unresectable stage III non-small cell lung cancer (NSCLC). However, in the US, patients with NSCLC commonly differ from clinical trial populations in terms of age, health, access to care, and treatment course, which may all factor into the efficacy of immunotherapy. Objective: To determine the outcomes of immunotherapy use in unresectable stage III NSCLC in the general US population. Design, Setting, and Participants: This cohort study analyzed the National Cancer Database for patients diagnosed with clinical stage III NSCLC between 2015 and 2017 with follow-up through the end of 2018 who were treated with chemotherapy and radiation. Data were analyzed January 2022. Main Outcomes and Measures: Mortality hazard in a multivariable Cox proportional hazards model and survival among a propensity-matched sample treated with chemotherapy and radiation, with and without immunotherapy. Results: A total of 23 811 patients with clinical stage III NSCLC with median (IQR) age 66 (59-72) years met inclusion criteria (10 454 [43.9%] women; 564 [2.4%] Asian, 2930 [12.3%] Black, 20 077 [84.3%] White patients), including 209 (16.1%) patients with multiple comorbidities and 1297 (5.4%) immunotherapy recipients. Immunotherapy after chemotherapy and radiation was associated with reduced mortality (hazard ratio [HR], 0.74; 95% CI, 0.67-0.82; P < .001). Among a propensity-matched sample, immunotherapy was associated with superior 3-year survival (52% [1297 patients at 0 months, 56 patients at 36 months] vs 44% [2594 patients at 0 months, 173 patients at 36 months]; P < .001). The treatment of 833 patients who received immunotherapy (64.2%) differed from the PACIFIC trial protocol, including 221 patients (17.0%) who received radiation doses outside of the protocol range and 731 patients (56.4%) who started immunotherapy more than 6 weeks after radiation was completed. The survival advantage of immunotherapy persisted when initiated up to 12 weeks after radiation was completed (HR, 0.75; 95% CI, 0.61-0.92). Among patients who received radiation outside the PACIFIC protocol range, the survival advantage of immunotherapy was not significant (HR, 0.87; 95% CI, 0.69-1.01). Conclusions and Relevance: In this cohort study, immunotherapy after chemotherapy and radiation for stage III NSCLC was associated with a survival advantage in the general US population despite two-thirds of patients treated differently than the PACIFIC protocol. The findings suggest there may be flexibility in the timing of immunotherapy initiation after radiation; further study is warranted to clarify the clinical benefits of immunotherapy.