Safety and Efficacy of Sequential Chemoimmunotherapy Followed by Concurrent Chemoradiation in Unresectable Stage III NSCLC.

Background: The eighth edition of the International Association for the Study of Lung Cancer staging project reports a 5-year overall survival (OS) for stage IIIA, B, and C NSCLC of 41%, 24%, and 12%, respectively, highlighting the need for improved treatment options. Induction chemotherapy and immune checkpoint inhibition (ID-chemo-ICI) followed by concurrent chemoradiation (cCRT) has not been adequately studied because of concerns about toxicity. We aim to describe the outcomes of patients with unresectable stage III NSCLC who received ID-chemo-ICI followed by cCRT with or without maintenance ICI. Methods: We conducted a retrospective analysis of patients with unresectable stage III NSCLC who received ID-chemo-ICI with the intent to proceed with cCRT across all Mayo Clinic sites. Clinical end points included progression-free survival (PFS), OS, overall response rate per the Response Evaluation Criteria in Solid Tumors version 1.1, and treatment-related adverse events defined using Common Terminology Criteria for Adverse Events version 5.0. Results: A total of 29 patients with unresectable stage III NSCLC, deemed unsuitable for upfront cCRT or surgery, with a plan to proceed with ID-chemo-ICI before cCRT, were identified. The median age was 66 years, 55% were male, most had a history of smoking (93.1%), and 100% identified as White. Tumor histologies were adenocarcinoma (69%), squamous cell carcinoma (24%), poorly differentiated NSCLC (3.4%), and sarcomatoid NSCLC (3.4%). Most were stage IIIB (44.8%), followed by IIIC (41.4%), and IIIA (13.8%). N2 and N3 disease were present in 37.9% and 55.2%, respectively. Programmed death-ligand 1 expression included less than 1% (n = 11, 38%), 1% to 49% (n = 9, 31%), greater than 50% (n = 5, 17%), and unknown (n = 4, 14%). Patients received ID-chemo-ICI with pembrolizumab (82.8%), nivolumab (13.8%), or atezolizumab (3.4%), with a median of four cycles. The overall response rate to ID-chemo-ICI was 93%. Of the cohort, 90% received cCRT, and 76% received maintenance ICI (pembrolizumab or durvalumab). The median PFS was 18 months, and the median OS was 24 months. Pneumonitis occurred in 37.9% (grade 1: 18.2%; grade 2: 63.6%; grade 3: 18%, no grade 4). Esophagitis occurred in 55.2% (grade 1-2: 93%; grade 3: 7%). Conclusions: ID-chemo-ICI followed by cCRT seems feasible and safe for unresectable stage III NSCLC, particularly for patients unsuitable for upfront cCRT. Larger prospective trials are needed to validate these findings and optimize patient selection.