Phase II prospective trial of primary lung tumor stereotactic body radiation therapy (SBRT) followed by concurrent mediastinal chemoradiation and adjuvant immunotherapy for locally-advanced non-small cell lung cancer (NSCLC): Planned toxicity analysis.

e21047 Background: The care of pts with locally-advanced NSCLC has continued to evolve. Dose escalation with conventional radiation and concurrent chemotherapy has failed to improve outcomes and is associated with low primary tumor control rates and high toxicity rates. We initiated a phase II study to evaluate full dose SBRT to the primary tumor followed by conventional chemoradiation to the involved lymph nodes followed by adjuvant immunotherapy in patients (pts) with unresectable locally-advanced NSCLC. Methods: Eligible pts included peripheral primary tumors ≤ 7cm or centrally based tumors that had at least 2 cm separation from involved nodal disease. Pts received SBRT to the primary tumor (50-54 Gy in 3-5 fractions) followed by standard radiation to 60 Gy in 30 fractions with concurrent chemotherapy (physician choice of carboplatin/paclitaxel or cisplatin/etoposide). Pts without disease progression after chemoradiation then received adjuvant durvalumab (PACIFIC trial). Planned analysis of early toxicity was performed given this is the first prospective trial to replace conventional fractionation and deliver full dose SBRT to the primary tumor in the locally advanced setting. Results: From May 2017 to January 2020, 35pts were enrolled. Median follow up is 7.9 months (range 0-27 months). Toxicity related to either SBRT or mediastinal radiation was lower than previous published prospective trials with a grade 2 radiation pneumonitis incidence of only 17%. There was no ≥grade 3 pneumonitis. Grade 3 esophagitis was observed in 1 pt (3%) with grade 2 esophagitis in 37%. No grade ≥3 toxicity has been attributed to SBRT with 26% of pts experiencing a grade 2 toxicity from SBRT. Overall incidence of grade ≥3 pulmonary toxicity attributed to any therapy was 9%. One pt died of neutropenic sepsis due to legionella while on therapy attributed to chemotherapy. No major cardiac events were reported to date. Conclusions: Full dose SBRT to the primary tumor followed by standard chemoradiation to the involved lymph nodes appears to have a favorable toxicity profile when compared with conventional dose escalation and to previously published experiences with SBRT boost following chemoradiation in the treatment of locally advanced NSCLC. Our trial continues to enroll with a target of 56 pts. Clinical trial information: NCT03141359 .