958P Intensity-modulated radiotherapy (IMRT)-adapted chemoradiotherapy (CRT) followed by durvalumab for locally advanced non-small cell lung cancer (NSCLC): A multicenter prospective observational study (WJOG12019L)

CRT followed by durvalumab is the standard of care for locally advanced NSCLC. In PACIFIC study, randomization was done after CRT, thus any information on radiation procedure was not collected. IMRT precisely irradiates target lesions and inflicts less damage to surrounding normal organs. This technique is currently utilized in thoracic CRT, but little prospective data has been shown regarding durvalumab following IMRT-adapted CRT. Eligible patients: cytologically or histologically confirmed unresectable locally advanced NSCLC: PS 0/1; aged <75; no severe co-morbidities; and no active double cancer were treated with IMRT (60Gy/30Fr). Primary endpoint was durvalumab introduction rate (threshold: 70% and expected: 90%). Between November 2019 and February 2021, 32 patients were enrolled. Except for two patients who withdrew their consent, durvalumab was introduced in 24 (80.0%, 90%CI: 64.3-90.9%) of 30 patients. The reasons for their non-introduction were: disease progression (n=2); participation in another clinical trial after CRT (n=2): intolerable adverse events (AEs) (n=1); or reception of 3 dimensional (3D)-CRT because of unstable disease (n=1). Efficacies were evaluated in 29 patients, excluding the two withdrawn patients and one patient who did not receive IMRT, but 3D-CRT. Fifteen (52%) partial response, 12 (41%) stable disease, and 2 (7%) progressive disease were confirmed, resulting in response rate of 51.7% and disease control rate of 93.1%. Neither median PFS nor OS were reached. One-year PFS and OS rates were 55% and 91%, respectively. There were neither treatment-related deaths nor grade 4 AEs. Pneumonitis: 13 (45%) grade 1; 7 (24%) grade 2; and 1 (4%) grade 3 were confirmed. Grade 3 AEs: 2 (7%) pulmonary infection; 1 (3%) esophagitis; 1 (3%) thromboembolism; and 1 (3%) oral mucositis were observed. IMRT-adapted CRT followed by durvalumab demonstrated favorable safety profiles including a low incidence of severe pneumonitis. Durvalumab was not introduced in some patients due to disease progression or AEs.