161P Intensity-modulated radiotherapy (IMRT)-adapted chemoradiotherapy (CRT) followed by durvalumab (Durva) for locally advanced non-small cell lung cancer (NSCLC): 2-year update from a multicenter prospective observational study (WJOG12019L)

CRT followed by Durva is the standard of care for unresectable 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 Durva following IMRT-adapted CRT. Eligible patients (pts): unresectable locally advanced NSCLC; PS 0/1; aged <75; no severe co-morbidities; and no active double cancer were treated with IMRT (60Gy/30Fr). Radiation procedures were set based on a unified protocol (e.g., lung V20 ≤35% and V5 ≤60%). RT quality assurance was mandatory for all the pts. Primary endpoint was Durva introduction rate (threshold/expected: 70%/90%). Between November 2019 and February 2021, 32 pts were enrolled. Except for 2 withdrawn pts, Durva was introduced in 24 (80.0%, 90% CI: 64.3-90.9%) of 30 pts. The reasons for non-introduction were: disease progression (n=2); enrollment to another clinical trial after CRT (n=2); intolerable adverse events (AEs) (n=1); or receiving 3D-CRT due to unstable disease (n=1). Among 27 pts of per protocol set, response and disease control rates were 67% and 93%, respectively. Based on survival analyses of Durva introduced pts (n=24), median PFS and OS were 20.9 months and not reached, respectively. Two-year PFS and OS rates were 44% and 73%, respectively. One-year Durva administration was completed in 12 (50%) of 24 pts. There were neither treatment-related deaths nor grade 4 non-hematological AEs. Pneumonitis: 13 (45%) grade 1; 7 (24%) grade 2; and 1 (3%) 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 Durva demonstrated efficacy and favorable safety profiles, including a lower incidence of severe pneumonitis. Durva was not introduced in some pts due to disease progression or AEs.