P3.02c-035 Comparison of RECIST to Immune-Related Response Criteria (irRC) in Patients with NSCLC Treated with Immune-Check Point Inhibitor: Topic: IT

Immune check point inhibitor has become essential therapeutic option for advanced non-small cell lung cancer (NSCLC). Immune-related response in NSCLC has not been well evaluated, thus we assessed the tumor response using Response Evaluation Criteria in Solid Tumors, version 1.1 (RECIST v1.1) and immune-related response criteria (irRC) to identify atypical response in patients with advanced NSCLC treated with immunotherapeutic agents. Patients received immune check point inhibitors (pembrolizumab, atezolizumab, nivolumab, pembrolizumab plus tremelimumab) at Samsung Medical Center between July 2014 and October 2015. The tumor response was assessed according to both RECIST v1.1 and irRC. Pseudoprogression was defined as progressive disease at any time of assessment and not at next assessment per RECIST v1.1 or irRC. Total 41 patients were analyzed, most of patients (80.5%) received anti-PD-1 agents (pembrolizumab or nivolumab) and 6 patients were treated with anti-PD-L1, atezolizumab, 2 patients received combination treatment with pembrolizumab and tremelimumab. Two patients showed pseudoprogression followed by regression per RECIST v1.1 not per irRC. 4 patients with progressive disease per RECIST v1.1 were partial response per irRC, objective response was 29.2% per RECIST v1.1 and 34.1% per irRC, respectively. There was no significant difference in response rate between two methods (p=0.923). The median duration of follow-up was 19.8 months, and the median progression-free survival of all patients was 4.5 months (95% CI 2.7-6.3). These results suggest that pseuoprogression is not frequently observed in NSCLC, and conventional RECIST v1.1 might underestimate the benefit of immune check point inhibitors. Given the small number of patients studied and short-term follow-up, further study will be warranted whether treatment with immune checkpoint inhibitor beyond RECIST progression can be benefit to patient with advanced NSCLC.