P3.01-99 Effect of Pembrolizumab on Patients Harboring Uncommon Epidermal Growth Factor Receptor Mutations

Abstract

The characteristics of non-small cell lung carcinoma (NSCLC) patients harboring uncommon epidermal growth factor receptor (EGFR) mutations differ from those of patients with common EGFR mutations. For example, male smokers were more common among patients with uncommon mutations. The efficacies of non-afatinib treatment strategies for patients harboring uncommon EGFR mutations are uncertain. The efficacy of immune checkpoint inhibitors (ICIs) in advanced NSCLC patients with EGFR mutations is limited. Furthermore, the efficacy of ICIs in patients harboring uncommon EGFR mutations is unknown. We retrospectively reviewed five NSCLC cases with uncommon EGFR mutations and high program death (PD)-ligand (L)1 expression (> 50%) on tumor cells that were treated with the ICI pembrolizumab in our institute from April 2017 to April 2018. We collected data include sex, age, performance status, smoking history, PD-L1 expression, EGFR mutations status and clinical outcome. Four cases were male, median age was 68 (45-78), 4 cases were former/current smokers, 1 case was stage IIIC, 2 cases were stage IVA and 2 cases were stage IVB, 4 cases had G719X and 1 case had both exon 19 deletion and T790M. Four cases were treated with pembrolizumab as first line treatment and 1 case were treated as second line treatment after afatinib. Median number of pembrolizumab doses were 4 (1-7) and best responses were 2 partial response (PR), 2 stable disease (SD) and 1 progressive disease (PD). As adverse events, 1 case had grade 3 colitis and 1 case had grade 1 pneumonitis. Four patients with the G719X mutation were male former/current smokers and were effectively treated (PR of SD) with pembrolizumab. However, one patient with both common mutation and de novo T790M did not respond to pembrolizumab (PD). ICI-based treatment for patients harboring uncommon EGFR mutations may be one of the treatment option.