P3.CR-20 The Effect of Pembrolizumab In EGFR Mutated Lung Adenocarcinoma Patients With PD-L1 Overexpression: Two Cases Report

Abstract

Recently, the immune checkpoint inhibitor (ICI) pembrolizumab was demonstrated to be superior to platinum doublet chemotherapy in the first-line setting in patients with tumor PD-L1 expression of at least 50%.However, because patients with epidermal growth factor receptor (EGFR) mutations of anaplastic lymphoma kinase (ALK) rearrangements were not included in that study, the efficacy of this agent in lung cancers carrying EGFR mutations could not be determined. We retrospectively evaluated the clinical effects of pembrolizumab treatment for EGFR mutated lung adenocarcinoma patients with PD-L1 overexpression. Between March 2017 and February 2018, 343 cases were evaluated immunohistochemical analysis of PD-L1 expression by tumor cells according to findings of transbronchial lung biopsies or surgically resected lung specimens at our institution. Of the 343 tumors analyzed, 12 had both TPS of at least 50% and positive for EGFR mutations. Only 2 cases of EGFR mutant NSCLC patients with PD-L1 overexpression treated with pembrolizumab. We describe two cases of response to pembrolizumab in EGFR mutated lung adenocarcinoma patients with PD-L1 overexpression. Case 1 involved a 75-year-old male, diagnosed with stage IVB lung adenocarcinoma. The tumor was found to have a PD-L1 tumor proportion score (TPS) of almost 100% and was EGFR mutation positive. First line treatment with erlotinib yielded no response. Case 2 involved an 83-year-old female, diagnosed with Stage IVA pulmonary adenocarcinoma with EGFR mutation, as determined from left pleural effusion cytology. Gefitinib was selected for the initial treatment. The tumor regressed remarkably, but then slightly progressed 11 months later. We performed re-biopsy and the tumor was found to have a PD-L1 TPS of at least 95% and to be harboring the same EGFR mutation as that in the initial biopsy but was negative for T790M. In both cases, second-line therapy was commenced using pembrolizumab after failure of first-line EGFR-TKI therapy. After administering pembrolizumab, both tumors were observed to be reduced on chest radiography. Therefore, pembrolizumab was observed to be effective. The cases presented in this report indicate that ICIs are an effective treatment for EGFR mutated lung adenocarcinoma patients with PD-L1 overexpression.