AUTHOR=Shigeta Naoko , Murakami Shuji , Yokose Tomoyuki , Miyagi Yohei , Saito Haruhiro TITLE=Case report: anaplastic lymphoma kinase (ALK) rearranged adenocarcinoma with high level of microsatellite instability response to pembrolizumab JOURNAL=Frontiers in Oncology VOLUME=13 YEAR=2023 URL=https://www.frontiersin.org/journals/oncology/articles/10.3389/fonc.2023.1110638 DOI=10.3389/fonc.2023.1110638 ISSN=2234-943X ABSTRACT=

The presence of anaplastic lymphoma kinase (ALK) rearrangement is reported to be related to the lack of efficacy of immune checkpoint inhibitors (ICIs). High levels of microsatellite instability (MSI-high) are important biomarkers of ICIs, particularly in colorectal cancer. The therapeutic effect of ICIs for MSI-high NSCLC is uncertain because of the rarity of these tumors. Here we report a case of ALK rearranged NSCLC with MSI-high. A 48-year-old male was diagnosed with lung adenocarcinoma, cT4N3M1a, stage IVA with ALK rearrangement, high PD-L1 expression with a tumor proportion score (TPS) of 100%, and MSI-high. The patient was treated with alectinib as the first-line therapy but progressed at five months with left atrial invasion re-expansion. The patient discontinued alectinib and was switched to pembrolizumab monotherapy. After two months, left atrial invasion significantly decreased. The patient continued pembrolizumab for a year without noticeable adverse events, and tumor shrinkage persisted. This case supports the efficacy of ICIs for MSI-high NSCLC, even in the presence of ALK rearrangement.