Acral Lentiginous Melanoma Harboring a ROS1 Gene Fusion With Clinical Response to Entrectinib.

Abstract

ROS1 gene fusions demonstrate oncogenic activity, and patients with non-small-cell lung cancer (NSCLC) harboring a ROS1 fusion benefit from the use of a ROS1 inhibitor; however, clinical response to ROS1 inhibitors remains largely uncharacterized outside of NSCLC. ROS1 fusions have been identified in multiple tumor types but have not been reported in cutaneous melanoma. Tumors from 22 patients with acral lentiginous melanoma (ALM) were analyzed with targeted RNA sequencing to detect fusions in ROS1, NTRK1, NTRK2, NTRK3, and ALK genes. A patient harboring a ROS1 fusion was enrolled in a phase I basket trial of a ROS1/TRK/ALK inhibitor (entrectinib). An additional 78 tumors with different subtypes of melanoma were screened by ROS1 immunohistochemistry. Targeted sequencing identified a GOPC-ROS1 fusion in a patient with ALM. The patient underwent a dramatic and durable response to entrectinib, with a RECIST (version 1.1) partial response of -38% at 3 months and -55% at 11 months. The response is ongoing, and the patient has not developed any new lesions. No additional ROS1 fusions were identified by immunohistochemistry, resulting in a frequency of 3.0% in ALM and 1.3% in all melanomas. ROS1 fusions occur and can respond to targeted therapy in cutaneous melanoma; however, they may be specific to ALM subtype. This report expands knowledge of ROS1 inhibitor response outside of NSCLC and identifies new therapeutic options for a subset of patients with ALM.