Genomic analysis for potential targetable mutations in relapsed and refractory germ cell tumors.

Abstract

407 Background: A large number of metastatic germ cell tumors (GCTs) are cured with platinum-based chemotherapy. Patients that have relapsed or refractory disease can be cured with salvage therapy including salvage surgery, standard dose or high-dose chemotherapy with stem-cell transplant. However, 15-20% of patients with metastatic GCT are incurable with current therapeutic options. We sought to perform a genetic analysis on a cohort of these incurable patients to determine the presence of therapeutically targetable genetic mutations. Methods: After obtaining IRB approval, patients treated at Indiana University for refractory or relapsed GCT from 2016-2019 were analyzed with a next-generation sequencing (NGS) platform. Clinically relevant genomic alterations were reviewed to determine the potential for targeted therapies. Results: 10 patients with testicular (9) or ovarian (1) GCT underwent an analysis of tissue (7), blood (1), or both (2) with a mean 2.9 potential targetable mutations per patient. Four patients had NGS from preserved gonadal tissue removed prior to chemotherapy while 6/10 sample specimens were obtained post standard (1) or high-dose (5) chemotherapy. Potential known therapeutic targets were found in 80% (8/10). Of the platforms that tested biomarkers, high microsatellite instability (MSI) (1/5), intermediate tumor mutational burden (1/4), and high PD-L1 expression of 90% (1/3) was appreciated. The MSI-high patient did not respond to pembrolizumab. A patient with a KIT only mutation did not achieve a response to imatinib. One patient with KRAS, KIT, RAF1, CCND2, MET, AR, CDK6, PDGFRA, EGFR, and BRAF mutations was treated with brentuximab and was progression free for 2.5 months. Common mutations were CCND2 (4/10), RAF1 (2/10), KIT (2/10), and KRAS (2/10). Other mutations actionable in non-GCT tumors included ERCC1, TUBB3, RRMI, PIK3CA, TOPO1 and TP53. Conclusions: NGS identifies potential clinically relevant genomic alterations. Genetic mutations may enable future effective therapies as our understanding of platinum-resistant disease evolves. To our knowledge, this is among the first reports utilizing next-generation sequencing in GCT to direct potential therapeutic agents.