Response to nivolumab in radiation induced, BRCA-2 N372H variant, programed death ligand-1 negative, pleomorphic undifferentiated sarcoma.

Abstract

61 Background: Early results from recent studies using immune checkpoint blockade targeting programmed death 1 (PD-1) have suggested that pleomorphic undifferentiated sarcomas may have response rates of over 40%. As of now predictive biomarkers for response and resistance have been incompletely characterized. Methods: A 58-year-old man who received radiation for a head and neck squamous cell cancer, developed a radiation-induced undifferentiated pleomorphic sarcoma (UPS) in his neck in 2014. His sarcoma was resected but recurred in 2015. He received adjuvant radiation after surgical debulking in September 2015 and was found on radiation simulation scan to have new widespread metastatic disease involving liver, lung, and bone. He started treatment on nivolumab in November 2015 and has had a sustained near complete response in all lesions. Results: All sites had a near complete response to nivolumab treatment. Pre treatment tissue analysis revealed no mutations or amplifications in 134 cancer-related genes, on the Oncomine Assay (Life Technologies, Inc.). Normal tissue was noted to be heterozygous for BRCA2 N372H, while the allelic fraction of the 372H variant in the tumor was found to be 85%. Programmed death ligand-1 (PDL-1) immunohistochemistry staining of the tumor tissue was negative. Tumor infiltrating lymphocytes were not noted in the tumor tissue specimen. Conclusions: This patient exhibited a near complete response to all sites of disease, with remaining PET avidity in a single hilar node. The role of the BRCA2 variant and radiation just prior to starting nivolumab is unknown. BRCA2 N372H is a common single nucleotide polymorphism (SNP) in the population with a minor allele frequency of 0.25. Although the effect of the 372H variant on BRCA2 protein structure is predicted to be minimal, population studies have suggested a slightly increased risk of breast and ovarian cancer in homozygotes. It is possible that the radiation treatment to the site of recurrence in the head and neck, resulted in an abscopal effect enhancing the therapeutic effect of nivolumab therapy. Additional testing on his tissue is being done to further investigate the response.