Genomic Characterization of Renal Medullary Carcinoma and Treatment Outcomes.

ABSTRACT

BACKGROUND: Renal medullary carcinoma (RMC) is a rare and aggressive type of kidney cancer that primarily affects young adults with sickle cell trait; outcomes are poor despite treatment. Identifying molecular features of this tumor could provide biologic rationale for novel targeted therapies. The objective was to report on clinical outcomes with systemic therapy and characterize molecular features. PATIENTS AND METHODS: This was a retrospective analysis on 36 patients given a pathologic diagnosis of RMC at one institution from 1995 to 2015. Tumors were analyzed for expression of SWI/SNF Related, Matrix Associated, Actin Dependent Regulator Of Chromatin, Subfamily B, Member 1 (SMARCB1) through immunohistochemistry and for genomic alterations with fluorescence in situ hybridization for SMARCB1, and targeted next-generation sequencing. Time from initiation of therapy to progression of disease and overall survival were calculated using the Kaplan-Meier method. RESULTS: The median age in the cohort was 28 (range, 12-72) years, and all patients tested had sickle cell trait. Overall survival was 5.8 months (95% confidence interval [CI], 4.1-10.9) and for 12 patients who received platinum-based therapy, median progression-free survival was 2.5 months (95% CI, 1.2-not reached). A total of 10 available tumors underwent analysis with fluorescence in situ hybridization for SMARCB1; this revealed loss of heterozygosity with concurrent translocation in 8, and biallelic loss in 2. Next-generation targeted sequencing showed no recurring mutations. CONCLUSIONS: Outcome was generally poor in this cohort of patients with RMC. Uniform loss of SMARCB1 is a key molecular feature in this tumor and mechanism of loss appears to be mostly through translocations and deletions.