Characterization of Clinical Cases of Collecting Duct Carcinoma of the Kidney Assessed by Comprehensive Genomic Profiling

Background Collecting duct carcinoma (CDC) is a rare type of renal cell carcinoma (RCC) originating from the renal medulla. Clinical outcomes are poor, and there are no consensus guidelines to guide therapy. Objective To determine genomic alterations (GAs) in a series of patients with locally advanced or metastatic CDC for whom genomic profiling was performed during the course of clinical care. Design, setting, and participants Formalin-fixed, paraffin-embedded blocks or slides were obtained for 17 patients with CDC. DNA was extracted and comprehensive genomic profiling was performed in a laboratory certified under the Clinical Laboratory Improvement Amendments. Outcome measurements and statistical analysis Bayesian algorithms and local alignment algorithms were used to detect substitutions and insertions/deletions, respectively. A comparison to normal control samples was used to detect copy number alterations. Clinically relevant GAs (CRGAs) were defined as those linked to approved or investigational targeted therapies. Results and limitations The median age in the cohort was 53 yr (range 26–73), and 14 primary tumors and three metastatic sites assessed. A total of 36 GAs were detected in this series of patients, with an average of 2.1 GAs per case. The most common GAs were in NF2 (5/17, 29%), SETD2 (4/17, 24%), SMARCB1 (3/17, 18%), and CDKN2A (2/17, 12%). Of nine cases assessed for FH GAs, two patients had FH homozygous loss. A limitation is that targeted interrogation of genes known to be implicated in other cancers was performed, so mutations outside of these cannot be excluded. Conclusions Recurrent CRGAs were detected in this series of CDC cases and suggest a possible benefit from targeted therapy. In particular, mTOR inhibitors may be of interest in patients with NF2 alterations. Alterations in FH and SMARCB1 also occurred in a mutually exclusive manner to NF2 alterations. Patient summary This report provides important genomic insights into collecting duct carcinoma, a rare type of renal cell carcinoma with a very aggressive course. These insights could further rationalize the use of targeted therapies for rare tumors according to the individual genomic alterations harbored.