Outcomes of Metastatic Chromophobe Renal Cell Carcinoma (chrRCC) in the Targeted Therapy Era: Results from the International Metastatic Renal Cell Cancer Database Consortium (IMDC).

Background: Treatment outcomes are poorly characterized in patients with metastatic chromophobe renal cell cancer (chrRCC), a subtype of renal cell carcinoma. Objective: This retrospective series aims to determine metastatic chrRCC treatment outcomes in the targeted therapy era. Methods: A retrospective data analysis was performed using the IMDC dataset of 4970 patients to determine metastatic chrRCC treatment outcomes in the targeted therapy era. Results: 109/4970 (2.2%) patients had metastatic chrRCC out of all patients with mRCC treated with targeted therapy. These patients were compared with 4861/4970 (97.8%) clear cell mRCC (ccRCC) patients. Patients with metastatic chrRCC had a similar OS compared to patients with ccRCC (23.8 months (95% CI 16.7 - 28.1) vs 22.4 months (95% CI 21.4 - 23.4), respectively (p = 0.0908). Patients with IMDC favorable (18%), intermediate (59%) and poor risk (23%) had median overall survivals of 31.4, 27.3, and 4.8 months, respectively (p = 0.028). Conclusions: To the authors' knowledge, this is the largest series of metastatic chrRCC patients and these results set new benchmarks for survival in clinical trial design and patient counseling. The IMDC criteria risk categories seem to stratify patients into appropriate favourable, intermediate, and poor risk groups, although larger patient numbers are required. It appears that outcomes between metastatic chrRCC and ccRCC are similar when treated with conventional targeted therapies. Patients with metastatic chrRCC can be treated with tyrosine kinase inhibitors and enrolled in clinical trials to further measure outcomes in this rare patient population.