A Prospective Multicenter Evaluation of Initial Treatment Choice in Metastatic Renal Cell Carcinoma Prior to the Immunotherapy Era: The MaRCC Registry Experience

Introduction: The Metastatic Renal Cell Carcinoma (MaRCC) Registry provides prospective data on real-world treatment patterns and outcomes in patients with metastatic renal cell carcinoma (mRCC). Methods and Materials: Patients with mRCC and no prior systemic therapy were enrolled at academic and community sites. End of study data collection was in March 2019. Outcomes included overall survival (OS). A survey of treating physicians assessed reasons for treatment initiations and discontinuations. Results: Overall, 376 patients with mRCC initiated first-line therapy; 171 (45.5%) received pazopanib, 75 (19.9%) sunitinib, and 74 (19.7%) participated in a clinical trial. Median (95% confidence interval) OS was longest in the clinical trial group (50.3 [35.8-not reached] months) versus pazopanib (39.0 [29.7-50.9] months) and sunitinib 26.2 [19.9-61.5] months). Non-clear cell RCC (21.5% of patients) was associated with worse median OS than clear cell RCC (18.0 vs. 47.3 months). Differences in baseline characteristics, treatment starting dose, and relative dose exposure among treatment groups suggest selection bias. Survey results revealed a de-emphasis on quality of life, toxicity, and patient preference compared with efficacy in treatment selection. Conclusion: The MaRCC Registry gives insights into real-world first-line treatment selection, outcomes, and physician rationale regarding initial treatment selection prior to the immunotherapy era. Differences in outcomes between clinical trial and off-study patients reflect the difficulty in translating trial results to real-world patients, and emphasize the need to broaden clinical trial eligibility. Physician emphasis on efficacy over quality of life and toxicity suggests more data and education are needed regarding these endpoints.