The very favorable metastatic renal cell carcinoma (mRCC) risk group: Data from the International Metastatic RCC Database Consortium (IMDC).

339 Background: The IMDC criteria have been used as a prognostic tool for patients with mRCC receiving single agent VEGF-targeted drugs, and more recently combination immuno-oncology (IO) +/- VEGF-targeted agents, which improve outcomes over VEGF TKI monotherapy. We sought to identify a subset of patients with very favorable outcomes, for which less intensive therapy might be considered. Methods: Utilizing the IMDC dataset, 1638 patients with IMDC favorable risk disease received first-line systemic therapy. Patients were randomly selected in a 2:1 ratio to the training and testing sets, stratified by year of systemic therapy initiation. Multivariable Cox regression estimated prognostic factors for overall survival (OS). Results: Median age was 63 (range 21-95) years and 98% had received prior nephrectomy. First-line systemic therapy consisted of targeted therapy (91%), IO-combination regimens (8%), or other (1%). From the training data, three variables (primary diagnosis to systemic therapy 80; presence of brain, liver, or bone metastasis) significantly predicted for OS in the multivariable model (hazard ratio 1.4~1.5, p-values<0.05). The model had similar performance in the test dataset (C-index=0.64). Using the 3 included risk factors, patients were classified to very favorable risk (0 risk factors, 29% of patients) or favorable risk disease (≥1 risk factors, 71% of patients). Clinical outcomes for the two risk groups are presented in the table below. Conclusions: We identified a very favorable risk group in the IMDC criteria in RCC patients treated with first-line therapy. External validation including populations receiving IO containing therapies is ongoing. Table: see text