Impact of Synchronous versus Metachronous Metastasis on Outcomes in Patients with Metastatic Renal Cell Carcinoma Treated with First-line Immune Checkpoint Inhibitor–based Combinations

Background and objective The impact of time of metastasis onset with respect toprimary renal cell carcinoma (RCC) diagnosis on survival outcomes is not well characterized in the era of immune checkpoint inhibitor (ICI)-based combinations. Herein, we assessed differences in clinical outcomes between synchronous and metachronous metastatic RCC (mRCC). Methods Data for patients with mRCC treated with first-line ICI-based combination therapies between 2014 and 2023 were retrospectively collected. Patients were categorized as having synchronous metastasis if present within 3 mo of RCC diagnosis; metachronous metastasis was defined as metastasis >3 mo after primary diagnosis. Time to treatment failure (TTF), overall survival (OS), and the disease control rate (DCR) were assessed. Key findings and limitations Our analysis included 223 eligible patients (126 synchronous and 97 metachronous). Median TTF did not significantly differ between the synchronous and metachronous groups (9 vs 19.8 mo; p = 0.063). Median OS was significantly shorter in the synchronous group (28.0 vs 50.9 mo; p = 0.001). Similarly, patients with synchronous metachronous metastasis (58.7% vs. 78.4%; p = 0.002). On multivariable analyses, synchronous metastasis remained independently associated with worse OS and DCR. Conclusions and clinical implications In this hypothesis-generating study, patients with mRCC with synchronous metastasis who were treated with first-line ICI-based combinations have a poorer OS and worse DCR than those with metachronous mRCC. If these results are externally validated, time to metastasis could be included in prognostic models for mRCC. Patient summary Our study demonstrates that patients treated with current first-line immunotherapies, who present with metastasis at the initial diagnosis of kidney cancer have worse overall survival compared to those who develop metastasis later. These results can help physicians and patients understand life expectancy.