Synchronous Bilateral RCC Is Associated With Poor Recurrence-Free Survival Compared With Unilateral RCC: A Single-Center Study With Propensity Score Matching Analysis

Background: Understanding the tumorigenesis of bilateral cancers occurring in paired organs is essential for treatment planning and follow-up strategies. To the best of our knowledge, only a few studies compared the survival outcomes in patients with unilateral and bilateral renal cell carcinoma (RCC). We aimed to evaluate the survival outcomes of these patients after surgery and perform a further comparison of synchronous and metachronous bilateral RCCs. Materials and Methods: We analyzed clinical data from a total of 2169 patients (98.0%) diagnosed with unilateral RCC and 44 patients (2.0%) diagnosed with bilateral RCC including 22 (50.0%) with synchronous (diagnosed concomitantly or within 3 months of the former tumor) and 22 (50.0%) with metachronous RCC at our institution. Comparative analysis of unilateral and bilateral RCC groups was conducted using propensity score matching analysis. Subgroup analysis of bilateral RCC including synchronous and metachronous RCCs was also performed. Results: Kaplan–Meier survival analysis showed a significantly decreased 5-year recurrence-free survival (RFS; 82.6% vs. 94.3%; log rank test, P =.045) in the bilateral RCC group compared with the unilateral group. In subgroup analysis, the metachronous RCC group showed significantly smaller mean pathologic tumor size (P =.011), and more favorable pathologic T stage (P =.036) compared with the synchronous RCC group. Kaplan–Meier survival analysis showed significantly decreased 5-year RFS in synchronous RCC compared with metachronous RCC (74.7% vs. 92.9%; log rank test, P =.028). Conclusion: The bilateral RCC group showed significantly decreased 5-year RFS compared with the unilateral RCC group. Importantly, the synchronous RCC group manifested more adverse features than the metachronous group.