Risk factors for metachronous bilateral renal cell carcinoma: A Surveillance, Epidemiology, and End Results analysis

Background Patients treated for renal cell carcinoma (RCC) may be diagnosed with a metachronous, contralateral tumor. We evaluated the risks of contralateral tumor development using the Surveillance, Epidemiology, and End Results database. Methods Among RCC patients, we identified those with a metachronous, contralateral RCC diagnosed ≥1 year after primary diagnosis. We performed a competing risks analysis to evaluate associations between clinicopathologic factors and metachronous, bilateral RCC. Cumulative incidence and standardized incidence ratios (SIRs) were calculated. Results There were 80,403 cases of RCC identified, with a median follow‐up of 8.3 years; of these, 1063 (1.3%) developed metachronous, contralateral RCC (median of 6 years after diagnosis). The cumulative incidence at 10, 20, and 30 years of follow‐up was 1.5%, 3.1%, and 4.7%, respectively. An increased risk was observed among men (hazard ratio [HR], 1.36; 95% confidence interval [CI], 1.20‐1.55), blacks (HR, 2.00; 95% CI, 1.71‐2.33), and those with papillary histology (HR, 1.72; 95% CI, 1.41‐2.10). Risk of metachronous disease decreased with increasing age at primary diagnosis (HR per 1‐year increase, 0.97; 95% CI, 0.96‐0.97). The SIRs were highest among those diagnosed at a younger age and remained elevated even after extended follow‐up (>10 years). Conclusions Our findings suggest that the cumulative incidence of metachronous, contralateral RCC may be higher than previously reported. Younger age, black race, papillary histology, and male sex increase the risk of metachronous, contralateral RCC development. The high SIRs seen in all demographic groups may support a rationale for lifelong surveillance, especially in high‐risk subgroups with early disease onset.