Syed JS, et al. - Researchers evaluated the risks of contralateral tumor development among patients treated for renal cell carcinoma (RCC) using the Surveillance, Epidemiology, and End Results database. They identified 80,403 cases of RCC, with a median follow-up of 8.3 years; metachronous, contralateral RCC developed in 1063 (1.3%) (median of 6 years after diagnosis) among these. At 10, 20, and 30 years of follow-up, they noted a cumulative incidence of 1.5%, 3.1%, and 4.7%, respectively. Findings suggest a higher cumulative incidence of metachronous, contralateral RCC than previously reported. The risk of metachronous, contralateral RCC development was higher in relation to younger age, black race, papillary histology, and male sex. All demographic groups had high standardized incidence ratios (SIRs), supporting a rationale for lifelong surveillance, especially in high-risk subgroups with early disease onset.