Real-world prognosis of sporadic bilateral RCC: a propensity score-based comparison of synchronous and metachronous...

To examine the prognostic differences between metachronous and synchronous sporadic bilateral renal cell carcinoma (BRCC).

This cohort study was conducted in the Surveillance, Epidemiology, and End Results database among patients diagnosed with BRCC between 2004 and 2021. Patients were categorized into synchronous and metachronous groups (synchronous tumors occurred within 6 months of the first RCC diagnosis, while metachronous tumors occurred more than 6 months after the first RCC diagnosis). The propensity score matching (PSM) approach was employed to compare these two groups. Cox's regression analysis evaluated cancer-specific survival (CSS) and overall survival (OS). Interaction, sensitivity, and subgroup analyses were also performed to test the results' robustness.

A total of 4694 patients with BRCC were included, with 2710 (57.7%) in the synchronous group and 1984 (42.3%) in the metachronous group. After applying PSM, patient characteristics between the two groups were well balanced. Over a median follow-up of 85 months (interquartile range: 43-132 months), significant differences were noted between the synchronous and metachronous groups in both CSS [hazard ratio (HR) = 2.661, 95% confidence interval (CI): 1.987-3.564, P < 0.001] and OS (HR = 2.481, 95% CI: 2.060-2.988, P < 0.001). Stratified Cox regression accounting for matched pairs indicated poorer CSS (HR = 3.170, 95% CI: 2.081-4.828, P < 0.001) and OS (HR = 2.631, 95% CI: 2.116-3.270, P < 0.001) in the synchronous group. The robustness of these results was supported by multivariate competing risk regression, as well as interaction, sensitivity, and subgroup analyses.

Synchronous BRCC was associated with poorer survival than the metachronous group. These findings may offer important insights for managing patients with BRCC.