Reassessing the Racial Survival Disparity in Renal Medullary Carcinoma: The Roles of Race-Ethnicity Misclassification and Access to Surgery.

BACKGROUND: Renal medullary carcinoma (RMC) is a rare, aggressive kidney cancer affecting young Black patients. A previous analysis of the Surveillance, Epidemiology and End Results (SEER) database reported an approximately five-fold higher mortality among Black patients. We reassessed whether this disparity is reproducible and examined the roles of race-ethnicity misclassification and access to surgery. METHODS: We identified RMC cases (histology code 8510/3) in the SEER database (2000-2022). Overall survival was modelled with multivariable Cox regression and cancer-specific survival with Fine-Gray competing-risks regression. The SEER race code was reclassified into the National Institutes of Health five-class race-ethnicity scheme, and access to surgery was examined with inverse-probability-of-treatment weighting. Robustness was assessed across six analytic approaches and a leave-one-cell-out diagnostic. RESULTS: Of 148 patients, 147 were analysed (median age 27 years; 79% Black; median overall survival 9 months). The five-fold difference was not reproduced: the adjusted hazard ratio (HR) for Black versus White race was 1.17 (95% confidence interval [CI] 0.71-1.93) and the Fine-Gray subdistribution HR was 1.01 (0.58-1.76), with every CI spanning 1.0. Of 29 patients coded 'White', 17 (59%) were Hispanic and only 12 were non-Hispanic White. An apparent sex×race interaction collapsed when any single cell was removed (P = 1.0). Surgery was associated with longer survival, but this apparent benefit is likely confounded by indication and should not be interpreted as causal. CONCLUSIONS: The previously reported racial disparity in RMC was not reproducible and is better explained by race-ethnicity misclassification and access to treatment than by tumour biology. These findings caution against crude Black-White comparisons in small registry cohorts.