Race Modifies Survival Benefit of Guideline-based Treatment: Implications for Reducing Disparities in Muscle Invasive Bladder Cancer

Background: Black individuals with muscle-invasive bladder cancer (MIBC) experienced 21% lower odds of guideline-based treatment (GBT) and differences in treatment explain 35% of observed Black-White differences in survival. Yet little is known of how interactions between race/ethnicity and receipt of GBT drive within- and between-race survival differences.

Methods: Black, White, and Latino individuals diagnosed with nonmetastatic, locally advanced MIBC from 2004 to 2013 within the National Cancer Database were included. Guideline-based treatment was defined as the receipt including one or more of the following treatment modalities: radical cystectomy (RC), neoadjuvant chemotherapy with RC, RC with adjuvant chemotherapy, and/or chemoradiation based on American Urological Association guidelines. Cox proportional hazards model of mortality estimated effects of GBT status, race/ethnicity, and the GBT-by-race/ethnicity interaction, adjusting for covariates.

Results: Of the 54 910 MIBC individuals with 125 821 person-years of posttreatment observation (max = 11 years), 6.9% were Black, and 3.0% were Latino. Overall, 51.4%, 45.3%, and 48.5% of White, Black, and Latino individuals received GBT. Latino individuals had lower hazard of death compared to Black (HR 0.81, 95% CI 0.75-0.87) and White individuals (HR 0.92, 95% 0.86-0.98). With GBT, Latino and White individuals had similar outcomes (HR = 1.00, 95% 0.91-1.10) and both fared better than Black individuals (HR = 0.88, 95% 0.79-0.99 and HR = 0.88, 95% 0.83-0.94, respectively). Without GBT, Latino individuals fared better than White (HR = 0.85, 95% 0.77-0.93) and Black individuals (HR = 0.74, 95% 0.67-0.82) while White individuals fared better than Black individuals (HR = 0.87, 95% 0.83-0.92). Black individuals with GBT fared worse than Latinos without GBT (HR = 1.02, 95% 0.92-1.14), although not statistically significant.

Conclusion: Low GBT levels demonstrated an "under-allocation" of GBT to those who needed it most-Black individuals. Interventions to improve GBT allocation may mitigate race-based survival differences observed in MIBC.