The association between facility case volume and overall survival in patients with metastatic renal cell carcinoma in the targeted therapy era

Background: Improved overall survival of cancer patients treated by high-volume providers has been reported in surgical oncology and radiation oncology literature. Whether this volume-outcome association exists in medical oncology-managed metastatic solid tumors is uncertain. This study aimed to investigate the effect of facility case volume (FCV) on overall survival in patients with metastatic renal cell carcinoma (mRCC) diagnosed in the targeted therapy era.

Materials and methods: Adult patients diagnosed with mRCC between 2006 and 2015 were identified in the National Cancer Database. The primary exposure was FCV, which was defined by mRCC case volume of each treating facility. The association between FCV and all-cause mortality in mRCC was investigated in multivariable Cox regression model and validated with inverse propensity-score weighting method. Logistic regression was used to identify independent predictors for treatment at high-volume facilities. Covariates adjusted for were sociodemographics, tumor characteristics and treatment modalities.

Results: There were 31,329 mRCC patients identified. The mean follow-up time was 14.3 months. When FCV was coded as a continuous variable, each increment of 10 mRCC cases/y was associated with reduced all-cause mortality after baseline covariates adjustment [adjusted hazard ratio: 0.93, 95% confidence interval: 0.90-0.96, P value:<0.0001]. In dichotomized models, improved all-cause mortality was observed at cutoffs of 85th (4.3 cases/y), 90th (5.4 cases/y) and 95th (7.4 cases/y) but not at 50th (2.2 cases/y) and 75th (3.4 cases/y) percentiles. For illustrative purpose, 95th percentile was chosen and inverse propensity-score weighting-adjusted Kaplan-Meier curve demonstrated improved overall survival for mRCC patients treated at high-volume facilities (adjusted hazard ratio: 0.90, 95% confidence interval: 0.88-0.94, P value <0.0001; the 1-, 2-, 3-year survival rates were 41%, 26%, and 19% vs. 36%, 22%, and 16% for patients treated at high and low-volume facilities, respectively). Patients without insurance or with Medicaid status, with shorter travel distance, living in nonmetropolitan area or in area with lower averaged education level were less likely to be treated at high-volume facilities.

Conclusions: Patients diagnosed with mRCC in the targeted therapy era have improved overall survival when treated at high mRCC-volume facilities, suggesting a volume-outcome association in medical oncology-managed metastatic solid tumors.