Body mass index at diagnosis, postdiagnosis change, and role of metabolic comorbidities in relation to survival in nonmetastatic renal cell carcinoma patients

BACKGROUND: Obesity is a recognized risk factor for renal cell carcinoma (RCC) incidence, but higher body mass index (BMI) measured at diagnosis has been paradoxically associated with improved survival. This study investigated whether postdiagnosis changes in BMI and metabolic comorbidities combined with BMI at diagnosis are associated with survival. METHODS: This study examined 1289 patients with nonmetastatic RCC (stage I-III) from the Oncology Research Information Exchange Network. BMI was assessed at diagnosis and at 2 and 3 years postdiagnosis. Multivariable Cox regression and restricted cubic spline models estimated hazard ratios (HRs) for overall survival (OS) and disease-free survival (DFS). RESULTS: Modest weight gain (<10%) and stability were most favorable trajectories. Compared with modest weight gain, postdiagnosis weight loss was associated with worse OS and DFS (>10% loss at 2 years: OS HR, 7.77; 95% CI, 3.00-20.16; DFS HR, 3.13; 95% CI, 1.68-5.82), independent of BMI at diagnosis, whereas substantial weight gain was associated with worse OS (>10% gain at 3 years: OS HR, 3.26; 95% CI, 1.14-9.32). Nonobese patients with diabetes had significantly worse DFS (HR, 1.83; 95% CI, 1.22-2.76), whereas the association between obesity and improved survival was mainly limited to patients without diabetes (HR, 0.75; 95% CI, 0.58-0.97). CONCLUSIONS: Postdiagnosis weight trajectory and metabolic health are important prognostic factors for nonmetastatic RCC. Weight stability and absence of diabetes were associated with more favorable outcomes. Incorporating repeated BMI measurements and diabetes status may improve risk stratification during RCC survivorship.