The Association Between Cytoreductive Nephrectomy and Overall Survival in Metastatic Renal Cell Carcinoma with Primary Tumor Size ≤4 cm

Background: It is unknown whether the survival benefit of cytoreductive nephrectomy (CN) in metastatic renal cell carcinoma (mRCC) applies to patients with primary tumor size ≤4 cm. Objective: To test the association between CN on overall survival (OS) of mRCC patients with primary tumor size ≤4 cm. Design, setting, and participants: Within the Surveillance, Epidemiology, and End Results (SEER) database (2006-2018), all mRCC patients with primary tumor size ≤4 cm were identified. Outcome measurements and statistical analysis: Propensity score matching (PSM), Kaplan-Meier plots, multivariable Cox regression analyses, and 6-mo landmark analyses addressed OS according to CN status. Sensitivity analyses examined specific populations of special interest: systemic therapy exposed versus naïve, clear-cell (ccmRCC) versus non-clear-cell (non-ccmRCC) mRCC histology, historical (2006-2012) versus contemporary (2013-2018), and young (≤65 yr) versus old (>65 yr) patients. Results and limitations: Of 814 patients, 387 (48%) underwent CN. After PSM, the median OS was 44 versus 7 mo (Δ = 37 mo; p < 0.001) in CN versus no-CN patients. CN was associated with higher OS in overall population (multivariable hazard ratio [HR]: 0.30; p < 0.001) as well as in landmark analyses (HR: 0.39; p < 0.001). In all sensitivity analyses, CN was independently associated with higher OS: systemic therapy exposed, HR: 0.38; systemic therapy naïve, HR: 0.31; ccmRCC, HR: 0.29; non-ccmRCC, HR: 0.37; historical, HR: 0.31; contemporary, HR: 0.30; young, HR: 0.23; and old, HR: 0.39 (all p < 0.001). Conclusions: The current study validates the association between CN and higher OS in patients with primary tumor size ≤4 cm. This association is robust, controlled for immortal time bias, and valid across systemic treatment exposure, histologic subtypes, years of surgery, and patient age. Patient summary: In the current study, we tested the association between cytoreductive nephrectomy (CN) and overall survival in patients with metastatic renal cell carcinoma and small primary tumor size. We found a strong association between CN and survival, which persists even after several significant variations in patient and tumor characteristics.