Synchronous Metastasis Rates in T1 Renal Cell Carcinoma: A Surveillance, Epidemiology, and End Results Database–based Study

Background: Synchronous metastasis (SM) rates in T1 renal cell carcinoma (RCC) patients relied on historical cohorts and may not take into account the favorable stage migration toward lower tumor size (TS) that occurred in more recent years. Objective: To investigate SM rates in T1 RCC patients according to histological subtype (HS), tumor grade (TG), and TS. Intervention: Partial nephrectomy, radical nephrectomy, focal ablation, and non-interventional management. Outcome measurements and statistical analysis: Within the Surveillance, Epidemiology, and End Results database (2004–2015), 60 640 stage T1 patients were identified. SM rates were tabulated and tested in multivariable logistic regression models. Results and limitations: According to HS, average SM rates were 0%, 0.5%, 1.1%, 1.4%, 3.7%, 21.5%, and 36.2% for multilocular cystic, chromophobe, papillary, clear cell TG 1–2, clear cell TG 3–4, collecting duct, and sarcomatoid RCC, respectively. In a multivariate logistic regression model, age, TS, HS, and TG were independent predictors of SM. Bone only was the commonest metastatic site (41.0%), followed by lung only (24.5%), liver only (3.6%), and brain only (3.8%). Of all SM patients, 72.8% harbored a single metastatic site. The major limitations of this study are lack of recurrence and metastatic progression data. Conclusions: Within T1 RCC, it was possible to identify five metastatic risk categories according to SM rates: (1) multilocular cystic RCC (0%), (2) chromophobe RCC (0–2.0%), (3) clear cell TG 1–2 and papillary RCC, (4) clear cell TG 3–4 RCC (1.2–8.9%), and (5) sarcomatoid and collecting duct RCC (7.0–49.1%). The most frequent metastatic location is bone only, followed by lung only, and virtually all SMs are solitary. Patient summary: Metastatic rate varies in T1 stage renal cell carcinoma patients according to tumor size, histology, and tumor grade.