Cryoablation is done in select patients with pT1b nonmetastatic renal cell carcinoma without convincing proof of efficacy. Our aim was to test for differences in the cancer specific mortality rate for cryoablation and partial nephrectomy in T1b nonmetastatic renal cell carcinoma cases.
Materials and Methods
In the 2004 to 2015 SEER (Surveillance, Epidemiology, and End Results) database we identified 5,763 patients with a T1b tumor treated with cryoablation or partial nephrectomy. Modeling relied on multivariable logistic regression models predicting cryoablation vs partial nephrectomy. After 1:2 ratio propensity score matching between patients treated with cryoablation vs partial nephrectomy we used cumulative incidence plot and competing risks regression to test differences in cancer specific mortality and other cause mortality rates.
Relative to the 5,521 patients who underwent partial nephrectomy the 242 treated with cryoablation were older, had smaller tumors and more frequently harbored unclassified renal cell carcinoma of low or unknown grade. Median followup was 38 months. In multivariable logistic regression models predicting cryoablation vs partial nephrectomy more advanced patient age was an independent predictor (OR 1.03; p=0.007). After propensity score matching and other cause mortality adjustment the 5-year cancer specific mortality rate was 2.5-fold higher after cryoablation than after partial nephrectomy (p=0.03). Conversely after propensity score matching and cancer specific mortality adjustment the 5-year other cause mortality rate was similar to that of partial nephrectomy after cryoablation (HR 1.45, p=0.12). The major limitation of this study was the lack of recurrence and metastatic progression data.
The current findings demonstrated a 2.5-fold increase in cancer specific mortality when cryoablation was performed in patients with pT1b renal cell carcinoma. This observation should be interpreted as a contraindication to cryoablation outside clinical trials or institutional protocols.