Impact of Tumor Size on Cancer-Specific Mortality Rate after Local Tumor Ablation in T1a Renal-Cell Carcinoma

Introduction: Institutional studies suggested that tumor size (TS) might be an independent predictor of recurrence after local tumor ablation (LTA). However, limited data exist to ascertain whether a larger TS may also predispose to a worse cancer-specific mortality (CSM) rate. Materials and Methods: Patients treated with LTA for T1a nonmetastatic renal-cell carcinoma were identified within the Surveillance, Epidemiology, and End Results (SEER) database (2004-2015). Estimated annual percentage change (EAPC) methodology, cumulative incidence plots, and multivariable competing risk regression (CRR) models before and after the 1:1 ratio propensity score (PS) adjustment were used to compare LTA for TS <= 30 mm vs TS >30 mm. A comparison of cryosurgery vs thermal ablation according to TS was also performed. Results: Of 3946 LTA patients, 2974 (75.3%) patients harbored TS <= 30 mm vs 972 (24.7%) harbored TS >30 mm. The latter was significantly older (median age 67 years vs 71 years, p < 0.001), compared with TS <= 30 mm. No differences were recorded in annual rates over time. In unmatched CRR models, after adjustment for other-cause mortality (OCM) rate, LTA for TS >30 mm showed a worse 5-year CSM rate (hazard ratio [HR] 2.3, p < 0.001), relative to TS <= 30 mm. In PS- and OCM rate-adjusted CRR models, LTA for TS >30 mm still showed a worse 5-year CSM rate (HR 2.86, p < 0.001), relative to TS <= 30 mm. Thermal ablation was associated with a higher 5-year CSM rate, compared with cryosurgery (7.6% vs 3.9%, p = 0.02), but only when TS was >30 mm. Conclusions: TS >30 mm is an independent predictor of higher 5-year CSM rates in patients treated with LTA, even after adjustment for OCM rate. In consequence, when LTA is considered, it ideally should be performed for TS <= 30 mm.