Population-based comparative effectiveness of nephron-sparing surgery vs ablation for small renal masses

Study Type - Prognosis (cohort) Level of Evidence 2a What's known on the subject? and What does the study add? Case series of patients undergoing various forms of ablation show that it is technically feasible and possible for ablation to achieve short- and intermediate-term cancer-specific survival rates similar to those of controls undergoing partial nephrectomy. This is the first well-powered study with a controlled design to compare effectiveness between partial nephrectomy and ablation. OBJECTIVE To determine, in a population-based cohort, if disease-specific survival (DSS) was equivalent in patients undergoing ablation vs nephron-sparing surgery (NSS) for clinical stage T1a renal cell carcinoma (RCC). PATIENTS AND METHODS A retrospective cohort study was performed using patients from the Surveillance, Epidemiology and End Results cancer registry with RCC < 4 cm and no evidence of distant metastases, who underwent ablation or NSS. Kaplan-Meier and Cox regression analyses were performed to determine if treatment type was independently associated with DSS. RESULTS Between 1998 and 2007, a total of 8818 incident cases of RCC were treated with either NSS (7704) or ablation (1114). The median (interquartile range) follow-up was 2.8 (1.2-4.7) years in the NSS group and 1.6 (0.7-2.9) years in the ablation group, although 10% of each cohort were followed up beyond 5 years. After multivariable adjustment, ablation was associated with a twofold greater risk of kidney cancer death than NSS (hazard ratio 1.9, 95% confidence interval 1.1-3.3, P= 0.02). Age, gender, marital status and tumour size were also significantly associated with outcome. The predicted probability of DSS at 5 years was 98.3% with NSS and 96.6% with ablation. CONCLUSION After controlling for age, gender, marital status and tumour size, the typical patient presenting with clinical stage T1a RCC, who undergoes ablation rather than NSS, has a twofold increase in the risk of kidney cancer death; however, at 5 years the absolute difference is small, and may only be realized by patients with long life expectancies.