[Value of bootstrapping for small series of patients: application to survival analysis for 26 patients followed for bilateral sporadic renal cell carcinoma].
OBJECTIVE: To use Bootstrapping to estimate the Kaplan-Meier survival of sporadic forms of bilateral renal cell carcinoma (RCC). PATIENTS AND METHODS: Over a period of 13 years, 759 patients were operated for RCC. 26 patients had bilateral sporadic RCC (3.4%) and 23 of them were reviewed with a median follow-up of 50 months (range: 7.8 to 143.4). The 95% confidence interval (95% CI) of Kaplan-Meier survival was estimated according to the Greenwood (Gw) normalized method and by Bootstrap percentile (B*) with B = 1000. RESULTS: The overall 1-year and 5-year survival rates were 95.8% (95% CI Gw: [87.6-100] and B*: [92.1-96.4]) and 73.6% (95% CI Gw: [54.9-92.15] and B*: [72.3-86.5%]), respectively. CONCLUSION: For diseases with a low incidence, Bootstrapping can improve the precision of the Kaplan-Meier survival estimate, by providing a narrower CI. This statistical technique provides the clinician with more precise results in a study limited by a small number of patients.