Inverse probability weighting to control for censoring in a post hoc analysis of quality-adjusted survival data from a clinical trial of temsirolimus for renal cell carcinoma
Objective: This post hoc analysis evaluated treatment-associated quality-adjusted survival (QAS) in patients randomly assigned to temsirolimus or interferon alfa (IFN-alfa), corrected for censoring using inverse probability weighting (IPW), in the Advanced Renal Cell Carcinoma (ARCC) trial. Methods: Follow-up was divided into 11 time intervals; Kaplan-Meier estimates for not being censored were estimated for each interval. The QAS for each interval was weighted by the inverse probability of not being censored in that interval. Overall treatment-associated QAS was calculated as the sum of the weighted QAS across all follow-up intervals. Differences in mean QAS between temsirolimus and IFN-alfa were evaluated with t-statistics at a two-sided αÎ± =0.05. Results: In total, 416 patients were randomly assigned to temsirolimus (n=209) or IFN-alfa (n=207); 400 patients were included in this analysis. Overall weighted mean (standard deviation) QAS during progression-free survival was 111.9 (5.3) days with temsirolimus (n=204) and 75.7 (6.3) days with IFN-alfa (n=196). The mean weighted QAS difference of 36.2 days in favor of temsirolimus was significant (p<0.05). Limitations: One potential limitation is that the weights developed by the Kaplan-Meier estimates did not allow for covariates to be adjusted among treatment arms. Another possible limitation is that the ARCC trial included patients with advanced renal cell carcinoma, and thus it cannot be conclusively determined how our findings would apply to patients with less advanced disease. Conclusions: Patients with poor-prognosis advanced renal cell carcinoma treated with temsirolimus had an incremental gain of 48% (36.2 days) in QAS compared with patients treated with IFN-alfa.
- Renal cell carcinoma
- Health outcomes research
- Inverse probability weighting
- Quality-adjusted survival