Feasibility of economic analysis of Radiation Therapy Oncology Group (RTOG) 91-11 using Medicare data

The specific aim of this analysis was to evaluate the feasibility of performing a cost-effectiveness analysis using Medicare data from patients treated on a randomized Phase III clinical trial.

Cost data included Medicare Part A and Part B costs from all providers--inpatient, outpatient, skilled nursing facility, home health, hospice, and physicians--and were obtained from the Centers for Medicare & Medicaid Services for patients eligible for Medicare, treated on Radiation Therapy Oncology Group (RTOG) 9111 between 1992 and 1996. The 47-month expected discounted (annual discount rate of 3%) cost for each arm of the trial was calculated in 1996 dollars, with Kaplan-Meier sampling average estimates of survival probabilities for each month and mean monthly costs. Overall and disease-free survival was also discounted 3%/year. The analysis was performed from a payer's perspective. Incremental cost-effectiveness ratios were calculated comparing the chemotherapy arms to the radiation alone arm.

Of the 547 patients entered, Medicare cost data and clinical outcomes were available for 66 patients. Reasons for exclusion included no RTOG follow-up, Medicare HMO enrollment, no Medicare claims since trial entry, and trial entry after 1996. Differences existed between groups in tumor characteristics, toxicity, and survival, all which could affect resource utilization.

Although we were able to test the methodology of economic analysis alongside a clinical trial using Medicare data, the results may be difficult to translate to the entire trial population because of non-random missing data. Methods to improve Medicare data capture and matching to clinical trial samples are required.