Quantifying the value of older adult-specific clinical trials: Post-lumpectomy irradiation among older adults with early-stage breast cancer.

Introduction: Although there is increasing interest in conducting cancer clinical trials in older adults, the benefit of such trials is unclear. We aimed to quantify the real-world clinical and economic effects of two phase 3 trials (CALGB 9343 and PRIME II) which showed that post-lumpectomy radiation therapy (RT) improves loco-regional recurrence but makes no improvement in overall survival among older women with early-stage breast cancer (ESBC).

Materials And Methods: We developed a health-transition model to quantify the incremental clinical and economic outcomes between scenarios with vs. without older adult-specific trial results from a societal perspective between 2004 and 2018. The transition probabilities in the model were mainly derived from the 10-year results of CALGB 9343. The total number of the affected patient population in the US and the change in the probability of omitting post-lumpectomy RT due to the CALGB 9343 and PRIME II results were derived from a retrospective analysis of the SEER registry data for patients with ESBC. Sensitivity analyses were conducted to calculate the 95% credible interval (CR) of the incremental clinical and economic outcomes between the two scenarios.

Results: Between 2004 and 2018, 32,936 (95% CR: 31,512, 34,357) fewer patients received post-lumpectomy RT among those aged 70 years or older diagnosed with ESBC in the US and there was a decrease cost of $419 M USD (95% CR: -$238 M, -$689 M) in scenarios with vs. without older adult-specific trial results. The difference in projected life years (1083 years, 95% CI: -2542, 7985) and QALYs (866 years, 95% CI: -2561, 7780) were not significant. At a willingness-to-pay threshold of $100 k/QALY, the probability of older adult-specific trial results generating a positive net monetary benefit was 98%.

Discussion: The CALGB 9343 and PRIME II trial results were associated with a substantial cost-saving in the US society. Our results suggest that older adult-specific clinical trials that demonstrate no survival benefit of an intervention in older adults could be correlated with a significant monetary benefit. Further case studies are needed for different types of older adult-specific trials to understand the value of older adult-specific trials comprehensively.