OP520 Evaluating Long-Term Survival From Clinical Trials: Does Real-World Evidence Change the Paradigm?

Introduction Both patient composition and medical care received in clinical trials may not be representative of clinical practice, yet health technology assessments (HTAs) commonly use extrapolation results from trials to estimate incremental benefit. Due to data limitations, external validation of trial extrapolations are uncommon. With the goal of better estimating the benefit of new therapies in practice, we compared long-term survival estimated from real-world patients who received therapy similar to the comparator arm of the OAK trial, a phase III study of patients with advanced non-small cell lung cancer (aNSCLC) who progressed following initial chemotherapy, to standard estimation approaches. Methods We estimated long-term survival from: (i) direct extrapolation of trial survival curves; and (ii) aNSCLC patients from the United States Flatiron Health Electronic Health Record ()-derived de-identified database diagnosed between January 2011 and August 2019 who received docetaxel monotherapy after platinum-doublet and had adequate organ function as well as functional status. Patients with unknown organ function and functional status were also included. Standard parametric extrapolations were applied and selected based on visual inspection and goodness-of-fit tests for each cohort. Results Using a log-logistic model to extrapolate the trial comparator arm (N = 425), estimated lifetime mean overall survival was 19.2 months (95% confidence interval [95% CI]: 16.5–22.6), and 14.4 months (95% CI: 12.4–17.0) for the real-world cohort (N = 415). Estimated 5-year overall survival rates were 5.4 percent (95% CI: 3.9–7.3) for the trial patients, compared to 3.7 percent (95% CI: 2.6–5.0) among real-world cohort patients. Conclusions Our results suggest that directly extrapolating observed survival for trial patients may overestimate the long-term survival compared to the experience of patients treated in routine practice. Our findings have implications for those wishing to estimate the incremental benefit for novel versus established treatments. We plan to compare our results to a generic patient cohort from national cancer registry. Further EHR-based studies utilizing real world data are needed to confirm our findings and to extend beyond this use case for other cancer types and anti-neoplastic therapies.