Study to Evaluate SBRT for EGFR Mutant NSCLC Patients Receiving Osimertinib (CULTRO)

Phase II study with a single-stage Fleming design based on a normal approximation to the binomial distribution, with a one-sided type I error of 10% and a power of 90% to detect 30 events related to disease progression. Under the alternative hypothesis to detect a 35% improvement in PFS, 35 patients are required to be recruited over 22 months, with a minimum median follow-up of 14 months. An interim analysis will be conducted to determine early termination of the study using a Lan-DeMets monitoring boundary and an O'Brien-Fleming stopping rule. The interim analysis will be performed when 20 out of the expected 30 events have been observed. Employing the O'Brien-Fleming statistic, the critical value for the Z-score in the interim analysis (to stop and reject the null hypothesis) will be 1.054, and the critical value for the Z-score to stop and reject the alternative (futility) will be -0.204.