Primary endpoints to assess the efficacy of novel therapeutic approaches in epidermal growth factor receptor-mutated, surgically resectable non-small cell lung cancer: A review

While the discovery of oncogenic driver mutations has personalized the metastatic non-small cell lung cancer (NSCLC) treatment landscape with effective targeted therapies, implementation of new treatments in resectable NSCLC has been limited due to the long follow-up needed for overall survival (OS). Until recently, treatment for patients with early-stage resectable NSCLC has been limited to perioperative chemotherapy, which provides modest benefits. However, the regulatory acceptance of two surrogate endpoints for OS has allowed recent approval of both adjuvant osimertinib and atezolizumab, providing patients with new treatment options to improve outcomes. In phase 3 oncology trials, OS has historically been viewed as the gold-standard efficacy measure, but disease-free survival and event-free survival (EFS) are now validated surrogate endpoints for OS in clinical trials and should be considered when mature OS data is unavailable. Another potential surrogate endpoint in the adjuvant NSCLC setting is circulating tumor DNA (ctDNA)-based minimal residual disease (MRD), although prospective validation is needed. For neoadjuvant targeted therapies, EFS, major pathologic response and ctDNA-based MRD are potential surrogate endpoints. To fully translate the success of the personalized treatment advances in the metastatic setting to earlier-stage disease, prospective validation studies of these potential surrogate endpoints that can accelerate the evaluation of drug efficacy are needed. A collaborative effort is also needed from all clinical and regulatory parties to collate surrogate endpoint data for large-scale validation. In this review we discuss the trends in surrogate endpoints used in oncology trials, with a focus on considerations for selecting appropriate primary endpoints in early-stage resectable EGFR-mutant NSCLC, an area of unmet need for novel treatment options.