Meta-analysis to Investigate the Correlation Between Event-Free Survival and Overall Survival in Patients with Resectable Locally Advanced Head and Neck Squamous Cell Carcinoma

While overall survival (OS) is a widely accepted trial endpoint in oncology, survival data are often immature in early-stage populations. Alternative time-to-event outcomes have been considered by regulatory and reimbursement agencies to allow for early patient access. Event-free survival (EFS) has shown strong correlations with OS in patients with locally advanced (LA) head and neck squamous cell carcinoma (HNSCC) and within the subgroup with unresectable tumors. With novel neoadjuvant and adjuvant immunotherapies being investigated in resectable LA-HNSCC, this study aimed to assess the trial-level correlation of EFS and OS in patients with resectable LA-HNSCC. A systematic review (October 29, 2024) identified randomized controlled trials evaluating surgery with adjuvant therapy, neoadjuvant therapy, or both in patients with resectable LA-HNSCC. Trials reporting hazard ratios (HRs) or Kaplan-Meier curves for OS (time from randomization to death) and EFS (time from randomization to disease progression/recurrence or death) were eligible for the analysis. Base case included trials comparing neoadjuvant therapy + surgery + adjuvant therapy versus surgery + adjuvant therapy. Sensitivity analyses included models with trials comparing broader regimens (e.g., adjuvant therapy versus adjuvant therapy), excluding an outlier trial and restricting to publications after 2004. Correlations were measured between log(EFS HR) and log(OS HR) using regression models, with their strength measured using Pearson's correlation coefficient (R). The review included 45 trials, with 20 trials qualifying for correlation analysis. R (95% confidence interval) was 0.91 (0.36, 0.99) in the base case (n = 5 trials) and 0.41 (−0.01, 0.71; n = 20), 0.78 (0.52, 0.91; n = 19), and 0.76 (0.41, 0.92; n = 13) in the three sensitivity analyses, respectively. Strong trial-level correlations were observed between EFS and OS, suggesting EFS is a valid surrogate for OS in patients with resectable LA-HNSCC, particularly in trials investigating neoadjuvant therapy + surgery + adjuvant therapy. When studying new cancer treatments, researchers often measure treatment success using overall survival. This assesses how long patients live after treatment. However, in early-stage cancers, it can take years to see differences in survival between treatment groups. This makes it difficult to quickly assess whether a new treatment is effective. Another measure, event-free survival, documents the time before a patient's cancer progresses or recurs, or the patient dies. Because these events usually happen sooner than death, event-free survival may help researchers and doctors evaluate treatments more quickly. In this study, we focused on head and neck squamous cell carcinoma that is locally advanced but still can be removed with surgery. We reviewed published clinical trials that tested treatments given before or after surgery, such as radiation or drug therapies. We examined how closely event-free survival matched overall survival across different trials. A strong match would mean event-free survival could be used as an early signal of treatment benefit. We found that in trials where patients received treatment before surgery (sometimes followed by additional treatment after surgery), there was a strong link between event-free survival and overall survival. This suggests that event-free survival is a good early indicator of how well patients do in the long term. Our findings support the use of event-free survival as a meaningful outcome in future clinical trials for this type of cancer.