Presentation (CTI)

OBJECTIVES: Lung cancer remains the leading cause of cancer-related mortality worldwide. Given that several immune checkpoint inhibitors (ICIs) have received accelerated approval based on surrogate endpoints, the validation of real-world surrogate measures has become increasingly important. This study aimed to evaluate the validity of time to next treatment (TTNT) and time to treatment discontinuation (TTD) as surrogate endpoints for overall survival (OS) in lung cancer patients receiving ICIs.
METHODS: Using K-CURE, a Korean National Health Insurance claims database, we identified patients with lung cancer who received ICIs (Pembrolizumab, Atezolizumab, or Nivolumab) during the study period (2012-2022). The index date was defined as the date of the first ICI prescription, with a minimum follow-up period of 42 days. TTNT was defined as the time from the index date to the initiation of subsequent chemotherapy or death, and TTD as the time to the last ICI prescription, excluding patients who received only a single administration. Spearman's and Kendall's rank correlations with OS were estimated. Kaplan-Meier analyses were conducted to estimate survival distributions. All analyses were performed using R version 4.1.0 and SAS Studio version 5.2.1.
RESULTS: Among 2,379 eligible patients, TTNT and TTD were evaluable in 2,107 and 1,903 patients, respectively. TTNT demonstrated a slightly stronger correlation with OS than TTD (Spearman’s ρ=0.717 [95% CI: 0.695-0.737]; Kendall's tau-b=0.585 [95% CI: 0.560-0.610]), whereas TTD showed lower correlation with OS (ρ=0.651 [95% CI: 0.624-0.676]; tau-b=0.482 [95% CI: 0.460-0.506]). Kaplan-Meier curves further demonstrated that TTNT showed a closer alignment with OS than TTD.
CONCLUSIONS: Both TTNT and TTD showed statistically significant correlations with OS, with TTNT demonstrating a stronger correlation, suggesting that TTNT and TTD may serve as surrogate endpoints for OS in lung cancer patients receiving ICI therapy.