Correlation of multiple endpoints in the first-line chemotherapy of advanced gastric cancer: Pooled analysis of individual patient data from Japanese Phase III trials.

ABSTRACT

BACKGROUND: Individual-level surrogates are important for management in patients treated for advanced gastric cancer (AGC). This study aimed to comprehensively investigate the correlation of multiple clinical endpoints in the first-line chemotherapy of AGC. METHODS: Individual patient data (IPD) were collected from four Japanese Phase III trials comparing S-1-based first-line chemotherapies (SPIRITS, START, GC0301/TOP-002, and G-SOX trials). Patients without Response Evaluation Criteria in Solid Tumors (RECIST)-based radiological assessments were excluded. Spearman's rank correlation coefficient was tested for correlation among overall survival (OS), progression-free survival (PFS), and postprogression survival (PPS). OS, PFS, and PPS were compared between responders (best response complete response or partial response) and nonresponders (best response stable disease or progressive disease). RESULTS: The study included a total of 1492 patients. Eighty percent of the patients (n = 1190) received subsequent chemotherapies after the failure of each trial's treatment protocol. PFS moderately correlated with OS (Spearman correlation coefficient = 0.66, p < 0.005), whereas the correlation between PPS and OS was strong (Spearman correlation coefficient = 0.87, p < 0.005). Responders had significantly longer OS (median, 17.7 vs. 9.1 months, p < 0.005), PFS (median, 6.9 vs. 2.8 months, p < 0.005), and PPS (median, 10.5 vs. 6.0 months, p < 0.005) than nonresponders. CONCLUSIONS: Our results reacknowledged the mild surrogacy of PFS and importance of postprogression treatments in patients with AGC receiving first-line chemotherapy. Consistent longer survival outcomes in better RECIST categories suggested that tumor response might be a useful individual-level surrogate.