Real-world treatment patterns, resource use, and costs in human epidermal growth factor receptor 2–negative advanced gastric/gastroesophageal junction cancer in the United States in the immune checkpoint inhibitor era

BACKGROUND: Since 2021, new therapies including immune checkpoint inhibitors (ICIs) have been approved in the United States for human epidermal growth factor receptor 2 (HER2)-negative advanced gastric or gastroesophageal junction cancer (G/GEJC) in biomarker-selected populations. However, recent data on treatment patterns, health care resource utilization (HCRU), and costs remain limited. OBJECTIVE: To describe real-world patient characteristics, treatment patterns, HCRU, and costs among patients with HER2-negative advanced G/GEJC in the Medicare and MarketScan databases. METHODS: Two retrospective observational cohort studies were conducted using the 100% Medicare Fee-for-Service database and the Merative MarketScan Commercial and Medicare Databases. Patients with advanced G/GEJC initiating first-line (1L) non-HER2-targeted systemic anticancer therapy from 2021 to 2024, continuously enrolled for at least 6 months before and at least 1 month after the 1L initiation (index date), were identified. Primary outcomes including treatment patterns, HCRU, and costs were assessed from the index to death, disenrollment, or study end, whichever occurred first. Real-world overall survival (rwOS) was assessed as a secondary outcome in the Medicare database. RESULTS: We identified 2,029 and 419 patients in the Medicare and MarketScan databases, respectively. Across both databases, chemotherapy was the most common 1L regimen (approximately 50%), followed by nivolumab-containing regimens (34.7% in Medicare; 44.2% in MarketScan) and pembrolizumab-containing regimens (9.9% and 5.3%, respectively). In both databases, 38.2% of patients received second-line (2L) therapy and 11.7% received third-line (3L) therapy. Nivolumab-containing regimens were the most common 2L treatment (36.3% in Medicare; 41.3% in MarketScan), whereas ramucirumab-containing regimens were most common in 3L (36.7% and 34.0%, respectively). Outpatient visits accounted for the majority of HCRU across lines of therapy, with mean visits per patient per month (PPPM) of 3.7, 3.8, and 3.6 in Medicare and 7.7, 6.5, and 6.6 in MarketScan for 1L, 2L, and 3L, respectively. Mean total all-cause health care costs increased with line of therapy and were higher in MarketScan than Medicare: $17,191, $19,572, and $19,373 PPPM in Medicare and $47,092, $62,358, and $73,192 PPPM in MarketScan for 1L, 2L, and 3L, respectively. Outpatient costs accounted for more than half of total health care costs in both databases. Among Medicare patients, median 1L rwOS was 10.9 months. CONCLUSIONS: Analyses of recent data from the Medicare and MarketScan databases showed that most treated patients with HER2-negative advanced G/GEJC received standard chemotherapy in the 1L setting. Treatment of advanced G/GEJC remains associated with poor rwOS and high economic burden, suggesting significant remaining unmet need.