OBJECTIVES: This study evaluated treatment patterns, healthcare resource utilization (HCRU) and costs, and clinical outcomes following first-line (1L) trastuzumab-contained therapy among advanced HER2-postive gastric or gastroesophageal junction (GEJ) adenocarcinoma patients.

METHODS: A retrospective cohort of patients aged ≥65 years with primary stage III/IV gastric/GEJ adenocarcinoma receiving 1L trastuzumab-contained therapies were identified from the Surveillance, Epidemiology, and End Results-Medicare linked database (2011–2019). All-cause HCRU and costs were assessed pre- and post-1L progression (proxy by second-line initiation), and during the terminal care period (30 days preceding death).

RESULTS: Among the 315 patients included, mean age was 73.9 years and 84.1% were in stage IV. Commonly used 1L regimens combined with trastuzumab were fluoropyrimidine + platinum (57.8%), chemo-monotherapy (15.9%), and taxane-based doublets (14.9%). The most frequently used regimen in second and third line was ramucirumab-based therapy. Inpatient admissions occurred in 55.9%, 66.2%, and 53.4% of patients during pre-progression, post-progression, and terminal care period, with mean length of stay being 1.2, 1.2, and 4.3 days/person-month, respectively. The mean monthly total healthcare costs were $12,356, $13,545, and $19,085 in the three periods, respectively. Treatment costs accounted for 55.7% and 56.7% during pre- and post-progression, respectively, while inpatient costs accounted for 63.8% during terminal care period. Almost half (48.9%) had ≥1 hospice visits during terminal care period. Median overall survival was 15.3 (95% confidence interval: 13.2, 16.9) months. Real-world time to next treatment or death (rwTNTD) and time on treatment (rwTOT) were 8.3 (6.7, 8.9) and 6.2 (5.8, 6.7) months, respectively.

CONCLUSIONS: These analyses characterized real-world treatment patterns and clinical outcomes in elderly patients with advanced HER2+ gastric/GEJ adenocarcinoma before the introduction of immuno-oncology therapy. This study highlights the substantial costs of care especially at the end of life and the importance of offering life-prolonging therapies to this population.