Real-World Treatment Patterns and Economic Burden Following First-Line Trastuzumab in Patients with Metastatic Gastric Cancer in the USA.

Background: Trastuzumab in combination with chemotherapy is the standard first-line (1L) treatment for HER2+ metastatic gastric cancer (mGC) in the USA.

Objective: This study characterizes the real-world treatment patterns, healthcare resource use (HRU), and costs in patients with HER2+ mGC post-1L trastuzumab before approval of fam-trastuzumab deruxtecan-nxki.

Patients and methods: This retrospective study used the IQVIA PharMetrics^® Plus Database (October 2014-September 2019) to identify adults with HER2+ mGC who discontinued trastuzumab-based regimens in 1L. Patient characteristics, second-line (2L) treatment patterns, and treatment duration were summarized. HRU and costs before and after discontinuation of 1L trastuzumab-based regimens as well as during 2L treatment were described.

Results: Of the 190 HER2+mGC patients who discontinued 1L trastuzumab-based regimens, 136 (71.58%) initiated 2L treatments. Trastuzumab-based regimens were the most common in 2L (50.74%), followed by ramucirumab + paclitaxel (19.85%). The median time to 2L discontinuation was 2.37 months. During a mean follow-up of 9.8 months, mean per-patient-per-month (PPPM) healthcare costs post-1L trastuzumab-based regimens were higher in patients receiving 2L treatment than those without subsequent treatment (US$25,178 vs. US$14,812). The mean PPPM cost during 2L treatment was US$30,838, primarily driven by outpatient infusion costs (US$22,262).

Conclusions: The short duration of 2L treatment observed in this study is consistent with a lack of effective treatments post-1L trastuzumab prior to 2020. Re-use of trastuzumab treatment was common despite its limited efficacy and high treatment cost. The findings highlight the unmet medical needs and substantial burden faced by patients with HER2 +mGC previously treated with trastuzumab.