795P - A prospective observational study on the optimal maintenance strategy in HER2-positive advanced gastric cancer treated with trastuzumab based therapy

Abstract

BackgroundTrastuzumab plus chemotherapy is an effective therapy in HER2 positive advanced gastric cancer (AGC). However, the optimal maintenance treatment in patients benefited from the initial therapy remains unclear. MethodsThis was a prospective observational study in patients with untreated HER2 positive AGC. After 6 cycles of trastuzumab combined with chemotherapy, patients who had not progression disease were divided into two arms: trastuzumab monotherapy (arm A) and trastuzumab plus single chemo-agent derived from the initial chemotherapy (arm B). Patients received CT/MRI for response evaluation every 8 weeks or anytime suspected treatment failure. Adverse effects and costs were recorded every cycles. The primary end point was overall survival (OS), secondary end points included progression free survival (PFS), cost-effectiveness ratio per progression-free life-year saved (PF-LYS) and safety. ResultsIn total, 115 HER2 positive AGC treated with trastuzumab based first line chemotherapy were registered. After 6 cycles, 78 patients (6 CR, 46 PR, 26 SD) were eligible: 30 patients were in arm A accepted trastuzumab monotherapy as their maintenance therapy, 48 were in arm B. The clinicalpathological characteristics of two arms were well balanced. There was no significant differences of median OS (16.5 vs 20.0 months, P=0.169) or PFS (7.9 vs 11.0, P=0.892) between two arms. Adverse effects were also similar including cardiac safety. Subgroup analysis showed chemotherapy additional to trastuzumab benefited on OS in patients who had stable disease (SD) of response (HR: 0.084, P=0.004), without liver metastasis (HR:0.271, P=0.008) or less than 2 organs of distance metastatic (HR: 0.263, P=0.005). The average cost per patients in arm A was 153,137 RMB and 165,195 RMB in arm B. While, PF-LYS in arm A was 1.29 times higher than arm B (19,384 vs 15,018 RMB). ConclusionsBoth maintenance therapy strategies are optional for patients who benefit from the initial 6 cycles of therapy. However, there is an advantage on PF-LYS in patients treated with trastuaumab plus single chemotherapy agent. Furthermore, continual single-chemotherapy agent was beneficial in Patients with certain characterisitic. Legal entity responsible for the studyZhongshan Hospital, Fudan University. FundingShanghai Science and Technology Funds 1741195400. DisclosureAll authors have declared no conflicts of interest.