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

Purpose: Trastuzumab plus chemotherapy is an effective therapy in HER2 positive advanced gastric cancer (AGC). However, the optimal maintenance treatment in patients benefited from the first line therapy remains unclear.

Methods: In this prospective observational study, patients with HER2 positive AGC who received six cycles of trastuzumab-based first line chemotherapy were divided into two arms according to the maintenance strategy: trastuzumab monotherapy (arm A) and trastuzumab plus mono-chemo-agent derived from the initial chemotherapy (arm B). The primary end point was overall survival (OS), the secondary end points were first line progression free survival (PFS), maintenance PFS, cost-effectiveness ratios (CERs), incremental cost-effectiveness ratios (ICERs) and safety.

Results: 30 patients were in arm A received trastuzumab monotherapy and 48 were in arm B. The clinical and pathological characteristics of two arms were well balanced. There was no significant difference of median OS (16.5 vs 20.0 months, HR 0.71 P = 0.169) or PFS (7.9 vs 11.0, HR 1.06, P = 0.892) between two arms, however, adding chemo-agent could lead to a 29% reduction in mortality risk. Adverse effects including cardiac safety were also similar. 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), elder than 65 years old (HR: 0.4, P = 0.015), without liver metastasis (HR: 0.271, P = 0.008) or less than two organs of distance metastasis (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, ICER in arm A was 1.29 times higher than arm B (CERs of two arms were 19,384 vs 15,018 RMB).

Conclusion: Mono-chemo-agent combined with trastuzumab showed an advantage of absolute value and hazard ratio on OS, in addition to ICER of PFS for patients who benefit from the initial six cycles of trastuzumab-based first line therapy, especially in patients with certain clinical or treatment-related characterisitics. A large sample randomized trial is warranted.