Background: Trastuzumab (T-mab) combined with cisplatin and fluoropyrimidines is a standard first-line treatment for HER2+ advanced gastric cancer (AGC). We conducted the first phase II trial among four Japanese study groups to assess the efficacy and safety of T-mab + S-1 and oxaliplatin (T-SOX130) for HER2+ AGC or recurrent gastric cancer.
Methods: Patients with IHC 3+ or IHC 2+/FISH+ tumors received 80 mg/m2 (80-120 mg/day) oral S-1 on days 1-14, 130 mg/m2 intravenous oxaliplatin on day 1, and intravenous T-mab (8 mg/kg loading dose, 6 mg/kg thereafter) on day 1 of a 21-day cycle. The primary endpoint was centrally assessed response rate (RR). Adverse events were based on the Common Terminology Criteria for Adverse Events (CTCAE) Ver.4.0.
Results: We enrolled 42 patients from June 2015 to May 2016. Efficacy and safety analyses were conducted for 39 patients. The data cutoff was May 31, 2018. The confirmed RR was 82.1% (32/39; 90% CI 70.0-90.0); the disease control rate was 87.2% (34/39; 95% CI 73.3-94.4). Nine patients underwent curative surgery after T-SOX130. Median Time to treatment failure (TTF), Progression-free survival (PFS) and Overall survival (OS) was 5.7 (95% CI 4.6-7.0), 7.0 (95% CI 5.5-14.1), and 27.6 (95% CI 15.6-Not reached) months, respectively. Incidences of grade 3-4 adverse events > 10% were thrombocytopenia (17.9%), anorexia (17.9%), anemia (12.8%), neutropenia (10.3%), and hyponatremia (10.3%).
Conclusions: T-SOX130 showed promising response and survival with a favorable safety profile and should be considered for patients with HER2+ AGC.
Keywords: HER2-positive advanced gastric cancer; SOX plus trastuzumab.