Trastuzumab in combination with docetaxel/cisplatin/S-1 (DCS) for patients with HER2-positive metastatic gastric cancer: feasibility and preliminary efficacy.

Abstract

We previously reported that a triplet combination of docetaxel, cisplatin, and S-1 (DCS) is active against metastatic gastric cancer with a very high response rate of 87.1 % in a phase II study. Recently, the efficacy of trastuzumab (T-mab) for the treatment of HER2-positive gastric cancer has been reported. Therefore, we investigated the feasibility and preliminary efficacy of DCS + T-mab (DCS-T) for unresectable HER2-positive metastatic gastric cancer. Patients received oral S-1 (40 mg/m(2) b.i.d.) on days 1-14, intravenous cisplatin (60 mg/m(2)), docetaxel (50 mg/m(2)), and T-mab (8 mg/kg in the first cycle and 6 mg/kg in the second cycle and thereafter) on day 8 every 3 weeks. The study included 16 patients: median age, 60 (34-76) years; males/females, 11:5; intestinal-type/diffuse-type histology, 11:5; and HER2 3+/2+(FISH+), 13:3. The completion rate until the third cycle was 87.5 % (14/16) (95 %CI 71.3-103.7 %). Adverse events of grade 3/4 severity during the first 3 cycles were: leukopenia/neutropenia, 50.0:75.0 %; febrile neutropenia, 12.5 %; diarrhea, 12.5 %; and stomatitis, 12.5 %. All of these side effects were manageable and well controlled. There were no treatment-related deaths. The overall response rate was 93.8 % (15/16), and the response rate in patients with measurable lesions was 100 % (15/15). The median cycle to response was only 1 (1-3 cycles). Non-curative factors disappeared in 56.3 % (9/16) of patients, and conversion surgery (R0 resection) was performed in all these cases. Pathological response rates in primary and metastatic lesions were 88.9 % (8/9) and 100 % (9/9), respectively. The median PFS and OS were not reached during the median follow-up time of 18.3 months ranged from 11.0 to 34.3 months. DCS-T was feasible in patients with unresectable HER2-positive metastatic gastric cancer. The observed response was very promising and warrants further investigation. UMIN000005603.