Phase II study of trastuzumab in combination with S-1 and cisplatin in the first-line treatment of human epidermal growth factor receptor HER2-positive advanced gastric cancer

PURPOSE

The use of trastuzumab, a monoclonal antibody targeting the HER2 protein, in combination with 5-fluorouracil/platinum-based chemotherapy improves survival in patients with HER2-positive advanced gastric cancer. In addition, TS-one (S-1)/platinum is also used as a standard of care in Asian countries. However, little is known about the combination of S-1/cisplatin chemotherapy and trastuzumab in patients with HER2-positive advanced gastric/gastroesophageal junction (GEJ) cancer.

METHODS

We conducted a single-arm, two-stage, open-label, multicenter phase II study. Trastuzumab was administered intravenously on day 1 of the first cycle at 8 mg/kg and 6 mg/kg on day 1 of subsequent cycles. Cisplatin was administered intravenously at 60 mg/m(2) on day 1 of each cycle after trastuzumab. S-1 was administered orally [based on body surface area (BSA)] twice a day for 14 days in a 3-weekly cycle. Patients with BSA of <1.25 received a total of 80 mg of S-1, those with BSA ≥1.5 received 120 mg, and the remaining received 100 mg daily in two divided doses.

RESULTS

All evaluable patients experienced tumor reduction during the trial. The primary end point (overall survival rate) was 59.3 %, with a clinical benefit rate of 66.7 %. Median progression-free survival was 7.4 months; 62.6 % patients were free from disease progression at 6 months. Median overall survival was 14.6 months, and the median time to treatment failure was 6.0 months.

CONCLUSION

The combination of trastuzumab with S-1 and cisplatin demonstrated good activity, was generally well tolerated, and is a feasible treatment option in the first-line treatment of HER2-positive advanced gastric/GEJ cancers.

Phase II study of sequential treatment with S-1 and cisplatin for metastatic gastric cancer

PURPOSE

This single-arm, phase II clinical study evaluated the efficacy and safety of sequential treatment with S-1 followed by cisplatin in patients with advanced or recurrent gastric cancer.

METHODS

Fifty patients with histologically confirmed advanced or recurrent gastric cancer and an Eastern Cooperative Oncology Group performance status of 0-2 who had measurable and/or assessable lesions and gave written informed consent were enrolled. S-1 (40 mg/m(2), bid) was administered on days 1-21, and cisplatin (70 mg/m(2)) was given as an intravenous infusion on day 22 of a 35-day cycle. Treatment was continued until disease progression or intolerable adverse events. Cisplatin was administered for 6 cycles. Adverse events were assessed according to Common Terminology Criteria of Adverse Events version 3.0, and efficacy was evaluated according to the Response Evaluation Criteria in Solid Tumors version 1.0 for patients with measurable lesions and by the criteria of the Japanese Research Society for Gastric Cancer for all patients.

RESULTS

Efficacy could be evaluated in 49 of the 50 enrolled patients. The median age was 62 years. Lesions were measurable in 38 patients and assessable in 11. The response rate was 44.7% in patients with measurable lesions and 40.8% overall. The progression-free survival and overall survival were, respectively, 233 days (7.8 months) and 574 days (19.0 months) in patients with measurable lesions and 192 days (6.4 months) and 402 days (13.4 months) overall. Serious adverse events (grade 3 or higher) included neutropenia (24.5%), anemia (20.4%), and anorexia (20.4%) and were safely managed.

CONCLUSION

The safety and effectiveness of sequential treatment with S-1 followed by cisplatin every 35 days is equivalent to that reported for conventional chemotherapeutic regimens in patients with advanced or recurrent gastric cancer.