937 - Phase II Study of Preoperative Radiotherapy Combined with S-1 plus Cisplatin in Clinically Resectable Type 4 or Large Type 3 Gastric Cancer: OGSG1205

Background

The prognosis of type 4 or large type 3-gastric cancer is extremely poor. Despite various perioperative adjuvant therapies; as JCOG0501, peritoneal recurrence is still difficult to control. Since the clinical efficacy of chemo-radiotherapy was suggested for the treatment of advanced gastric cancer, chemo-radiotherapy is a promising strategy for curatively resectable type 4 or large type 3-gastric cancer. This multicenter, phase II study evaluated the efficacy and safety of radiotherapy combined with S-1 plus cisplatin for this target.

Methods

Eligibility criteria included pathologically confirmed gastric adenocarcinoma with macroscopically type 4 or large type 3, without peritoneal or distant metastases. Patients received preoperative chemo-radiotherapy with S-1 80 mg/m2/day from Day 1 to 14 and cisplatin 60 mg/m2 on Day 1, and radiotherapy at a total dose of 40 Gy in 20 fractions was delivered for 4 weeks, followed by D2 gastrectomy, and received S-1 monotherapy for one year postoperatively. The primary endpoint was the pathological complete response rate (% protocol completion). Secondary endpoints were safety, overall survival, and the response rate (RR). The sample size was calculated to be 30 cases, under the hypothesis of expected % pathological complete response rate of 15% and threshold pathological complete response rate of 2% with one-sided testing at the 10% significance level and power of 90%.

Results

From November 2012 to April 2018, 20 patients were enrolled. A median age of 20 patients was 67 years. Nineteen patients had protocol operation, and two of them showed pathological complete response (10.5%; 95% confidence interval 1.3–33.1%, p < 0.001). During preoperative chemotherapy, grade 3/4 neutropenia occurred in 25%, and grade 3/4 non-hematological adverse events occurred in 10%. The incidence of adverse events related to surgery was occurred in 31.6% patients. There were no treatment-related deaths. Follow-up for long-term survival is continuing. Notably the pathological RR (residual tumor < 2/3) was 100% (19/19).

Conclusions

Preoperative chemo-radiotherapy with S-1 plus CDDP is a safe and promising treatment for type 4 or large type 3 gastric cancer.

Clinical trial identification

Editorial acknowledgement

Legal entity responsible for the study

Osaka Gastointestinal Cancer Chemotherapy Study Group.

Funding

Has not received any funding.

Disclosure

All authors have declared no conflicts of interest.