Long-term results of a multicenter phase II study of preoperative chemoradiotherapy with S-1 plus oxaliplatin for locally advanced rectal cancer (JACCRO CC-04: SHOGUN Trial).

PURPOSE: The study was designed to evaluate the safety and efficacy of adding oxaliplatin to py (CRT) with S-1 in patients with locally advanced rectal carcinoma (LARC). We report here the final results of the study. PATIENTS AND METHODS: Patients with histopathologically confirmed LARC (cT3-T4, any N) were eligible. They received oral S-1 (80 mg/m2/day on days 1-5, 8-12, 22-26, and 29-33) and infusional oxaliplatin (60 mg/m2/day on days 1, 8, 22, 29) plus radiotherapy (1.8 Gy/day, total dose of 50.4 Gy in 28 fractions), with a chemotherapy gap in the third week of radiotherapy. Primary endpoint of the study was pathological complete response (pCR) rate. Secondary endpoints were rates of R0 resection, down-staging, cumulative 3-year local recurrence, 3-year disease-free survival (DFS), and toxicity. RESULTS: Forty-five patients were enrolled at six centers in Japan. All patients received CRT, and 44 underwent operation. The pCR rate was 27.3% (12/44). The R0 resection rate was 95.5% (42/44). T-down-staging rate was 59.1% (26/44), and N-down staging rate was 65.9% (29/44); the combined pathological down-staging rate was 79.5% (35/44). There were no grade 4 adverse events, but 11.1% of the patients had grade 3 adverse events. Cumulative 3-year local recurrence rate was 0%. However, 13 (30.0%) patients suffered from distant metastasis, and one patient suffered from secondary esophageal cancer that was unrelated to rectal cancer. Eight patients had lung metastasis, 4 had liver metastasis, and 3 patients died of the metastatic disease. The 3-year DFS rate of the 44 patients was 67.5% (median follow-up 36.3 months), and the 3-year overall survival (OS) rate was 93.0% (median follow-up 39.6 months). The patients were then divided into the pCR (12 patients) group and non pCR (32 patients) group. The 3-year rate of DFS for each group was 91.7% and 58.1% and that of OS was 100% and 90.3%, respectively. CONCLUSIONS: The study showed a high pCR rate with no severe toxicity, good follow-up results, and good loco-regional control. Therefore, addition of oxaliplatin to preoperative CRT with S-1 in patients with LARC might be feasible and lead to better local control than standard treatment.