Phase II Study of Preoperative Chemoradiotherapy With S-1 Plus Oxaliplatin for Locally Advanced Rectal Cancer (PerSeUS-RC01).

BACKGROUND/AIM: We report the end results of a study evaluating the safety and efficacy of preoperative chemoradiotherapy with S-1 plus oxaliplatin.

PATIENTS AND METHODS

Eligible patients had histopathologically confirmed locally advanced rectal carcinoma (LARC; cT3-T4, any N). They received oral S-1 (80 mg/m/day on days 1-5, 8-12, 22-26, and 29-33) and oxaliplatin by infusion (50 mg/m/day on days 1, 8, 22, and 29) along with radiotherapy (1.8 Gy/day, total dose: 45 Gy/25 fractions). A chemotherapy gap was included in the third week of radiotherapy. The study endpoint was pathological response rate (Grade 2, 3). Secondary endpoints included rates of pathologic complete response (pCR), R0 resection, disease-free survival (DFS), overall survival (OS), local and distant recurrence, and safety and relative dose intensity.

RESULTS

The study enrolled 23 patients at three Centres in Gifu, Japan. All patients received chemoradiotherapy, and 22 underwent surgery. Rates of pathological response, R0 resection, and pathological down-staging were 56.5% (13/23), 95.7% (22/23), and 63.6% (14/22), respectively. There were no grade 4 adverse events, but grade 3 events occurred in 21.7% of patients. The cumulative 3-year local recurrence rate was 8.7%. Distant metastasis occurred in 10 (43.5%) patients, 2 (8.7%) from local recurrence and 2 from secondary pancreatic cancer and lung cancer. There were 8 patients with lung metastasis, 2 with liver metastasis, one with ovarian metastasis, and one with bone metastasis. Three-year rates of DFS and OS were 51.1% (median follow-up 34.3 months) and 91.1% (45.2 months), respectively.

CONCLUSION

The study showed high pathological response rate without severe toxicity and good follow-up results. Unexpectedly, however, this regimen could not control local recurrence and distant metastasis. Nevertheless, adding oxaliplatin to preoperative chemoradiotherapy with S-1 in patients with LARC appears feasible and may safely result in better local control than standard treatment. The study suggests adding treatment with induction chemotherapy in consideration of CEA level and N factor.