Background: The purpose of this phase I study of the dose escalation of oxaliplatin in combination with oral S-1 and pelvic radiation preoperatively for poor-risk lower rectal cancer was to determine the dose-limiting toxicity (DLT) and recommended dose of oxaliplatin.
Methods: Patients with cT4 and lateral pelvic lymph node metastasis, and without distant metastasis (cM0), were treated with weekly oxaliplatin, oral S-1 40 mg/m(2) twice daily for 5 days a week, and radiation. A total of 5 weekly doses of oxaliplatin were planned. RT was administered to a total dose of 50.4 Gy in 28 fractions.
Results: We enrolled 11 patients between December 2009 and January 2012. DLTs were observed at dose level 1 (50 mg/m(2)) in two patients, one of whom experienced grade 3 aspartate aminotransferase elevation and a grade 3 alanine aminotransferase increase, and the other developed grade 4 hypokalemia and a grade 3 alanine aminotransferase increase. Five patients at dose level 2 (60 mg/m(2)) showed no DLTs. The hematological toxicities in all patients were mild and reversible. One patient showed distant metastasis after chemoradiation. Ten of the 11 patients achieved R0 resection by mesorectal resection and lateral lymph node dissection; three of the 10 underwent combined resection of the other organs.
Conclusion: This phase I trial of preoperative S-1 in combination with oxaliplatin and radiation for lower rectal cancer with T4 and lateral pelvic lymph node metastasis revealed that the recommended dose of oxaliplatin was 60 mg/m(2) weekly.