Totally neoadjuvant chemoradiation therapy with mFOLFOX6 in locally advanced rectal cancer: A single arm phase II study (FOTAC).

TPS816 Background: Preoperative 5-Fluorouracil based chemoradiotherapy is the standard of treatment for locally advanced rectal cancer. About 15% to 18% of patients would achieve pathologic complete response (pCR) after 5-Fluorouracil based chemoradiation. And the survival outcome of patients with pCR was much better than that of non-pCR. In our previous FOWARC study, in the group of preoperative systemic chemotherapy with mFOLFOX6 combined with radiation, the pCR rate was up to 27.5%. In another study, adding mFOLFOX6 after neoadjuvant chemo radiation in locally advanced rectal cancer improve the pCR rate to 38%. This phase II study aimed to explore whether totally neoadjuvant chemoradiation therapy with mFOLFOX6 could further improve the pCR rate in locally advanced rectal cancer. Methods: The primary endpoint is the pathologic complete response rate (pCR).The secondary endpoint included 3-year disease free survival rate, 3-year local recurrence rate, and safety. We hypothesized that totally neoadjuvant chemoradiation therapy with mFOLFOX6 could improve the pCR rate from 18% to 45% with 5% type I error and 80% power. Fifty patients met inclusion criteria will be enrolled in the trial. All patients will receive long term radiation for 25 times and 50Gy before surgery. Four cycles of mFOLFOX6 would be performed every 2 weeks during radiotherapy, and another 4-6 cycles would be added after radiotherapy and before operation. Totally, the patients will receive 8-10 cycles of chemotherapy before surgery. MRI of the pelvic will be performed every 4 cycles of the therapy to assess clinical response. Then the patient will receive total mesorectal excision at least 8 weeks after radiotherapy. The post-operative chemotherapy will be omitted and all the patients go to surveillance. Clinical trial information: NCT02887313.