Effects of mesorectal fascia (MRF) status for locally advanced rectal cancer: Results of a multicenter, randomized, controlled, phase II trial (FDRT-002)

Abstract

Background: To identity the effects of high‐dose intensitymodulated radiation therapy(IMRT) for locally advanced rectal cancer according to MRF status. Methods: Eligible patients from multicenter who had histologically confirmed locally advanced rectal adenocarcinoma (cT3‐T4 and/or cN+) located within 12 cm from the anal verge, were randomly assigned (1:1) to either the low intensity group (50 Gy/25Fxs concurrent with oxaliplatin 50 mg/m2 weekly and capecitabine 625 mg/m2 bid d1‐5 weekly) or the high intensity group (50 Gy/25Fxs and a concomitant boost of 5Gy to the primary tumor, followed by one cycle of XELOX two weeks after the completion of chemoradiotherapy). Surgery was scheduled eight weeks after the completion of CRT. All patients were recommended to receive postoperative XELOX chemotherapy regardless of pathological stage. The primary endpoint was pathological complete response rate (pCR). Secondary endpoints included LC, OS, DFS and toxicities. Results: From February 2010 to December 2011, 120 locally advanced rectal cancer patients (60 in high intensity group and 60 in low intensity group) were involved. The data were analyzed by MRF status (74 in the MRF‐ group and 46 in the MRF+ group). Patients in the MRF‐ group had better pCR (21.6% vs. 13.0%, p=0.238), LC (p=0.012), DFS (p=0.002) and OS (p=0.007) than those in MRF+ group. While stratified with MRF status, high intensity group showed a better tumor response, especially in positive MRF group. But no significant interaction between MRF and intensity was found in long‐term prognosis. Conclusions: MRF is a strong prognostic factor and a predictor of tumor regression. High‐dose treatment may be beneficial to MRF+ patients via improving tumor response.