Clinical efficacy of preoperative SIB-IMRT for 26 cases of locally-advanced low rectal cancer

Abstract

Objective To evaluate the feasibility and clinical efficacy of preoperative simultaneous integrated boost intensity-modulated radiotherapy (SIB-IMRT) combined with neoadjuvant chemotherapy of capecitabine in patients with locally-advanced low rectal cancer. Methods Between 2015 and 2016, 26 patients admitted to 301 Hospital who were diagnosed with locally-advanced low rectal cancer, which was located within 5 cm from the anal verge, were enrolled in this investigation. Dose fractionation pattern was delivered: 58.75 Gy in 25 fractions (2.35 Gy/fraction) for rectal cancer and lymph node metastasis and 50 Gy in 25 fractions for the pelvic lymphatic drainage area and simultaneously combined with capecitabine chemotherapy (825 mg/m2, bid d1-5 weekly). One cycle of capecitabine (1 250 mg/m2, twice daily, d1-14) was given at one week after the completion of chemoradiotherapy (CRT). Total mesorectal excision (TME) was performed at 6 to 8 weeks after the completion of CRT.The primary endpoints included pathological complete response rate (ypCR) and sphincter-preserving rate. The secondary endpoints included acute toxicity, tumor downstaging rate and postoperative complications. Results Twenty-six patients successfully completed neoadjuvant CRT, 25 of them underwent surgical resection and one patient failed to receive surgery due to perianal edema. Postoperative ypCR rate was 32%(8/25), the sphincter-preserving rate was 60%(15/25), the tumor downstaging rate was 92%(23/25) and the R0 resection rate was 100%.During the period of CRT, grade 1 and 2 adverse events occurred in 24 patients, grade 3 radiation dermatitis was noted in 2 cases. No ≥ grade 4 acute adverse event was observed. Postoperative complications included ureteral injury in one case and intestinal obstruction in one patient. Conclusions Preoperative SIB-IMRT combined with neoadjuvant chemotherapy of capecitabine is a feasible and safe treatment for patients with locally-advanced low rectal cancer, which yields expected ypCR rate, R0 resection rate and sphincter-preserving rate. Nevertheless, the long-term clinical benefits remain to be elucidated. Clinical Trial Registry Chinese Clinical Trial Registry, registration number: ChiCTR-ONC-12002387. Key words: Rectal neoplasm; Anal neoplasm; Neoadjuvant chemoradiotherapy; Sphincter-preserving surgery