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 d 1-5 weekly).One cycle of capecitabine (1 250 mg/m2,twice daily,d 1-14)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 pxrianal 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 locallyadvanced 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.

Objective:To evaluate the efficacy of preoperative neoadjuvant chemoradiotherapy for low and locally advanced rectal cancer.Methods:Clinical data of 46 patients with low rectal tumors located within 6 cm from the edge of anal admitted to our hospital between February 2014 and December 2018 were retrospectively analyzed. SIB-IMRT technique was adopted for preoperative radiotherapy. Rectal tumors and positive lymph nodes were irradiated with a dose of 58.75 Gy in 25 fractions (2.35 Gy/fraction), and pelvic lymphatic drainage area was given with 50 Gy in 25 fractions (2.0 Gy/fraction). Oral administration of capecitabine was delivered for concurrent chemotherapy. Radical surgery for rectal cancer was performed at 6 to 12 weeks after the end of chemoradiotherapy. The overall survival (OS), disease-free survival (DFS), progression-free survival (PFS), local recurrence-free survival (LRFS) and metastasis-free survival (MFS) were calculated by using Kaplan- Meier method. Univariate analysis was conducted by log-rank test, and multivariate analysis was performed by Cox’s regression model. Results:After a median follow-up of 47 months, local recurrence occurred in 3 patients and distant metastasis in 6 patients. The ypCR rate was 26%(12/46), the sphincter-preservation rate was 74%(34/46), the R 0 resection rate was 100%(44/44), the overall tumor response TN down staging rate was 87%(40/46), and the postoperative complication rate was 13%(6/46). The 3-year OS, DFS, and PFS were 93%, 91% and 87%, respectively. In univariate analysis, ypN staging was an important factor affecting OS, DFS, PFS, LRFS and MFS (all P<0.05). In multivariate analysis, ypN staging was significantly correlated with DFS, PFS, LRFS and MFS (all P<0.05). Conclusions:Preoperative SIB-IMRT 58.75 Gy in 25 fractions combined with capecitabine chemotherapy is a safe and efficacious treatment for patients with low and locally advanced rectal cancer, which improves the ypCR rate and quality of life, and yields tolerable adverse reactions. Nevertheless, the long-term survival benefits remain to be validated.

Objective To investigate the dosimetric feasibility of volumetric modulated arc therapy (VMAT)with a simultaneous integrated boost(SIB-VMAT58.75 Gy)for preoperative chemoradiotherapy in patients with locally advanced rectal cancer(LARC),and to provide a basis for clinical practice.Methods Nine patients with stage Ⅱ-Ⅲ rectal cancer who underwent preoperative concurrent chemoradiotherapy were involved in the study,and two plans were performed for each patient:SIB-VMAT58.75 Gy and VMAT50.00 Gy. For the SIB-VMAT58.75 Gy plan,the prescribed dose was 58.75 Gy(2.35 Gy/fraction)for the local rectal tumor and positive lymph nodes(GTV 58.75 Gy),and 50 Gy(2 Gy/fraction)for the regions at high risk of harboring microscopic disease(pelvic lymphatic drainage area)(PTV 50Gy).For the VMAT50.00 Gy plan,the prescribed dose was 50 Gy(2 Gy/fraction)for the regions at high risk of harboring microscopic disease(pelvic lymphatic drainage area)without a boost. The conformity index(CI),homogeneity index (HI),and dose for target areas and organs at risk(OAR)were assessed according to the dose-volume histogram. The paired t-test or nonparametric rank test was used to compare the differences between the two plans. Results Both plans met the prescription goal for PTV dose coverage. There was no significant difference in CI for the PTV between the two plans(1.0±0.0 vs. 1.0±0.0,P>0.05).The SIB-VMAT58.75 Gy plan had a worse HI than the VMAT50.00 Gy plan(0.2± 0.2 vs. 0.1± 0.0,P<0.05).There was no significant difference in V10-V50of the small intestine,bladder,femoral heads,and pelvis between the two plans(P>0.05),but D 2 cm3of the small intestine was significantly higher in the SIB-VMAT58.75 Gy plan than in the VMAT50.00 Gy plan(P=0.038). Conclusions The SIB-VMAT58.75 Gy plan for LARC achieves required target volume dose coverage and OAR dose constraints,which is safe and feasible in terms of dosimetry,and its clinical efficacy and adverse effects need further evaluation.