title: Is the irradiated small bowel volume still a predictor for acute lower gastrointestinal toxicity during preoperative concurrent chemo-radiotherapy for rectal cancer when using intensity-modulated radiation therapy?
abstract: BACKGROUND
  The small bowel (SB) represents the most important dose-limiting structure in pelvic radiotherapy (RT). However, we observed that the majority of rectal cancer patients who received preoperative pelvic intensity modulated RT (IMRT) developed acute tenesmus without watery diarrhea. The objective of this study is to determine if the RT dose to SB affects the acute lower gastrointestinal toxicity (ALGIT) in rectal cancer patients who received neoadjuvant concurrent chemotherapy-IMRT. We will also evaluate if patient and tumor factors affect the ALGIT.
  
  
  METHODS
  We retrospectively analyzed 63 rectal cancer patients that consecutively received preoperative IMRT (45 Gy for pelvis and 50 Gy for gross tumor in 25 fractions) with concurrent chemotherapy (oxaliplatin 130 mg/m(2) on day 1 and capecitabine 825 mg/m(2), twice per day from day 1 to day 14, week 1 and 4) between May 2012 and May 2013. The ALGIT was assessed with Common Terminology Criteria for Adverse Events version 3. The patients were stratified into two groups (with and without grade ≥2 ALGIT). The effect of SB volume receiving 5 to 40 Gy (V5 to V40) at a 5 Gy interval dose level on grade ≥2 ALGIT was evaluated. The volume of small bowel is defined as the volume of the small bowel loop. Other factors evaluated include patient's age and gender, tumor size and location and preexisting number of daily bowel movements.
  
  
  RESULTS
  Overall, grade ≥2 ALGIT occurred in 57 % (36/63) patients. There was no significant difference between the two groups of patients (with and without grade ≥2 ALGIT) in SB V5 to V40, patient's age and gender, tumor location and preexisting number of daily bowel movements. There was a significant difference between the two groups of patients in tumor volume (with grade ≥2 ALGIT: 115.5 ± 85.5 cm(3) versus without grade ≥2 ALGIT: 58.5 ± 25.2 cm(3), p = 0.0001). Multivariate analysis revealed no association between the dose SB received (V5 to V40) and the grade ≥2 ALGIT after adjusting for the tumor volume.
  
  
  CONCLUSIONS
  With IMRT technique used in rectal cancer patients undergoing preoperative chemo-radiotherapy, the acute lower GI toxicity is not associated with small bowel V5 to V40; instead it is associated with rectal tumor size.
authors.affiliation: Department of Radiation Oncology, The Fujian Medical University Union Hospital, Fuzhou, Fujian, P.R. China, 350001. benhuaxu@163.com.
authors.forename: Benhua
authors.initials: B
authors.lastname: Xu
authors.affiliation: Department of Radiation Oncology, The Fujian Medical University Union Hospital, Fuzhou, Fujian, P.R. China, 350001. guoyuyan1202@sina.com.
authors.forename: Yuyan
authors.initials: Y
authors.lastname: Guo
authors.affiliation: Department of Radiation Oncology, The Fujian Medical University Union Hospital, Fuzhou, Fujian, P.R. China, 350001. 2000cyg@sohu.com.
authors.forename: Yuangui
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Radiation Oncology, The Fujian Medical University Union Hospital, Fuzhou, Fujian, P.R. China, 350001. lihaijie1971@hotmail.com.
authors.forename: Haijie
authors.initials: H
authors.lastname: Lu
authors.affiliation: Department of Radiation Oncology, The Fujian Medical University Union Hospital, Fuzhou, Fujian, P.R. China, 350001. tanglian@126.com.
authors.forename: Tianlan
authors.initials: T
authors.lastname: Tang
authors.affiliation: Institute of Life Sciences, Fuzhou University, Fuzhou, Fujian, P.R. China, 350108. yuefzdx@163.com.
authors.forename: Zhicao
authors.initials: Z
authors.lastname: Yue
authors.affiliation: Department of General Surgery, The Fujian Medical University Union Hospital, Fuzhou, Fujian, P.R. China, 350001. gxguan1107@163.com.
authors.forename: Guoxian
authors.initials: G
authors.lastname: Guan
authors.affiliation: Department of General Surgery, The Fujian Medical University Union Hospital, Fuzhou, Fujian, P.R. China, 350001. cpxhyydcwk@163.com.
authors.forename: Pan
authors.initials: P
authors.lastname: Chi
authors.affiliation: Department of Radiation Oncology, University of Nebraska Medical Center, 987521 Nebraska Medical Center, Omaha, NE, 68106, USA. clin@unmc.edu.
authors.forename: Chi
authors.initials: C
authors.lastname: Lin
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000532:radiotherapy*; D000328:Adult; D000368:Aged; D059248:Chemoradiotherapy / Q000009:adverse effects / Q000379:methods; D005260:Female; D006801:Humans; D007421:Intestine, Small / Q000528:radiation effects*; D008297:Male; D008875:Middle Aged; D058958:Organs at Risk / Q000528:radiation effects; D011832:Radiation Injuries / Q000473:pathology*; D050397:Radiotherapy, Intensity-Modulated / Q000009:adverse effects*; D012004:Rectal Neoplasms / Q000188:drug therapy / Q000532:radiotherapy*; D012189:Retrospective Studies