title: The dose-volume relationship of acute small bowel toxicity from concurrent 5-FU-based chemotherapy and radiation therapy for rectal cancer.
abstract: OBJECTIVE
  A direct relationship between the volume of small bowel irradiated and the degree of acute small bowel toxicity experienced during concurrent 5-fluorouracil (5-FU)-based chemoradiotherapy for rectal carcinoma is well recognized but poorly quantified. This study uses three-dimensional treatment-planning tools to more precisely quantify this dose-volume relationship.
  
  
  METHODS
  Forty patients receiving concurrent 5-FU-based chemotherapy and pelvic irradiation for rectal carcinoma had treatment-planning CT scans with small bowel contrast. A median isocentric dose of 50.4 Gy was delivered using a posterior-anterior and opposed lateral field arrangement. Bowel exclusion techniques were routinely used, including prone treatment position on a vacuum bag cradle to allow anterior displacement of the abdominal contents and bladder distension. Individual loops of small bowel were contoured on each slice of the planning CT scan, and a small bowel dose-volume histogram was generated for the initial pelvis field receiving 45 Gy. The volume of small bowel receiving each dose between 5 and 40 Gy was recorded at 5-Gy intervals.
  
  
  RESULTS
  Ten patients (25%) experienced Common Toxicity Criteria Grade 3+ acute small bowel toxicity. A highly statistically significant association between the development of Grade 3+ acute small bowel toxicity and the volume of small bowel irradiated was found at each dose level. Specific dose-volume threshold levels were found, below which no Grade 3+ toxicity occurred and above which 50-60% of patients developed Grade 3+ toxicity. The volume of small bowel receiving at least 15 Gy (V15) was strongly associated with the degree of toxicity. Univariate analysis of patient and treatment-related factors revealed no other significant predictors of severe toxicity.
  
  
  CONCLUSIONS
  A strong dose-volume relationship exists for the development of Grade 3+ acute small bowel toxicity in patients receiving concurrent 5-FU-based chemoradiotherapy for rectal carcinoma.
authors.affiliation: Department of Radiation Oncology, William Beaumont Hospital, Royal Oak, MI 48073, USA.
authors.forename: Kathy L
authors.initials: KL
authors.lastname: Baglan
authors.forename: Robert C
authors.initials: RC
authors.lastname: Frazier
authors.forename: Di
authors.initials: D
authors.lastname: Yan
authors.forename: Raywin R
authors.initials: RR
authors.lastname: Huang
authors.forename: Alvaro A
authors.initials: AA
authors.lastname: Martinez
authors.forename: John M
authors.initials: JM
authors.lastname: Robertson
mesh_terms: D000208:Acute Disease; D000230:Adenocarcinoma / Q000188:drug therapy* / Q000532:radiotherapy*; D000704:Analysis of Variance; D000964:Antimetabolites, Antineoplastic / Q000008:administration & dosage; D003131:Combined Modality Therapy; D003967:Diarrhea / Q000209:etiology*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005472:Fluorouracil / Q000008:administration & dosage; D006801:Humans; D007421:Intestine, Small / Q000528:radiation effects*; D008297:Male; D012004:Rectal Neoplasms / Q000188:drug therapy* / Q000532:radiotherapy*; D014057:Tomography, X-Ray Computed
chemical_list: D000964:Antimetabolites, Antineoplastic; D005472:Fluorouracil