title: Predictors of late bowel toxicity using three different methods of contouring in patients undergoing post-operative radiation for cervical cancer.
abstract: OBJECTIVE
  This study investigates the correlation between dose-volume histogram derived from three bowel contouring methods and late toxicity in patients undergoing post-operative radiation therapy (PORT) for cervical cancer.
  
  
  METHODS
  From June 2010 to May 2013, 103 patients undergoing PORT were included. Three different contouring methods were used: (a) individual small bowel (SB) and large bowel (LB) loops, (b) total bowel (TB; including SB and LB) and (c) peritoneal cavity (PC). The volume of SB, LB, TB and PC receiving 15, 30 and 40 Gy was calculated. Acute and late bowel toxicities were scored using Common Terminology Criteria for Adverse events v. 3.0. Receiver operating characteristic curve identified thresholds predicting late toxicity with the highest specificity. All data were dichotomized across these thresholds. Univariate and multivariate analyses were performed using SPSS(®) v. 20 (IBM Corporation, Armonk, NY; formerly SPSS Inc., Chicago, IL).
  
  
  RESULTS
  On univariate analysis, V30 PC ≥ 900 cm(3) (p = 0.01), V40 PC ≥ 750 cm(3) (p = 0.03) and V40 TB ≥ 280 cm(3) (p = 0.03) and use of concurrent chemotherapy (p = 0.03) predicted grade ≥II acute toxicity. On multivariate analysis, use of concurrent chemotherapy [odds ratio (OR) 3.5, 95% confidence interval (CI) 1.1-11.1, p = 0.03] and V30 PC ≥ 900 cm(3) (OR 2.3, 95% CI 1-5.5, p = 0.05) predicted acute grade ≥II toxicity. On univariate analysis for late toxicity, SB (V30 ≥ 190 cm(3), p = 0.009; V40 ≥ 150 cm(3), p = 0.03), LB (V15 ≥ 250 cm(3), p = 0.04), V40 PC (V40 ≥ 750 cm(3), p = 0.001) and presence of acute grade ≥III toxicity (p = 0.006), treatment technique (three-dimensional conformal radiation or intensity modulated radiotherapy, p = 0.02) predicted more than or equal to grade ll late bowel toxicity. On multivariate analysis, only body mass index ≥25 kg m(-2) (OR 7.3, 95% CI 1.6-31.6, p = 0.008) and presence of acute grade III toxicity predicted toxicity (OR 5.1, 95% CI 1.4-18.1, p = 0.007).
  
  
  CONCLUSIONS
  V30 PC ≥ 900 cm(3) and use of concurrent chemotherapy independently predicts acute toxicity. Presence of acute grade ≥III toxicity independently predicts late toxicity. Minimizing dose to PC subvolumes can therefore reduce both acute and late toxicities.
  
  
  CONCLUSIONS
  Study establishes PC thresholds that can minimize both acute and late bowel toxicities.
authors.affiliation: 1 Department of Radiation Oncology, Advanced Centre for Treatment, Research and Education in Cancer, Mumbai, India.
authors.forename: Supriya
authors.initials: S
authors.lastname: Chopra
authors.affiliation: 2 Department of Radiation Oncology, Tata Memorial Hospital, Mumbai, India.
authors.forename: Rahul
authors.initials: R
authors.lastname: Krishnatry
authors.affiliation: 1 Department of Radiation Oncology, Advanced Centre for Treatment, Research and Education in Cancer, Mumbai, India.
authors.forename: Tapas
authors.initials: T
authors.lastname: Dora
authors.affiliation: 3 Epidemiology and Clinical Trials Unit, Advanced Centre for Treatment, Research and Education in Cancer, Mumbai, India.
authors.forename: Sadhna
authors.initials: S
authors.lastname: Kannan
authors.affiliation: 1 Department of Radiation Oncology, Advanced Centre for Treatment, Research and Education in Cancer, Mumbai, India.
authors.forename: Biji
authors.initials: B
authors.lastname: Thomas
authors.affiliation: 1 Department of Radiation Oncology, Advanced Centre for Treatment, Research and Education in Cancer, Mumbai, India.
authors.forename: Supriya
authors.initials: S
authors.lastname: Sonawone
authors.affiliation: 2 Department of Radiation Oncology, Tata Memorial Hospital, Mumbai, India.
authors.forename: Reena
authors.initials: R
authors.lastname: Engineer
authors.affiliation: 1 Department of Radiation Oncology, Advanced Centre for Treatment, Research and Education in Cancer, Mumbai, India.
authors.forename: Siji
authors.initials: S
authors.lastname: Paul
authors.affiliation: 1 Department of Radiation Oncology, Advanced Centre for Treatment, Research and Education in Cancer, Mumbai, India.
authors.forename: Reena
authors.initials: R
authors.lastname: Phurailatpam
authors.affiliation: 2 Department of Radiation Oncology, Tata Memorial Hospital, Mumbai, India.
authors.forename: Umesh
authors.initials: U
authors.lastname: Mahantshetty
authors.affiliation: 2 Department of Radiation Oncology, Tata Memorial Hospital, Mumbai, India.
authors.forename: Shyam
authors.initials: S
authors.lastname: Shrivastava
mesh_terms: D000368:Aged; D059248:Chemoradiotherapy / Q000379:methods; D005260:Female; D006801:Humans; D007422:Intestines / Q000528:radiation effects*; D008875:Middle Aged; D058958:Organs at Risk / Q000528:radiation effects*; D010537:Peritoneum / Q000528:radiation effects*; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000209:etiology; D011879:Radiotherapy Dosage; D012307:Risk Factors; D014057:Tomography, X-Ray Computed; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery