title: The impact of body mass index on rectal dose in locally advanced cervical cancer treated with high-dose-rate brachytherapy.
abstract: OBJECTIVE
  The impact of body mass index (BMI) on rectal dose in brachytherapy for cervical cancer is unknown. We assessed the association of BMI on rectal dose and lower gastrointestinal (GI) toxicity.
  
  
  METHODS
  Between 2007 and 2010, 51 patients with 97 brachytherapy planning images were reviewed. Volumetric measurements of the maximum percentage, mean percentage, dose to 2cc (D2cc), and dose to 1cc (D1cc) of the rectum, and the Internal Commission on Radiation Units and Measurement (ICRU) rectal point were recorded. Linear mixed effect models, analysis of variance, and regression analyses were used to determine the correlation between multiple observations or to detect a difference in the mean. The GI acute and late toxicity were prospectively recorded and retrospectively analyzed.
  
  
  RESULTS
  The average BMI (kg/m(2)) was 27.7 with a range of 17.4-46.6. Among the patients, 8% were morbidly obese, 25% obese, 25% overweight, 40% normal weight, and 2% underweight. The mean D1cc, D2cc, mean rectal dose (%), maximum rectal dose (%), and ICRU rectum was 3.03 Gy, 2.78 Gy, 20%, 60%, and 2.99 Gy, respectively. On multivariate analysis, there was a significant decrease in the D1cc and D2cc rectal dose (p=0.016), ICRU rectal point dose (p=0.022), and mean rectal dose percentage (p=0.021) with an increase in BMI. There was, however, no statistically significant relationship between BMI and GI toxicity.
  
  
  CONCLUSIONS
  Obesity decreases the rectal dose given in high-dose-rate brachytherapy for locally advanced cervical cancer because of an increase in fatty tissue in the recto-uterine space. There is no significant correlation between BMI and acute or late GI toxicity.
authors.affiliation: University of California Davis School of Medicine, University of California Davis, Sacramento, CA.
authors.forename: Jihoon
authors.initials: J
authors.lastname: Lim
authors.forename: Blythe
authors.initials: B
authors.lastname: Durbin-Johnson
authors.forename: Richard
authors.initials: R
authors.lastname: Valicenti
authors.forename: Matthew
authors.initials: M
authors.lastname: Mathai
authors.forename: Robin L
authors.initials: RL
authors.lastname: Stern
authors.forename: Jyoti
authors.initials: J
authors.lastname: Mayadev
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D015992:Body Mass Index; D001918:Brachytherapy / Q000379:methods*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D005500:Follow-Up Studies; D006801:Humans; D021621:Imaging, Three-Dimensional; D008875:Middle Aged; D009367:Neoplasm Staging; D009767:Obesity, Morbid / Q000150:complications*; D011879:Radiotherapy Dosage; D011882:Radiotherapy, High-Energy / Q000379:methods*; D012007:Rectum / Q000528:radiation effects; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D016896:Treatment Outcome; D002583:Uterine Cervical Neoplasms / Q000150:complications / Q000175:diagnosis / Q000532:radiotherapy*
keywords: Brachytherapy; Cervical cancer; Rectal dose