title: Factors for predicting rectal dose of high-dose-rate intracavitary brachytherapy after pelvic irradiation in patients with cervical cancer: a retrospective study with radiography-based dosimetry.
abstract: OBJECTIVE
  To evaluate the predictive factors for rectal dose of the first fraction of high-dose-rate intracavitary brachytherapy (HDR-ICBT) in patients with cervical cancer.
  
  
  METHODS
  From March 1993 through February 2008, 946 patients undergoing pelvic irradiation and HDR-ICBT were analyzed. Examination under anesthesia (EUA) at the first implantation of the applicator was usually performed in the early period. Rectal point was determined radiographically according to the 38th Report of the International Commission of Radiation Units and Measurements (ICRU). The ICRU rectal dose (PRD) as a percentage of point A dose was calculated; multiple linear regression models were used to predict PRD.
  
  
  RESULTS
  Factors influencing successful rectal dose calculation were EUA (p < 0.001) and absence of diabetes (p = 0.047). Age (p < 0.001), body weight (p = 0.002), diabetes (p = 0.020), and EUA (p < 0.001) were independent factors for the PRD. The predictive equation derived from the regression model was PRD (%) = 57.002 + 0.443 x age (years) - 0.257 x body weight (kg) + 6.028 x diabetes (no: 0; yes: 1) - 8.325 x EUA (no: 0; yes: 1)
  
  
  CONCLUSIONS
  Rectal dose at the first fraction of HDR-ICBT is positively influenced by age and diabetes, and negatively correlated with EUA and body weight. A small fraction size at point A may be considered in patients with a potentially high rectal dose to reduce the biologically effective dose if the ICRU rectal dose has not been immediately obtained in the first fraction of HDR-ICBT.
authors.affiliation: Department of Radiation Oncology, Chang Gung Memorial Hospital-Kaohsiung Medical Center, Chang Gung University College of Medicine, Taiwan. huangengyen@giga.net.tw
authors.forename: Eng-Yen
authors.initials: EY
authors.lastname: Huang
authors.forename: Chong-Jong
authors.initials: CJ
authors.lastname: Wang
authors.forename: Jen-Hong
authors.initials: JH
authors.lastname: Lan
authors.forename: Hui-Chun
authors.initials: HC
authors.lastname: Chen
authors.forename: Fu-Min
authors.initials: FM
authors.lastname: Fang
authors.forename: Hsuan-Chih
authors.initials: HC
authors.lastname: Hsu
authors.forename: Yu-Jie
authors.initials: YJ
authors.lastname: Huang
authors.forename: Chang-Yu
authors.initials: CY
authors.lastname: Wang
authors.forename: Yu-Ming
authors.initials: YM
authors.lastname: Wang
mesh_terms: D000230:Adenocarcinoma / Q000000981:diagnostic imaging / Q000532:radiotherapy; D001918:Brachytherapy / Q000009:adverse effects / Q000379:methods*; D002294:Carcinoma, Squamous Cell / Q000000981:diagnostic imaging / Q000532:radiotherapy; D005260:Female; D006801:Humans; D007496:Iridium Radioisotopes / Q000627:therapeutic use; D008875:Middle Aged; D011349:Proctitis / Q000209:etiology / Q000517:prevention & control; D011832:Radiation Injuries / Q000517:prevention & control; D011859:Radiography; D011879:Radiotherapy Dosage; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D012007:Rectum / Q000528:radiation effects*; D012044:Regression Analysis; D012062:Relative Biological Effectiveness; D012189:Retrospective Studies; D002583:Uterine Cervical Neoplasms / Q000000981:diagnostic imaging* / Q000532:radiotherapy*
chemical_list: D007496:Iridium Radioisotopes