title: High external parametrial dose can increase the probability of radiation proctitis in patients with uterine cervix cancer.
abstract: OBJECTIVE
  The aim of this study was to evaluate the relationship between external parametrial dose and radiation proctitis after external irradiation and high-dose-rate intracavitary (HDR-IC) brachytherapy among patients with cervical cancer.
  
  
  METHODS
  From May 1993 through December 1996, 191 patients with stage IB-IVA cervical cancer were managed by curative-intent radiotherapy. External irradiation to the whole pelvis (44-45 Gy/ 22-25 fractions) was delivered to all patients initially. One hundred twenty-seven patients received additional bilateral parametrial and sidewall boost (5.4-14.4 Gy/ 3-8 fractions) with 4-cm midline shielding. HDR-IC brachytherapy, 19.2-24 Gy/ 5 fractions to Point A, was given after external irradiation. Patients receiving an external dose of 44-45, 50-54, and >54 Gy were categorized as no parametrial boost (NPMB), low parametrial boost (LPMB), and high parametrial boost (HPMB) group, respectively. The actuarial proctitis rate was compared among the three groups.
  
  
  RESULTS
  Three-year overall and Grade 2-4 proctitis rates were 30 and 15%, respectively. Overall proctitis rates were 12, 34, and 51% in the NPMB, LPMB, and HPMB groups (P < 0.0001), respectively. Grade 2-4 proctitis rates were 5, 17, and 27% in the NPMB, LPMB, and HPMB groups (P = 0.0022), respectively. In multivariate analysis of overall and Grade 2-4 radiation proctitis, external parametrial dose was the only independent prognostic factor (P = 0.0002 and 0.0030, respectively).
  
  
  CONCLUSIONS
  Regardless of central shielding after 44-45 Gy whole pelvis irradiation, more patients with high external parametrial dose developed radiation proctitis. Incomplete midline shielding of the upper rectum may be the cause. Diminishing the external beam doses further may decrease rectal complications.
authors: Department of Radiation Oncology, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung Hsien, Taiwan.
authors: E Y
authors: EY
authors: Huang
authors: H
authors: H
authors: Lin
authors: H C
authors: HC
authors: Hsu
authors: C J
authors: CJ
authors: Wang
authors: H C
authors: HC
authors: Chen
authors: L M
authors: LM
authors: Sun
authors: C Y
authors: CY
authors: Hsiung
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000009:adverse effects; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008875:Middle Aged; D015999:Multivariate Analysis; D011349:Proctitis / Q000209:etiology* / Q000473:pathology; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000209:etiology* / Q000473:pathology; D011835:Radiation Protection; D011878:Radiotherapy / Q000009:adverse effects / Q000379:methods; D012007:Rectum / Q000528:radiation effects; D012189:Retrospective Studies; D015996:Survival Rate; D002583:Uterine Cervical Neoplasms / Q000532:radiotherapy*; D014599:Uterus / Q000528:radiation effects