title: Predictors of toxicity after image-guided high-dose-rate interstitial brachytherapy for gynecologic cancer.
abstract: OBJECTIVE
  To identify predictors of grade 3-4 complications and grade 2-4 rectal toxicity after three-dimensional image-guided high-dose-rate (HDR) interstitial brachytherapy for gynecologic cancer.
  
  
  METHODS
  Records were reviewed for 51 women (22 with primary disease and 29 with recurrence) treated with HDR interstitial brachytherapy. A single interstitial insertion was performed with image guidance by computed tomography (n = 43) or magnetic resonance imaging (n = 8). The median delivered dose in equivalent 2-Gy fractions was 72.0 Gy (45 Gy for external-beam radiation therapy and 24 Gy for brachytherapy). Toxicity was reported according to the Common Toxicity Criteria for Adverse Events. Actuarial toxicity estimates were calculated by the Kaplan-Meier method.
  
  
  RESULTS
  At diagnosis, the median patient age was 62 years and the median tumor size was 3.8 cm. The median D90 and V100 were 71.4 Gy and 89.5%; the median D2cc for the bladder, rectum, and sigmoid were 64.6 Gy, 61.0 Gy, and 52.7 Gy, respectively. The actuarial rates of all grade 3-4 complications at 2 years were 20% gastrointestinal, 9% vaginal, 6% skin, 3% musculoskeletal, and 2% lymphatic. There were no grade 3-4 genitourinary complications and no grade 5 toxicities. Grade 2-4 rectal toxicity was observed in 10 patients, and grade 3-4 complications in 4; all cases were proctitis with the exception of 1 rectal fistula. D2cc for rectum was higher for patients with grade 2-4 (68 Gy vs 57 Gy for grade 0-1, P=.03) and grade 3-4 (73 Gy vs 58 Gy for grade 0-2, P=.02) rectal toxicity. The estimated dose that resulted in a 10% risk of grade 2-4 rectal toxicity was 61.8 Gy (95% confidence interval, 51.5-72.2 Gy).
  
  
  CONCLUSIONS
  Image-guided HDR interstitial brachytherapy results in acceptable toxicity for women with primary or recurrent gynecologic cancer. D2cc for the rectum is a reliable predictor of late rectal complications. Three-dimensional-based treatment planning should be performed to ensure adequate tumor coverage while minimizing the D2cc to the rectum.
authors.affiliation: Department of Radiation Oncology, Brigham and Women's Hospital and Dana-Farber Cancer Institute, Harvard Medical School, Boston, Massachusetts, USA.
authors.forename: Larissa J
authors.initials: LJ
authors.lastname: Lee
authors.forename: Akila N
authors.initials: AN
authors.lastname: Viswanathan
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001918:Brachytherapy / Q000009:adverse effects* / Q000379:methods; D012809:Colon, Sigmoid / Q000528:radiation effects; D005260:Female; D041981:Gastrointestinal Tract / Q000528:radiation effects; D005833:Genital Neoplasms, Female / Q000532:radiotherapy*; D006801:Humans; D021621:Imaging, Three-Dimensional; D008875:Middle Aged; D009364:Neoplasm Recurrence, Local / Q000532:radiotherapy*; D058958:Organs at Risk / Q000528:radiation effects*; D011832:Radiation Injuries / Q000209:etiology*; D011881:Radiotherapy, Computer-Assisted / Q000379:methods; D061089:Radiotherapy, Image-Guided / Q000009:adverse effects* / Q000379:methods; D012007:Rectum / Q000528:radiation effects*; D012867:Skin / Q000528:radiation effects; D047368:Tumor Burden; D001743:Urinary Bladder / Q000528:radiation effects; D014621:Vagina / Q000528:radiation effects