title: Computed tomography-planned interstitial brachytherapy for locally advanced gynecologic cancer: Outcomes and dosimetric predictors of urinary toxicity.
abstract: OBJECTIVE
  To identify dosimetric predictors of outcome and toxicity in patients receiving CT-planned interstitial brachytherapy (ISBT) for gynecologic cancers.
  
  
  METHODS
  Patients who received ISBT between 2009 and 2014 were reviewed. Demographic, disease specific, treatment, and toxicity data were collected. Logistic regression was used to model toxicity. A least absolute shrinkage and selection operator penalty was used to identify relevant predictors. Receiver operating characteristic curves were used to analyze the relation between dosimetric factors and urinary toxicity.
  
  
  RESULTS
  Seventy-three patients received ISBT (21 at time of cancer recurrence and 52 at the first presentation). Thirty-six patients had cervical cancer, 16 had vaginal cancer, 13 had uterine cancer, and 8 had vulvar cancer. ISBT was performed using both high-dose-rate and low-dose-rate 192Ir sources (27 low dose rate and 46 high dose rate). With a median followup of 12 months, Grade 3 vaginal, urinary, and rectal toxicity occurred in 17.8%, 15.1%, and 6.8% of patients, respectively. No patients experienced Grade 4 or 5 toxicity. Dose to 0.1cc of urethra predicted for development of Grade 3 urinary toxicity (area under the curve of 0.81; 95% confidence interval: 0.66, 0.96). A 10% probability of a Grade 3 urinary toxicity associated with a dose of 23.1 equivalent dose in 2 Gy fractions (95% confidence interval: 9.51, 36.27 equivalent dose in 2 Gy fractions).
  
  
  CONCLUSIONS
  ISBT is a safe treatment for gynecologic malignancies. The dose to 0.1cc significantly predicts for severe urinary toxicity. Our data suggests that dose to a small urethral volume may be the most significant predictor of urinary toxicity in patients receiving ISBT for gynecologic cancer.
authors.affiliation: Department of Radiation Oncology, University of Louisville, Louisville, KY.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Amsbaugh
authors.affiliation: Department of Radiation Oncology, University of Louisville, Louisville, KY.
authors.forename: Neal
authors.initials: N
authors.lastname: Bhatt
authors.affiliation: Department of Radiation Oncology, University of Louisville, Louisville, KY.
authors.forename: Thomas
authors.initials: T
authors.lastname: Hunter
authors.affiliation: Department of Bioinformatics and Biostatistics, University of Louisville, Louisville, KY.
authors.forename: Jeremy
authors.initials: J
authors.lastname: Gaskins
authors.affiliation: Department of Obstetrics Gynecology and Women's Health, University of Louisville, Louisville, KY.
authors.forename: Lynn
authors.initials: L
authors.lastname: Parker
authors.affiliation: Department of Obstetrics Gynecology and Women's Health, University of Louisville, Louisville, KY.
authors.forename: Daniel
authors.initials: D
authors.lastname: Metzinger
authors.affiliation: Department of Anesthesia and Perioperative Medicine, University of Louisville, Louisville, KY.
authors.forename: Ashley
authors.initials: A
authors.lastname: Amsbaugh
authors.affiliation: Department of Radiation Oncology, University of Louisville, Louisville, KY.
authors.forename: Keith
authors.initials: K
authors.lastname: Sowards
authors.affiliation: Department of Radiation Oncology, University of Louisville, Louisville, KY. Electronic address: Moataz.elghamry@louisville.edu.
authors.forename: Moataz N
authors.initials: MN
authors.lastname: El-Ghamry
mesh_terms: D000328:Adult; D000368:Aged; D001918:Brachytherapy / Q000009:adverse effects / Q000379:methods*; D005260:Female; D005833:Genital Neoplasms, Female / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D007496:Iridium Radioisotopes / Q000627:therapeutic use; D008875:Middle Aged; D058958:Organs at Risk / Q000528:radiation effects; D011829:Radiation Dosage; D011832:Radiation Injuries / Q000209:etiology*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D012007:Rectum / Q000528:radiation effects*; D012189:Retrospective Studies; D014057:Tomography, X-Ray Computed; D014521:Urethra / Q000528:radiation effects*; D001743:Urinary Bladder / Q000528:radiation effects*; D014621:Vagina / Q000528:radiation effects*
chemical_list: D007496:Iridium Radioisotopes
keywords: Brachytherapy; Cervical cancer; Dosimetric predictors of toxicity; Endometrial cancer; Gynecologic cancer; Interstitial brachytherapy; Vaginal cancer; Vulvar cancer