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Title: Predictors of Rectal Tolerance Observed in a Dose-Escalated Phase 1-2 Trial of Stereotactic Body Radiation Therapy for Prostate Cancer

Purpose: To convey the occurrence of isolated cases of severe rectal toxicity at the highest dose level tested in 5-fraction stereotactic body radiation therapy (SBRT) for localized prostate cancer; and to rationally test potential causal mechanisms to guide future studies and experiments to aid in mitigating or altogether avoiding such severe bowel injury. Methods and Materials: Clinical and treatment planning data were analyzed from 91 patients enrolled from 2006 to 2011 on a dose-escalation (45, 47.5, and 50 Gy in 5 fractions) phase 1/2 clinical study of SBRT for localized prostate cancer. Results: At the highest dose level, 6.6% of patients treated (6 of 91) developed high-grade rectal toxicity, 5 of whom required colostomy. Grade 3+ delayed rectal toxicity was strongly correlated with volume of rectal wall receiving 50 Gy >3 cm{sup 3} (P<.0001), and treatment of >35% circumference of rectal wall to 39 Gy (P=.003). Grade 2+ acute rectal toxicity was significantly correlated with treatment of >50% circumference of rectal wall to 24 Gy (P=.010). Conclusion: Caution is advised when considering high-dose SBRT for treatment of tumors near bowel structures, including prostate cancer. Threshold dose constraints developed from physiologic principles are defined, and if respected can minimize risk ofmore » severe rectal toxicity.« less
Authors:
 [1] ;  [2] ;  [1] ;  [3] ;  [4] ;  [1] ;  [5] ;  [6] ;  [7] ;  [8] ; ;  [1] ;  [5] ;  [3] ;  [1]
  1. Department of Radiation Oncology, University of Texas Southwestern Medical Center, Dallas, Texas (United States)
  2. Department of Radiation Oncology, University of Minnesota, Minneapolis, Minnesota (United States)
  3. Harold C. Simmons Comprehensive Cancer Center, University of Texas Southwestern Medical Center, Dallas, Texas (United States)
  4. Department of Urology, University of Texas Southwestern Medical Center, Dallas, Texas (United States)
  5. Department of Radiation Oncology, University of Colorado, Denver, Colorado (United States)
  6. Department of Radiation Oncology, University of Florida Health Cancer Center at Orlando Health, Orlando, Florida (United States)
  7. Department of Radiation Oncology, University of California, Los Angeles, Los Angeles, California (United States)
  8. Prairie Lakes Hospital, Watertown, South Dakota (United States)
Publication Date:
OSTI Identifier:
22420334
Resource Type:
Journal Article
Resource Relation:
Journal Name: International Journal of Radiation Oncology, Biology and Physics; Journal Volume: 89; Journal Issue: 3; Other Information: Copyright (c) 2014 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
62 RADIOLOGY AND NUCLEAR MEDICINE; HAZARDS; NEOPLASMS; PATIENTS; PLANNING; PROSTATE; RADIOTHERAPY; RECTUM; THRESHOLD DOSE; TOXICITY