Late Rectal Toxicity on RTOG 94-06: Analysis Using a Mixture Lyman Model
- Department of Radiation Physics, University of Texas M.D. Anderson Cancer Center, Houston, TX (United States)
- Image-Guided Therapy QA Center, Washington University, St. Louis, MO (United States)
- Department of Radiation Oncology, Washington University, St. Louis, MO (United States)
- American College of Radiology, Philadelphia, PA (United States)
- Department of Radiation Oncology, University of California Davis Cancer Center, Sacramento, CA (United States)
- Department of Radiation Oncology, University of Texas M.D. Anderson Cancer Center, Houston, TX (United States)
- Department of Biostatistics, University of Texas M.D. Anderson Cancer Center, Houston, TX (United States)
Purpose: To estimate the parameters of the Lyman normal-tissue complication probability model using censored time-to-event data for Grade {>=}2 late rectal toxicity among patients treated on Radiation Therapy Oncology Group 94-06, a dose-escalation trial designed to determine the maximum tolerated dose for three-dimensional conformal radiotherapy of prostate cancer. Methods and Materials: The Lyman normal-tissue complication probability model was fitted to data from 1,010 of the 1,084 patients accrued on Radiation Therapy Oncology Group 94-06 using an approach that accounts for censored observations. Separate fits were obtained using dose-volume histograms for whole rectum and dose-wall histograms for rectal wall. Results: With a median follow-up of 7.2 years, the crude incidence of Grade {>=}2 late rectal toxicity was 15% (n = 148). The parameters of the Lyman model fitted to dose-volume histograms data, with 95% profile-likelihood confidence intervals, were TD{sub 50} = 79.1 Gy (75.3 Gy, 84.3 Gy), m = 0.146 (0.107, 0.225), and n = 0.077 (0.041, 0.156). The fit based on dose-wall histogram data was not significantly different. Patients with cardiovascular disease had a significantly higher incidence of late rectal toxicity (p = 0.015), corresponding to a dose-modifying factor of 5.3%. No significant association with late rectal toxicity was found for diabetes, hypertension, rectal volume, rectal length, neoadjuvant hormone therapy, or prescribed dose per fraction (1.8 Gy vs. 2 Gy). Conclusions: These results, based on a large cohort of patients from a multi-institutional trial, are expected to be widely representative of the ability of the Lyman model to describe the long-term risk of Grade {>=}2 late rectal toxicity after three-dimensional conformal radiotherapy of prostate cancer.
- OSTI ID:
- 21438063
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Vol. 78, Issue 4; Other Information: DOI: 10.1016/j.ijrobp.2010.01.069; PII: S0360-3016(10)00272-5; Copyright (c) 2010 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0360-3016
- Country of Publication:
- United States
- Language:
- English
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