Estimation of {alpha}/{beta} for Late Rectal Toxicity Based on RTOG 94-06
- Department of Biostatistics, University of Texas M.D. Anderson Cancer Center, Houston, TX (United States)
- Department of Radiation Oncology, Washington University, St. Louis, MO (United States)
- Department of Radiation Physics, University of Texas M.D. Anderson Cancer Center, Houston, TX (United States)
- American College of Radiology, Philadelphia, PA (United States)
- Department of Radiation Oncology, University of Texas M.D. Anderson Cancer Center, Houston, TX (United States)
- Department of Radiation Oncology, University of California Davis Cancer Center, Sacramento, CA (United States)
Purpose: To estimate {alpha}/{beta}, the parameter ratio from the linear-quadratic (LQ) model, for Grade {>=}2 late rectal toxicity among patients treated on Radiation Therapy Oncology Group (RTOG) protocol 94-06; and to determine whether correcting the rectal dose-volume histogram (DVH) for differences in dose per fraction, based on the LQ model, significantly improves the fit to these data of the Lyman-Kutcher-Burman (LKB) normal-tissue complication probability (NTCP) model. Methods and Materials: The generalized LKB model was fitted to the Grade {>=}2 late rectal toxicity data in two ways: by using DVHs representing physical dose to rectum, and by using a modified approach in which dose bins in the rectal DVH were corrected for differences in dose per fraction using the LQ model, with {alpha}/{beta} estimated as an additional unknown parameter. The analysis included only patients treated with the same treatment plan throughout radiotherapy, so that the dose per fraction to each voxel of rectum could be determined from the DVH. The likelihood ratio test was used to assess whether the fit of the LQ-corrected model was significantly better than the fit of the LKB model based on physical doses to rectum. Results: The analysis included 509 of the 1,084 patients enrolled on RTOG 94-06. The estimate of {alpha}/{beta} from the LQ-corrected LKB model was 4.8 Gy, with 68% confidence interval 0.6 Gy to 46 Gy. The fit was not significantly different from the fit of the LKB model based on physical dose to rectum (p = 0.236). Conclusions: The estimated fractionation sensitivity for Grade {>=}2 late rectal toxicity is consistent with values of {alpha}/{beta} for rectum found previously in human beings and in rodents. However, the confidence interval is large, and there is no evidence that LQ correction of the rectal DVH significantly changes the fit or predictions of the LKB model for this endpoint.
- OSTI ID:
- 21587732
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 2 Vol. 81; ISSN IOBPD3; ISSN 0360-3016
- Country of Publication:
- United States
- Language:
- English
Similar Records
Do Intermediate Radiation Doses Contribute to Late Rectal Toxicity? An Analysis of Data From Radiation Therapy Oncology Group Protocol 94-06
Grading-System-Dependent Volume Effects for Late Radiation-Induced Rectal Toxicity After Curative Radiotherapy for Prostate Cancer