Comparison of Radiation-Induced Normal Lung Tissue Density Changes for Patients From Multiple Institutions Receiving Conventional or Hypofractionated Treatments
- Department of Radiation Oncology, University of Colorado School of Medicine, Aurora, Colorado (United States)
- Department of Radiation Oncology, University of North Carolina, Chapel Hill, North Carolina (United States)
- Division of Biostatistics and Bioinformatics, University of Maryland Greenbaum Cancer Center, and Department of Epidemiology and Public Health, University of Maryland School of Medicine, Baltimore, Maryland (United States)
- Department of Radiation Oncology, VU University Medical Center, Amsterdam (Netherlands)
- London Regional Cancer Program, London, Ontario (Canada)
Purpose: To quantitatively assess changes in computed tomography (CT)–defined normal lung tissue density after conventional and hypofractionated radiation therapy (RT). Methods and Materials: The pre-RT and post-RT CT scans from 118 and 111 patients receiving conventional and hypofractionated RT, respectively, at 3 institutions were registered to each other and to the 3-dimensional dose distribution to quantify dose-dependent changes in normal lung tissue density. Dose-response curves (DRC) for groups of patients receiving conventional and hypofractionated RT were generated for each institution, and the frequency of density changes >80 Hounsfield Units (HU) was modeled depending on the fractionation type using a Probit model for different follow-up times. Results: For the pooled data from all institutions, there were significant differences in the DRC between the conventional and hypofractionated groups; the respective doses resulting in 50% complication risk (TD{sub 50}) were 62 Gy (95% confidence interval [CI] 57-67) versus 36 Gy (CI 33-39) at <6 months, 48 Gy (CI 46-51) versus 31 Gy (CI 28-33) at 6-12 months, and 47 Gy (CI 45-49) versus 35 Gy (32-37) at >12 months. The corresponding m values (slope of the DRC) were 0.52 (CI 0.46-0.59) versus 0.31 (CI 0.28-0.34) at <6 months, 0.46 (CI 0.42-0.51) versus 0.30 (CI 0.26-0.34) at 6-12 months, and 0.45 (CI 0.42-0.50) versus 0.31 (CI 0.27-0.35) at >12 months (P<.05 for all comparisons). Conclusion: Compared with conventional fractionation, hypofractionation has a lower TD{sub 50} and m value, both suggesting an increased degree of normal tissue density sensitivity with hypofractionation.
- OSTI ID:
- 22420349
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 3 Vol. 89; ISSN IOBPD3; ISSN 0360-3016
- Country of Publication:
- United States
- Language:
- English
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