Radiation Pneumonitis After Hypofractionated Radiotherapy: Evaluation of the LQ(L) Model and Different Dose Parameters
- Department of Radiation Oncology, Netherlands Cancer Institute-Antoni van Leeuwenhoek Hospital, Amsterdam (Netherlands)
- Department of Radiology, Hokkaido University School of Medicine, Sapporo (Japan)
Purpose: To evaluate the linear quadratic (LQ) model for hypofractionated radiotherapy within the context of predicting radiation pneumonitis (RP) and to investigate the effect if a linear (L) model in the high region (LQL model) is used. Methods and Materials: The radiation doses used for 128 patients treated with hypofractionated radiotherapy were converted to the equivalent doses given in fractions of 2 Gy for a range of {alpha}/{beta} ratios (1 Gy to infinity) according to the LQ(L) model. For the LQL model, different cut-off values between the LQ model and the linear component were used. The Lyman model parameters were fitted to the events of RP grade 2 or higher to derive the normal tissue complication probability (NTCP). The lung dose was calculated as the mean lung dose and the percentage of lung volume (V) receiving doses higher than a threshold dose of xGy (V{sub x}). Results: The best NTCP fit was found if the mean lung dose, or V{sub x}, was calculated with an {alpha}/{beta} ratio of 3 Gy. The NTCP fit of other {alpha}/{beta} ratios and the LQL model were worse but within the 95% confidence interval of the NTCP fit of the LQ model with an {alpha}/{beta} ratio of 3 Gy. The V{sub 50} NTCP fit was better than the NTCP fit of lower threshold doses. Conclusions: For high fraction doses, the LQ model with an {alpha}/{beta} ratio of 3 Gy was the best method for converting the physical lung dose to predict RP.
- OSTI ID:
- 21436134
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 5 Vol. 77; ISSN IOBPD3; ISSN 0360-3016
- Country of Publication:
- United States
- Language:
- English
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