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Acta Oncol. 2010 Oct;49(7):1052-7. doi: 10.3109/0284186X.2010.498835.

Hypofractionation does not increase radiation pneumonitis risk with modern conformal radiation delivery techniques.

Author information

1
Department of Human Oncology, University of Wisconsin School of Medicine and Public Health, Madison, WI 53792, USA.

Abstract

PURPOSE:

To study the interaction between radiation dose distribution and hypofractionated radiotherapy with respect to the risk of radiation pneumonitis (RP) estimated from normal tissue complication probability (NTCP) models.

MATERIAL AND METHODS:

Eighteen non-small cell lung cancer patients previously treated with helical tomotherapy were selected. For each patient a 3D-conformal plan (3D-CRT) plan was produced in addition to the delivered plan. The standard fractionation schedule was set to 60 Gy in 30 fractions. Iso-efficacy comparisons with hypofractionation were performed by changing the fractionation and the physical prescription dose while keeping the equivalent tumor dose in 2 Gy fractions constant. The risk of developing RP after radiotherapy was estimated using the Mean Equivalent Lung Dose in 2-Gy fractions (MELD(2)) NTCP model with α/β=4 Gy for the residual lung. Overall treatment time was kept constant.

RESULTS:

The mean risk of clinical RP after standard fractionation was 7.6% for Tomotherapy (range: 2.8-15.9%) and 9.2% for 3D-CRT (range 3.2-20.2%). Changing to 20 fractions, the Tomotherapy plans became slightly less toxic if the tumor α/β ratio, (α/β)(T), was 7 Gy (mean RP risk 7.5%, range 2.8-16%) while the 3D-CRT plans became marginally more toxic (mean RP risk 9.8%, range 3.2-21%). If (α/β)(T) was 13 Gy, the mean estimated risk of RP is 7.9% for Tomotherapy (range: 2.8-17%) and 10% for 3D-CRT (range 3.2-22%).

CONCLUSION:

Modern highly conformal dose distributions are radiobiologically more forgiving with respect to hypofractionation, even for a normal tissue endpoint where α/β is lower than for the tumor in question.

PMID:
20831495
DOI:
10.3109/0284186X.2010.498835
[Indexed for MEDLINE]

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