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

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


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.

Publication types

  • Comparative Study
  • Evaluation Study
  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Calibration
  • Carcinoma, Non-Small-Cell Lung / diagnostic imaging
  • Carcinoma, Non-Small-Cell Lung / radiotherapy*
  • Dose Fractionation, Radiation*
  • Down-Regulation
  • Humans
  • Lung Neoplasms / diagnostic imaging
  • Lung Neoplasms / radiotherapy*
  • Radiation Dosage
  • Radiation Pneumonitis / etiology*
  • Radiation Tolerance
  • Radiotherapy Planning, Computer-Assisted / methods
  • Radiotherapy Planning, Computer-Assisted / standards
  • Radiotherapy, Conformal / adverse effects*
  • Radiotherapy, Conformal / methods*
  • Radiotherapy, Conformal / standards
  • Risk Factors
  • Social Change
  • Therapeutic Equivalency
  • Tomography, Spiral Computed / methods
  • Tomography, Spiral Computed / standards