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.
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 cancerpatients 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.
Authors: Jing Zhao; Ellen D Yorke; Ling Li; Brian D Kavanagh; X Allen Li; Shiva Das; Moyed Miften; Andreas Rimner; Jeffrey Campbell; Jinyu Xue; Andrew Jackson; Jimm Grimm; Michael T Milano; Feng-Ming Spring Kong Journal: Int J Radiat Oncol Biol Phys Date: 2016-03-25 Impact factor: 7.038
Authors: Till Tobias Böhlen; Jean-François Germond; Jean Bourhis; Marie-Catherine Vozenin; Claude Bailat; François Bochud; Raphaël Moeckli Journal: Med Phys Date: 2021-10-22 Impact factor: 4.506