title: Intensity-modulated radiotherapy with an integrated boost to the macroscopic tumor volume in the treatment of high-grade gliomas.
abstract: Integrated boost radiotherapy (IBRT) delivers a higher fraction size to the gross tumor volume and a conventional fraction size to the surrounding tissue of microscopic spread. We compared stereotactic conformal radiotherapy (SCRT) and intensity-modulated radiotherapy (IMRT) with regard to their suitability for IBRT in the treatment of high-grade gliomas. In 20 patients treated with conventional radiotherapy, an additional treatment plan for IBRT [planning target volume (PTV1) defined as contrast-enhancing lesion plus margin due to setup errors 75 Gy, PTV2 defined as edema plus margin due to microscopic spread and setup error 60 Gy] with 7 non-coplanar beams for IMRT and for SCRT was carried out and compared. The part of the PTV2 irradiated with more than 107% of the prescribed dose was 13.9% for IMRT and 30.9% for SCRT (P < 0.001). Dose coverage of PTV2 (volume above 95% of the prescribed dose) was improved with IMRT (88.4% vs. 75.3% with SCRT, P < 0.001). Dose coverage of PTV1 was slightly higher with SCRT (93.7% vs. 87.5% with IMRT), but the conformity to the boost shape was improved by IMRT [conformity index (COIN95) = 0.85 vs. 0.69 with SCRT]. Simultaneously the brain volume irradiated with > 50 Gy was reduced from 60 to 33 cc (P < 0.001). We conclude that IMRT is suitable for local dose escalation in the enhancing lesion and for delivering a homogeneous dose to the PTV2 outside the PTV1 at the same time. Our encouraging results justify application of IMRT for IBRT in the treatment of high-grade gliomas. For clinical evaluation a phase III study has been initiated.
authors.affiliation: Department of Radiotherapy, German Cancer Research Center, Heidelberg, Germany. c.thilmann@dkfz.de
authors.forename: C
authors.initials: C
authors.lastname: Thilmann
authors.forename: A
authors.initials: A
authors.lastname: Zabel
authors.forename: K H
authors.initials: KH
authors.lastname: Grosser
authors.forename: A
authors.initials: A
authors.lastname: Hoess
authors.forename: M
authors.initials: M
authors.lastname: Wannenmacher
authors.forename: J
authors.initials: J
authors.lastname: Debus
mesh_terms: D001932:Brain Neoplasms / Q000473:pathology / Q000532:radiotherapy*; D005910:Glioma / Q000473:pathology / Q000532:radiotherapy*; D006801:Humans; D011879:Radiotherapy Dosage