Hypofractionation Regimens for Stereotactic Radiotherapy for Large Brain Tumors
Received 23 October 2007; accepted 28 December 2007. published online 27 March 2008.
Purpose
To investigate equivalent regimens for hypofractionated stereotactic radiotherapy (HSRT) for brain tumor treatment and to provide dose-escalation guidance to maximize the tumor control within the normal brain tolerance.
Methods and Materials
The linear-quadratic model, including the effect of nonuniform dose distributions, was used to evaluate the HSRT regimens. The α/β ratio was estimated using the Gammaknife stereotactic radiosurgery (GKSRS) and whole-brain radiotherapy experience for large brain tumors. The HSRT regimens were derived using two methods: (1) an equivalent tumor control approach, which matches the whole-brain radiotherapy experience for many fractions and merges it with the GKSRS data for few fractions; and (2) a normal-tissue tolerance approach, which takes advantages of the dose conformity and fractionation of HSRT to approach the maximal dose tolerance of the normal brain.
Results
A plausible α/β ratio of 12 Gy for brain tumor and a volume parameter n of 0.23 for normal brain were derived from the GKSRS and whole-brain radiotherapy data. The HSRT prescription regimens for the isoeffect of tumor irradiation were calculated. The normal-brain equivalent uniform dose decreased as the number of fractions increased, because of the advantage of fractionation. The regimens for potential dose escalation of HSRT within the limits of normal-brain tolerance were derived.
Conclusions
The designed hypofractionated regimens could be used as a preliminary guide for HSRT dose prescription for large brain tumors to mimic the GKSRS experience and for dose escalation trials. Clinical studies are necessary to further tune the model parameters and validate these regimens.
∗Department of Radiation Medicine, The Ohio State University, Columbus, OH
†Department of Neurosurgery, The Ohio State University, Columbus, OH
‡Department of Radiology, The Ohio State University, Columbus, OH
Reprint requests to: Jian Z. Wang, Ph.D., Department of Radiation Medicine, James Cancer Hospital and Solove Research Institute, The Ohio State University, 300 West 10th Ave., Rm. 094, Columbus, OH 43210. Tel: (614) 293-6502; Fax: (614) 293-4044
ABSTRACT