Jiankui Yuan PhD, Abstract Co-Author: Nothing to Disclose

Jian Wang, Presenter: Nothing to Disclose

Simon Lo, Abstract Co-Author: Nothing to Disclose

John Christopher Grecula MD, Abstract Co-Author: Nothing to Disclose

William T.C. Yuh MD, MSEE, Abstract Co-Author: Nothing to Disclose

Nina A. Mayr MD, Abstract Co-Author: Nothing to Disclose

To investigate equivalent regimens for hypofractionated stereotactic radiotherapy (HSRT) for brain tumor treatment and to provide a dose-escalation guidance to maximize the tumor control within the normal brain tolerance.

The linear-quadratic (LQ) model, including the effect of non-uniform dose distribution, was used to evaluate the HSRT regimens. The α/β ratio was estimated based on the GKSRS experience for large tumor. Two different approaches were taken to derive the HSRT regimens: (1) To match the clinical experience of tumor control: for few fractions, the regimens will merge to GK data and for a large number of fractions, match the WBRT experience; (2) To approach the maximum tolerance of normal brain: take the advantages of dose conformity and fractionation of HSRT for tumor dose escalation.

A plausible α/β ratio of 12 Gy was determined from the equivalence study of GKSRS and WBRT for large brain tumor. The HSRT prescription regimens for isoeffect of tumor irradiation have been calculated. These regimens could be used as a reference for HSRT dose prescription in clinical practice. Potential dose escalation was derived from the maximum tolerance of normal brain. The normal brain equivalent uniform dose in 2 Gy fractions was found to decrease with the increase of the number of fractions, indicating the advantage of hypofractionation, and room for dose escalation increases as the number of fractions increases. For example, in order to achieve the same tumor control as one fraction 15 Gy GKSRS, the dose prescription for 10-fraction HRST could be 33.2 Gy, while in order to achieve the same maximum normal brain tolerance the dose prescription could be 54.9 Gy.

The designed hypofractionated regimens could be used as a preliminary guide of HSRT dose prescription for large brain tumors to mimic GKSRS experience and for dose escalation trials. Data of clinical outcome are necessary to further tune the model parameters and validate these regimens.

The study presented hypofractionation regimens for stereotactic radiotherapy of large brain tumors.

Yuan, J, Wang, J, Lo, S, Grecula, J, Yuh, W, Mayr, N, Hypofractionation Regimens for Stereotactic Radiotherapy of Large Brain Tumors.  Radiological Society of North America 2007 Scientific Assembly and Annual Meeting, November 25 - November 30, 2007 ,Chicago IL. http://archive.rsna.org/2007/5015827.html