Hypofractionated Stereotactic Radiotherapy in brain metastasis using Nomostat® System

Abstract

In metastatic brain lesions treatment, stereotac-tic radiation therapy represents a valid alternative to surgery, which indication is limited to single lesions, in accessible brain sites and in patients presenting an optimal performance status. The aim of this study was to develop a novel method for delivering fractionated stereotactic in-tensity-modulated radiotherapy. We present treat-ment parameters, dosimetry analysis, and prelimi-nary clinical outcome. The method incorporates high-precision invasive fixation and reduced dimen-sion pencil beams. In our hospital, since January 2008 Hypofraction-ated Stereotactic Radiation Therapy is performed using Serial Tomotherapy with Nomostat® System, connected to a 6 MV Linac. This system realizes an IMRT with dynamic gantry and a beam modulation by a binary multileaf collimator (MIMiC® multi-vane intensity-modulating collimator) attached to the Linac head. During gantry rotation, collimator automatically modifies its morphology following target shape. In treatment of lesion smaller than 1,5cm, a post-collimation device called Beak® pro-vides leaves opening limitation to 4mm, allowing an high dose conformation around the target and an high dose fall-off in surrounding healthy tissues. For stereotactic radiation therapy in brain malignan-cies, we use Talon® immobilization device, a mini-mally invasive system which consists in two tita-nium screws fixed in patient scalp; this device, making the patient in solidarity with the couch, pro-vides high accuracy in his positioning during radio-therapy sessions. In our experience, the technique has proven to be easy in implementation and highly reliable, allow-ing accurate repositioning in the hypofractionated treatments.