The need of irradiating cancers with high doses, as well as to conform treatment irradiation to different target shapes, has induced the aa., since 1990, to carry out therapies with a variable number of polycentric 180° arcs using narrow beams and 12 MV photons. In this way it was obtained a relative dose distribution similar to those of brachitherapy. Small distances between isocenters are used. This technique makes it possible: a) to deliver a high dose to the target volume whilst avoiding the surrounding tissue; b) to adapt the isodoses to the shape of any target volume, combining 3D variable cilinders. c) to choose any dose fractionation without admitting the patient, avoiding the use of invasive techniques (i.e. brachytherapy) and mantaining ample freedom in the total dose prescription. The aa. believe that the policentric multiple arcs technique may be employed in the radiotherapy of many kinds of solid tumours. Since 1993 at the Radiotherapy Department of Mestre this technique has been used in the treatment of brain cancers. Fifteen patients have already been treated, 6 affected by low grade and 9 by high grade gliomas. All patients with low grade tumors are alive; 4 of them obtained a C.R. and are NED after 26, 25, 18, 7 months, 1 obtained a P.R. (but with only 2 months of follow-up) while 1 is not yet evaluable because of the short period of follow-up (1 month). Three cases were treated with 25 Gy/5 fractions (at reference isodose) with a higher internal dose up to 40 Gy/5 fractions and a rapid decrease of the dose at the periphery, and 3 with 60 Gy/30 fractions with an inner dose up to 90 Gy/30 fractions. Seven of 9 patients affected by high grade gliomas are dead, with a median survival of 9.7 months (range 6-12 months), 2 patients are alive. They are NED but with a very short period of follow-up (7-2 months respectively). All cases were treated with 25 Gy/5 fractions at reference isodose, with an inner dose up to 40 Gy. This phase I-II study underlines that the use of polycentric multiple arcs treatment technique is well tolerated, with a low acute toxicity. Besides a dose-escalation program is necessary in high grade malignancies, because of the poor local control of prescribed dose.
|Translated title of the contribution||The polycentric multiple arcs treatment technique (or external beam brachitherapy) in the radiation treatment of the brain tumors. Phase I-II study|
|Number of pages||8|
|Journal||Rivista di Neurobiologia|
|Publication status||Published - 1995|
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