Para-ventricular Radiation Necrosis after Radiation Therapy for Malignant Astrocytomas

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Purpose/Objective(s)

We initiated hypofractionated high-dose IMRT (hhIMRT) for the treatment of malignant astrocytomas (MA) in 2001, and frequently observed necroses in the para-ventricular (pV) regions, even though these regions were not included in the high-dose field. Recently, neural progenitor cells have been known to exist in the pV area, and prevention of these cells is recognized as important to keep cognitive functions of pts after treatment. In this study, we investigated the pV necrosis, to clarify the

Materials/Methods

In this study, 171 MAs were enrolled. Among these pts, 96 were treated by conventional radiation therapy (cRT), and the remaining 75 were treated by hhIMRT. For IMRT, three-layered PTVs (PTV-1: GTV+5mm, PTV-2: GTV+20mm, PTV-3: perifocal edema) were drawn and 68Gy for PTV-1, 40Gy for PTV-2 and 32Gy for PTV-3 were delivered by eight fractions. Enhanced lesion which shrunk its volume by steroid was diagnosed as necrosis. Regardless of the response to steroid, the lesion was also diagnosed as

Results

After hhIMRT, necrosis was more frequently observed in pV area (15/75) than original tumor site (11/75), although the irradiated dose was smaller in pV area. Furthermore, there was no significant correlation between development of pV necrosis and the volume of PTV. The T/N ratio of methionine-uptake was not significantly different (p = 0.235) but lower in pV necrosis (1.12) in compared with regional necrosis (1.85). The time to necrosis was significantly shorter after hhIMRT in compared with

Conclusions

The pV necrosis showed no correlation with irradiated dose but with fractionation scheme. The pV area had high risk for necrosis especially after hypofractionated RT. We should pay attention to protect this area to keep cognitive function of patients when we use hypofractionated RT scheme.

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Author Disclosure: T. Iuchi: None. K. Hatano: None. T. Imagunbai: None. T. Kodama: None. Y. Uchino: None. N. Tohyama: None. T. Sakaida: None. K. Kawasaki: None. Y. Hasegawa: None.

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