Neural stem cells in the brain are thought to be involved in injury repair and tumor inhibition. This study assesses the feasibility of sparing NSC niches during radiotherapy. The aim of this study was to analyse the feasibility of sparing ipsilateral, contralateral and bilateral neural stem cell (NSC) compartment during partial brain radiotherapy (PBRT) in brain tumors.
Twenty two consecutive patients of brain tumor were evaluated (14 GBM, 3 astrocytoma, 3 gliomas, 1 ependymoma & 1 pituitary macroadenoma). The post-op tumor bed was contoured as CTV with appropriate margin (2-3 cm) and the PTV margin (0.3 to 0.5 cm) was created. The NSC was contoured on fused MRI and CTscans as area encompassing 0.5cm around the lateral ventricles of the brain. Ipsilateral, contralateral and bilateral NSC regions were labelled as avoidance structures. IMRT treatment plans were created using the Precise treatment planning system using 5 non-coplanar beams and delivered with Cone beam CTscan image guidance. Analysis was done for period of February 2013 to November 2013.
IMRT was delivered to 22 brain tumor patients using 5 beams to a dose of 60Gy/30fractions over 6 weeks. The median age of patients was 57.5 years (range: 23-75 years).The median volume of tumor was 56 cc (range:1.4-332.8 cc). The maximum, mean & minimum dose delivered to ipsilateral NSC was 50.4 Â± 16.2Gy, 27 Â± 20.4Gy & 9 Â± 15.6Gy respectively. The maximum, mean & minimum dose to contralateral NSC was 52.2 Â± 15Gy, 28.2 Â± 18.6Gy and 13.2 Â± 16.8Gy respectively. The maximum, mean & minimum dose delivered to bilateral NSC was 54.6 Â± 12.6, 27 Â± 15 & 7.8 Â± 13.2 Gy respectively. After a median follow up of 10 months, 11 pts (50 %) were free of disease, 3 pts (13.6%) progressed, 2 (9%)pts were loss to follow up, 4(18.1%) pts were dead, 1(4.5%) patient died during treatment & 1 (4.5%) patient defaulted. The overall survival, calculated using Kaplan meier survival analysis was 50% at 5 months.
IMRT is a feasible option for neural stem cell sparing PBRT in brain tumors with comparable survival rates and minimum neuro-cognitive function decline.
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All authors have declared no conflicts of interest.