Abstract
Background: The survival rates of GBM patients have shown improvement. This increases the likelihood of manifesting radiation induced sequelae such as neurocognitive dysfunction, alopecia, and memory loss. This increases the focus on dosimetry of hippocampus, scalp, and normal brain. The present study was designed to compare the dosimetric efficacy of two conformal techniques in terms of OAR’s sparing and PTV coverage. Materials and Methods: A total of 10 patients with GBM who had received radical radiotherapy by 3DCRT technique were selected. A corresponding IMRT plan was generated for study purpose (n=20 plans). The dose prescribed to the PTV was 60 Gy in 30 fractions. Other than critical structures, additional delineation of hippocampus, normal brain and skin was done. The dosimetric parameters of PTV and OAR’s were compared amongst the two techniques. Results: The IMRT technique led to significant advantage in PTV coverage, dose homogeneity and conformity. A clear advantage with either technique could not be demonstrated in terms of point dose of critical structures. The normal brain and scalp showed significant reduction in doses with IMRT technique. The contralateral Hippocampal avoidance Zone also showed better sparing with IMRT technique but significant difference could not be demonstrated. Conclusion: The better coverage with IMRT technique was particularly observed in cases where PTV was overlapping with critical OAR’S while in rest of the cases coverage was comparable amongst both the techniques. The better sparing of scalp and normal brain may decrease the incidence of alopecia, neurocognitive dysfunction that needs to be clinically validated in future studies. Keywords: GBM, 3DCRT, IMRT.
Highlights
There has been an improvement in survival of Glioblastoma multiforme (GBM) patients due to emerging novel approaches like targeted therapy, immunotherapy and tumor treating fields. 1,2 Recent meta-analysis suggests that the two and three year survival rates for GBM patients have nearly doubled in the past 15 years. 3 This raises the concern about treatment induced toxicity
The dosimetry of planning target volume (PTV) showed a significant advantage in terms of dose coverage (V95, D95, D90), conformity (p=0.0001) and homogeneity (p=0.003) with Intensity Modulated Radiotherapy (IMRT) technique. (Figures 1, 2, 3 and 4)
The volume of overdosed regions receiving more than 107% of the prescribed dose were significantly reduced with IMRT technique (p =0.008)
Summary
There has been an improvement in survival of Glioblastoma multiforme (GBM) patients due to emerging novel approaches like targeted therapy, immunotherapy and tumor treating fields. 1,2 Recent meta-analysis suggests that the two and three year survival rates for GBM patients have nearly doubled in the past 15 years. 3 This raises the concern about treatment induced toxicity. The importance of Organs at risk (OAR’s) like brainstem, optic chiasma, optic nerves, and eyes are well established but structures like scalp, hippocampus and normal brain are not routinely considered in radiotherapy planning. They have proven association with alopecia, neurocognitive dysfunction, and memory loss and that can have a profound impact on the patient’s quality of life. The survival rates of GBM patients have shown improvement This increases the likelihood of manifesting radiation induced sequelae such as neurocognitive dysfunction, alopecia, and memory loss. This increases the focus on dosimetry of hippocampus, scalp, and normal brain. The better sparing of scalp and normal brain may decrease the incidence of alopecia, neurocognitive dysfunction that needs to be clinically validated in future studies
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