Comparison of Hippocampal Sparing Intensity Modulated Radiotherapy Plans in Patients of Brain Tumors treated by Three-dimensional Conformal Radiotherapy

Abstract

Introduction: Radiotherapy plays a key role in brain tumors
after surgery. However, concerns regarding neurocognitive
toxicity after radiotherapy are being raised. Newer radiotherapy
techniques can deliver radiotherapy with better precision
planning and delivery. Effective hippocampal sparing is possible
with IMRT which governs the neurocognitive functions. The
present study is done to compare whether hippocampal sparing
is possible in brain tumors by 3D Conformal Radiotherapy
and Intensity Modulated Radiotherapy and their effects on
neurocognitive functions.
Materials and Methods: Twenty-two patients with brain cancer
were recruited from November 2019 to April 2021. Patients were
treated with 3D-CRT technique and alternate IMRT plans were
generated. Dosimetric parameters of PTV, organs at risk along
with hippocampus were evaluated and compared for 3DCRT
and IMRT plans. Neurocognitive functions were evaluated
using MMSE score.
Result: In study group, there were 16 males and 6 females with
median age 45 years. Brain tumors were commonly located in
frontal lobe (36%) followed by parieto-occipital lobe (18%) and
fronto-temporo-parietal lobe (13.63%). PTV parameters were
better for IMRT and statistically significant. The OARs did not
show significant difference except in both lens though they are
within tolerance limits. There is no significant difference in the
dosimetric parameters of hippocampus in 3D-CRT and IMRT
plans. The p-value for Dmax is 0.79, Dmean is 0.26, Dmin is
0.18 between hippocampal sparing radiotherapy plans.
Conclusion: Anatomic location of tumor plays a key role in
deciding hippocampal sparing. Patients whose NCFs showed
improvement on subsequent visits, highlights the fact that
primary tumor control is a key factor in deciding decline or
improvement in NCFs. It should be beneficial for LGG that have
better survival and prognosis as compared to HGG cases.