Hippocampal sparing for brain tumor radiotherapy: A retrospective study comparing intensity-modulated radiotherapy and volumetric-modulated arc therapy

Context: Radiotherapy may have side effects on the brain, such as radiation necrosis, cognitive impairment, and a high chance of tumor recurrence, which has been considered the most common cause of treatment failure. Aims: Using intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) techniques, we aimed to test the potential outcome of sparing the contralateral hippocampus (CLH) in radiotherapy for brain tumors by comparing dosimetric parameters. Settings and Design: A prospective clinical comparative study. Subjects and Methods: Using IMRT and VMAT, sparing CLH in radiotherapy of brain tumors was tested in ten patients, and various dosimetric parameters were compared. The treatment plans were accepted only if they met the set of planning objectives defined in the protocol. Results: The dose delivered to 95% of the CLH volume (CLH D95), and the mean (CLH Dmean) and max (CLH Dmax) doses were found to be significantly highest in the standard IMRT (P = 0.002, <0.001, and < 0.001, respectively). The lowest CLH D95, CLH Dmean and CLH Dmax for the hippocampus were detected in sparing VMAT planning than in the other plans (P < 0.05). None of the post hoc comparisons for CLH D95 was different among any of the plans, whereas the mean dose to CLH was statistically different among all paired comparisons (P < 0.008). The maximum dose to CLH was also statistically different among all paired plans (P < 0.008), except the dose difference between standard VMAT and IMRT plans. Conclusions: Although VMAT planning is troublesome and time-consuming, the advantage of sparing the hippocampus is beneficial, preserving the hippocampus and cognitive functions during radiotherapy.