Non-coplanar VMAT plans for postoperative primary brain tumour to reduce dose to hippocampus, temporal lobe and cochlea: a planning study

Abstract

Objectives: This study aimed to compare radiotherapy plan quality of coplanar VMAT (CO-VMAT) and non-coplanar VMAT (NC-VMAT) for postoperative primary brain tumour. Methods: A total of 16 patients who were treated for primary brain tumours were retrospectively selected for this study. For each patient, identical CT sets with structures were used for both CO-VMAT and NC-VMAT planning. For CO-VMAT, one full arc and two coplanar half arcs were used. For NC-VMAT, one full coplanar and two non-coplanar half arcs with couch rotation of 315° or 45°. Dose constraints were adhered to the RTOG0614 and 0933. Dose volumetric parameters were collected for statistical analysis. Results: There were no significant differences for the PTV, HI, CN and μ between the CO-VMAT and NC-VMAT. For the brainstem, Dmean of CO-VMAT and NC-VMAT were 6.04 ± 3.94 Gy and 4.69 ± 2.56 Gy respectively (p < 0.05). For the ipsilateral OARs including temporal lobe, TM joint and cochlear, Dmean of CO-VMAT and NC-VMAT were 31.80 ± 12.78 Gy and 25.51 ± 17.54 Gy (p < 0.01) ; 14.12 ± 8.6 Gy and 3.35 ± 4.12 Gy (p < 0.001); 11.96 ± 11.68 Gy and 6.62 ± 9.74 Gy (p < 0.01) respectively. For contralateral OARs including hippocampus, temporal lobe, TM joint, Optic nerve, lens, eyeball and cochlear, the Dmean of CO-VMAT and NC-VMAT were 6.16 ± 2.44 Gy and 4.49 ± 2.00 Gy (p < 0.01) ; 6.48 ± 2.76 Gy and 3.68 ± 1.76 Gy (p < 0.0001); 11.96 ± 11.68 Gy and 6.62 ± 9.74 Gy (p < 0.01) respectively. Conclusion: The proposed NC-VMAT showed more favourable plan quality than the CO-VMAT for primary brain tumours, in particular to OARs located to the contralateral side-of tumours. Advances in knowledge: For primary brain tumours RT, NC-VMAT can reduce doses to the brainstem, ipsilateral temporal lobe, TM joint and cochlear, as well as OARs located to the contralateral side-of tumours.

Comparison between volumetric modulated arc therapy based coplanar and noncoplanar planning for stereotactic body radiation therapy of Comparison between Volumetric Modulated arc Therapy based Coplanar and Noncoplanar Planning for Stereotactic Body Radiation Therapy of Liver

“…We compared several dosimetric and technical parameters between non-coplanar and coplanar VMAT plans to evaluate the plan quality. The PTV coverage was similar with both the plans as well as the sparing of OARs as stated by the previous studies [ 13 , 17 ]. The D 1cc of the spine was much lesser with the non-coplanar plans.…”

“…In contrast, the coplanar full arc SBRT VMAT planning involves a simple beam arrangement but increases the irradiated volume. Some studies have compared NC-VMAT with C-VMAT for various sites like the lung, Brain, and Nasopharynx which showed the benefit of NC-VMAT plans over C-VMAT plans [16][17][18]. However, to the best of our knowledge, the application of manually selected beam orientation in VMAT plans generated with a limited number of ipsilateral partial arcs to avoid the possibility of gantry collision with the couch for liver SBRT has not been well studied.…”

Multi-Planar VMAT Plans for High-Grade Glioma and Glioblastoma Targeting the Hypothalamic-Pituitary Axis Sparing

“…It has been applied for treating prostate cancer [6,7] and liver cancer [8,9] in coplanar VMAT and lung cancer in non-coplanar VMAT [10]. In view of cranial regions, previous studies suggested that non-coplanar VMAT demonstrated a dose reduction to organs at risk (OARs) located in the peripheral regions, including the hippocampus [11][12][13], normal brain tissue, the temporal lobe and the cochlea [14,15]. A significant dose reduction to these organs helped to minimize the side effects, such as cognitive decline and auditory impairment.…”

Modified VMAT Plans for Locally Advanced Centrally Located Non-Small Cell Lung Cancer (NSCLC)

“…Several studies have demonstrated that modification of co-planar VMAT plans may reduce dose to OARs [11][12][13][14][15][16]. For example, non-coplanar VMAT plans reduced the low dose to the heart during dose delivery, while an ipsilateral lung might expose to higher radiation dose [11].…”