3D-CRT versus RapidArc in Deep Tempero-Parietal High Grade Gliomas: Do We Really Need Higher Technology?

The aim of this study was to dosimetrically compare single arc RapidArc with conventional 3D-CRT plans for tempero-parietal high grade gliomas with respect to PTV coverage and doses perceived by surrounding critical organs at risk.

Thirty patients with the pathological diagnosis of high grade gliomas (WHO grade III-IV) were selected to be enrolled in our study. Patients were referred to our center (center of Clinical Oncology and Radiotherapy, Cairo University) during the period March 2020 till June 2021 for post-operative irradiation using 3D-CRT technique. For all patients, the dose prescribed to the planning target volume (PTV) was 60 Gy in 30 fractions. A RA plan was performed for each patient and dosimetrically was compared to the 3D-CRT plan.

The PTV coverage in terms of V95% was significantly superior in the RA plans with values of 98.4 ± 1.7 compared to 94.4 ± 2.6 for the 3D-CRT plans (p-value of 0.004). The doses risk structures ( eyes, optic nerves and cochleae)  was lower with the RA plans as contrasted to the 3D-CRT plan with an exception for the  intraocular lens which received higher doses in the RA plan with a statistically significant p-value of 0.001 and 0.002 for the  Ipsilateral and contralateral lens, respectively. The average number of MUs ± SD was 358.6± 44.4 for the RA plans versus 247.6 ± 16.1 for 3D-CRT plans (p-value 0.001). The Dmean of healthy brain tissue was nearly equal for both plans (p-value of 0.071).

The plans achieved by RA showed superior dose conformity, PTV coverage, more homogeneous dose distribution when contrasted to 3D-CRT plans. With the exception of both intraocular lenses, the RA plans showed better OAR sparing and utilized a higher number of MUs compared to the 3D-CRT.