Effects of tumor treating fields (TTF) arrays on the radiation doses to glioblastoma / 中华放射医学与防护杂志

ABSTRACT

Objective:To preliminarily explore the effects of tumor treating fields (TTF) arrays on the dose distribution in the treatment of Glioblastoma (GBM) using combined radiotherapy and concurrent TTF.Methods:EDR2 and MatriXX plate ionization chamber were employed to measure the absorbed doses of tissues at different depths (< 1 mm, 3 mm, 5 mm, 1 cm, 1.5 cm, 3 cm, 5 cm, 10 cm, and 15 cm) in the case that TTF arrays and latex-free foam were attached and not attached on the surface. Then the absorbed doses were calculated, compared, and analyzed. For the volumetric arc therapy (VMAT) of 10 GBM patients, deep dose verification was performed using the Sun Nuclear ArcCheck 3D dose verification system and the D99%, Dmean, and D1% of tumors and OARs were assessed. Results:The surface dose increased by 173% in the case that TTF arrays and latex-free foam were attached to the surface compared with the case of the surface with nothing attached. The surface dose increased by 61.7% due to the attachment of low-density latex-free foam. The dose deviation gradually decreased with an increase in the depth and stabilized (about 4%) at a depth of greater than 1.5 cm. As indicated by the VMAT verification result, the D99%, Dmean, and D1% of PTV and CTV decreased by 1.1%-1.2% and the Dmean and D1% of OARs (i.e., brainstem, pituitary gland, optic chiasma, optic nerve, eyeball, and eye crystal) decreased by 0.7%-1.5% in the case that TTF array and latex-free foam were attached on the surface compared with the case the surface with nothing attached. Conclusions:The combined radiotherapy and concurrent TTF in the GBM treatment will lead to a slight reduction of the absorbed doses of targets and OARs but a significant increase in the absorbed doses of the scalp. Therefore, it is recommended that the scalp doses should be reduced as far as possible in the design of the radiation treatment plan to reduce the adverse reactions on the scalp of GBM patients.