Dosimetric evaluation of helical tomotherapy and volumetric-modulated arc therapy for malignant pleural mesothelioma: a planning study for dose escalation

Abstract

Background To compare the dosimetric differences between helical tomotherapy (HT) and volumetric-modulated arc therapy (VMAT) treatment plans for inoperable malignant pleural mesothelioma (MPM). Methods Ten patients with inoperable MPM were retrospectively planned with the HT and VMAT techniques, and the dose-volume histogram (DVH)-based parameters of the planning target volume (PTV) and organs at risk (OARs) were compared. Results Compared with the VMAT plans, the target homogeneity index (HI) and conformity index (CI) of the HT plans were significantly better (HI: 1.04±0.01 vs. 1.11±0.03, CI: 0.80±0.07 vs. 0.71±0.12, respectively) (P<0.001, P=0.013, respectively). Regarding the OARs, including the ipsilateral lung, contralateral lung, heart, and spinal cord, the differences among the V30 (Vx: fraction of volume receiving >5, 10, 20, and 30 Gy, respectively) of the ipsilateral lung and V5, V10, and V20 of the contralateral lung were statistically significant (P=0.031, P=0.030, P=0.021, P=0.003, respectively). However, there was no significant differences between HT plans and VMAT plans, regarding the V5, V10 and V20 of the ipsilateral lung, V3 of the contralateral lung, V5 and Dmean of the heart, and Dmax of the cord. The treatment delivery time of the VMAT was significantly shorter than that of the HT (mean delivery time: 3.27±1.65 vs. 11.11±3.75 min, respectively) (P<0.001). Conclusions Compared to the VMAT plans, the HT plans not only demonstrated more optimal target coverage and conformity but also considerably reduced the dose-volume parameters of the OARs in both low-dose areas in contralateral lung and high-dose areas in ipsilateral lung and contralateral lung, which is correlated to radiation injury. However, the treatment delivery time of the HT plans was longer.

Dosimetric and Radiobiological Impact of Flattening Filter‐Free Beam and Dose Calculation Algorithm Using RapidArc Plans for Cervical Cancer Treatment

“…15 Zhang et al dosimetrically evaluated patients with cervical cancer after hysterectomy and found similar targets and OAR sparing using VMAT with FFF beams. 17 In the current study, no significant differences were found in D max , D 98% , and CI between the FF and FFF beams with AAA and AXB plans; D min and D mean exhibited statistically significant differences. In a similar study, Bell et al found that the combination of a high dose rate and mARC resulted in a decrease in treatment time and out-of-field dose for prostate cancer.…”