Comparison of helical tomotherapy, VMAT, and DMLC-IMRT techniques used in radiotherapy of pleural disseminated thymic tumors.

Pleural disseminated thymic tumors are therapeutically challenging due to their complex target volumes and the need to preserve lung function. This retrospective study aimed to compare the dosimetric parameters of helical tomotherapy (TOMO), volumetric modulated arc therapy (VMAT), and dynamic multileaf collimator intensity-modulated radiotherapy (DMLC-IMRT) for the treatment of pleural disseminated thymic tumors, focusing on target coverage and organ at risk (OAR) sparing, particularly the lungs. Twenty patients requiring ipsilateral whole-pleural irradiation were enrolled. Three distinct radiotherapy plans (TOMO, VMAT, and DMLC-IMRT) were designed for each patient and collaboratively evaluated by radiation oncologists and medical physicists. Dosimetric parameters for the planning target volume (PTV) and OARs, including the lungs, spinal cord, heart, esophagus, liver, and whole body, were compared. The optimal plan for each technique was selected for dosimetric comparison. All enrolled patients ultimately underwent TOMO-based radiation treatment planning. TOMO demonstrated superior PTV coverage (95.12% ± 2.76%) compared with VMAT and DMLC-IMRT (p < 0.0001). TOMO also demonstrated better control of hotspots and dose gradients outside the target area. For OARs, TOMO significantly reduced the mean dose and V5, V10, and V20 values for the ipsilateral and total lungs compared with VMAT and DMLC-IMRT (p < 0.05). Specifically, the ipsilateral lung V20 was reduced by more than 12% (TOMO: 60.15% ± 16.21%; VMAT: 72.61% ± 20.26%; DMLC-IMRT: 72.03% ± 18.82%), and the contralateral lung V5 was reduced by 11% (TOMO: 34.07% ± 24.35%; VMAT: 45.91% ± 25.88%; DMLC-IMRT: 44.57% ± 21.63%). The mean lung dose with TOMO was 13.45 Gy, with V20 < 30% and V5 < 65%, meeting stringent lung-sparing criteria. No significant differences were observed in the dose to other OARs between the 3 techniques. For the treatment of pleural disseminated thymomas, TOMO offered significant dosimetric advantages over VMAT and DMLC-IMRT in terms of target coverage and protection of the lungs. These differences could be clinically meaningful, with the potential to reduce the risk of radiation pneumonitis, a critical consideration in thoracic radiotherapy. Therefore, we recommend TOMO as the first-line clinical approach in these cases, with further studies required to validate long-term clinical outcomes.