A novel x-Ray and γ-Ray combination strategy for radiotherapy after breast-conserving surgery in patients with right breast cancer

Abstract

Background and purpose: Radiotherapy is a primary therapeutic approach for breast cancer following breast-conserving surgery. The TaiChiB dual-modality radiotherapy system combining X-ray and focused γ-ray, offers a new approach to reduce the radiation dose of organs at risk (OARs) and has the potential to mitigate the adverse effects of radiotherapy. Currently, there are few studies on the dosimetric characteristics of the TaiChiB dual-modality system for actual treatment plans for specific diseases. The purpose of this work is to study the dosimetric advantages of dual-modal systems for right breast patients after breast-conserving surgery.

Material and methods: Treatment plans for 20 patients with right breast cancer were generated for a linear accelerator (LINAC) based system and the TaiChiB dual-modality system, respectively. Volumetric modulated arc therapy plans with simultaneous integrated boost (VMAT-SIB) were made for the LINAC. Focused γ-ray was used to deliver the boost dose with the dual-modality system. The dosimetric parameters of the target and OARs were evaluated and compared between the treatment plans generated for the two systems.

Results: The TaiChiB dual-modality plans exhibit a higher conformal index (CI) and lower gradient index (GI) for the PGTV and PTV compared with the LINAC-based VMAT-SIB plans. Compared to VMAT-SIB plans, the PTV Dmax, PTV Dmean, PTV V110, PGTV Dmax, and PGTV Dmean of the TaiChiB dual-modality plans are significantly lower. Meanwhile, the dose to OARs, such as the Dmean of the heart, the V5 of liver, the Dmean of ipsilateral lung, the V30 of ipsilateral lung, the V20 of ipsilateral lung, the V5 of ipsilateral lung, the Dmean of contralateral lung, Dmax of contralateral breast and the Dmean of contralateral breast are significantly reduced.

Conclusions: Our study demonstrates the dosimetric advantages of the novel TaiChiB dual-modality radiotherapy system for the treatment of right-sided breast cancer. Overall, for the TaiChiB dual-modality radiotherapy system, the radiation dose outside the target region decreases rapidly, thereby minimizing radiation exposure to neighboring organs and ensuring the conformity of the target area. Our research confirms the potential of the TaiChiB dual-modality system for future radiotherapy.

Keywords: dosimetric evaluation; radiotherapy after breast-conserving surgery; right breast cancer; x-ray and γ-Ray combination strategy; x-ray strategy.

Figure 1

Details of the concept layout and machine profile of TaiChiB system. (A) TaiChiB concept layout. Linac, gamma, and kV x-ray are installed in a donut ring gantry with slip ring power supply, and share a same IsoCenter. Blue: 6MV Linac x-ray Beam. Red: Focusing Gamma Beam. Green: KV x-ray Beam; (B) TaiChiB machine profile. TaiChiB is a novel teletherapy device combined linear accelerator, rotating gamma radiosurgery system, MV EPID panel and kV image system within an enclosed slip ring gantry, EPID panel has its own track, and can move to linac or gamma opposite position for QA to the above system (20).

Figure 2

DVH (A) and dose distribution (B) were analyzed for a patient undergoing treatment with TaiChi dual-modality plans and VMAT-SIB plans. The difference in the dose distributions (TaiChi dual-modality-VMAT-SIB) was illustrated in (C).