Dosimetric Comparison of Radiation Techniques for Comprehensive Regional Nodal Radiation Therapy for Left-Sided Breast Cancer: A Treatment Planning Study

Abstract

Background: Radiotherapy (RT) target volumes in breast cancer treatment increasingly include the internal mammary nodes, potentially increasing doses delivered to the heart and lung. The aim of this study was to compare cardiac and pulmonary doses in three-dimensional conformal radiotherapy (3DCRT), volumetric modulated arc therapy (VMAT), and proton beam therapy (PBT) with and without continuous positive airway pressure (CPAP), delivered in conventional fractionation (CF) or in hypofractionated (HF) schedules.Methods: In a dataset of 15 patients with left-sided breast cancer, partial wide tangential 3DCRT delivered in CF (50/25) and in HF (40/15) schedules as well as PBT delivered in CF and two-partial arc VMAT delivered in a HF schedule, each under CPAP and free breathing (FB) conditions were extensively examined. Target volume coverage and doses to organs-at-risk (OARs) were calculated for each technique. Outcomes were compared with one-way analysis of variance and the Bonferroni test, with P-values <0.05 considered significant. Results: Target volume coverage was within acceptable levels in all interventions, except for internal mammary lymph nodes D90 (99% in PBT, 90% in VMAT-CPAP, 84% in VMAT-FB, and 74% in 3DCRT). Mean heart dose (MHD) was the lowest and highest in PBT (<1 Gy) and 3DCRT with CF/FB (7.8 Gy), respectively. In photon-based techniques, the use of VMAT in HF schedules with CPAP resulted in an MHD of 2.2 Gy. Lung V20 and mean lung dose (MLD) were the highest in 3DCRT-CF-FB (44% and 20 Gy, respectively) and lowest in both VMAT-HF-CPAP and PBT (7–9% and approximately 5–6 Gy, respectively). VMAT-HF-CPAP and PBT delivered a comparable maximum dose to the left ascending artery (7.2 Gy and 6.70 Gy, respectively, with the highest dose delivered by 3DCRT [47.6 Gy]). The average doses to the contralateral breast were 0.004, 1, and 2.1 Gy in PBT, 3DCRT, and VMAT, respectively.Conclusions: PBT delivered the lowest doses to most OARs in RT for left-sided breast cancer with regional nodal irradiation. However, the dosimetric gap between proton and photon RT has narrowed substantially with modern techniques such as VMAT and CPAP; the clinical relevance of these differences is yet to be elucidated.

Automated coronary artery calcium scoring in patients with breast cancer to assess the risk of heart disease following adjuvant radiation therapy

“…To reduce the radiation dose and irradiated volume of the heart, modern RT techniques, including DIBH, prone, partial breast RT, and IMRT, are being widely adopted [ 27 ], and prospective proton RT trials (NCT02603341 and NCT04291378) are expected to reduce ACEs' potential risk. However, because individual patient anatomy varies and some require an extended RT field, keeping a cardiac dose below 1–3 Gy in all patients may be difficult [ 28 ]. Furthermore, there is a paucity of data demonstrating what dose would be sufficiently low to ensure that there is no positive linear dose-response component.…”

Use of Continuous Positive Airway Pressure (CPAP) to Limit Diaphragm Motion—A Novel Approach for Definitive Radiation Therapy for Inoperable Pleural Mesothelioma: A Pilot Study

“…The authors concluded that the slight decrease in radiation dose to the lungs would likely be clinically insignificant [ 19 ]. CPAP has also been studied in breast cancer [ 33 ]. In a study of three patients who were unable to maintain and reproduce DIBH, stimulated with FB vs. CPAP, CPAP significantly increased the total lung volume and increased distance from the sternal notch to the superior portion of heart by 0.5–1.25, the heart volume within the left-sided tangential fields was substantially decreased by more than 92%.…”