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

Abstract

PurposeHow modern cardiac sparing techniques and beam delivery systems using advanced x-ray and proton beam therapy (PBT) can reduce incidental radiation exposure doses to cardiac and pulmonary organs individually or in any combination is poorly investigated.MethodsAmong 15 patients with left-sided breast cancer, partial wide tangential 3D-conformal radiotherapy (3DCRT) delivered in conventional fractionation (CF) or hypofractionated (HF) schedules; PBT delivered in a CF schedule; and volumetric modulated arc therapy (VMAT) delivered in an HF schedule, each under continuous positive airway pressure (CPAP) and free-breathing (FB) conditions, were 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.ResultsTarget volume coverage was within acceptable levels in all interventions, except for the internal mammary lymph node D95 (99% in PBT, 90% in VMAT-CPAP, 84% in VMAT-FB, and 74% in 3DCRT). The mean heart dose (MHD) was the lowest in PBT (<1 Gy) and VMAT-CPAP (2.2 Gy) and the highest in 3DCRT with CF/FB (7.8 Gy), respectively. The mean lung dose (MLD) was the highest in 3DCRT-CF-FB (20 Gy) and the lowest in both VMAT-HF-CPAP and PBT (approximately 5–6 Gy). VMAT-HF-CPAP and PBT delivered a comparable maximum dose to the left ascending artery (7.2 and 6.13 Gy, respectively).ConclusionsBoth proton and VMAT in combination with CPAP can minimize the radiation exposure to heart and lung with optimal target coverage in regional RT for left-sided breast cancer. The clinical relevance of these differences is yet to be elucidated. Continued efforts are needed to minimize radiation exposures during RT treatment to maximize its therapeutic index.

Dosimetric analysis of six whole-breast irradiation techniques in supine and prone positions

“…This outcome is attributed to the excellent depth-dose distributions of PBT, allowing for a substantial reduction in OAR doses while preserving target coverage. Prior research has consistently reported that proton therapy offers significant advantages in sparing the heart and lungs compared to XRT [25][26][27][28] . Ischemic heart disease can persist for up to 20 years after radiation exposure, and there is a proportional increase in coronary events with the mean dose to the heart, without a clear cutoff value.…”

“…robustness, has been documented 23,24 . Studies have examined dosimetric variations among different treatment techniques to mitigate long-term radiation side effects in breast cancer radiation therapy and have assessed the effects of CTV size, organs at risk (OARs), target distances, treatment positions, and other factors on treatment planning [25][26][27][28][29][30][31][32] . However, there has been limited focus on arc-delivery PBT, including CIRT.…”

External-Beam-Accelerated Partial-Breast Irradiation Reduces Organ-at-Risk Doses Compared to Whole-Breast Irradiation after Breast-Conserving Surgery

“…Furthermore, various in silico WBI planning trials described contralateral breast mean doses for different scenarios (free breathing, breath hold, various field geometrics etc.) between 0.32 and 4.80 Gy [ 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 , 34 ]. In the present analysis, the mean dose to the contralateral breast was comparatively low at 0.80 Gy for all patients after WBI.…”

Hypofractionated radiotherapy in postmastectomy locally advanced breast cancer: an interim report on acute toxicities and dosimetry

“…As information on dosimetry becomes more evident, efforts have been made to develop more sophisticated planning techniques to achieve improved dosimetry than would otherwise be expected from traditional techniques. With volume-based planning, use of partially wide tangents in hypofractionated radiotherapy yielded ipsilateral lung V20 values of 41% in a treatment planning study [ 26 ]. In our study, with the use of 3D-CRT and volume-based planning, we were able to achieve adequate target coverage and acceptable heart doses although with a slightly higher ipsilateral lung dose than intended.…”