Elsevier

Radiotherapy and Oncology

Volume 154, January 2021, Pages 101-109
Radiotherapy and Oncology

Original Article
Dose-sparing effect of deep inspiration breath hold technique on coronary artery and left ventricle segments in treatment of breast cancer

https://doi.org/10.1016/j.radonc.2020.09.019Get rights and content

Highlights

Abstract

Background and purpose

The risk of radiation-induced cardiac injury remains a challenging problem in the treatment of breast cancer. Certain cardiac structures receive higher doses than others, which results in variable frequencies of radiation-induced injuries across these structures. Radiation dose can be reduced using the deep inspiration breath hold (DIBH) technique. We aimed to investigate the dose reductions from DIBH in individual cardiac segments.

Materials and methods

A dosimetric analysis was performed on left-sided breast cancer patients who underwent breast-conserving surgery and whole breast irradiation. Radiation doses to the cardiac structures were compared between the DIBH and free-breathing (FB) techniques and the dose reductions with DIBH were correlated to the lung expansion.

Results

For the 75 patients included in our study, DIBH effectively reduced doses to the heart, left lung, left anterior descending coronary artery (LAD) and left ventricle (LV), but the degree of dose reductions was variable across different structures. The absolute dose reductions were greatest in the distal LAD (14.4 Gy) and apical LV (12.1 Gy) segments, compared with the other LAD (middle 9.7 Gy, proximal 1.6 Gy) and LV (anterior 5.3 Gy, lateral 2.9 Gy, septal 2.0 Gy, inferior 0.2 Gy) segments. Left lung expansion was significantly correlated with the dose reductions in the LAD (Spearman’s rank correlation coefficient, ρ, 0.304) and LV (ρ, 0.420) segments.

Conclusions

Our study demonstrates the dose-sparing effects of DIBH in various cardiac structures, especially the distal LAD and apical LV segments. The large dose reductions seen in the distal LAD and apical LV segments could potentially translate into clinical benefit of reduced cardiac toxicity, as these structures have been previously shown to receive the highest doses and are associated with radiation-induced injury.

Section snippets

Patient selection

Institutional Review Board approval was obtained prior to study commencement. In this retrospective dosimetric analysis, patients with left-sided invasive breast cancer or ductal carcinoma in situ (DCIS) who have been treated with breast conserving surgery and adjuvant whole breast irradiation using DIBH technique were identified and included in the study. Since the introduction of the DIBH technique at our institution in 2017, all patients who were treated using the DIBH technique between

Image acquisition

Patients were simulated with computed tomography (CT) scans using both the DIBH and FB techniques on the same day. CT scans were acquired using 3 mm thick slices, as patients rested in the supine position on a breast board with both arms above the head and a cushion under the knees. Radio-opaque wires were placed to delineate the anatomical border of the entire left breast, with the medial boarder at mid-sternum and the lateral border at the mid-axillary line, and small permanent tattoos were

Contouring structures

The following structures were contoured on both DIBH and FB scans using Elekta Monaco® Treatment Planning Software (TPS) v.5.11.02 (Elekta, Stockholm, Sweden): right and left lung, breast, surgical scar, heart, right coronary artery (RCA), left main coronary artery (LMCA), left circumflex coronary artery (LCX), left anterior descending coronary artery (LAD) and left ventricle (LV). LAD was then further divided into proximal (pLAD), middle (mLAD) and distal (dLAD) segments, and LV was further

Treatment planning and dose calculation

The contoured structures on both DIBH and FB scans were then submitted for treatment planning using Elekta Monaco® TPS v.5.11.02 (Elekta, Stockholm, Sweden) (Fig. 1). Treatments were delivered using three-dimensional conformal radiotherapy (3D-CRT) with two parallel opposed pair tangent beams. These consisted of a combination of 6MV and 10MV photons. Sub-fields were used to improve target coverage and maximize dose homogeneity within the breast, while minimizing the dose to the organs at risk

Results

A total of 75 patients were identified and included in the study. Median age at the time of treatment was 59 years (range 37–78 years) and the majority (80%) of patients had invasive cancer, while the rest (20%) had DCIS. Fifty-six percent of patients received 42.5 Gy in 16 fractions and 44% of patients received 40 Gy in 15 fractions. Forty-seven percent of patients received a boost dose to the tumor bed ranging between 10 Gy and 12.5 Gy in 4–5 fractions.

Mean volumes of the whole heart, LAD and

Discussion

The results from our study demonstrate that DIBH effectively reduces doses to the heart and left lung in left-sided breast cancer patients treated with whole breast irradiation. The dose reductions from DIBH were pronounced in certain cardiac structures, especially the LAD and LV, while the reductions were less significant in other structures, including the whole heart and other coronary arteries, such as the RCA, LCX and LMCA. In addition, when individual segments of the LAD and LV were taken

Role of the funding source

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.

Declaration of Competing Interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Acknowledgement

None.

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    Presented in part at the following: 2019 ASTRO Annual Meeting, September 2019, Chicago, IL, USA. Annual Scientific Meeting of the 2019 Canadian Association of Radiation Oncology (CARO), October 2019, Halifax, NS, Canada.

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