Abstract
PurposeTo compare cardiac doses of different whole-breast optimization schemes including free-breathing (FB) tangential radiotherapy (TRT), deep-inspiration breath-hold (DIBH) TRT, and FB helical tomotherapy (HT).MethodsEarly-stage left-sided breast cancer patients who underwent breast-conserving surgery followed by adjuvant radiotherapy were included in the study. Planning images included FB and DIBH CT scans acquired in the same supine treatment position with both arms abducted. A hypofractionated regimen of 42.5 Gy in 16 fractions was used. Clinical target volume delineation was aided through the use of a radio-opaque wire. A 7-mm margin was used in generating the planning target volumes. TRT plans were generated both in FB and DIBH. For the FB tomotherapy technique, a first plan (Tomo 1) was optimized limiting the maximum contralateral breast dose to 3.1 Gy. A second tomotherapy plan (Tomo 2) focused on the reduction of the mean heart dose without controlling the contralateral breast dose. All plans were optimized to obtain an equivalent planning target volume (PTV) coverage of ≥95% of the prescribed dose while minimizing the dose to organs at risk.ResultsTwenty-three patients treated between October 2012 and March 2016 were included in this retrospective study. Eleven patients (48%) had at least one major cardiovascular risk factors including one patient (4%) with a history of myocardial infarction. Six patients (26%) had been exposed to cardiotoxic chemotherapy agents. The average mean dose to the heart was 3.1 Gy with FB TRT, 1.1 with DIBH TRT, 2.4 Gy for Tomo 1, and 1.5 Gy for Tomo 2. The mean dose to the left anterior descending artery was 27.0 Gy, 8.0 Gy, 13.7 Gy and 6.6 Gy for FB TRT, DIBH TRT, Tomo 1 and Tomo 2 plans respectively.ConclusionDifferent cardiac-sparing optimization schemes are possible when treating left breast cancer. Although DIBH offers clear mean heart dose reductions, tomotherapy can be an interesting alternative treatment modality to spare the heart and coronary vessels, notably in patients who cannot comply with DIBH.
Highlights
Adjuvant whole-breast radiotherapy following breast-conserving surgery significantly reduces locoregional recurrence and improves long-term survival [1]
The average mean dose to the heart was 3.1 Gy with FB tangential radiotherapy (TRT), 1.1 with deepinspiration breath-hold (DIBH) TRT, 2.4 Gy for Tomo 1, and 1.5 Gy for Tomo 2
We provide a comprehensive comparison of modern photon-based breast radiotherapy treatments with different cardiac-sparing approaches relying on delivery techniques, dosimetry optimization approaches, as well as a selection of low-recurrence risk patients amenable to reduced target volumes
Summary
Adjuvant whole-breast radiotherapy following breast-conserving surgery significantly reduces locoregional recurrence and improves long-term survival [1]. Breast irradiation carries an increased risk of major coronary events, which rises linearly with the mean dose to the heart [2]. Advances in photon-based radiotherapy such as personalized field-shaping using multileaf collimator (MLC), rotating gantry techniques, and flattening filter-free (FFF) beams have expanded the available techniques for personalized cardiac-sparing breast treatments. Improvement in imageguided radiation therapy (IGRT) and selection of patients amenable to more targeted radiotherapy have paved the way to much smaller irradiated volumes with less cardiac exposition. Reduction of the irradiated cardiac volume can be accomplished through MLC in tangential radiotherapy (TRT), it often presents suboptimal heart doses in free-breathing (FB). Compared to FB TRT, deepinspiration breath-hold (DIBH) TRT can be used to move the cardiac silhouette outside of the tangential fields by creating a separation between the heart and chest wall through lung inflation.
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