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. 2022 Mar 29;14(3):e23613.
doi: 10.7759/cureus.23613. eCollection 2022 Mar.

Dosimetric Analysis of Axillary Lymph Node Coverage Using High Tangents in the Prone Position for Left-Sided Breast Cancers

Timothy D Malouff  1 , Laura A Vallow  1 , Wilza L Magalhaes  1 , Danushka S Seneviratne  1 , Mark R Waddle  2 , Katherine S Tzou  1
Affiliations

Dosimetric Analysis of Axillary Lymph Node Coverage Using High Tangents in the Prone Position for Left-Sided Breast Cancers

Timothy D Malouff et al. Cureus. .

Abstract

Aim/objective: Prone positioning is often used to reduce the dose to organs at risk during adjuvant breast irradiation. High tangents are used with supine treatments in patients with the low-volume nodal disease to increase nodal coverage while minimizing toxicities. Our study aims to evaluate nodal coverage for patients treated in the prone position with high tangents.

Materials and methods: Our study analyzed the plans for 20 patients with early-stage, left-sided breast cancers treated at our institution from 2018 to 2019. All patients were treated in the prone position. Axillary nodal levels I-III were contoured, and treatment plans were generated using high tangents. The heart, bilateral lungs, and breast tissue were retrospectively contoured. All plans were evaluated to a dose of 42.4 Gy in 16 fractions.

Results: Level I lymph node levels had a mean coverage of 99% of the prescription dose (range: 98-100%). Similarly, level II coverage was approximately 88% (range: 65-100%). The mean coverage for level III was approximately 25% (range: 0-52%). The mean heart dose, mean lung volume receiving ≥20 Gy (V20) for the bilateral lungs, and ipsilateral V20 were 1.69 Gy, 1.64%, and 3.56%, respectively.

Conclusion: Treating patients in the prone position with high tangents provides excellent coverage of axillary levels I and II, although there is minimal coverage of axillary level III. Prospective trials are needed to evaluate the clinical outcomes when treating patients with high tangents in the prone position.

Keywords: breast; high tangents; micrometastatic; prone; radiation.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Figure 1
Figure 1. Representative beams-eye view of the lateral tangent for a patient treated for left-sided breast cancer. The superior border is the inferior aspect of the humeral head, with an inferior border approximately 2 cm below the inframammary line. Lymph node levels I (yellow), II (green), and III (blue) are contoured.
Figure 2
Figure 2. Representative CT simulation image in the sagittal plane of the field borders for high tangents.
Figure 3
Figure 3. Representative CT simulation images in the axial plane from the superior-most border (left top) to the inferior-most border (bottom right). Lymph node levels I (yellow), II (green), and III (blue) are contoured and the field borders are included.
See this image and copyright information in PMC

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