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. 2018 May 31:6:71-76.
doi: 10.1016/j.phro.2018.05.006. eCollection 2018 Apr.

Breast-shape changes during radiation therapy after breast-conserving surgery

Tanja Alderliesten  1 , Wilma D Heemsbergen  1 , Anja Betgen  1 , Rajko Topolnjak  1 , Paula H M Elkhuizen  1 , Corine van Vliet-Vroegindeweij  1 , Peter Remeijer  1
Affiliations

Breast-shape changes during radiation therapy after breast-conserving surgery

Tanja Alderliesten et al. Phys Imaging Radiat Oncol. .

Abstract

Background & purpose: With the introduction of more conformal techniques for breast cancer radiation therapy (RT), motion management is becoming increasingly important. We studied the breast-shape variability during RT after breast-conserving surgery (BCS).

Materials & methods: Planning computed tomography (CT) and follow-up cone-beam CT (CBCT) scans were available for 71 fractions of 17 patients undergoing RT after BCS. First, the CT and the CBCT scans were registered on bones. Subsequently, breast-contour data were generated. The CBCT contours were analyzed in 3D in terms of deviations (mean and standard deviation) relative to the contour of the CT scan for the upper medial, lower medial, upper lateral, and lower lateral breast quadrants, and the axilla.

Results: Regional systematic and random standard deviations of the breast quadrants varied between 1.5 and 2.1 mm and 1.0-1.6 mm, respectively, and were larger for the axilla (3.0 mm). An absolute average shape change of ≥4.0 mm in at least one region was present in 21/71 fractions (30%), predominantly in breast volumes > 800 cc (p = <0.01). Furthermore, seroma was associated with larger shape changes (p = 0.04).

Conclusions: Breast-shape variability varies between anatomic locations. Changes in the order of 4 mm are frequently observed during RT, especially for large breasts. This should be taken into account in the development of protocols for partial breast irradiation and boost treatment.

Keywords: Breast cancer; Breast-conserving surgery; Cone-beam computed tomography; Radiation therapy; Shape variability.

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Figures

Fig. 1
Fig. 1
Left: Illustration of the different regions of interest investigated in this study: the four breast quadrants and the axilla. The nipple area was excluded from the analysis. Right: Figure indicating how shape changes were assessed from the extracted CT and CBCT contours. The distance between each contour element in the planning CT contour and the nearest neighbor contour element in the CBCT contour was calculated. A negative distance value indicates that the corresponding CBCT contour element lies closer to the ribs than the CT contour element and a positive distance value indicates that the CBCT contour element lies further away from the ribs than the CT contour element.
Fig. 2
Fig. 2
The inter-fractional shape changes (per patient: left: mean, right: standard deviation) illustrated by color-coded breast contours for all study patients (n = 17).
See this image and copyright information in PMC

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