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Multicenter Study
. 2016;89(1058):20150603.
doi: 10.1259/bjr.20150603. Epub 2015 Nov 20.

A multicentre study of the evidence for customized margins in photon breast boost radiotherapy

Emma J Harris  1 , Mukesh B Mukesh  2   3 , Ellen M Donovan  4 , Anna M Kirby  4 , Joanne S Haviland  5   6 , Raj Jena  2 , John Yarnold  1 , Angela Baker  7 , June Dean  2 , Sally Eagle  4 , Helen Mayles  7 , Claire Griffin  5 , Rosalind Perry  8 , Andrew Poynter  9 , Charlotte E Coles  2 , Philip M Evans  10 ; IMPORT high trialists
Affiliations
Multicenter Study

A multicentre study of the evidence for customized margins in photon breast boost radiotherapy

Emma J Harris et al. Br J Radiol. 2016.

Abstract

Objective: To determine if subsets of patients may benefit from smaller or larger margins when using laser setup and bony anatomy verification of breast tumour bed (TB) boost radiotherapy (RT).

Methods: Verification imaging data acquired using cone-beam CT, megavoltage CT or two-dimensional kilovoltage imaging on 218 patients were used (1574 images). TB setup errors for laser-only setup (dlaser) and for bony anatomy verification (dbone) were determined using clips implanted into the TB as a gold standard for the TB position. Cases were grouped by centre-, patient- and treatment-related factors, including breast volume, TB position, seroma visibility and surgical technique. Systematic (Σ) and random (σ) TB setup errors were compared between groups, and TB planning target volume margins (MTB) were calculated.

Results: For the study population, Σlaser was between 2.8 and 3.4 mm, and Σbone was between 2.2 and 2.6 mm, respectively. Females with larger breasts (p = 0.03), easily visible seroma (p ≤ 0.02) and open surgical technique (p ≤ 0.04) had larger Σlaser. Σbone was larger for females with larger breasts (p = 0.02) and lateral tumours (p = 0.04). Females with medial tumours (p < 0.01) had smaller Σbone.

Conclusion: If clips are not used, margins should be 8 and 10 mm for bony anatomy verification and laser setup, respectively. Individualization of TB margins may be considered based on breast volume, TB and seroma visibility.

Advances in knowledge: Setup accuracy using lasers and bony anatomy is influenced by patient and treatment factors. Some patients may benefit from clip-based image guidance more than others.

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Figures

Figure 1.
Figure 1.
Example images used for setup error analysis. (a) and (b) show sagittal planning CT images (pink) overlaid with sagittal cone-beam CT images (green). Figures (c) and (d) show planning axial CT images in grey and axial megavoltage CT in yellow. Figures (e) and (f) show two-dimensional kilovoltage projection images overlaid on digitally reconstructed images from the planning CT; planning CT clips positions are marked with yellow crosses. Images in the left-hand column (a, c and e) show bone-matched images and images in the right hand column (b, d and f) show clip-matched images. For colour image see online.
Figure 2.
Figure 2.
Schematic diagram showing (a) tumour bed (TB) position viewed on axial CT slice (1 =medial, 2 =chest wall, 3 =anterior and 4 =lateral) and (b) TB superior–inferior position viewed on sagittal CT slice (1 = superior, 2 = middle and 3 = inferior).
See this image and copyright information in PMC

References

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