A simple method to test if the internal mammary lymph nodes are covered by the wide tangent technique in radiotherapy for high-risk breast cancer.
OBJECTIVE
It is often complicated to include the internal mammary lymph nodes in the radiation field after breast-conserving therapy. Using the wide tangent technique the internal mammary lymph nodes are generally presumed to be included if the medial tangential field border is placed 3 cm across the midline. The current study was designed to test the validity of this assumption, and if possible, to correct the wide tangents without using computed tomography (CT) scanning.


METHODS
Twenty-one consecutive, high-risk, post-lumpectomy patients were included. An arrangement of three copper wires was mounted in wax placed perpendicular to the skin surface at the ipsilateral border of sternum at intercostal spaces 2 to 4. During a standard simulation for wide tangents, it was examined if the length of the copper wires projected beneath the skin surface (representing the depth of the internal mammary lymph nodes, measured by ultrasound) were included in the wide tangent fields.


RESULTS
In only one patient were the internal mammary lymph nodes covered by the wide tangent technique. In 14 of the remaining 20 patients the lateral tangential field border was subsequently moved in the posterior direction, and the internal mammary lymph nodes could be included without unacceptable normal tissue involvement. In the last six patients the irradiated heart and lung volumes exceeded acceptable tolerance levels with this correction, and these patients were referred for three-dimensional CT dose planning.


CONCLUSIONS
The presented simple technique may be helpful if CT scanning is not available. In all other cases CT-based dose plan should ideally be used as a standard in the planning of radiotherapy after breast-conserving surgery to assure optimal inclusion of the relevant target, and to avoid irradiation of large volumes of critical normal tissue.
Nielsen
H M
HM
Department of Oncology, Aarhus University Hospital, 8000 Aarhus C, Denmark. hmn@oncology.dk
Christensen
J J
JJ
Aagaard
T
T
Thingholm
J
J
Overgaard
M
M
Grau
C
C
D000328:Adult; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008198:Lymph Nodes / Q000000981:diagnostic imaging; D015182:Lymphatic Irradiation; D015412:Mastectomy, Segmental; D008875:Middle Aged; D011880:Radiotherapy Planning, Computer-Assisted; D018714:Radiotherapy, Adjuvant; D014057:Tomography, X-Ray Computed