Radiotherapy of internal mammary lymph nodes in breast cancer. Principle considerations on the basis of dosimetric data.
BACKGROUND
Radiotherapy of internal mammary lymph nodes (IMN) in breast cancer is discussed controversially due to its potential toxicity and debatable efficacy. Aim of the present study was to assess the cardiac and lung dose in 3-D planned radiotherapy and to discuss these results with regard to arguments pro and contra IMN irradiation.


METHODS
32 patients underwent 3-D planning (Helax TMS) for irradiation of breast and IMN in three different techniques either using separate IMN fields (A, B) or a wide tangent (C). For each technique the respective doses to the heart (including the base of the aorta and the ostium of the coronary arteries) and lung were analyzed in dose volume histograms.


RESULTS
The mean dose to the heart (left side irradiation) was 6.4 Gy (A), 8.1 Gy (B) and 3.8 Gy (C). The mean dose to the lung was 11.7 Gy (A), 15.4 Gy (B) and 10.2 Gy (C). The 10-Gy isodose comprised 19.5% (A), 32.9% (B) and 5.6% (C) of the heart (left breast). The respective values for the 20-Gy isodose were 7.8, 11.5 and 4.4%. The irradiated volumes of the lung were 37.7% (A), 52.7% (B) and 20% (C) in the 10-Gy isodose. The 20-Gy isodose comprised 16.7% (A), 28.3% (B) and 17.8% (C).


CONCLUSIONS
Whether radiotherapy of the IMN may improve treatment results in breast cancer is currently unresolved. However, the present data indicate that relevant cardiovascular side effects are unlikely to occur. Thus, the indication should be considered on the basis of individual risk factors.
Sautter-Bihl
Marie-Luise
ML
Department of Radiotherapy, Städtisches Klinikum Karlsruhe, Germany. strahlentherapie@klinikum-karlsruhe.de
Hültenschmidt
Beatrix
B
Melcher
Ute
U
Ulmer
Hans Ulrich
HU
D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy* / Q000601:surgery; D003131:Combined Modality Therapy; D005260:Female; D006321:Heart / Q000528:radiation effects; D006801:Humans; D008168:Lung / Q000528:radiation effects; D008198:Lymph Nodes / Q000000981:diagnostic imaging / Q000528:radiation effects*; D015182:Lymphatic Irradiation; D008408:Mastectomy; D011182:Postoperative Care; D011829:Radiation Dosage; D011874:Radiometry; D011878:Radiotherapy / Q000009:adverse effects; D011880:Radiotherapy Planning, Computer-Assisted; D012307:Risk Factors; D014057:Tomography, X-Ray Computed