Coverage of axillary lymph nodes in supine vs. prone breast radiotherapy.
OBJECTIVE
To compare the dosimetry of target and normal tissue when tangents with the breast tissue were applied in a subset of breast cancer patients who had undergone computed tomography (CT) planning both supine and prone.


METHODS
The CT images of 20 patients who had undergone simulation in supine and prone positions were used for planning. The axillary lymph node regions (level I-III), breast tissue, tumor bed, heart, and bilateral lungs were manually contoured. Standard tangent fields were designed for the whole breast to deliver a prescribed dose of 50 Gy. Dose-volume histograms were compared between the two sets.


RESULTS
In each patient, coverage of breast tissue and tumor bed was readily achieved by either technique. In either position, treatment of the nodal regions was inadequate. On average, the mean dose to the nodal regions for levels I-III was approximately 50% less in the prone as compared with the supine position. The mean ipsilateral lung volume receiving 95% of the prescribed dose was 6.3% in the supine position compared to 0.43% in the prone position. When planned supine, the mean heart volume receiving 30 Gy was 0.56% compared with 0.30% in the prone position.


CONCLUSIONS
Planning in either position was found to achieve adequate coverage of the breast tissue and tumor bed for all patients. Lung was better spared prone. Coverage of axillary nodes was inadequate in either position, but further reduced in the prone vs. supine position. The choice of optimal setup should take into considerations stage and risk of nodal recurrence.
Alonso-Basanta
Michelle
M
Department of Radiation Oncology, New York University School of Medicine, New York, NY 10016, USA.
Ko
Jane
J
Babcock
Melissa
M
Dewyngaert
J Keith
JK
Formenti
Silvia C
SC
D001365:Axilla; D001940:Breast / Q000033:anatomy & histology; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000473:pathology / Q000532:radiotherapy*; D005240:Feasibility Studies; D005260:Female; D006321:Heart / Q000000981:diagnostic imaging; D006801:Humans; D008168:Lung / Q000000981:diagnostic imaging; D008198:Lymph Nodes / Q000000981:diagnostic imaging; D015182:Lymphatic Irradiation / Q000379:methods* / Q000592:standards; D009929:Organ Size; D016684:Prone Position; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D016683:Supine Position; D014057:Tomography, X-Ray Computed; D047368:Tumor Burden