Individual positioning: a comparative study of adjuvant breast radiotherapy in the prone versus supine position.
OBJECTIVE
To study breast radiotherapy in the prone vs. supine positions through dosimetry and clinical implementation.


METHODS
Conformal radiotherapy plans in 61 patients requiring only breast irradiation were developed for both the prone and supine positions. After evaluation of the of the first 20 plan pairs, the patients were irradiated in the prone or supine position in a randomized fashion. These cases were analyzed for repositioning accuracy and skin reactions related to treatment position and patient characteristics.


RESULTS
The planning target volume covered with 47.5-53.5 Gy in the prone vs. the supine position was 85.1% +/- 4.2% vs. 89.2 +/- 2.2%, respectively (p < 0.0001). Radiation exposure of the ipsilateral lung, expressed in terms of the mean lung dose and the V(20Gy), was dramatically lower in the prone vs. supine position (p < 0.0001), but the doses to the heart did not differ. There was no difference in the need to correct positioning during radiotherapy, but the extent of displacement was significantly higher in the prone vs. supine position (p = 0.021). The repositioning accuracy in the prone position exhibited an improvement over time and did not depend on any patient-related parameters. Significantly more radiodermatitis of Grade 1-2 developed following prone vs. supine irradiation (p = 0.025).


CONCLUSIONS
Conformal breast radiotherapy is feasible in the prone position. Its primary advantage is the substantially lower radiation dose to the ipsilateral lung. The higher dose inhomogeneity and increased rate of Grade 1-2 skin toxicity, however, may be of concern.
Varga
Zoltán
Z
Department of Oncotherapy, University of Szeged, Szeged, Hungary.
Hideghéty
Katalin
K
Mezo
Tamás
T
Nikolényi
Alíz
A
Thurzó
László
L
Kahán
Zsuzsanna
Z
D000328:Adult; D000368:Aged; D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D005240:Feasibility Studies; D005260:Female; D006321:Heart / Q000528:radiation effects; D006801:Humans; D008168:Lung / Q000528:radiation effects; D008875:Middle Aged; D016684:Prone Position; D011446:Prospective Studies; D011855:Radiodermatitis / Q000209:etiology / Q000473:pathology; D011859:Radiography; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D018714:Radiotherapy, Adjuvant / Q000379:methods; D020266:Radiotherapy, Conformal / Q000009:adverse effects / Q000379:methods*; D012044:Regression Analysis; D016037:Single-Blind Method; D016683:Supine Position