Improving dose homogeneity in large breasts by IMRT: efficacy and dosimetric accuracy of different techniques.
OBJECTIVE
Evaluation of a simplified intensity-modulated irradiation (IMRT), a three-field (MFT), and a conventional two-tangential-field technique regarding dose homogeneity, target coverage, feasibility and, for the first time, dosimetric reliability in patients with large breasts treated postoperatively for breast cancer on a low-energy linac.


METHODS
CT datasets of ten patients with relatively large breast volumes treated for breast cancer were selected. For each patient, four treatment plans were created: low-energy conventional (C-LE), high-energy conventional (C-HE), three-field (MFT), and a two-field aperture-based IMRT technique. Apertures for the IMRT and MFT were created with the aid of a three-dimensional dose display. Dosimetric accuracy of each technique was evaluated in an anthropomorphic thorax/breast phantom.


RESULTS
The mean of planning target volumes receiving < 95% or > 105% of the prescribed total dose was reduced from 16.0% to 13.9% to 10.4% to 8.9% in the C-LE, C-HE, MFT, and IMRT plans, respectively. Phantom dose measurements agreed well with the calculated dose within the breast tissue.


CONCLUSIONS
Aperture-based IMRT using two tangential incident beam directions, as well as a three-field technique with inverse optimization, provide a better alternative to the standard wedged tangential beams for patients with large breasts treated on low-energy linacs while maintaining the efficiency of the treatment-planning and delivery process.
Abo-Madyan
Yasser
Y
Department of Radiation Oncology, Mannheim Medical Center, University of Heidelberg, Mannheim, Germany. abomadyan.yasser@radonk.ma.uni-heidelberg.de
Polednik
Martin
M
Rahn
Angelika
A
Schneider
Frank
F
Dobler
Barbara
B
Wenz
Frederik
F
Lohr
Frank
F
D000465:Algorithms; D001940:Breast / Q000503:physiopathology; D001943:Breast Neoplasms / Q000503:physiopathology* / Q000532:radiotherapy*; D003198:Computer Simulation; D005260:Female; D006801:Humans; D008954:Models, Biological; D009929:Organ Size; D011874:Radiometry / Q000379:methods*; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods*; D020266:Radiotherapy, Conformal / Q000379:methods*; D012062:Relative Biological Effectiveness; D015203:Reproducibility of Results; D012542:Scattering, Radiation; D012680:Sensitivity and Specificity