Direct aperture optimization-based intensity-modulated radiotherapy for whole breast irradiation.
OBJECTIVE
To investigate the technical and dosimetric advantages and the efficacy of direct aperture optimized intensity-modulated radiation therapy (DAO-IMRT) over standard (e.g., beamlet optimized) IMRT and conventional three-dimensional conformal radiotherapy (3D-CRT) for whole breast irradiation in supine and prone positions.


METHODS
We retrospectively designed DAO-IMRT plans for 15 breast cancer patients in supine (10 patients) and prone (5 patients) positions with a goal of uniform dose coverage of the whole breast. These DAO-IMRT plans were compared with standard IMRT using beamlet optimization and conventional 3D-CRT plans using wedges. All plans used opposed tangential beam arrangements.


RESULTS
In all cases, the DAO-IMRT plans were equal to or better than those generated with 3D-CRT and standard beamlet-IMRT. For supine cases, DAO-IMRT provided higher uniformity index (UI, defined as the ratio of the dose to 95% of breast volume to the maximum dose) than either 3D-CRT (0.88 vs. 0.82; p = 0.026) or beamlet-IMRT (0.89 vs. 0.85; p = 0.003). Direct aperture optimized IMRT also gave lower lung doses than either 3D-CRT (V20 = 7.9% vs. 8.6%; p = 0.024) or beamlet-IMRT (V20 = 8.4% vs. 9.7%; p = 0.0008) for supine patients. For prone patients, DAO-IMRT provided higher UI than either 3D-CRT (0.89 vs. 0.83; p = 0.027) or beamlet-IMRT (0.89 vs. 0.85; p = 0.003). The planning time for DAO-IMRT was approximately 75% less than that of 3D-CRT. The monitor units for DAO-IMRT were approximately 60% less than those of beamlet-IMRT.


CONCLUSIONS
Direct aperture optimized IMRT improved the overall quality of dose distributions as well as the planning and delivery efficiency for treating whole breast in both supine and prone positions.
Ahunbay
Ergun E
EE
Department of Radiation Oncology, Medical College of Wisconsin, Milwaukee, WI 53226, USA. eahunbay@radonc.mcw.edu
Chen
Guang-Pei
GP
Thatcher
Steven
S
Jursinic
Paul A
PA
White
Julia
J
Albano
Katherine
K
Li
X Allen
XA
D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D016684:Prone Position; D011879:Radiotherapy Dosage; D020266:Radiotherapy, Conformal; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods*; D012189:Retrospective Studies; D016683:Supine Position