Dosimetric improvements following 3D planning of tangential breast irradiation.
OBJECTIVE
To evaluate the dosimetric difference between a simple radiation therapy plan utilizing a single contour and a more complex three-dimensional (3D) plan utilizing multiple contours, lung inhomogeneity correction, and dose-based compensators.


METHODS
This is a study of the radiation therapy (RT) plans of 85 patients with early breast cancer. All patients were considered for breast-conserving management and treated by conventional tangential fields technique. Two plans were generated for each patient. The first RT plan was based on a single contour taken at the central axis and utilized two wedges. The second RT plan was generated by using the 3D planning system to design dose-based compensators after lung inhomogeneity correction had been made. The endpoints of the study were the comparison between the volumes receiving greater than 105% and greater than 110% of the reference dose, as well as the magnitude of the treated volume maximum dose. Dosimetric improvement was defined to be of significant value if the volume receiving > 105% of one plan was reduced by at least 50% with the absolute difference between the volumes being 5% or greater. The dosimetric improvements in 49 3D plans (58%) were considered of significant value. Patients' field separation and breast size did not predict the magnitude of improvement in dosimetry.


CONCLUSIONS
Dose-based compensator plans significantly reduced the volumes receiving > 105%, >110%, and volume maximum dose.
Aref
A
A
Barbara Ann Karmanos Cancer Institute, Detroit, MI, USA. amr.aref@stjohn.org
Thornton
D
D
Youssef
E
E
He
T
T
Tekyi-Mensah
S
S
Denton
L
L
Ezzell
G
G
D001943:Breast Neoplasms / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D008168:Lung; D011835:Radiation Protection / Q000295:instrumentation; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted / Q000379:methods; D020266:Radiotherapy, Conformal / Q000379:methods*; D014057:Tomography, X-Ray Computed