Multileaf field-in-field forward-planned intensity-modulated dose compensation for whole-breast irradiation is associated with reduced contralateral breast dose: a phantom model comparison.
OBJECTIVE
Static multileaf collimated field-in-field forward-planned intensity-modulated radiation treatment (FiF-IMRT) has been shown to improve dose homogeneity compared to conventional wedged fields. However, a direct comparison of the scattered dose to the contralateral breast resulting from wedged and FiF-IMRT plans remains to be documented.


METHODS
The contralateral scattered breast dose was measured in a custom-designed anthropomorphic breast phantom in which 108 thermoluminescent dosimeters (TLDs) were volumetrically placed every 1-2cm. The target phantom breast was treated to a dose of 50Gy using three dose compensation techniques: No medial wedge and a 30-degree lateral wedge (M0-L30), 15-degree lateral and medial wedges (M15-L15), and FiF-IMRT. TLD measurements were compared using analysis of variance.


RESULTS
For FiF-IMRT, the mean doses to the medial and lateral quadrants of the contralateral breast were 112cGy (range 65-226cGy) and 40cGy (range 18-91 cGy), respectively. The contralateral breast doses with FiF-IMRT were on average 65% and 82% of the doses obtained with the M15-L15 and M0-L30 techniques, respectively (p<0.001). Compared to the M15-L15 technique, the maximum dose reduction obtained with FiF-IMRT was 115cGy (range 13-115cGy).


CONCLUSIONS
The dose to the contralateral breast is significantly reduced with FiF-IMRT compared to wedge-compensated techniques. Although long-term follow-up is needed to establish the clinical relevance of this finding, these results, along with the previously reported improvement in ipsilateral dose homogeneity, support the use of FiF-IMRT if resources permit.
Borghero
Yerko O
YO
Department of Radiation Oncology, Pontificia Universidad Católica de Chile, Santiago, Chile. yborghero@mdanderson.org
Salehpour
Mohammad
M
McNeese
Marsha D
MD
Stovall
Marilyn
M
Smith
Susan A
SA
Johnson
Jennifer
J
Perkins
George H
GH
Strom
Eric A
EA
Oh
Julia L
JL
Kirsner
Steven M
SM
Woodward
Wendy A
WA
Yu
Tse-Kuan
TK
Buchholz
Thomas A
TA
D001943:Breast Neoplasms / Q000532:radiotherapy*; D005260:Female; D006801:Humans; D019047:Phantoms, Imaging; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D050397:Radiotherapy, Intensity-Modulated; D012542:Scattering, Radiation; D013819:Thermoluminescent Dosimetry