The delivery of intensity modulated radiotherapy to the breast using multiple static fields.
OBJECTIVE
To develop a method of using a multileaf collimator (MLC) to deliver intensity modulated radiotherapy (IMRT) for tangential breast fields, using an MLC to deliver a set of multiple static fields (MSFs).


METHODS
An electronic portal imaging device (EPID) is used to obtain thickness maps of medial and lateral tangential breast fields. From these IMRT deliveries are designed to minimize the volume of breast above 105% of prescribed dose. The deliveries are universally-wedged beams augmented with a set of low dose shaped irradiations. Dosimetric and planning QA of this method has been compared with the standard, wedged treatment and the corresponding treatment using physical compensators. Several options for delivering the MSF treatment are presented.


RESULTS
The MSF technique was found to be superior to the standard technique (P value=0.002) and comparable with the compensated technique. Both IMRT methods reduced the volume of breast above 105% dose from a mean value of 12.0% of the total breast volume to approximately 2.8% of the total breast volume.


CONCLUSIONS
This MSF method may be used to reduce the high dose volume in tangential breast irradiation significantly. This may have consequences for long-term side effects, particularly cosmesis.
Evans
P M
PM
Joint Department of Physics, Institute of Cancer Research and Royal Marsden NHS Trust, Downs Road, Surrey, SM2 5PT, Sutton, UK.
Donovan
E M
EM
Partridge
M
M
Childs
P J
PJ
Convery
D J
DJ
Eagle
S
S
Hansen
V N
VN
Suter
B L
BL
Yarnold
J R
JR
D001943:Breast Neoplasms / Q000532:radiotherapy*; D004307:Dose-Response Relationship, Radiation; D005260:Female; D006801:Humans; D008280:Magnetics; D011379:Prognosis; D011836:Radiation Tolerance; D011879:Radiotherapy Dosage; D011880:Radiotherapy Planning, Computer-Assisted; D020266:Radiotherapy, Conformal / Q000379:methods*; D012680:Sensitivity and Specificity