The delivery of intensity modulated radiotherapy to the breast using multiple static fields

Background and purpose: To develop a method of using a multileaf collimator (MLC) to deliver intensity modulated radiotherapy (IMRT) for tangential br east fields, using an MLC to deliver a set of multiple static fields (MSFs) . Materials and methods: An electronic portal imaging device (EPID) is used t o obtain thickness maps of medial and lateral tangential breast fields. Fro m these IMRT deliveries are designed to minimize the volume of breast above 105% of prescribed dose. The deliveries are universally-wedged beams augme nted with a set of low dose shaped irradiations. Dosimetric and planning QA of this method has been compared with the standard, wedged treatment and t he 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 techniq ue (P value = 0.002) and comparable with the compensated technique. Both IM RT methods reduced the volume of breast above 105% dose from a mean value o f 12.0% of the total breast volume to similar to2.8% of the total breast vo lume. 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. (C) 2000 Elsevier Science I reland Ltd. All rights reserved.