Intensity-modulated radiation therapy (IMRT) reduces the dose to the contralateral breast when compared to conventional tangential fields for primary breast irradiation: initial report

PURPOSE This study was designed to compare the dose received by the contralateral breast during primary breast irradiation using intensity-modulated radiotherapy with the dose received via conventional tangential field techniques. METHODS/MATERIALS Between March 2003 and March 2004, 44 patients with breast carcinoma were treated using 6-, 10-, or mixed 6/18-MV photons (36 with tangential intensity-modulated radiotherapy technique and eight with three-dimensional technique using tangential fields with wedges) for primary breast irradiation after breast-conserving surgery. Paired thermoluminescent dosimeters were placed on each patient's contralateral breast, 4 cm from the center of the medial border of the tangential field. The thermoluminescent dosimeters were left on the patient during a single fraction and then measured 24 hours later. RESULTS The mean dose delivered with photons to the primary breast for all patients was 4998 cGy [SD = 52], and the mean single fraction dose was 200 cGy [SD = 9]. The mean percent of the prescribed dose to the contralateral breast was 7.74% (SD = 2.35) for patients treated with intensity-modulated radiotherapy, compared with 9.74% [SD = 2.04] for the patients treated with conventional tangential field techniques. This represented a 20% reduction in the mean dose to the contralateral breast with the use of intensity-modulated radiotherapy when compared with the dose received via the three-dimensional technique, a result that was statistically significant. CONCLUSION Primary breast irradiation with tangential intensity-modulated radiotherapy technique significantly reduces the dose to the contralateral breast when compared with conventional tangential techniques.