USEFULNESS OF SIMPLE SHIELDING TECHNIQUE USING MULTILEAF COLLIMATOR IN BREAST RADIATION THERAPY

초록

This study was designed to assess whether the conventional tangential technique, using a multileaf collimator(MLC), allows a reduced dose to the organs at risk (OAR) in breast radiation therapy. A total of forty right andleft 20 for each breast cancer patients that underwent radiation therapy after breast conserving surgery were includedin this study. For each patient, the planning target volume (PTV) and OAR (heart, left anterior descendingartery (LAD), liver and lung) were defined and dose distribution were produced for conventional tangential beamsusing 6 MV photons. The treatment plans were made using the following two techniques for all patients. For thefirst plan (P1), MLC was designed to shield as much of OAR as possible without compromising the coverage ofPTV. In the second plan (P2), the treatment plan was created without using MLC. Dose-volume histograms forOARs were calculated for all plans. For left breast cancer, the percentage of maximum dose (Dmax%) and meandose (Dmean%) of OARs (heart and LAD) were calculated, and for right breast cancer, the percentage of the meandose (Dmean%) of the liver was calculated. The Dmean% of the lung was calculated in all patients. The mean values of Dmax% of the heart (86.9±19.5% range, 35.1-100.6%) in P1 were significantly lower than inP2 (98.3±3.4% range, 91.7-105.2%) (p=0.001). The mean values of Dmax% of LAD (78.4±22.5% range, 26.5-99.7%) inP1 was significantly lower than in P2 (93.3±8.1% range, 67.9-102.1%) (p<0.001). In P1, the mean values ofDmean% of the liver (4.8±2.0%) were significantly lower than in P2 (6.2±2.5%) (p<0.001). The mean values ofDmean% of the lung were significantly lower in P1 (9.3±2.3%) than in P2 (9.7±2.4%) (p<0.001). P1, by using MLC,allows a significantly reduced dose to OAR compared with P2. We can suggest that it is reasonable to routinelyuse MLC in the conventional tangential technique for breast radiation therapy considering the primary tumorlocation.

키워드