External radiotherapy of intact breast: A comparison between 2D (single CT- slice) and 3D (full CT-slices) plans

Background: Tangential irradiation of intact breast is one of the most common procedures performed in any radiotherapy center. This method is performed by using 2D and 3D treatment planning. The aim of this study was to compare 2D with 3D plans in breast conserving radiotherapy. Homogeneity of isodose, and lung received dose were compared. Materials and Methods: Twenty patients with breast cancer undergoing lumpectomy were included in this study. Two dosimetry plans were generated for each patient. The first plan was performed on one CT-slice (central) by using Eclipse-TPS. The second plan was based on full CT-slices using the same TPS. For both plans, the volumes receiving lower than 95% (cold areas), greater than 105% (hot areas) of the reference dose and the volume of lung receiving ≥30Gy (Vol≥30Gy) were derived from dose volume histogram (DVH). All calculations were done for 6MV photon beams. Results: By the 2D plans, the mean values of cold and hot areas were 26.4% and 8.1%, respectively. These values were reduced to 18.9% and 6.9% in 3D plans, respectively (p<0.000, p<0.01). Dose homogeneity was obtained 65.4% in the 2D and improved to 74.8% in the 3D plans (P<0.000). By the use of 3D plans, received dose within lung volume was decreased to 6.7% as compared with 8.9% of 2D plans (P<0.01). Conclusion: Application of 3D plans can lead to a more tumor control probability and cosmetic results, but less skin and lung side effects in patients with conserved breast. Iran. J. Radiat. Res., 2011 9(2): 121-125