Evaluation of changes in excision cavity volume during whole breast irradiation using secondary CT image

The aim of this study was to evaluate the reduction in excision cavity volume [ECV] during the whole breast radiotherapy [WBRT]. The delineating of reduced cavity volume on secondary CT [computed tomography] might decrease the field size of boost plan. Twenty patients were treated having breast conservative surgery. At first, primary CT simulation [CT-1] was done prior to WBRT. Treatment planning was performed by a 3D treatment planning system. A CT-2 was performed after WBRT. Then the excision cavity was contoured on CT-1 and CT-2 for each patient. Boost irradiation was planned on both ECV-1 and ECV-2. In Comparison of CT-1 and CT-2: The contoured volumes for ECV-1 and ECV-2 were on average of 42.9 cm3and 23.4 cm3, respectively [p< 0.002]. The ECV-2 was reduced in 85% of the patients. Patients with ECV-1 greater than the mean value of ECV-1 [ECV-1> 35.5 cm3] had more reduction in ECV-2 than patient with ECV-1 smaller than the mean value [p < 0.000]. The volume of normal breast tissue on CT-2 was decreased from the volume of CT-1 [p< 0.03]. A significant reduction in excision cavity volume was shown during WBRT. This volume reduction made smaller sizes of boost field and remaining breast received lower doses. The reduction was more significant in patient with primary large ECV. The Secondary CT for boost planning is suggested for patients with larger cavities after WBRT

External radiotherapy of intact breast: a comparison between 2D [single CT- slice] and 3D [full CT-slices] plans

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. 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. 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]. 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