24 State of the art for breast cancer treatment in radiotherapy. Comparison of mono/multi isocentric conformational and helical techniques

Introduction Breast cancers treatment are various in radiotherapy due to plenty combinations between tumor volumes to irradiate. This retrospective study aims to allow the best selection strategy according to tumor volumes location. A comparison between four dosimetric planification corresponding to helical [1] and direct tomotherapy and mono [2] and multi isocentric is realized on two treatment devices: Tomotherapy and conventional. Methods The dosimetric study has been realized for 3 bilateral lesions, 3 left-side reaches, and 3 right side reaches. The chosen cases correspond to the more disadvantageous concerning to apparition frequencies, dosimetric planification complexity and patient installation under the device. For the left reaches, the patients were not under respiratory control. The existing dosimetry corresponding to the delivered treatment has been retained. Those for the 3 other techniques have been calculated for the same prescription and volumes. For each patient, the fourth dosimetry are medically approved and evaluated according to the following criteria: conformation and homogeneity index for the tumor volumes, hotspots and dosimetric constraints: lungs: V30Gy, V20Gy, V5Gy; heart: Dmax, Dmean, V25Gy; contralateral breast: V5Gy; esophagus: Dmax, V20Gy. Results The selected dosimetric planification is the one allowing the best protection of the healthy tissues, optimal homogeneity and conformation index values and the minimal hotspots proportion, weighted by the patient treatment care duration. The achieved outcomes permit to provide discussion elements to choose the more beneficial technic option to take charge of all the studied situations. Conclusions This dosimetric comparison permit to provide the treatment strategies for breast cancers patients depending on tumor areas and to objectivise the technic choice.