Comparison of treatment planning techniques at the linear accelerator for left-sided breast carcinoma considering the treatment volume and organs at risk

Breast cancer is the most common type of cancer in women. Nowadays, postoperative radiation therapy is one of the standard treatment procedures. However, the radiation used may not only lead to a positive therapeutic outcome, but also has a negative impact on the surrounding organs at risk. Organs, such as the heart, can also have damaged and serious late effects can occur. In recent decades, there has been a significant development in the field of equipment technology and radiation planning. Today various radiation planning techniques are available, such as 3DCRT (three-dimensional conformal radiation therapy), VMAT (Volumetric Intensity Modulated Arc Therapy) or IMRT (Intensity Modulated Radiation Therapy). The question arises as to which of the radiation techniques is most suitable for breast cancer radiation. In this study, the radiotherapeutic treatment of left-sided breast carcinoma using linear accelerators has been investigated. The radiation techniques 3DCRT, HYBT (hybrid technique [3DCRT+VMAT]), VMAT and IMRT were compared. In addition, the breast volumes/shapes were divided into breast groups in order to show a possible dependence on the target volume. CT images of 20 different patients were used; the patients were divided into four breast groups. All irradiation techniques were applied to the same CT. A total of 80 radiation plans were created and compared. In the evaluation, the mean dose or max dose values, the MU count of the irradiation plan, the breast group, the homogeneity index and the conformity index were considered, depending on the organs at risk. 3DCRT has historically been the most widely used technique. It has been found that 3DCRT normally provides a better sparing of the dose to OAR, when compared to newer techniques. Regardless of the radiation techniques, for technical reasons, complete protection of the organs at risk, such as the heart, cannot always be achieved even when the planning system is fully utilized. This is due to anatomical reasons, as the chest practically wraps around the thorax in the supine position.