Comparison of radiotherapy planning techniques for breast cancer

Abstract

Radiotherapy is an integral part of the comprehensive treatment of breast cancer, which accounts for over 20% of all cancer cases among women in Poland. Along with technological progress, methods are developed that improve the effectiveness of treatment, patient comfort and reduce the toxicity of therapy. The most popular irradiation technique for breast cancer is Three-Dimensional Conformal Radiotherapy (3DCRT), as it provides the lowest doses of radiation absorbed by the contralateral organs. Compared to static techniques, dynamic techniques provide a more uniform dose distribution in the target volume (PTV, Planning Target Volume), but higher doses in the critical organs (OAR, Organ at Risk). The hybrid method combining the advantages of static and dynamic plans is becoming more and more popular.

The aim of the study was to compare four breast irradiation techniques: 3DCRT, rotary volumetric modulated arc therapy (VMAT), B-VMAT so-called butterfly, in which the emission of the therapeutic beam is blocked in a certain angular range of the arc, and a hybrid technique combining 3D and VMAT fields in one treatment plan.

For a group of 11 patients, plans were prepared in the Eclipse Treatment Planning System (TPS) (Varian Medical Systems, Palo Alto, USA) and compared for each of the discussed techniques. Dose distributions, Dose Volume Histograms (DVH) and mean doses in critical organs: lungs, contralateral lung, heart and healthy breast were evaluated.

Based on the DVH analysis, all treatment plans were found to be clinically acceptable. The 3DCRT treatment plans can be considered the most favorable in terms of doses in OAR. At the same time, it should be noted that in the hybrid technique these doses are only slightly higher. For the VMAT plans, an increase in the percentage of critical organ volumes covered by low dose isodoses was observed, especially for contralateral organs. Blocking the beam emission in the part of the arc in the B-VMAT technique partially offset this effect, but as in the case of VMAT, the OAR volumes in which low doses are deposited are noticeably higher than for the 3DCRT and hybrid plans.

The hybrid technique of breast irradiation is a good alternative to 3DCRT plans and can be implemented for clinical use, shortening the time of implementation of treatment plans on a medical accelerator and improving the comfort of treated patients.