Comparison of total body irradiation using TomoTherapy and volume-modulated rotational radiation therapy Elekta. A single center experience on pediatric patients

Abstract

This study presents the experience of one center in the development and implementation of two different methods of totalbody irradiation (ТОТ) based on radiation therapy with intensity modulation, namely, Helical TomoTherapy (HT) and Volumetric Modulated Arc Therapy (VMAT), implemented on the classic linear accelerator Elekta Synergy. The aim of the work is the comparison of two TBI methods, as well as a description of the process of introducing these methods into the routine practice of the radiotherapy department. The study was approved by the Independent Ethics Committee of the Dmitry Rogachev Nationa Medical Research Center of Pediatric Hematology, Oncology and Immunology. Prescribed total doses: PTV – 12.0 Gy with a single fraction of 2.0 Gy twice per a day, at least 95% of PTV should have received a dose of 11.4 Gy, the volume of each lung receiving 8.0 Gy should not exceed 40%, the average dose in each of the kidneys should not exceed 9.0 Gy, the dose in the anterior segment of the eye should be reduced as much as possible while maintaining the dose in surrounding part of PTV. In total, from July 2014 to December 2018, 156 patients received TBI, 128 of which on TomoTherapy and 28 on Elekta. The use of a standardized approach to TBI from July 2015 to December 2018 made it possible to introduce TBI into the routine practice of the radiotherapy department. A standardized approach to TBI was implemented with the irradiation of 17 on Elekta and 91 on TomoTherapy. It allowed us toobtain uniform reproducible results in terms of dosimetric criteria. The volume of lungs receiving a dose of 8.0 Gy did not exceed 40% for TomoTherapy and for Elekta, the average dose in the kidneys did not exceed 8.0 Gy for both modalities. In the standardized versions of TBI, 10.0 Gy cover at least 95% of the ribs volume, in accordance with the prescription. In both cases, the quality of PTV coverage met the prescribed criteria, namely, at least 95 percent of the volume of PTV received at least 95% of the prescribed dose (11.4 Gy). The minimum dose in the lungs was 6.2 ± 0.2 Gy and 5.1 ± 0.4 Gy, for TomoTherapy and Elekta respectively. The presence or absence of the clinical significance of this criterion is to be assessed. The developed TBI methods allow to deliver the prescribed dose to the target while maintaining the specified dose levels in the organs at risk. However, TomoTherapy plans have better target coverage and homogeneity than VMAT-based plans for Elekta. The use of a standardized approach makes it possible to quantify treatment plans for these techniques.