Abstract
Optimized conformal total body irradiation (OC-TBI) is a highly conformal image guided method for irradiating the whole human body while sparing the selected organs at risk (OARs) (lungs, kidneys, lens). This study investigated the safety and feasibility of pediatric OC-TBI with the helical TomoTherapy (TomoTherapy) and volumetric modulated arc (VMAT) modalities and their implementation in routine clinical practice. This is the first study comparing the TomoTherapy and VMAT modalities in terms of treatment planning, dose delivery accuracy, and toxicity for OC-TBI in a single-center setting. The OC-TBI method with standardized dosimetric criteria was developed and implemented with TomoTherapy. The same OC-TBI approach was applied for VMAT. Standardized treatment steps, namely, positioning and immobilization, contouring, treatment planning strategy, plan evaluation, quality assurance, visualization and treatment delivery procedure were implemented for 157 patients treated with TomoTherapy and 52 patients treated with VMAT. Both modalities showed acceptable quality of the planned target volume dose coverage with simultaneous OARs sparing. The homogeneity of target irradiation was superior for TomoTherapy. Overall assessment of the OC-TBI dose delivery was performed for 30 patients treated with VMAT and 30 patients treated with TomoTherapy. The planned and delivered (sum of doses for all fractions) doses were compared for the two modalities in groups of patients with different heights. The near maximum dose values of the lungs and kidneys showed the most significant variation between the planned and delivered doses for both modalities. Differences in the patient size did not result in statistically significant differences for most of the investigated parameters in either the TomoTherapy or VMAT modality. TomoTherapy-based OC-TBI showed lower variations between planned and delivered doses, was less time-consuming and was easier to implement in routine practice than VMAT. We did not observe significant differences in acute and subacute toxicity between TomoTherapy and VMAT groups. The late toxicity from kidneys and lungs was not found during the 2.3 years follow up period. The study demonstrates that both modalities are feasible, safe and show acceptable toxicity. The standardized approaches allowed us to implement pediatric OC-TBI in routine clinical practice.
Highlights
Total body irradiation (TBI) is used in the treatment of hematological malignancies as part of conditioning regimens before hematopoietic stem cell transplantation (HSCT)
Treatment Planning Strategy in Relation to Patient Size for VMAT-Based optimized conformal total body irradiation (OC-TBI) To obtain a desired dose distribution, we developed three different treatment planning strategies depending on patient height
We evaluated whether our OC-TBI methods provide sufficient plan robustness when applied to patients of varying sizes
Summary
Total body irradiation (TBI) is used in the treatment of hematological malignancies as part of conditioning regimens before hematopoietic stem cell transplantation (HSCT). Conventional TBI at extended source-surface distances has been established and demonstrated to be a reliable method, but its use is limited by its high toxicity [1–3]. There are methods of optimized TBI with a relatively short source-to-surface distance and intensity modulation [4, 5]. They make it possible to use more homogeneous targeted irradiation than conventional TBI by reducing the dose to the organs at risk (OARs), but such methods are still not considered conformal. The first optimized conformal TBI and total marrow irradiation (TMI) methods were tested using helical TomoTherapy [6–8] and later with a standard linac [9, 10]. A benefit with regard to dose distribution and selective OAR dose sparing was demonstrated by other authors in an adult cohort [11–13] and by Gruen et al in a pediatric cohort [14]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
