Optimized Conformal Total Body Irradiation methods with Helical TomoTherapy and Elekta VMAT: Implementation, Imaging, Planning and Dose Delivery for Pediatric Patients

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.

Volumetric modulated arc therapy based total marrow and lymphoid irradiation: Workflow and clinical experience

“…Further, beam-on time for VMAT plans was about 50% shorter. Larger studies have evaluated the use of VMAT TMLI to a total dose of 12 Gy ( 22 , 23 ). In the study by Mancosu et al., plans for 21 patients were evaluated, demonstrating 95% of prescription dose covered greater than 99% of the PTV in junctional regions between isocenters ( 22 ).…”

“…In the study by Mancosu et al., plans for 21 patients were evaluated, demonstrating 95% of prescription dose covered greater than 99% of the PTV in junctional regions between isocenters ( 22 ). In the study by Loginova et al, 157 patients treated with helical tomotherapy and 52 patients treated with VMAT were evaluated ( 23 ). There were no observed differences in acute, subacute, or late toxicities, as well as similar dose distributions.…”

Full Body Surface Coverage with Water-Equivalent Bolus as Novel Technique for Total Body Irradiation before Hematopoietic Stem Cell Transplantation in Pediatric Acute Lymphoid Leukemia

“…During the short term follow-up, VMAT-TBI provides a safe alternative to conventional AP/PA and lateral TBI. The dose modulation capability of VMAT-TBI may lead to new treatment opportunities, such as simultaneous or consecutive boost to the central nervous system, and to better OAR protection, better malignant cell eradication and immune suppression, and lower toxicities [ 17 , 18 ].…”

Treatment robustness of total body irradiation with volumetric modulated arc therapy

“…Mancosu demonstrated dosimetric junction robustness for in-silico shifts of up to 10 mm [9] . However, in-vivo robustness against daily recorded isocenter shifts was not addressed in previous publications on VMAT-TBI [2] , [3] , [5] , [10] . The aim of this study was to analyze online-corrected longitudinal HFS/FFS isocenter shifts and to evaluate the robustness of VMAT-TBI dose distribution in the HFS-FFS overlap region during treatment delivery.…”