American College of Radiology (ACR) and American Society for Radiation Oncology (ASTRO) Practice Guideline for the Performance of Total Body Irradiation (TBI)

Dose to organs at risk for total body irradiation: Single-institution data using the modulated arc total body irradiation technique

BACKGROUND

Organs at risk (OAR) dose reporting for total body irradiation (TBI) patients is limited, and standardly reported only as mean doses to the lungs and kidneys. Consequently, dose received and effects on other OAR remain unexplored. To remedy this gap, this study reports dose data on an extensive list of OAR for patients treated at a single institution using the modulated arc total body irradiation (MATBI) technique.

METHOD

An audit was undertaken of all patients treated with MATBI between January 2015 and March 2021 who had completed their course of treatment. OAR were contoured on MATBI patient treatment plans, with 12 Gy in six fraction prescription. OAR dose statistics and dose volume histogram data are reported for the whole body, lungs, kidneys, bones, brain, lens, heart, liver and bowel bag.

RESULTS

The OAR dose data for 29 patients are reported. Mean dose results are body 11.77 Gy, lungs 9.86 Gy, kidneys 11.84 Gy, bones 12.03 Gy, brain 12.12 Gy, right lens 12.31 Gy, left lens 12.64 Gy, heart 11.07 Gy, liver 11.81 Gy and bowel bag 12.06 Gy. Dose statistics at 1-Gy intervals of V6-V13 for lungs and V10-V13 for kidneys are also included.

CONCLUSION

This is the first time an extensive list of OAR data has been reported for any TBI technique. Due to the paucity of reporting, this information could be used by centres implementing the MATBI technique, in addition to aiding comparison between TBI techniques, with the potential for greater understanding of the relationship between dose volume data and toxicity.

Idiopathic Pneumonitis Syndrome After Total Body Irradiation in Pediatric Patients Undergoing Myeloablative Hematopoietic Stem Cell Transplantation: A PENTEC Comprehensive Review

PURPOSE

Pulmonary complications, especially idiopathic pneumonitis syndrome (IPS), are potentially life altering or fatal sequelae of hematopoietic cell transplantation (HCT). Total body irradiation (TBI) as part of the conditioning regimen has been implicated in IPS. A comprehensive PENTEC (Pediatric Normal Tissues in the Clinic) review was performed to increase our understanding of the role of TBI in the development of acute, noninfectious IPS.

METHODS AND MATERIALS

A systematic literature search was conducted using the MEDLINE, PubMed, and Cochrane library databases for articles describing pulmonary toxicity in children treated with HCT. Data pertaining to TBI and pulmonary endpoints were extracted. Risk of IPS was analyzed in relation to patient age, TBI dose, fractionation, dose rate, lung shielding, timing, and type of transplant, with the goal to better understand factors associated with this complication in children undergoing HCT. A logistic regression model was developed using a subset of studies with comparable transplant regimens and sufficient TBI data.

RESULTS

Six studies met criteria for modeling of the correlation of TBI parameters with IPS; all consisted of pediatric patients undergoing allogeneic HCT with a cyclophosphamide-based chemotherapy regimen. IPS was variably defined, but all studies that reported IPS were included in this analysis. The mean incidence of post-HCT IPS was 16% (range, 4%-41%). Mortality from IPS, when it occurred, was high (median, 50%; range, 45%-100%). Fractionated TBI prescription doses encompassed a narrow range of 9 to 14 Gy. Many differing TBI methods were reported, and there was an absence of 3-dimensional dose analysis of lung blocking techniques. Thus, a univariate correlation between IPS and total TBI dose, dose fractionation, dose rate, or TBI technique could not be made. However, a model, built from these studies based on prescribed dose using a normalized dose parameter of equivalent dose in 2-Gy fractions (EQD2), adjusted for dose rate, suggested correlation with the development of IPS (P = .0004). The model-predicted odds ratio for IPS was 24.3 Gy-1 (95% confidence interval, 7.0-84.3). Use of TBI lung dose metrics (eg, midlung point dose) could not be successfully modeled, potentially because of dosimetric uncertainties in the actual delivered volumetric lung dose and imperfections in our modeling process.

CONCLUSIONS

This PENTEC report is a comprehensive review of IPS in pediatric patients receiving fractionated TBI regimens for allogenic HCT. IPS was not clearly associated with 1 single TBI factor. Modeling using dose-rate adjusted EQD2 showed a response with IPS for allogeneic HCT using a cyclophosphamide-based chemotherapy regimen. Therefore, this model suggests IPS mitigation strategies can focus on not just the dose and dose per fraction but also the dose rate used in TBI. More data are needed to confirm this model and to determine the influence of chemotherapy regimens and contribution from graft-versus-host disease. The presence of confounding variables (eg, systemic chemotherapies) that affect risk, the narrow range of fractionated TBI doses found in the literature, and limitations of other reported data (eg, lung point dose) may have prevented a more straightforward link between IPS and total dose from being observed.

Total body irradiation delivered using a dedicated Co-60 TBI unit: Evaluation of dosimetric uniformity and dose verification

This work presents the dosimetric characteristics of Total Body Irradiation (TBI) delivered using a dedicated Co-60 TBI unit. We demonstrate the ability to deliver a uniform dose to the entire patient without the need for a beam spoiler or patient-specific compensation. Full dose distributions are calculated using an in-house Monte Carlo treatment planning system, and cumulative dose distributions are created by deforming the dose distributions within two different patient orientations. Sample dose distributions and profiles are provided to illustrate the plan characteristics, and dose and DVH statistics are provided for a heterogeneous cohort of patients. The patient cohort includes adult and pediatric patients with a range of 132-198 cm in length and 16.5-37.5 cm in anterior-posterior thickness. With the exception of the lungs, a uniform dose of 12 Gy is delivered to the patient with nearly the entire volume receiving a dose within 10% of the prescription dose. Mean lung doses (MLDs) are maintained below the estimated threshold for radiation pneumonitis, with MLDs ranging from 7.3 to 9.3 Gy (estimated equivalent dose in 2 Gy fractions (EQD2 ) of 6.2-8.5 Gy). Dose uniformity is demonstrated across five anatomical locations within the patient for which mean doses are all within 3.1% of the prescription dose. In-vivo dosimetry demonstrates excellent agreement between measured and calculated doses, with 78% of measurements within ±5% of the calculated dose and 99% within ±10%. These results demonstrate a state-of-the-art TBI planning and delivery system using a dedicated TBI unit and hybrid in-house and commercial planning techniques which provide comprehensive dosimetric data for TBI treatment plans that are accurately verified using in-vivo dosimetry.

Oocyte Cryopreservation for Medical and Planned Indications: A Practical Guide and Overview

Oocyte cryopreservation (OC) is the process in which ovarian follicles are stimulated, the follicular fluid is retrieved, and mature oocytes are isolated and vitrified. Since the first successful pregnancy utilizing previously cryopreserved oocytes in 1986, OC has become increasingly utilized as an option for future biologic children in patients facing gonadotoxic therapies, such as for the treatment of cancer. Planned OC, also termed elective OC, is growing in popularity as a means to circumvent age-related fertility decline. In this narrative review, we describe both medically indicated and planned OC, focusing on the physiology of ovarian follicular loss, OC technique and risks, timing of when OC should be performed, associated financial considerations, and outcomes.

Optimised conformal total body irradiation: a heterogeneous practice, so where next?

The use of volumetric arc therapy and inverse planning has been in routine use in radiotherapy for two decades. However, use in total body irradiation (TBI) has been more recent and few guidelines exist as to how to plan or verify. This has led to heterogeneous approaches. The goal of this review is to provide an overview of current advanced planning and dosimetry verification protocols used in optimised conformal TBI as a basis for investigating the need for greater standardisation in TBI.

Commissioning and performance evaluation of commercially available mobile imager for image guided total body irradiation

BACKGROUND

The setup of lung shield (LS) in total body irradiation (TBI) with the computed radiography (CR) system is a time-consuming task and has not been quantitatively evaluated. The TBI mobile imager (TBI-MI) can solve this problem through real-time monitoring. Therefore, this study aimed to perform commissioning and performance evaluation of TBI-MI to promote its use in clinical practice.

METHODS

The source-axis distance in TBI treatment, TBI-MI (CNERGY TBI, Cablon Medical B.V.), and the LS position were set to 400, 450, and 358 cm, respectively. The evaluation items were as follows: accuracy of image scaling and measured displacement error of LS, image quality (linearity, signal-to-noise ratio, and modulation transfer function) using an EPID QC phantom, optimal thresholding to detect intra-fractional motion in the alert function, and the scatter radiation dose from TBI-MI.

RESULTS

The accuracy of image scaling and the difference in measured displacement of the LS was <4 mm in any displacements and directions. The image quality of TBI imager was slightly inferior to the CR image but was visually acceptable in clinical practice. The signal-to-noise ratio was improved at high dose rate. The optimal thresholding value to detect a 10-mm body displacement was determined to be approximately 5.0%. The maximum fraction of scattering radiation to irradiated dose was 1.7% at patient surface.

CONCLUSION

MI-TBI can quantitatively evaluate LS displacement with acceptable image quality. Furthermore, real-time monitoring with alert function to detect intrafraction patient displacement can contribute to safe TBI treatment.

Total body irradiation using volumetric modulated arc therapy, experience of a cancer hospital in Pakistan

Introduction:

To report the planning parameters, efficacy and toxicity of total body irradiation using volumetric modulated arc therapy (VMAT).

Methods:

From July 2019 till May 2021, nine patients treated with VMAT-based total body irradiation as a part of the myeloablative regimen for homologous stem cell transplant were evaluated. The CT acquisition, planning parameters, doses to target volume and critical structures were evaluated retrospectively.

Results:

Median age was 24 with median height 172 cm. Average Mean Lung dose was 9·5 Gy, mean dose to kidney was kidney dose 8·4 Gy, planning target volume (PTV) 95% was 98 % and mean heterogeneity index of PTV was 1·2 all patients. Total fraction delivery time including setup was 3·1 h while beam on time was 23 min. Main toxicity observed was mucositis and fatigue, while no Grade 3 or more acute radiation toxicity was observed.

Conclusion:

At our institution, high dose TBI performed with multi-isocentric VMAT is now a standard procedure. Though it is cumbersome and time-consuming process but VMAT offers an advantage of increased dose homogeneity in the target volume with reduction in doses to critical organs especially lungs and kidneys in comparison to standard source to skin distance technique, longer follow-up time is necessary to evaluate our method and long-term toxicity.

ESTRO ACROP and SIOPE recommendations for myeloablative Total Body Irradiation in children

BACKGROUND AND PURPOSE

Myeloablative Total Body Irradiation (TBI) is an important modality in conditioning for allogeneic hematopoietic stem cell transplantation (HSCT), especially in children with high-risk acute lymphoblastic leukemia (ALL). TBI practices are heterogeneous and institution-specific. Since TBI is associated with multiple late adverse effects, recommendations may help to standardize practices and improve the outcome versus toxicity ratio for children.

MATERIAL AND METHODS

The European Society for Paediatric Oncology (SIOPE) Radiotherapy TBI Working Group together with ESTRO experts conducted a literature search and evaluation regarding myeloablative TBI techniques and toxicities in children. Findings were discussed in bimonthly virtual meetings and consensus recommendations were established.

RESULTS

Myeloablative TBI in HSCT conditioning is mostly performed for high-risk ALL patients or patients with recurring hematologic malignancies. TBI is discouraged in children <3-4 years old because of increased toxicity risk. Publications regarding TBI are mostly retrospective studies with level III-IV evidence. Preferential TBI dose in children is 12-14.4 Gy in 1.6-2 Gy fractions b.i.d. Dose reduction should be considered for the lungs to <8 Gy, for the kidneys to ≤10 Gy, and for the lenses to <12 Gy, for dose rates ≥6 cGy/min. Highly conformal techniques i.e. TomoTherapy and VMAT TBI or Total Marrow (and/or Lymphoid) Irradiation as implemented in several centers, improve dose homogeneity and organ sparing, and should be evaluated in studies.

CONCLUSIONS

These ESTRO ACROP SIOPE recommendations provide expert consensus for conventional and highly conformal myeloablative TBI in children, as well as a supporting literature overview of TBI techniques and toxicities.

The impact of different optimization strategies on the agreement between planned and delivered doses during volumetric modulated arc therapy for total marrow irradiation

Aim of the study

To evaluate the agreement between planned and delivered doses and its potential correlation with the plans' complexity subjected to dosimetric verification.

Material and methods

Four isocentre volumetric modulated arc therapy for total marrow irradiation plans optimized simultaneously with (P1) and without (P2) MU reduction were evaluated dosimetrically by γ method performed in a global mode for 4 combinations of γ-index criteria (2%/2 mm, 2%/3 mm, 3%/2 mm, and 3%/3 mm). The evaluation was conducted for 4 regions (head and neck, chest, abdomen and upper pelvis, and lower pelvis and thighs) that were determined geometrically by the isocentres. The Wilcoxon test was used to detect significant differences between γ passing rate (GPR) analysis results for the P1 and P2 plans. The Pearson correlation was used to check the relationship between GPR and the plans' complexity.

Results

Except for the head and neck region, the P2 plans had better GPRs than the P1 plans. Only for hard combinations of γ-index criteria (i.e. 2%/3 mm, 2%/2 mm) were the GPRs differences between P1 and P2 clinically meaningful, and they were detected in the chest, abdomen and upper pelvis, and lower pelvis and thighs regions. The highest correlations between GPR and the indices describing the plans' complexity were found for the chest region. No correlation was found for the head and neck region.

Conclusions

The P2 plans showed better agreement between planned and delivered doses compared to the P1 plans. The GPR and the plans' complexity depend on the anatomy region and are most important for the chest region.

Image-guided volumetric-modulated arc therapy of total body irradiation: An efficient workflow from simulation to delivery

Introduction

Using multi‐isocenter volumetric‐modulated arc therapy (VMAT) for total body irradiation (TBI) may improve dose uniformity and vulnerable tissue protection compared with classical whole‐body field technique. Two drawbacks limit its application: (1) VMAT‐TBI planning is time consuming; (2) VMAT‐TBI plans are sensitive to patient positioning uncertainties due to beam matching. This study presents a robust planning technique with image‐guided delivery to improve dose delivery accuracy. In addition, a streamlined sim‐to‐treat workflow with automatic scripts is proposed to reduce planning time.

Materials

Twenty‐five patients were included in this study. Patients were scanned in supine head‐first and feet‐first directions. An automatic workflow was used to (1) create a whole‐body CT by registering two CT scans, (2) contour lungs, kidneys, and planning target volume (PTV), (3) divide PTV into multiple sub‐targets for planning, and (4) place isocenters. Treatment planning included feathered AP/PA beams for legs/feet and VMAT for the body. VMAT‐TBI was evaluated for plan quality, planning/delivery time, and setup accuracy using image guidance.

Results

VMAT‐TBI planning time can be reduced to a day with automatic scripts. Treatment time took around an hour per fraction. VMAT‐TBI improved dose coverage (PTV V100 increased from 76.8 ± 10.5 to 88.5 ± 2.6; p < 0.001) and reduced lung dose (lung mean dose reduced from 10.8 ± 0.7 Gy to 9.4 ± 0.8 Gy, p < 0.001) compared with classic AP/PA technique.

Conclusion

A VMAT‐TBI sim‐to‐treat workflow with robust planning and image‐guided delivery was proposed. VMAT‐TBI improved the plan quality compared with classical whole‐body field techniques.

Commissioning of a three-dimensional arc-based technique for total body irradiation

The purpose of this study is to describe the commissioning of a novel three‐dimensional arc‐based technique for total body irradiation (TBI) treatments. The development and implementation of this technique allowed our institution to transition from a bilateral two‐dimensional (2D) technique to a methodology based on volumetric dose calculation. The methodology described in this work is a derivation from the MATBI technique, with the static fields being replaced by four contiguous arc‐fields for each anterior and posterior incidence. The reduced number of fields we employed makes it possible to reach a satisfactory dose uniformity through manual optimization in a straightforward process. We use the Eclipse anisotropic analytical algorithm (AAA) algorithm, commissioned with preconfigured beam data for a 6 MV photon beam, at standard SSD (100 cm). A thorough evaluation of the accuracy of the AAA algorithm at an extended distance (approximately 200 cm) was carried out. For the evaluation, we compared measured and calculated percentage depth–dose and profiles that included open‐field, penumbra, and out‐of‐field regions. The analysis was performed for both static and arc fields, taking into consideration unshielded fields and also in the presence of lung shielding blocks. End‐to‐end tests were carried out for our institutional template plan by two means: with a 2D ion chamber array detector in solid phantom and using Gafchromic films in an anthropomorphic phantom. The results obtained in this work demonstrate that the Eclipse AAA algorithm commissioned for standard treatments can be safely used with our TBI planning technique. Moreover, this technique proved to be a highly efficient path to replace conventional treatment techniques, providing a homogeneous dose distribution, dosimetric robustness, and shorter treatment times. In addition, as inherited from the MATBI technique, our methodology can be implemented in small treatment rooms, with no need for ancillary equipment.

The effects of rotational setup errors in total body irradiation using helical tomotherapy

Purpose

Helical tomotherapy (HT) is a form of intensity‐modulated radiation therapy that is employed in total body irradiation (TBI). Because TBI targets the whole body, accurate setup positioning at the edge of the treatment volume is made difficult by the whole‐body rotational posture. The purpose of this study is to clarify the tolerance for rotational setup error (SE) in the vertical direction. In addition, we perform a retrospective analysis of actually irradiated dose distributions using previous patients’ irradiation data.

Methods

To clarify the effects of rotational SE on the dose distribution, the planned CT images of 10 patients were rotated by 1–5° in the vertical (pitch) direction to create a pseudo‐rotational SE image. Then, the effect of the magnitude of the rotational SE on the dose distribution was simulated. In addition, the irradiated dose to the patients was analyzed by obtaining recalculated dose distributions using megavoltage CT images acquired before treatment.

Results

The simulation results showed that the average value of the lung volume receiving at least 10 Gy did not exceed the allowable value when the SE value was ≤2°. When the rotational SE was ≤3°, it was possible to maintain the clinical target volume dose heterogeneity within ±10% of the prescribed dose, which is acceptable according to the guidelines. A retrospective analysis of previous patients’ irradiation data showed their daily irradiation dose distribution. The dose to the clinical target volume was reduced by up to 3.4% as a result of the residual rotational SE. Although whole‐course retrospective analyses showed a statistically significant increase in high‐dose areas, the increase was only approximately 1.0%.

Conclusions

Dose errors induced by rotational SEs of ≤2° were acceptable in this study.

Determining the incidence of interstitial pneumonitis and chronic kidney disease following full intensity haemopoetic stem cell transplant conditioned using a forward-planned intensity modulated total body irradiation technique

PURPOSE/OBJECTIVE

Total body irradiation (TBI) remains a key component of conditioning for allogeneic haemopoietic stem cell transplant (HSCT), with interstitial pneumonitis (IP) and chronic kidney disease (CKD) important late sequelae. We undertook a retrospective service evaluation of TBI patients treated with a forward-planned intensity modulated radiotherapy technique (FP IMRT).

MATERIAL/METHODS

74 adult patients were identified; all received step and shoot FP IMRT TBI, 14.4 Gy in 8 fractions over 4 days. Mean doses to the lungs and kidneys were 12-12.5 Gy. Toxicities were defined as per CTCAE v4.0: IP as multilobar infiltrates on CT with symptoms of dyspnoea, and renal dysfunction as an Estimated Glomerular Filtration rate (eGFR) < 60 ml/min/1.73 m2 for > 3 months. Secondary endpoints were overall survival (OS), progression free survival (PFS), cumulative incidence of non-relapse mortality (NRM), relapse risk and of acute and chronic GvHD.

RESULTS

Patients received treatment for the following diagnosis: ALL/LBL (n = 37); AML (n = 33), CML-BC (n = 2) and High grade NHL (n = 2). The rate of IP due to any cause was 30%; positive microbiological evidence in 73% (16 /22). Idiopathic IP was seen in 8%, with only 4% (n = 3) having IP Grade ≥ 3. Two (4%) of 52 long term survivors developed CKD, one with thrombotic microangiopathy. 4 year NRM was 16% (CI 11-32%); no treatment related deaths in matched sibling or umbilical cord blood HSCT.

CONCLUSION

FP IMRT TBI, reducing dose to the lungs and kidneys, has lower rates of idiopathic IP and CKD compared to the literature. This technique is safe and effective conditioning for full intensity HSCT.

Acute lymphoblastic leukemia

The survival of patients with acute lymphoblastic leukemia (ALL) has improved significantly with the use of intensive multimodality treatment regimens including chemotherapy, high-dose chemotherapy and stem cell rescue, and radiation therapy when indicated. This report summarizes the treatment strategies, especially radiation therapy in the Children's Oncology Group for children with ALL. Currently, radiation therapy is only indicated for children with high-risk CNS involvement at diagnosis or relapse, testicular relapse and as part of the conditioning regimen for hematopoietic stem cell transplantation. Future research strategies regarding the indications for and dosages of radiation therapy and novel radiation techniques are discussed.

Commissioning of total body irradiation using plastic bead bags

The goal of total body irradiation (TBI) is to deliver a dose to the whole body with uniformity within ±10%. The purpose of this study was to establish the technique of TBI using plastic bead bags. A lifting TBI bed, Model ORP-TBI-MN, was used. The space between the patient's body and the acrylic walls of the bed was filled with polyacetal bead bags. Patients were irradiated by a 10 MV photon beam with a source to mid-plane distance of 400 cm. The monitor unit (MU) was calculated by dose-per-MU, tissue-phantom-ratio and a spoiler factor measured in solid water using an ionization chamber. The phantom-scatter correction factor, off-center ratio and the effective density of the beads were also measured. Diode detectors were used for in vivo dosimetry (IVD). The effective density of the beads was 0.90 ± 0.09. The point doses calculated in an I'mRT phantom with and without heterogeneity material showed good agreement, with measurements within 3%. An end-to-end test was performed using a RANDO phantom. The mean ± SD (range) of the differences between the calculated and IVD-measured mid-plane doses was 1.1 ± 4.8% (-5.9 to 5.0%). The differences between the IVD-measured doses and the doses calculated with Acuros XB of the Eclipse treatment planning system (TPS) were within 5%. For two patients treated with this method, the differences between the calculated and IVD-measured doses were within ±6% when excluding the chest region. We have established the technique of TBI using plastic bead bags. The TPS may be useful to roughly estimate patient dose.

Integration of automation into an existing clinical workflow to improve efficiency and reduce errors in the manual treatment planning process for total body irradiation (TBI)

Purpose

To identify causes of error, and present the concept of an automated technique that improves efficiency and helps to reduce transcription and manual data entry errors in the treatment planning of total body irradiation (TBI).

Methods

Analysis of incidents submitted to incident learning system (ILS) was performed to identify potential avenues for improvement by implementation of automation of the manual treatment planning process for total body irradiation (TBI). Following this analysis, it became obvious that while the individual components of the TBI treatment planning process were well implemented, the manual ‘bridging’ of the components (transcribing data, manual data entry etc.) were leading to high potential for error. A C#‐based plug‐in treatment planning script was developed to remove the manual parts of the treatment planning workflow that were contributing to increased risk.

Results

Here we present an example of the implementation of “Glue” programming, combining treatment planning C# scripts with existing spreadsheet calculation worksheets. Prior to the implementation of automation, 35 incident reports related to the TBI treatment process were submitted to the ILS over a 6‐year period, with an average of 1.4 ± 1.7 reports submitted per quarter. While no incidents reached patients, reports ranged from minor documentation issues to potential for mistreatment if not caught before delivery. Since the implementation of automated treatment planning and documentation, treatment planning time per patient, including documentation, has been reduced; from an average of 45 min pre‐automation to <20 min post‐automation.

Conclusions

Manual treatment planning techniques may be well validated, but they are time‐intensive and have potential for error. Often the barrier to automating these techniques becomes the time required to “re‐code” existing solutions in unfamiliar computer languages. We present the workflow here as a proof of concept that automation may help to improve clinical efficiency and safety for special procedures.

Incidence, Risk Factors, and Outcomes of Idiopathic Pneumonia Syndrome after Allogeneic Hematopoietic Cell Transplantation

Our current knowledge of idiopathic pneumonia syndrome (IPS) predates improved specificity in the diagnosis of IPS and advances in hematopoietic cell transplantation (HCT) and critical care practices. In this study, we describe and update the incidence, risk factors, and outcomes of IPS. We performed a retrospective cohort study of all adults who underwent allogeneic HCT at the Fred Hutchinson Cancer Research Center between 2006 and 2013 (n = 1829). IPS was defined using the National Heart, Lung, and Blood Institute consensus definition: multilobar airspace opacities on chest imaging, absence of lower respiratory tract infection, and hypoxemia. We described IPS incidence and mortality within 120 and 365 days after HCT. We examined conditioning intensity (nonmyeloablative versus myeloablative with high-dose total body irradiation [TBI] versus myeloablative with low-dose TBI) as an IPS risk factor in a time-to-event analysis using Cox models, controlled for age at transplant, HLA matching, stem cell source, and pretransplant Lung function Score (a combined measure of impairment in Forced Expiratory Volume in the first second (FEV₁) and Diffusion capacity for carbon monoxide (DLCO)). Among 1829 HCT recipients, 67 fulfilled IPS criteria within 120 days (3.7%). Individuals who developed IPS were more likely to be black/non-Hispanic versus other racial groups and have severe pulmonary impairment but were otherwise similar to participants without IPS. In adjusted models, myeloablative conditioning with high-dose TBI was associated with increased risk of IPS (hazard ratio, 2.5; 95% confidence interval, 1.2 to 5.2). Thirty-one patients (46.3%) with IPS died within the first 120 days of HCT and 47 patients (70.1%) died within 365 days of HCT. In contrast, among the 1762 patients who did not acquire IPS in the first 120 days, 204 (11.6%) died within 120 days of HCT and 510 (29.9%) died within 365 days of HCT. Our findings suggest that although the incidence of IPS may be declining, it remains associated with post-transplant mortality. Future study should focus on early detection and identifying pathologic mediators of IPS to facilitate timely, targeted therapies for those most susceptible to lung injury post-HCT.

Effect of changes in monitor unit rate and energy on dose rate of total marrow irradiation based on Linac volumetric arc therapy

Background

This study set out to evaluate the effect of dose rate on normal tissues (the lung, in particular) and the variation in the treatment efficiency as determined by the monitor unit (MU) and energy applied in Linac-based volumetric arc therapy (VMAT) total marrow irradiation (TMI).

Methods

Linac-based VMAT plans were generated for the TMI for six patients. The planning target volume (PTV) was divided into six sub-volumes, each of which had their own isocenter. To examine the effect of the dose rate and energy, a range of MU rates (40, 60, 80, 100, 300, and 600 MU/min) were selected for 6, 10, and 15 MV. All the plans were verified by portal dosimetry.

Results

The dosimetric parameters for the target and normal tissue were consistent in terms of the energy and MU rate. The beam-on time was changed from 59.6 to 6 min for 40 and 600 MU/min. When 40 MU/min was set for the lung, the dose rate delivered to the lung was less than 6 cGy/min (that is, 90%), while the beam-on time was approximately 10 min. The percentage volume of the lung receiving 20 cGy/min was 1.47, 3.94, and 6.22% at 6, 10, and 15 MV, respectively. However, for 600 MU/min, the total lung volume received over 6 cGy/min regardless of the energy, and over 20 cGy/min for 10 and 15 MV (i.e., 54.4% for 6 MV).

Conclusions

In TMI treatment, reducing the dose rate administered to the lung can decrease the incidence of pulmonary toxicity. To reduce the probability of normal tissue complications, the selection of the lowest MU rate is recommended for fields including the lung. To minimize the total treatment time, the maximum MU rate can be applied to other fields.

Electronic supplementary material

The online version of this article (10.1186/s13014-019-1296-y) contains supplementary material, which is available to authorized users.

Current Status and Perspectives of Irradiation-Based Conditioning Regimens for Patients with Acute Leukemia Undergoing Hematopoietic Stem Cell Transplantation

Acute myeloid leukemia and acute lymphoblastic leukemia are the most common indications for allogeneic hematopoietic stem cell transplantation. Total body irradiation (TBI) is an important part of conditioning regimens. TBI-based regimens offer advantages in sanctuary sites but are associated with significant risks of early and late side effects, including pulmonary toxicity, growth retardation, and second malignancy. TBI is also associated with technical problems, such as dose heterogeneity. With evolving techniques in radiation oncology, it is possible to focus the dose to the entire skeleton while sparing the rest of the body. This technique is called total marrow irradiation (TMI). TMI is able to deliver the same or higher doses to bone marrow while reducing toxicity. With the success of TMI, we are moving toward ultra-personalized conditioning. We review the clinical role of the irradiation-based regimens currently in clinical use, emphasizing on their strengths and limitations. Novel technologies with targeted irradiation accompanied by the modern imaging techniques and increased knowledge of the disease process can help us achieve our goal of maximum response with minimum toxicity.

Dose evaluation indices for total body irradiation using TomoDirect with different numbers of ports: A comparison with the TomoHelical method

TomoDirect has been reported to have some advantages over TomoHelical in delivering total body irradiation (TBI). This study aimed to investigate the relationships between the number of ports and the dose evaluation indices in low‐dose TBI in TomoDirect mode using 2–12 ports and to compare these data with those for the TomoHelical mode in a simulation study. Thirteen patients underwent low‐dose TBI in TomoHelical mode from June 2015 to June 2016. We used the same computed tomography data sets for these patients to create new treatment plans for upper‐body parts using TomoDirect mode with 2–12 beam angles as well as TomoHelical mode. The prescription was 4 Gy in two equal fractions. For the TomoDirect data, we generated plans with 2–12 ports with approximately equally spaced angles; the modulation factor, field width, and pitch were 2.0, 5.0 cm, and 0.500, respectively. For the TomoHelical plans, the modulation factor, field width, and pitch were 2.0, 5.0 cm, and 0.397, respectively. D2, D98, D50, and the homogeneity index (HI) were evaluated to compare TomoDirect plans having 2–12 ports with the TomoHelical plan. Using TomoDirect plans, D2 with four ports or fewer, D98 with 10 ports or fewer, D50 with four ports or fewer and HI with five ports or fewer showed statistically significantly worse results than the TomoHelical plan. With the TomoDirect plans, D2 with seven ports or more, D50 with eight ports or more, and HI with eight ports or more showed statistically significant improvement compared with the TomoHelical plan. All of the dose evaluation indices of the TomoDirect plans showed a tendency to improve as the number of ports increased. TomoDirect plans showed statistically significant improvement of D2, D50, and HI compared with the TomoHelical plan. Therefore, we conclude that TomoDirect can provide better dose distribution in low‐dose TBI with TomoTherapy.

Appropriate treatment planning method for field joint dose in total body irradiation using helical tomotherapy

Total body irradiation (TBI) using helical tomotherapy (HT) has advantages over the standard linear accelerator-based approach to the conditioning regimen for hematopoietic cell transplantation. However, the radiation field has to be divided into two independent irradiation plans to deliver a homogeneous dose to the whole body. A clinical target volume near the skin increases the skin surface dose; therefore, high- or low-dose regions arise depending on the set-up position accuracy because the two radiation fields are somewhat overlapped or separated. We aimed to determine an adequate treatment planning method robust to the set-up accuracy for the field joint dose distribution using HT-TBI. We calculated treatment plans reducing target volumes at the interface between the upper and lower body irradiations and evaluated these joint dose distributions via simulation and experimental studies. Target volumes used for the optimization calculation were reduced by 0, 0.5, 1.0, 2.0, 2.5, and 3.0 cm from the boundary surface on the upper and lower sides. Combined dose distributions with set-up error simulated by modifying coordinate positions were investigated to find the optimal planning method. In the ideal set-up position, the target volume without a gap area caused field junctional doses of up to approximately 200%; therefore, target volumes reduced by 2.0-3.0 cm could suppress the maximum dose to within 150%. However, with set-up error, high-dose areas exceeding 150% and low-dose areas below 100% were found with 2.0 and 3.0 cm target volume reduction. Using the dynamic jaw (DJ) system, dose deviations caused by set-up error reached approximately 20%, which is not suitable for HT-TBI. Moreover, these dose distributions can be easily adjusted when combined with the intensity modulation technique for field boundary regions. The results of a simulation and experimental study using a film dosimetry were almost identical, which indicated that reducing the target volume at the field boundary surface by 2.5 cm produces the most appropriate target definition.

Effect of dose rate on pulmonary toxicity in patients with hematolymphoid malignancies undergoing total body irradiation

BACKGROUND

This study evaluated the effect of radiation dose rate in patients with hematolymphoid malignancies undergoing myeloablative conditioning with total body irradiation (TBI), for hematopoietic stem cell transplantation.

METHODS

The incidence of pulmonary toxicity (PT) and treatment efficacy were compared between the conventional (≥ 6 cGy/min) and reduced dose rate (< 6 cGy/min). Seventy-seven patients receiving once-daily TBI between 2000 and 2016 were reviewed. We compared the cumulative rate of PT, overall survival (OS), relapse, and transplantation-related mortality (TRM) between conventional (n = 54) and reduced (n = 23) groups. Factors associated with PT were assessed in the presence of competing risks.

RESULTS

The median follow-up time was 40.7 months, and PT occurred in 50 patients (64.9%). On multivariate analyses, the groups classified by the dose rate (P = 0.010), total dose (P = 0.025), and conditioning regimen (P = 0.029) were significant factors for the development of PT. OS was significantly reduced when PT occurred (P < 0.001). However, the OS, relapse, and TRM were not different between the two groups.

CONCLUSIONS

In summary, about two-thirds of the patients undergoing daily TBI experienced PT, which affected OS. Therefore, reducing the dose rate (less than 6 cGy/min) of TBI can decrease the risk of PT, without compromising the treatment efficacy.

Influence of Total Body Irradiation Dose Rate on Idiopathic Pneumonia Syndrome in Acute Leukemia Patients Undergoing Allogeneic Hematopoietic Cell Transplantation

PURPOSE

To determine the relationship between dose rate and other factors in the development of idiopathic pneumonia syndrome (IPS) in patients with acute lymphoblastic leukemia or acute myeloid leukemia who are undergoing total body irradiation (TBI)-based myeloablative conditioning for allogeneic hematopoietic cell transplantation (HCT).

METHODS AND MATERIALS

From 2006 to 2016, 202 patients with acute leukemia (111 acute lymphoblastic leukemia, 91 acute myeloid leukemia) ranging in age from 1 to 57 years (median, 25 years) underwent allogeneic HCT at University of Minnesota. Pretransplantation conditioning included cyclophosphamide (120 mg/kg) with (68%) or without fludarabine (75 mg/m²) followed by 13.2 Gy TBI given in 8 twice-daily fractions of 1.65 Gy over 4 days. Dose rate varied based on linear accelerator availability and ranged from 8.7 to 19.2 cGy/min. Patients were stratified by receipt of high-dose-rate (HDR; >15 cGy/min; 56%) or low-dose-rate (LDR; ≤15 cGy/min; 44%) TBI for all 8 fractions. IPS was defined as pulmonary injury based on clinical symptoms, radiographic evidence, or pulmonary function testing within 100 days of HCT in the absence of concurrent infection.

RESULTS

IPS developed in 42 patients (21%) between 4 and 73 days (median, 16 days) after transplantation. HDR TBI was associated with a higher rate of IPS compared with LDR TBI (29% vs 10%; P < .01). On multiple regression analysis, HDR remained a significant predictor of IPS (hazard ratio, 2.6; 95% confidence interval, 1.2-5.3; P = .01), and this led to inferior 1-year overall survival (60% vs 76%; P = .01) and increased 1-year nonrelapse mortality (28% vs 15%; P = .02).

CONCLUSIONS

TBI dose rates ≤15 cGy/min reduce the risk of posttransplantation IPS and improve overall survival. LDR TBI should be strongly considered as an easily implemented parameter to improve the safety of pretransplantation TBI-based conditioning.

National survey of myeloablative total body irradiation prior to hematopoietic stem cell transplantation in Japan: survey of the Japanese Radiation Oncology Study Group (JROSG)

A myeloablative regimen that includes total-body irradiation (TBI) before hematopoietic stem cell transplantation results in higher patient survival rates than achieved with regimens without TBI. The TBI protocol, however, varies between institutions. In October 2015, the Japanese Radiation Oncology Study Group initiated a national survey of myeloablative TBI (covering 2010-2014). Among the 186 Japanese institutions performing TBI, 90 (48%) responded. The 82 institutions that had performed myeloablative TBI during this period treated 2698 patients with malignant disease [leukemia (2082 patients, 77.2%), malignant lymphoma (378, 14%)] and 37 with non-malignant disease [severe aplastic anemia (20, 54%), inborn errors of metabolism (5, 14%)]. A linear accelerator was used at all institutions. The institutions were divided into 41 large and 41 small institutions based on the median number of patients. The long source-surface distance technique was the method of choice in the 34 institutions (82.9%) and the moving-couch technique in the 7 (17.1%) in the large institutions. The schedules most routinely used by the participating institutions consisted of 12 Gy/6 fractions/3 days (26 institutions, 63.5%) in the large institutions. The dose rate varied from 5 to 26 cGy/min. The lungs and lenses were routinely shielded in 23 large institutions (56.1%), and only the lungs in 9 large institutions (21.9%). At lung-shielding institutions, the most frequent maximum acceptable total dose for the lungs was 8 Gy (19 institutions, 27.5%). Our results reveal considerable differences in the TBI methods used by Japanese institutions and thus the challenges in designing multicenter randomized trials based on TBI.

Volumetric modulated arc therapy for total body irradiation: A feasibility study using Pinnacle3 treatment planning system and Elekta Agility™ linac

A study was undertaken to explore the use of volumetric modulated arc therapy (VMAT) for total body irradiation (TBI). Five patient plans were created in Pinnacle3 using nine 6 MV photon dynamic arcs. A dose of 12 Gy in six fractions was prescribed. The planning target volume (PTV) was split into four subsections for the head, chest, abdomen, and pelvis. The head and chest beams were optimized together, followed by the abdomen and pelvis beams. The last stage of the planning process involved turning all beams on and performing a final optimization to achieve a clinically acceptable plan. Beam isocenters were shifted by 3 or 5 mm in the left-right, anterior-posterior, and superior-inferior directions to simulate the effect of setup errors on the dose distribution. Treatment plan verification consisted of ArcCheck measurements compared to calculated doses using a global 3%/3 mm gamma analysis. All five patient plans achieved the planning aim of delivering 12 Gy to at least 90% of the target. The mean dose in the PTV was 12.7 Gy. Mean lung dose was restricted to 8 Gy, and a dose reduction of up to 40% for organs such as the liver and kidneys proved feasible. The VMAT technique was found to be sensitive to patient setup errors particularly in the superior-inferior direction. The dose predicted by the planning system agreed with measured doses and had an average pass rate of 99.2% for all arcs. VMAT was found to be a viable treatment technique for total body irradiation.

Total body irradiation in allogeneic bone marrow transplantation conditioning regimens: A review

Hematologic malignancies may require, at one point during their treatment, allogeneic bone marrow transplantation. Total body irradiation combined with chemotherapy or radiomimetic used in allogeneic bone marrow transplantation is known to be very toxic. Total body irradiation (TBI) induces immunosuppression to prevent the rejection of donor marrow. TBI is also used to eradicate malignant cells and is in sanctuary organs that are not reached by chemotherapy drugs. TBI has evolved since its introduction in the late fifties, but acute and late toxicities remain. Helical tomotherapy, which is widely used for some solid tumors, is a path for the improvement of outcomes and toxicities in TBI because of its sparing capacities. In this article, we first review the practical aspects of TBI with patient positioning, radiobiological considerations and total dose and fractionation prescriptions. Second, we review the use of intensity modulated radiation therapy in bone marrow transplantation with a focus on helical tomotherapy TBI, helical tomotherapy total marrow irradiation (TMI) and total marrow and lymphoid irradiation (TMLI) and their dosimetric and clinical outcomes. Finally, we review the perspective of dose escalation and the extension to older patients and patients with comorbidity who do not benefit from a standard bone marrow transplantation conditioning regimen.

Factors associated with pulmonary toxicity after myeloablative conditioning using fractionated total body irradiation

Purpose

Pulmonary toxicities, including infectious pneumonia (IP) and idiopathic pneumonia syndrome (IPS), are serious side effects of total body irradiation (TBI) used for myeloablative conditioning. This study aimed to evaluate clinical factors associated with IP and IPS following TBI.

Materials and Methods

Fifty-eight patients with hematologic malignancies who underwent TBI before allogeneic hematopoietic stem cell transplantation between 2005 and 2014 were reviewed. Most patients (91%) received 12 Gy in 1.5 Gy fractions twice a day. Pulmonary toxicities were diagnosed based on either radiographic evidence or reduced pulmonary function, and were subdivided into IP and IPS based on the presence or absence of concurrent infection.

Results

Pulmonary toxicities developed in 36 patients (62%); 16 (28%) had IP and 20 (34%) had IPS. IP was significantly associated with increased treatment-related mortality (p = 0.028) and decreased survival (p = 0.039). Multivariate analysis revealed that the risk of developing IPS was significantly higher in patients who received stem cells from a matched unrelated donor than from a matched sibling donor (p = 0.021; hazard ratio [HR] = 12.67; 95% confidence interval [CI], 1.46–110.30). Combining other conditioning agents with cyclophosphamide produced a higher tendency to develop IP (p = 0.064; HR = 6.19; 95% CI, 0.90–42.56).

Conclusion

IP and IPS involve different risk factors and distinct pathogeneses that should be considered when planning treatments before and after TBI.

Adequate target volume in total-body irradiation by intensity-modulated radiation therapy using helical tomotherapy: a simulation study

Recently, intensity-modulated radiation therapy (IMRT) has been used for total-body irradiation (TBI). Since the planning target volume (PTV) for TBI includes the surrounding air, a dose prescription to the PTV provides high fluence to the body surface. Thus with just a small set-up error, the body might be exposed to a high-fluence beam. This study aims to assess which target volume should be prescribed the dose, such as a clinical target volume (CTV) with a margin, or a CTV that excludes the surface area of the skin. Three treatment plans were created for each patient: the 5-mm clipped plan (Plan A), the 0-mm margin plan (Plan B) and the 5-mm margin plan (Plan C). The CTV was the whole body. PTVs were the CTV with the exception of 5 mm from the skin surface in Plan A, equal to the CTV in Plan B, and the CTV with a 5 mm margin in Plan C. The prescribed dose was 12 Gy in six fractions. To assess the influence of the set-up error, dose distributions were simulated on computed tomography (CT) images shifted 2 pixels (= 4.296 mm), 5 pixels (= 10.74 mm) and 10 pixels (= 21.48 mm) in the lateral direction from the original CT. With a set-up error of 10.74 mm, V110% was 8.8%, 11.1% and 23.3% in Plans A, B and C, respectively. The prescription to the PTV containing the surrounding air can be paradoxically vulnerable to a high-dose as a consequence of a small set-up error.

Low-dose irradiation prior to bone marrow transplantation results in ATM activation and increased lethality in Atm-deficient mice

Ataxia telangiectasia is a genetic instability syndrome characterized by neurodegeneration, immunodeficiency, severe bronchial complications, hypersensitivity to radiotherapy and an elevated risk of malignancies. Repopulation with ATM-competent bone marrow-derived cells (BMDCs) significantly prolonged the lifespan and improved the phenotype of Atm-deficient mice. The aim of the present study was to promote BMDC engraftment after bone marrow transplantation using low-dose irradiation (IR) as a co-conditioning strategy. Atm-deficient mice were transplanted with green fluorescent protein-expressing, ATM-positive BMDCs using a clinically relevant non-myeloablative host-conditioning regimen together with TBI (0.2-2.0 Gy). IR significantly improved the engraftment of BMDCs into the bone marrow, blood, spleen and lung in a dose-dependent manner, but not into the cerebellum. However, with increasing doses, IR lethality increased even after low-dose IR. Analysis of the bronchoalveolar lavage fluid and lung histochemistry revealed a significant enhancement in the number of inflammatory cells and oxidative damage. A delay in the resolution of γ-H2AX-expression points to an insufficient double-strand break repair capacity following IR with 0.5 Gy in Atm-deficient splenocytes. Our results demonstrate that even low-dose IR results in ATM activation. In the absence of ATM, low-dose IR leads to increased inflammation, oxidative stress and lethality in the Atm-deficient mouse model.

Norm- and hypo-fractionated radiotherapy is capable of activating human dendritic cells

Despite the transient immunosuppressive properties of local radiotherapy (RT), this classical treatment modality of solid tumors is capable of inducing immunostimulatory forms of tumor-cell death. The resulting 'immunotoxicity' in the tumor, but not in healthy tissues, may finally lead to immune-mediated destruction of the tumor. However, little is known about the best irradiation scheme in this setting. This study examines the immunological effects of differently irradiated human colorectal tumor cells on human monocyte-derived dendritic cells (DC). Human SW480 tumor cells were irradiated with a norm-fractionation scheme (5 × 2 Gy), a hypo-fractionated protocol (3 × 5 Gy), and with a high single irradiation dose (radiosurgery; 1 × 15 Gy). Subsequently, human immature DC (iDC) were co-incubated with supernatants (SN) of these differently treated tumor cells. Afterwards, DC were analyzed regarding the expression of maturation markers, the release of cytokines, and the potential to stimulate CD4(+) T-cells. The co-incubation of iDC with SN of tumor cells exposed to norm- or hypo-fractionated RT resulted in a significantly increased secretion of the immune activating cytokines IL-12p70, IL-8, IL-6, and TNFα, compared to iDC co-incubated with SN of tumor cells that received a high single irradiation dose or were not irradiated. In addition, DC-maturation markers CD80, CD83, and CD25 were also exclusively elevated after co-incubation with the SN of fractionated irradiated tumor cells. Furthermore, the SN of tumor cells that were irradiated with norm- or hypo-fractionated RT triggered iDC to stimulate CD4(+) T-cells not only in an allogenic, but also in an antigen-specific manner like mature DC. Collectively, these results demonstrate that norm- and hypo-fractionated RT induces a fast human colorectal tumor-cell death with immunogenic potential that can trigger DC maturation and activation in vitro. Such findings may contribute to the improvement of irradiation protocols for the most beneficial induction of anti-tumor immunity.