Dosimetric comparison of five different techniques for craniospinal irradiation across 15 European centers: analysis on behalf of the SIOP-E-BTG (radiotherapy working group). Acta Oncol 2018;57:1240-1249. [PMID: 29698060 DOI: 10.1080/0284186x.2018.1465588]

Helical tomotherapy craniospinal irradiation in primary brain tumours: Toxicities and outcomes in a peadiatric and adult population

Objective

As craniospinal irradiation (CSI) is delivered more frequently by helical tomotherapy (HT) with few reports about late effects, we analysed all patients treated in our centre over an 11-year period.

Methods and materials

Our study included all patients that underwent CSI by HT, between September 2009 and January 2020, in the Department of Radiation Oncology of the Toulouse Cancer Institute. Acute radiotherapy toxicities were reported and medium- to long-term outcomes analysed.

Results

Among the 79 patients included, 70.9 % were younger than 18 years at diagnosis, the median age was 13 (range: 1-52) at the time of radiation therapy, 67.1 % of patients had medulloblastoma. Half of them (49.4 %) had a metastatic disease at diagnosis. The median dose of CSI was 36 Gy (range, 18-36). Seventy-seven patients received a radiation boost to the original location of the primary tumour (97.5 %), 32 patients also received a boost to their metastatic sites (40.5 %). Median follow-up was 55.5 months (95 %CI = [41.2; 71.8]). The 3-year event-free survival rate was 66.3 % (95 %CI = [54.2; 75.9]). Most patients presented with acute haematological toxicities during CSI (85.9 %), predominantly severe thrombocytopenia (39.7 %). Among the 64 patients assessed for medium- and long-term outcomes, 52 survived and 47 were alive and disease-free at the latest follow-up visit on record. There were 3.8 % secondary tumours: two meningiomas and one diffuse intrinsic pontine glioma. Adult and paediatric patients respectively presented with secondary cataract (4.3 % vs 22.0 %), persistent hearing disorders (26.1 % vs 29.3 %), pulmonary or cardiac late effects (4.3 % vs 2.4 %), hormonal pituitary gland deficiencies (30.0 % vs 56.8 %) and psycho-cognitive disorders (56.5 % vs 53.7 %).

Conclusion

CSI dispensed by HT, did not result in any additional acute or late toxicities when compared to 3D-CSI. There was no increase in the secondary tumour rate compared to that reported in the literature.

Current practices of craniospinal irradiation techniques in Turkey: a comprehensive dosimetric analysis

OBJECTIVE

This study evaluates various craniospinal irradiation (CSI) techniques used in Turkish centers to understand their advantages, disadvantages and overall effectiveness, with a focus on enhancing dose distribution.

METHODS

Anonymized CT scans of adult and pediatric patients, alongside target volumes and organ-at-risk (OAR) structures, were shared with 25 local radiotherapy centers. They were tasked to develop optimal treatment plans delivering 36 Gy in 20 fractions with 95% PTV coverage, while minimizing OAR exposure. The same CT data was sent to a US proton therapy center for comparison. Various planning systems and treatment techniques (3D conformal RT, IMRT, VMAT, tomotherapy) were utilized. Elekta Proknow software was used to analyze parameters, assess dose distributions, mean doses, conformity index (CI), and homogeneity index (HI) for both target volumes and OARs. Comparisons were made against proton therapy.

RESULTS

All techniques consistently achieved excellent PTV coverage (V95 > 98%) for both adult and pediatric patients. Tomotherapy closely approached ideal Dmean doses for all PTVs, while 3D-CRT had higher Dmean for PTV_brain. Tomotherapy excelled in CI and HI for PTVs. IMRT resulted in lower pediatric heart, kidney, parotid, and eye doses, while 3D-CRT achieved the lowest adult lung doses. Tomotherapy approached proton therapy doses for adult kidneys and thyroid, while IMRT excelled for adult heart, kidney, parotid, esophagus, and eyes.

CONCLUSION

Modern radiotherapy techniques offer improved target coverage and OAR protection. However, 3D techniques are continued to be used for CSI. Notably, proton therapy stands out as the most efficient approach, closely followed by Tomotherapy in terms of achieving superior target coverage and OAR protection.

ESTRO-SIOPE guideline: Clinical management of radiotherapy in atypical teratoid/rhabdoid tumors (AT/RTs)

BACKGROUND AND PURPOSE

Treatment of patients with atypical teratoid/rhabdoid (AT/RT) is challenging, especially when very young (below the age of three years). Radiotherapy (RT) is part of a complex trimodality therapy. The purpose of this guideline is to provide appropriate recommendations for RT in the clinical management of patients not enrolled in clinical trials.

MATERIALS AND METHODS

Nine European experts were nominated to form a European Society for Radiotherapy and Oncology (ESTRO) guideline committee. A systematic literature search was conducted in PubMed/MEDLINE and Web of Science. They discussed and analyzed the evidence concerning the role of RT in the clinical management of AT/RT.

RESULTS

Recommendations on diagnostic imaging, therapeutic principles, RT considerations regarding timing, dose, techniques, target volume definitions, dose constraints of radiation-sensitive organs at risk, concomitant chemotherapy, and follow-up were considered. Treating children with AT/RT within the framework of prospective trials or prospective registries is of utmost importance.

CONCLUSION

The present guideline summarizes the evidence and clinical-based recommendations for RT in patients with AT/RT. Prospective clinical trials and international, large registries evaluating modern treatment approaches will contribute to a better understanding of the best treatment for these children in future.

Dosimetry and efficiency comparison of knowledge-based and manual planning using volumetric modulated arc therapy for craniospinal irradiation

BACKGROUND

Craniospinal irradiation (CSI) poses a challenge to treatment planning due to the large target, field junction, and multiple organs at risk (OARs) involved. The aim of this study was to evaluate the performance of knowledge-based planning (KBP) in CSI by comparing original manual plans (MP), KBP RapidPlan initial plans (RPI), and KBP RapidPlan final plans (RPF), which received further re-optimization to meet the dose constraints.

PATIENTS AND METHODS

Dose distributions in the target were evaluated in terms of coverage, mean dose, conformity index (CI), and homogeneity index (HI). The dosimetric results of OARs, planning time, and monitor unit (MU) were evaluated.

RESULTS

All MP and RPF plans met the plan goals, and 89.36% of RPI plans met the plan goals. The Wilcoxon tests showed comparable target coverage, CI, and HI for the MP and RPF groups; however, worst plan quality was demonstrated in the RPI plans than in MP and RPF. For the OARs, RPF and RPI groups had better dosimetric results than the MP group (P < 0.05 for optic nerves, eyes, parotid glands, and heart). The planning time was significantly reduced by the KBP from an average of 677.80 min in MP to 227.66 min (P < 0.05) and 307.76 min (P < 0.05) in RPI, and RPF, respectively. MU was not significantly different between these three groups.

CONCLUSIONS

The KBP can significantly reduce planning time in CSI. Manual re-optimization after the initial KBP is recommended to enhance the plan quality.

Automating the Treatment Planning Process for Volumetric Modulated Arc Therapy Craniospinal Irradiation

PURPOSE

The purpose of this work is to develop a method to automate the treatment planning process of craniospinal irradiation (CSI) using volumetric modulated arc therapy.

METHODS AND MATERIALS

Two scripts were developed using the Eclipse Scripting Application Programming Interface to perform auto-plan preparation and optimization. Ten patients (age, 5-44 years) previously treated at our institution with low dose volumetric modulated arc therapy CSI (prescription of 12 Gy) before total body irradiation were selected to evaluate the efficacy of the proposed auto-planning process. Paired t tests compared the dosimetric indices of the auto-plans to the manually generated clinical plans. All plans were normalized to 95% of planning target volume (PTV) coverage with the prescription dose. Two physicians and one physicist were asked to evaluate the manual plans and auto-plans of each patient in a blinded retrospective review and to indicate clinical acceptability and which plans were preferred for treatment.

RESULTS

Compared with the manual CSI plans, the auto plans obtained significant reductions in Dmean to the parotids, submandibular glands, larynx, thyroid, and significant reduction in the plan PTV Dmax and D0.03 cc. The standard deviation range of the dosimetric parameters was greatly reduced for auto plans (range, 0.1-1.3 Gy) relative to manual plans (range, 0.4-5.9 Gy) indicating better plan consistency. Among the 10 patients, the auto-plans were preferred over the manual plans 90% of the time by the reviewing experts. The required time for auto-planning was approximately 1 hour compared with estimated 4 or more hours for manual planning.

CONCLUSIONS

Reductions in planning time without sacrifices in plan quality were obtained using the auto-planning process compared with manual planning. Variation in plan quality was also reduced. The auto-planning scripts will be made freely available to other institutions and clinics.

Proton PBS Planning Techniques, Robustness Evaluation, and OAR Sparing for the Whole-Brain Part of Craniospinal Axis Irradiation

Proton therapy is a promising modality for craniospinal irradiation (CSI), offering dosimetric advantages over conventional treatments. While significant attention has been paid to spine fields, for the brain fields, only dose reduction to the lens of the eye has been reported. Hence, the objective of this study is to assess the potential gains and feasibility of adopting different treatment planning techniques for the entire brain within the CSI target. To this end, eight previously treated CSI patients underwent retrospective replanning using various techniques: (1) intensity modulated proton therapy (IMPT) optimization, (2) the modification/addition of field directions, and (3) the pre-optimization removal of superficially placed spots. The target coverage robustness was evaluated and dose comparisons for lenses, cochleae, and scalp were conducted, considering potential biological dose increases. The target coverage robustness was maintained across all plans, with minor reductions when superficial spot removal was utilized. Single- and multifield optimization showed comparable target coverage robustness and organ-at-risk sparing. A significant scalp sparing was achieved in adults but only limited in pediatric cases. Superficial spot removal contributed to scalp V30 Gy reduction at the expense of lower coverage robustness in specific cases. Lens sparing benefits from multiple field directions, while cochlear sparing remains impractical. Based on the results, all investigated plan types are deemed clinically adoptable.

Evolution of dosimetric treatment planning for pediatric total lymphoid irradiation (TLI): a single-institution experience

Background

Total lymphoid irradiation (TLI) is a conditioning regimen in allogeneic hematopoietic stem cell transplantation (allo-HSCT) which may reduce long-term toxicities attributed to other techniques, such as total body irradiation (TBI). At our institution, TLI treatments were first planned with the three-dimensional conformal radiation therapy (3D-CRT) technique and later with volumetric modulated arc therapy (VMAT). With the recent availability of a basic helical tomotherapy (HT), the possible dosimetric gain of the latter for TLI is studied.

Materials and methods

22 pediatric patients were planned for VMAT and HT, prescribed to 8 Gy in 4 fractions. VMAT was planned with template based on a single cost function, using the Monaco treatment planning system (TPS). HT plans were planned using Accuray Precision TPS for a basic HT without the dynamic jaws feature or VOLO-Ultra algorithm. Plan quality was analyzed based on four quality indices, mean and maximum doses to planning target volume (PTV) and organs at risk (OARs), dose gradient and integral doses. Differences were analyzed with Wilcoxon signed-rank test.

Results

HT plans resulted in improved conformity (CI) and homogeneity indices (HI) (p < 0.05) but less steep dose gradient (p = 0.181). VMAT plans created larger areas with high doses within the PTV, while comparable doses to OARs, except mainly for the spinal marrow, for which a reduction of 37.7% in D2% was obtained (p < 0.05). Integral dose for non-tumor tissue was 11.3% lower with the VMAT template (p < 0.05).

Conclusion

HT achieves better conformity and homogeneity even without its more advanced features. Nevertheless, the VMAT template achieves dosimetric results close to those of HT, both with similar clinical outcome.

Radiation Therapy in the Management of Leptomeningeal Disease From Solid Tumors

Purpose

Leptomeningeal disease (LMD) is clinically detected in 5% to 10% of patients with solid tumors and is a source of substantial morbidity and mortality. Prognosis for this entity remains poor and treatments are palliative. Radiation therapy (RT) is an essential tool in the management of LMD, and a recent randomized trial demonstrated a survival benefit for proton craniospinal irradiation (CSI) in select patients. In the setting of this recent advance, we conducted a review of the role of RT in LMD from solid tumors to evaluate the evidence basis for RT recommendations.

Methods and Materials

In November 2022, we conducted a comprehensive literature search in PubMed, as well as a review of ongoing clinical trials listed on ClinicalTrials.gov, to inform a discussion on the role of RT in solid tumor LMD. Because of the paucity of high-quality published evidence, discussion was informed more by expert consensus and opinion, including a review of societal guidelines, than evidence from clinical trials.

Results

Only 1 prospective randomized trial has evaluated RT for LMD, demonstrating improved central nervous system progression-free survival for patients with breast and lung cancer treated with proton CSI compared with involved-field RT. Modern photon CSI techniques have improved upon historical rates of acute hematologic toxicity, but the overall benefit of this modality has not been prospectively evaluated. Multiple retrospective studies have explored the use of involved-field RT or the combination of RT with chemotherapy, but clear evidence of survival benefit is lacking.

Conclusions

Optimal management of LMD with RT remains reliant upon expert opinion, with proton CSI indicated in patients with good performance status and extra-central nervous system disease that is either well-controlled or for which effective treatment options are available. Photon-based CSI traditionally has been associated with increased marrow and gastrointestinal toxicities, though intensity modulated RT/volumetric-modulated arc therapy based photon CSI may have reduced the toxicity profile. Further work is needed to understand the role of radioisotopes as well as combined modality treatment with intrathecal or central nervous system penetrating systemic therapies.

Comparison of passive-scattered and intensity-modulated proton beam therapy of craniospinal irradiation with proton beams for pediatric and young adult patients with brain tumors

PURPOSE

To investigate the dose stability of craniospinal irradiation based on irradiation method of proton beam therapy (PBT).

METHODS AND MATERIALS

Twenty-four pediatric and young adult brain tumor patients (age: 1-24 years) were examined. Treatment method was passive-scattered PBT (PSPT) in 8 patients and intensity-modulated PBT (IMPT) in 16 patients. The whole vertebral body (WVB) technique was used in 13 patients whose ages were younger than 10, and vertebral body sparing (VBS) technique was used for the remaining 11 patients aged 10 and above. Dose stability of planning target volume (PTV) against set-up error was investigated.

RESULTS

The minimum dose (Dmin) of IMPT was higher than that of PSPT (p = 0.01). Inhomogeneity index (INH) of IMPT was lower than that of PSPT (p = 0.004). When the irradiation field of the cervical spinal cord level (C level) was shifted, the maximum dose (Dmax) was lower in IMPT, and mean dose (Dmean) was higher than PSPT as movement became greater to the cranial-caudal direction (p = 0.000-0.043). Dmin was higher and INH was lower in IMPT in all directions (p = 0.000-0.034). When the irradiation field of the lumber spinal cord level (L level) was shifted, Dmax was lower in IMPT as movement became greater to the cranial direction (p = 0.000-0.028). Dmin was higher and INH was lower in IMPT in all directions (p = 0.000-0.022).

CONCLUSIONS

The PTV doses of IMPT and PSPT are robust and stable in both anterior-posterior and lateral directions at both C level and L level, but IMPT is more robust and stable than PSPT for cranial-caudal movements.

TRIAL REGISTRY

Clinical Trial Registration number: No. 04-03.

Prevalence, risk factors, and optimal way to determine overweight, obesity, and morbid obesity in the first Dutch cohort of 2338 long-term survivors of childhood cancer: a DCCSS-LATER study

BACKGROUND

Overweight and obesity are common challenges among childhood cancer survivors. Overweight may be disguised, as survivors can have normal weight but high fat percentage (fat%) on dual-energy X-ray absorptiometry (DXA). We aimed to assess prevalence, identify determinants and biomarkers, and assess which method captures overweight best, in a nationwide cohort.

METHODS

The prevalence of overweight and obesity, primarily defined by body mass index (BMI), was assessed in the DCCSS-LATER cohort of adult survivors treated from 1963-2002, with the LifeLines cohort as reference. The associations between risk factors and overweight metrics were investigated using logistic regression. Additional overweight metrics included DXA fat%, waist circumference (WC), waist/hip ratio (WHR), waist/height ratio (WHtR), and high-molecular-weight (HMW) adiponectin.

RESULTS

A total of 2338 (mean age 35.5 years, follow-up 28.3 years) survivors participated. The overweight prevalence was 46.3% in men and 44.3% in women (obesity 11.2% and 15.9%, morbid obesity 2.4% and 5.4%), with highest rates among brain tumor survivors. Compared to controls, there was no overall increased overweight rate, but this was higher in women > 50 years, morbid obesity in men > 50 years. Overweight at cancer diagnosis (adjusted odds ratio [aOR] = 3.83, 95% CI 2.19-6.69), cranial radiotherapy (aOR = 3.21, 95% CI 1.99-5.18), and growth hormone deficiency (separate model, aOR = 1.61, 95% CI 1.00-2.59) were associated with overweight. Using BMI, WC, WHR, and WHtR, overweight prevalence was similar. Low HMW adiponectin, present in only 4.5% of survivors, was an insensitive overweight marker. Dual-energy X-ray absorptiometry-based classification identified overweight in an additional 30%, particularly after abdominal radiotherapy, total body irradiation, anthracyclines, and platinum.

CONCLUSIONS

Overweight occurs in almost half of long-term survivors. There was no overall increased incidence of overweight compared to controls. We identified factors associated with overweight, as well as subgroups of survivors in whom DXA can more reliably assess overweight.

Successful Implementation of Image-Guided Pencil-Beam Scanning Proton Therapy in Medulloblastomas

Medulloblastoma is the most common malignant brain tumour in children, while much rarer in adults. Although the prognosis and outcomes have greatly improved in the era of modern multidisciplinary management, long-term treatment-induced toxicities are common. Craniospinal irradiation followed by a boost to the primary and metastatic tumour sites forms the backbone of treatment. Proton therapy has been endorsed over conventional photon-based radiotherapy due to its superior dosimetric advantages and subsequently lower incidence and severity of toxicities. We report here our experience from South-East Asia's first proton therapy centre of treating 40 patients with medulloblastoma (38 children and adolescents, 2 adults) who received image-guided, intensity-modulated proton therapy with pencil-beam scanning between 2019 and 2023, with a focus on dosimetry, acute toxicities, and early survival outcomes. All patients could complete the planned course of proton therapy, with mostly mild acute toxicities that were manageable on an outpatient basis. Haematological toxicity was not dose-limiting and did not prolong the overall treatment time. Preliminary data on early outcomes including overall survival and disease-free survival are encouraging, although a longer follow-up and data on long-term toxicities are needed.

Novel hybrid treatment planning approach for irradiation a pediatric craniospinal axis

This study presents a new treatment planning approach merging 3D-CRT and VMAT fields into a hybrid treatment plan (HybTP), in order to achieve an optimum dose coverage of the planning target volume (PTV) and protection of OAR. Craniospinal axis irradiation (CSI) treated with 3D conformal radiotherapy (3D-CRT) is associated with high doses to the heart and eye lenses but provides better sparing of lungs and kidneys compared to volumetric modulated arc therapy (VMAT). VMAT treatment spares eye lenses and the heart, but lungs and kidneys are not as effective as 3D-CRT. Thus, a combination of both techniques (HybTP) may be optimal in sparing all these organs at risk (OAR). The results of HybTP are compared with helical tomotherapy (HT), intensity modulated radio therapy (IMRT), VMAT, and 3D-CRT plans. Hybrid, HT, VMAT, IMRT, and 3D-CRT treatment plans for a male child (age 6 years) with medulloblastoma were created and compared. A total dose of 35.2 Gy (PTV) with a dose per fraction of 1.6 Gy was prescribed. The following dose acceptance criteria were defined: The plans were compared regarding dose homogeneity index (HI) and conformity index (CI), PTV coverage, (particularly at cribriform plate) and doses at OARs. Best conformity was achieved with HT (CI = 0.98) followed by VMAT (CI = 0.96), IMRT (CI = 0.91), HybTP (CI = 0.86), and 3D-CRT (CI = 0.83). The homogeneity index varied marginally. For both HT and IMRT the HI was 0.07, and for 3D-CRT, VMAT and HybTP the HI was between 0.13 and 0.15. The cribriform plate was sufficiently covered by HybTP, VMAT, and 3D-CRT. The dose acceptance criteria for OARs were met by HT and HybTP. VMAT did not meet the criteria for lung (Dmean = right 10.4 Gy/left 10.2 Gy), 3D-CRT did not meet the criteria for eye lenses (Dmax = right 32.3 Gy/left 33.1), and heart (V25≈44%) and IMRT did not meet the criteria for lung (Dmean = right 11.1 Gy/left 11.2 Gy) and eye lenses (Dmax = right 12.2 Gy/left 13.1). HybTP meets all defined acceptance criteria and has proved to be a reasonable alternative for CSI. With HybTP that combines VMAT at the brain and heart with 3D-CRT posterior spinal fields (to spare lungs and kidneys), both appropriate coverage of the PTV and sparing of OAR can be achieved.

Validation of an automated contouring and treatment planning tool for pediatric craniospinal radiation therapy

Purpose

Treatment planning for craniospinal irradiation (CSI) is complex and time-consuming, especially for resource-constrained centers. To alleviate demanding workflows, we successfully automated the pediatric CSI planning pipeline in previous work. In this work, we validated our CSI autosegmentation and autoplanning tool on a large dataset from St. Jude Children's Research Hospital.

Methods

Sixty-three CSI patient CT scans were involved in the study. Pre-planning scripts were used to automatically verify anatomical compatibility with the autoplanning tool. The autoplanning pipeline generated 15 contours and a composite CSI treatment plan for each of the compatible test patients (n=51). Plan quality was evaluated quantitatively with target coverage and dose to normal tissue metrics and qualitatively with physician review, using a 5-point Likert scale. Three pediatric radiation oncologists from 3 institutions reviewed and scored 15 contours and a corresponding composite CSI plan for the final 51 test patients. One patient was scored by 3 physicians, resulting in 53 plans scored total.

Results

The algorithm automatically detected 12 incompatible patients due to insufficient junction spacing or head tilt and removed them from the study. Of the 795 autosegmented contours reviewed, 97% were scored as clinically acceptable, with 92% requiring no edits. Of the 53 plans scored, all 51 brain dose distributions were scored as clinically acceptable. For the spine dose distributions, 92%, 100%, and 68% of single, extended, and multiple-field cases, respectively, were scored as clinically acceptable. In all cases (major or minor edits), the physicians noted that they would rather edit the autoplan than create a new plan.

Conclusions

We successfully validated an autoplanning pipeline on 51 patients from another institution, indicating that our algorithm is robust in its adjustment to differing patient populations. We automatically generated 15 contours and a comprehensive CSI treatment plan for each patient without physician intervention, indicating the potential for increased treatment planning efficiency and global access to high-quality radiation therapy.

Comparison of Craniospinal Irradiation Using Proton Beams According to Irradiation Method and Initial Experience Treating Pediatric Patients

Purpose

This study compared craniospinal irradiation using proton beam therapy (PBT) according to irradiation method and investigated the initial effects.

Methods and Materials

Twenty-four pediatric patients (1-24 years old) who received proton craniospinal irradiation were examined. Passive scattered PBT (PSPT) and intensity modulated PBT (IMPT) were used in 8 and 16 patients, respectively. The whole vertebral body technique was used for 13 patients <10 years old, and the vertebral body sparing (VBS) technique was used for the remaining 11 patients aged ≥10 years. The follow-up period was 17 to 44 (median, 27) months. Organ-at-risk and planning target volume (PTV) doses and other clinical data were examined.

Results

The maximum lens dose using IMPT was lower than that using PSPT (P = .008). The mean thyroid, lung, esophagus, and kidney doses were lower in patients treated using the VBS technique compared with the whole vertebral body technique (all P < .001). The minimum PTV dose of IMPT was higher than that of PSPT (P = .01). The inhomogeneity index of IMPT was lower than that of PSPT (P = .004).

Conclusions

IMPT is better than PSPT at reducing the dose to the lens. The VBS technique can decrease the doses to neck-chest-abdomen organs. The PTV coverage of IMPT is superior to that of PSPT.

Development and Quality Assurance of Multileaf Collimator (MLC) Auto-Feathering Junctions for Multi-Isocenter Supine Volumetric Modulated Arc Therapy (VMAT) Craniospinal Axis Irradiation on Halcyon

Currently, there is a lack of methods and tools that efficiently evaluate the auto-feathering junctions created by multileaf collimator (MLCs) for supine volumetric modulated arc therapy (VMAT) craniospinal irradiation (CSI) plans. We have investigated the feasibility of stitching together multi-isocenter fluence maps to then analyze the feathered junctions for patient-specific quality assurance (QA). Furthermore, we investigated the capability of Halcyon for the treatment of CSI patients. Three patients, who previously underwent VMAT CSI treatment on TrueBeam (6-MV flattening filter-free (FFF)) for 36 Gy in 20 fractions were replanned for Halcyon. A multi-isocenter approach with only translational superior-inferior shifts was used for both platforms. Each isocenter consists of two full arcs with anterior avoidance sectors, ±5° collimator rotations between arcs, and 5-8 cm of overlapping MLC auto-feathering junctions. All plans were QA'd via electronic portal imaging device (EPID) portal dosimetry and analyzed with a gamma criteria of 3%/3 mm. A variety of plan quality metrics were analyzed to evaluate dose distributions to the target, doses to organs at risk (OARs), and integral dose to the patient. A MATLAB script was developed to stitch the calculated and measured fluence maps in order to perform patient-specific QA for the composite fluence. The Halcyon plans provided highly conformal and homogenous dose distributions to the entire CSI target, superior to the clinical TrueBeam plans, while sparing critical organs with significantly lower values of V10Gy and V18Gy by up to 2% and 2.5%, respectively. Qualitative depictions of vertical dose profiles from the stitched DICOM of the entire CSI target for both planned and delivered fluence maps demonstrated equivalency, with slightly lower average pass rates with Halcyon (97%) compared to TrueBeam (99.9%). This approach to stitch multiple measured versus calculated EPID fluence maps has shown to be a feasible and accurate method and will be helpful for comprehensive VMAT CSI QA on both platforms. Further implementation of this script will be used in examining dosimetric impacts of daily patient positioning errors at MLC auto-feathering junctions.

Clinical Characterization of a Table Mounted Range Shifter Board for Synchrotron-Based Intensity Modulated Proton Therapy for Pediatric Craniospinal Irradiation

Purpose: To report our design, manufacturing, commissioning and initial clinical experience with a table-mounted range shifter board (RSB) intended to replace the machine-mounted range shifter (MRS) in a synchrotron-based pencil beam scanning (PBS) system to reduce penumbra and normal tissue dose for image-guided pediatric craniospinal irradiation (CSI). Methods: A custom RSB was designed and manufactured from a 3.5 cm thick slab of polymethyl methacrylate (PMMA) to be placed directly under patients, on top of our existing couch top. The relative linear stopping power (RLSP) of the RSB was measured using a multi-layer ionization chamber, and output constancy was measured using an ion chamber. End-to-end tests were performed using the MRS and RSB approaches using an anthropomorphic phantom and radiochromic film measurements. Cone beam CT (CBCT) and 2D planar kV X-ray image quality were compared with and without the RSB present using image quality phantoms. CSI plans were produced using MRS and RSB approaches for two retrospective pediatric patients, and the resultant normal tissue doses were compared. Results: The RLSP of the RSB was found to be 1.163 and provided computed penumbra of 6.9 mm in the phantom compared to 11.8 mm using the MRS. Phantom measurements using the RSB demonstrated errors in output constancy, range, and penumbra of 0.3%, -0.8%, and 0.6 mm, respectively. The RSB reduced mean kidney and lung dose compared to the MRS by 57.7% and 46.3%, respectively. The RSB decreased mean CBCT image intensities by 86.8 HU but did not significantly impact CBCT or kV spatial resolution providing acceptable image quality for patient setup. Conclusions: A custom RSB for pediatric proton CSI was designed, manufactured, modeled in our TPS, and found to significantly reduce lateral proton beam penumbra compared to a standard MRS while maintaining CBCT and kV image-quality and is in routine use at our center.

Multi-isocenter VMAT craniospinal irradiation using feasibility dose-volume histogram-guided auto-planning technique

This study aims to propose a novel treatment planning methodology for multi-isocenter volumetric modulated arc therapy (VMAT) craniospinal irradiation (CSI) using the special feasibility dose-volume histogram (FDVH)-guided auto-planning (AP) technique. Three different multi-isocenter VMAT -CSI plans were created, including manually based plans (MUPs), conventional AP plans (CAPs) and FDVH-guided AP plans (FAPs). The CAPs and FAPs were specially designed by combining multi-isocenter VMAT and AP techniques in the Pinnacle treatment planning system. Specially, the personalized optimization parameters for FAPs were generated using the FDVH function implemented in PlanIQ software, which provides the ideal organs at risk (OARs) sparing for the specific anatomical geometry based on the valuable assumption of the dose fall-off. Compared to MUPs, CAPs and FAPs significantly reduced the dose for most of the OARs. FAPs achieved the best homogeneity index (0.092 ± 0.013) and conformity index (0.980 ± 0.011), while CAPs were slightly inferior to the FAPs but superior to the MUPs. As opposed to MUPs, FAPs delivered a lower dose to OARs, whereas the difference between FAPs and CAPs was not statistically significant except for the optic chiasm and inner ear_L. The two AP approaches had similar MUs, which were significantly lower than the MUPs. The planning time of FAPs (145.00 ± 10.25 min) was slightly lower than that of CAPs (149.83 ± 14.37 min) and was substantially lower than that of MUPs (157.92 ± 16.11 min) with P < 0.0167. Overall, introducing the multi-isocenter AP technique into VMAT-CSI yielded positive outcomes and may play an important role in clinical CSI planning in the future.

Critical Appraisal of Paediatric Embryonal Cancers Treated with Image-guided Intensity-modulated Proton Therapy

AIM

To carry out a comprehensive critical appraisal of image-guided intensity-modulated proton therapy practice for craniospinal irradiation (CSI).

MATERIALS AND METHODS

An image-guided intensity-modulated proton therapy database of 45 consecutive paediatric patients with central nervous system embryonal malignancies treated between January 2019 and April 2022 were critically appraised for demography, diagnosis, treatment planning strategy and treatment delivery accuracy.

RESULTS

Most patients (median age: 7.5 years; male:female ratio: 34:11) had medulloblastoma (56%), followed by recurrent ependymoma (19%), pinealoblastoma (5%), germ cell (5%) and others (15%). The dose to the planning target volume-craniospinal (PTV-CS; length 39.06-79.59 cm) varied from 21 to 35 GyRBE, whereas the combined median dose to craniospinal and boost was 54 GyRBE. In all patients, the 95% isodose line covered the cribriform plate completely and optic nerves mostly, with a median V95% of 100% and 82.96%, keeping Dmax to the lens <3.9 GyRBE. In skeletally immature patients (88.38%), the anterior vertebral body was completely covered in 18.18% and underdosed in 70.15% of the cases, resulting in a median Dmean of 10.11 GyRBE to the oesophagus. Lateral spine coverage was maintained on the edges of the vertebral body in 52.2%, whereas it extended beyond in 48.8%. The median V98% for clinical target volumes and V95% for PTVs of the brain, spine and craniospinal were >97%, with excellent conformity (0.89) and homogeneity (0.07) indices for PTV-CS. All neurological organs at risk received a median Dmax ranging from 36 to 44 GyRBE from the combined CSI and boost regimens. Analysis of patient-specific quality assurance results revealed that 545 (97.67%) planar dosage verification had gamma (3% at 3 mm) values >95%. The online patient set-up verification showed translational and rotational deviation within 2 mm and 0.5° in 88-94% and 97% of the cases. Systematic and random error were within 0.90 mm and 1.71 mm in translation and 0.1° and 0.2° in rotation.

CONCLUSION

A change in practice pattern was observed. The findings from our comprehensive critical appraisal add to the growing library of CSI practice and may serve as a reference for inter-institutional comparison.

Craniospinal Irradiation: A Dosimetric Comparison Between O-Ring Linac and Conventional C-arm Linac

Purpose

The aim of this study was to perform a dosimetric evaluation between craniospinal irradiation volumetric modulated arc therapy plans designed for an O-Ring and a conventional C-arm Linac.

Methods and Materials

Two adult patients were selected for this study. Two plans were designed one for a TrueBeam Edge and one for Halcyon O-ring Linac for each patient. The evaluation of the plans was conducted in terms of dose volume histogram analysis of the target volume and organs at risk (OARs) along with total plan monitor units and beam-on time. Paired sample t test was performed to compare D_max and D_mean of OARs for each plan's comparison. The delivery of volumetric modulated arc therapy plans was evaluated using Octavius 4D phantom.

Results

All plans demonstrated dose distributions with sufficient planned target volume conformity and homogeneity. The Homogeneity Index and Conformity Index for all plans were found comparable. The paired sample t test did not demonstrate significant difference in terms of D_max and D_mean of OARs between plans for both patients. All plans met the threshold of 90%, with Halcyon plans having higher gamma passing rates.

Conclusions

Craniospinal irradiation plans generated for Halcyon and Edge are equivalent in terms of plan quality and dose sparing at OARs. The small variations may have originated from the differences in beam profile or mean energy, the degree of the modulation for each plan and characteristics of multi leaf collimators for each treatment unit. Halcyon is able to deliver a distinctly faster treatment, but Edge provides an automatic rotational correction for patient positioning.

Tomotherapy for Cranio-Spinal Irradiation

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Tomotherapy is safe and effective for cranio-spinal irradiation, both in paediatric patients and in adults, with similar disease-specific outcomes and toxicities as other techniques such as 3DCRT or IMRT/VMAT.

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Tomotherapy offers several technical advantages when compared to other radiotherapy techniques such as higher target conformity and better dose homogeneity.

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Helical Tomotherapy provides good organ-at-risk sparing for several structures, especially the vertebrae, parotids, and optic system.

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Reported treatment time/ beam-on-time is longer with helical Tomotherapy compared to other techniques.

Tomotherapy is a method of delivering rotational IMRT offering various advantages, notably for complex and large targets such as the cranio-spinal axis. This systematic literature review reports on main clinical outcomes and toxicities in patients with various cancer types that received whole craniospinal axis irradiation (CSI) using Tomotherapy and offers a comprehensive comparison between Tomotherapy and other radiotherapy delivery techniques. Databases including PubMed, PubMed Central, Embase, and Cochrane were searched using the keywords “tomotherapy” AND “craniospinal”. Fifty-six papers were included in the review. Patient population was adult in 9 papers, paediatric in 26 papers and mixed in 14 papers. Patients treated with helical Tomotherapy had similar disease-specific clinical outcomes and toxicities as patients treated using other techniques. Compared to any other technique, Tomotherapy provides better target coverage, homogeneity, and conformity in 23, 34 and 22 reports. Tomotherapy showed better organ-at-risk sparing for the thyroid, parotids, cochlea, eyes, heart and esophagus. Beam-On-Time (BOT) was reported to be longer for Tomotherapy in most studies (Median BOT: HT = 11 min, VMAT = 5.49 min, 3DCRT = 1.46 min). In conclusion, Tomotherapy offers good cranio-spinal axis coverage with improved homogeneity and conformity compared to other techniques, but with a considerably longer treatment time. Clinical outcome and toxicities suggest using Tomotherapy for CSI is efficient and safe.

Enabling non-isocentric dynamic trajectory radiotherapy by integration of dynamic table translations

Objective. The purpose of this study is to develop a treatment planning process (TPP) for non-isocentric dynamic trajectory radiotherapy (DTRT) using dynamic gantry rotation, collimator rotation, table rotation, longitudinal, vertical and lateral table translations and intensity modulation and to validate the dosimetric accuracy. Approach. The TPP consists of two steps. First, a path describing the dynamic gantry rotation, collimator rotation and dynamic table rotation and translations is determined. Second, an optimization of the intensity modulation along the path is performed. We demonstrate the TPP for three use cases. First, a non-isocentric DTRT plan for a brain case is compared to an isocentric DTRT plan in terms of dosimetric plan quality and delivery time. Second, a non-isocentric DTRT plan for a craniospinal irradiation (CSI) case is compared to a multi-isocentric intensity modulated radiotherapy (IMRT) plan. Third, a non-isocentric DTRT plan for a bilateral breast case is compared to a multi-isocentric volumetric modulated arc therapy (VMAT) plan. The non-isocentric DTRT plans are delivered on a TrueBeam in developer mode and their dosimetric accuracy is validated using radiochromic films. Main results. The non-isocentric DTRT plan for the brain case is similar in dosimetric plan quality and delivery time to the isocentric DTRT plan but is expected to reduce the risk of collisions. The DTRT plan for the CSI case shows similar dosimetric plan quality while reducing the delivery time by 45% in comparison with the IMRT plan. The DTRT plan for the breast case showed better treatment plan quality in comparison with the VMAT plan. The gamma passing rates between the measured and calculated dose distributions are higher than 95% for all three plans. Significance. The versatile benefits of non-isocentric DTRT are demonstrated with three use cases, namely reduction of collision risk, reduced setup and delivery time and improved dosimetric plan quality.

Adult Medulloblastoma: Updates on Current Management and Future Perspectives

Medulloblastoma (MB) is a malignant embryonal tumor of the posterior fossa belonging to the family of primitive neuro-ectodermic tumors (PNET). MB generally occurs in pediatric age, but in 14–30% of cases, it affects the adults, mostly below the age of 40, with an incidence of 0.6 per million per year, representing about 0.4–1% of tumors of the nervous system in adults. Unlike pediatric MB, robust prospective trials are scarce for the post-puberal population, due to the low incidence of MB in adolescent and young adults. Thus, current MB treatments for older patients are largely extrapolated from the pediatric experience, but the transferability and applicability of these paradigms to adults remain an open question. Adult MB is distinct from MB in children from a molecular and clinical perspective. Here, we review the management of adult MB, reporting the recent published literature focusing on the effectiveness of upfront chemotherapy, the development of targeted therapies, and the potential role of a reduced dose of radiotherapy in treating this disease.

Encouraging early outcomes with image guided pencil beam proton therapy for cranio-spinal irradiation: first report from India

Background

To report our experience with image guided pencil beam proton beam therapy (PBT) for craniospinal irradiation (CSI).

Materials and Methods

Between January 2019 and December 2021, we carried out a detailed audit of the first forty patients treated with PBT. We had recorded acute toxicities, reporting early outcomes and discuss limitations of current contouring guidelines during CSI PBT planning.

Results

Median age of the patient cohort was 8 years, and histologies include 20 medulloblastoma, 7 recurrent ependymoma, 3 pineoblastoma, 3 were germ cell tumors and remaining 7 constituted other diagnoses. Forty percent patients received concurrent chemotherapy. Median CSI dose was 23.4 Gy (Gray; range 21.6–35 Gy). Thirty-five patients (87.5%) completed their CSI without interruption, 5 required hospital admission. No patient had grade 2/ > weight loss during the treatment. Forty-five percent (18) developed grade 1 haematological toxicities and 20% (8) developed grade 2 or 3 toxicities; none had grade 4 toxicities. At median follow up of 12 months, 90% patients are alive of whom 88.9% are having local control. Special consideration with modification in standard contouring used at our institute helped in limiting acute toxicities in paediatric CSI patients.

Conclusion

Our preliminary experience with modern contemporary PBT using pencil beam technology and daily image guidance in a range of tumours suitable for CSI is encouraging. Patients tolerated the treatment well with acceptable acute toxicity and expected short-term survival outcome. In paediatric CSI patients, modification in standard contouring guidelines required to achieve better results with PBT.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13014-022-02085-4.

Long-term outcomes and late toxicity of adult medulloblastoma treated with combined modality therapy: A contemporary single-institution experience

BACKGROUND

Medulloblastoma (MB) is a rare central nervous system malignancy of adults, with limited contemporary studies to define treatment guidelines and expected late toxicity.

METHODS

A single-center, retrospective study was conducted of patients age ≥18 years from 1997-2019 with MB and who were treated with postoperative radiotherapy. Late toxicity was defined as a minimum of 18 months from diagnosis. Overall survival (OS) and progression-free survival (PFS) were characterized using Kaplan-Meier and Cox regression analyses.

RESULTS

Fifty-nine patients met criteria, with median age of 25 years (range 18-62 y) and median follow-up of 6.5 years (range 0.7-23.1 y). At diagnosis, 68% were standard-risk, 88% Chang M0, and 22% with anaplastic histology. Gross total resection was achieved in 75%; median craniospinal irradiation dose was 30.6 Gy (relative biological effectiveness [RBE]), median total dose was 54.0 Gy (RBE), 80% received proton radiotherapy; 81% received chemotherapy. 5 year PFS and OS were 86.5% and 95.8%, respectively; 10 year PFS and OS were 83.9% and 90.7%, respectively. Anaplastic histology was associated with worse PFS (P = .04). Among eight recurrences, 25% presented after 5 years. Most common grade ≥2 late toxicities were anxiety/depressive symptoms (30%), motor dysfunction (25%), and ototoxicity (22%). Higher posterior fossa radiation dose was associated with increased risk of late toxicity, including worse cognitive dysfunction (P = .05).

CONCLUSIONS

Adults with MB have favorable survival outcomes, but late failures and toxicity are not uncommon. Better understanding of prognostic factors, possibly from molecular subtyping, may help to define more personalized treatments for patients with high risk of recurrence and long-term treatment sequelae.

Pulmonary toxicity of craniospinal irradiation using helical tomotherapy

Craniospinal irradiation using helical tomotherapy (HT-CSI) has advantages in aspects of homogeneous dose distribution. Physicians, however, still have concerns of pulmonary toxicity due to HT-CSI’s relatively large, low-dose irradiated volume from continuous and 360° rotation delivery. In this study, we investigated the pulmonary toxicity of HT-CSI. We retrospectively reviewed 105 patients who received HT-CSI between January 2014 and December 2019. Grade 2 + pulmonary toxicities were evaluated. Intensive systemic treatment was defined as systemic treatment administration before, during, and after HT-CSI. V_{X Gy} was defined as % volume receiving ≥ X Gy. Thirteen patients (12.4%) presented with grade 2 + pulmonary toxicities after HT-CSI. Of these patients, only one experienced grade 2 radiation pneumonitis combined with pembrolizumab-induced pneumonitis. Conversely, pneumonia was observed in 12 patients. Intensive systemic treatment (p = 0.004), immunosuppressive drugs (p = 0.031), and bilateral lung V_{5 Gy} ≥ 65% (p = 0.031) were identified as independent risk factors for pneumonia. The risk factor for pneumonia in pediatric patients were immunosuppressive drugs (p = 0.035) and bilateral lung V_{5 Gy} ≥ 65% (p = 0.047). HT-CSI can be a safe treatment modality with tolerable pulmonary toxicities. Intensive systemic treatment, immunosuppressive drugs, and bilateral lung V_{5 Gy} ≥ 65% were significantly associated with pneumonia. In these patients, close follow-up should be considered for proper management of pneumonia.

Out-of-field doses in pediatric craniospinal irradiations with 3D-CRT, VMAT and scanning proton radiotherapy - a phantom study

PURPOSE

Craniospinal irradiation (CSI) has greatly increased survival rates for patients with a diagnosis of medulloblastoma and other primitive neuroectodermal tumors. However, as it includes exposure of a large volume of healthy tissue to unwanted doses, there is a strong concern about the complications of the treatment, especially for the children. To estimate the risk of second cancers and other unwanted effects, out-of-field dose assessment is necessary. The purpose of this study is to evaluate and compare out-of-field doses in pediatric CSI treatment using conventional and advanced photon radiotherapy (RT) and advanced proton therapy. To our knowledge, it is the first such comparison based on in-phantom measurements. Additionally, for out-of-field doses during photon RT in this and other studies, comparisons were made using analytical modeling.

METHODS

In order to describe the out-of-field doses absorbed in a pediatric patient during actual clinical treatment, an anthropomorphic phantom which mimics the 10-year-old child was used. Photon 3D-conformal radiotherapy (3D-CRT) and two advanced, highly conformal techniques: photon volumetric modulated arc therapy (VMAT) and active pencil beam scanning (PBS) proton radiotherapy were used for CSI treatment. Radiophotoluminescent (RPL) and poly-allyl-diglycol-carbonate (PADC) nuclear track detectors were used for photon and neutron dosimetry in the phantom, respectively. Out-of-field doses from neutrons were expressed in terms of dose equivalent. A two-Gaussian model was implemented for out-of-field doses during photon RT.

RESULTS

The mean VMAT photon doses per target dose to all organs in this study were under 50% of the target dose (i.e., <500 mGy/Gy), while the mean 3D-CRT photon dose to oesophagus, gall bladder and thyroid, exceeded that value. However, for 3D-CRT, better sparing was achieved for eyes and lungs. The mean PBS photon doses for all organs were up to 3 orders of magnitude lower compared to VMAT and 3D-CRT and exceeded 10 mGy/Gy only for the oesophagus, intestine and lungs. The mean neutron dose equivalent during PBS for 8 organs of interest (thyroid, breasts, lungs, liver, stomach, gall bladder, bladder, prostate) ranged from 1.2 mSv/Gy for bladder to 23.1 mSv/Gy for breasts. Comparison of out-of-field doses in this and other phantom studies found in the literature showed that a simple and fast two-Gaussian model for out-of-field doses as a function of distance from the field edge can be applied in a CSI using photon RT techniques.

CONCLUSIONS

PBS is the most promising technique for out-of-field dose reduction in comparison to photon techniques. Among photon techniques, VMAT is a preferred choice for most of out-of-field organs and especially for the thyroid, while doses for eyes, breasts and lungs, are lower for 3D-CRT. For organs outside the field edge, a simple analytical model can be helpful for clinicians involved in treatment planning using photon RT but also for retrospective data analysis for cancer risk estimates and epidemiology in general. This article is protected by copyright. All rights reserved.

Volumetric Modulated Arc Therapy (VMAT) Craniospinal Irradiation (CSI) for Children and Adults: A Practical Guide for Implementation

PURPOSE

Volumetric modulated arc therapy (VMAT) craniospinal irradiation (CSI) has been shown to have significant dosimetric advantages compared to 3D-conformal therapy, but is a technically complex process. We sought to develop a guide for all aspects of the VMAT CSI process and report patient dosimetry results.

METHODS AND MATERIALS

We initiated VMAT CSI in 2017 and have regularly revised our standard operating procedure (SOP) for this process since then. Herein, we report a detailed template for the entire VMAT CSI process from initial patient setup and immobilization at time of CT simulation to contouring and treatment planning, quality assurance, and therapy delivery. The records of 12 patients who were treated with VMAT CSI were also retrospectively reviewed.

RESULTS

Patient age ranged from 2 to 59 years with 5 pediatric patients (age<18 years), 5 young adults (age 18-35 years) and 2 older adults (age>35 years). The majority of patients (67%) had medulloblastoma. CSI dose ranged from 21.6 Gy to 36 Gy, with a median of 36 Gy. The median CSI planning target volume (PTV) was 2383cc with a median V95% of 99.8% and median 0.03 cc hotspot of 112.5%. The average V107% was 7.4% and the average conformality index was 1.01.

CONCLUSIONS

VMAT CSI has potentially significant dosimetric and acute toxicity advantages compared to 3D-conformal. However, proper procedures need to be in place throughout the process in order to be able to realize these potential advantages. We herein describe our detailed SOP for VMAT CSI. Recognizing the scarcity of proton beam centers in many areas, VMAT CSI represents a feasible treatment with more widespread availability.

Radiotherapy in Medulloblastoma-Evolution of Treatment, Current Concepts and Future Perspectives

Simple Summary

Craniospinal irradiation (CSI) is the backbone of medulloblastoma treatment and the first treatment to achieve a cure in many patients. Within the last decades, significant efforts have been made to enhance efficacy in combination with chemotherapy. With this approach, a majority of low- and standard-risk patients can be cured. In parallel, many clinical trials have dealt with CSI-dose reduction and reduction of boost volume in order to decrease long-term toxicity, particularly neurotoxicity. Within these trials, standardized quality assurance has helped to increase the accuracy of treatment and improve prognosis. More recently, advances of radiotherapy techniques such as proton treatment allowed for better sparing of healthy tissue in order to further diminish detrimental long-term effects. Major future challenges are the adaption of radiotherapy regimens to different molecularly defined disease groups alone or together with new targeted agents. Moreover, and even more importantly, innovative combinatorial treatments are needed in high- and very-high risk situations.

Abstract

Medulloblastoma is the most frequent malignant brain tumor in children. During the last decades, the therapeutic landscape has changed significantly with craniospinal irradiation as the backbone of treatment. Survival times have increased and treatments were stratified according to clinical and later molecular risk factors. In this review, current evidence regarding the efficacy and toxicity of radiotherapy in medulloblastoma is summarized and discussed mainly based on data of controlled trials. Current concepts and future perspectives based on current risk classification are outlined. With the introduction of CSI, medulloblastoma has become a curable disease. Due to combination with chemotherapy, survival rates have increased significantly, allowing for a reduction in radiation dose and a decrease of toxicity in low- and standard-risk patients. Furthermore, modern radiotherapy techniques are able to avoid side effects in a fragile patient population. However, high-risk patients remain with relevant mortality and many patients still suffer from treatment related toxicity. Treatment needs to be continually refined with regard to more efficacious combinatorial treatment in the future.

Simple template-based optimization for pediatric total lymphoid irradiation (TLI) radiotherapy treatments

Total lymphoid irradiation (TLI) is used in the management of pediatric allogeneic hematopoietic stem cell transplantation (HSCT. This work aims to simplify the treatment planning process for TLI via a proposed template using the volumetric modulated arc therapy (VMAT) technique. Fifteen pediatric patients were planned, prescribed to 8 Gy in 4 fractions. Cost functions included in the template were the ones for the planning target volume (PTV), and conformality cost function (CCF) for the rest of the patient's volume. Conformity index (CI), homogeneity index (HI), conformation number (CN), gradient index (GI), integral dose, and doses to the organs at risk achieved with the template were reported. Cost function influence over various indexes was studied by Wilcoxon signed ranks test. Same 15 patients were planned with 3-dimensional conventional radiotherapy (3D-CRT) technique for comparison. Mean CI and HI were 1.33 and 0.13, respectively, which indicates good dose conformation and homogeneity. Mean CN and GI values were 0.69 and 4.51, respectively. Mean PTV coverage was reached (V_100% > 95%). No correlation between the CCF and indexes values was found (p > 0.05). Doses to organs at risk (OARs) were as low as possible without losing PTV coverage. VMAT plan showed higher levels of conformation and similar homogeneity as 3D-CRT plans. Doses to OARs were inferior with VMAT except for the right kidney. The proposed template simplifies the planning of TLI treatments, and it is able to create acceptable plans with little modification in order to reduce doses to certain organs like the kidneys or the heart. VMAT technique showed higher conformation and lower doses to OAR compared to 3D-CRT.

Current treatments of medulloblastoma

PURPOSE OF REVIEW

The biological knowledge and the new biopathological classification of medulloblastoma subtypes have dramatically changed the therapeutic indications, taking into account not only age and staging but also biopathological risk criteria. This review covers the multidisciplinary approach including surgery, radiation oncology and medical treatments.

RECENT FINDINGS

The neurosurgical management of tumor-related hydrocephalus has been modified by the introduction of third ventriculostomy. The initial complete excision is no longer always the first choice, to preserve neurological function. The recent technical improvements of radiotherapy are also implemented to optimize outcome in terms of survival as well as quality of survival. The different medical treatments are adapted according to age and risk factors. The role of high-dose chemotherapy with autologous hematopoietic stem cell rescue has become larger in the high-risk situations.

SUMMARY

The rarity of the disease and the high-level of technicity of diagnosis, biopathological subtyping and treatments justifies the referral of these patients to highly specialized centers where all these techniques can be routinely applied, most often in the context of international prospective studies.

Chronological Analysis of Acute Hematological Outcomes after Proton and Photon Beam Craniospinal Irradiation in Pediatric Brain Tumors

Purpose

This study aimed to compare the early hematological dynamics and acute toxicities between proton beam craniospinal irradiation (PrCSI) and photon beam craniospinal irradiation (PhCSI) for pediatric brain tumors.

Materials and Methods

We retrospectively reviewed patients with pediatric brain tumors who received craniospinal irradiation (CSI). The average change in hemoglobin levels (ΔHb_avg), absolute lymphocyte counts (ΔALC_avg), and platelet counts (ΔPLT_avg) from baseline values was evaluated and compared between the PrCSI and PhCSI groups at 1 and 2 weeks after the initiation of CSI, 1 week before and at the end of radiotherapy, and 3–4 weeks after the completion of radiotherapy using t-test and mixed-model analysis.

Results

The PrCSI and PhCSI groups consisted of 36 and 30 patients, respectively. There were no significant differences in ΔHb_avg between the two groups at any timepoint. However, ΔALC_avg and ΔPLT_avg were significantly lower in the PhCSI group than in PrCSI group at every timepoint, demonstrating that PrCSI resulted in a significantly lower rate of decline and better recovery of absolute lymphocyte and platelet counts. The rate of grade 3 acute anemia was significantly lower in the PrCSI group than in in the PhCSI group.

Conclusion

PrCSI showed a lower rate of decline and better recovery of absolute lymphocyte and platelet counts than PhCSI in the CSI for pediatric brain tumors. Grade 3 acute anemia was significantly less frequent in the PrCSI group than in the PhCSI group. Further large-scale studies are warranted to confirm these results.

Impact of spot positional errors in robustly optimized intensity-modulated proton therapy plan of craniospinal irradiation

We investigated the influence of random spot positioning errors (SPEs) on dosimetric outcomes of robustly optimized intensity-modulated proton therapy (RB-IMPT) plans in craniospinal irradiation (CSI). Six patients with CSI treated using the RB-IMPT technique were selected. An in-house MATLAB code was used to simulate a random SPE of 1 mm in positive, negative, and both directions for 25%, 50%, and 75% of the total spot positions in the nominal plan. The percentage dose variation (ΔD_%) in the six nominal and 54 error-introduced plans was evaluated using standard dose-volume indices, line dose difference, and 3D gamma analysis method. The introduction of a random SPE of 1 mm resulted in a reduction in D_99%, D_98%, and D_95% of both CTVs and PTVs by < 2% compared with the corresponding nominal plans. However, this leads to an increase in D_1% of the lens by up to 16.9%. The line dose in the junction region showed ΔD_% < 2% for the brain and upper spine and < 4% for the upper and lower spine. The 3D gamma values for 3% at 3 mm and 2% at 2 mm were above 99% and 95%, respectively, in all 54 error-introduced plans. The worst decrease in gamma values was observed for 1% at 1 mm, with values ranging from 64 to 78% for all types of SPE. The RB-IMPT plan for CSI investigated in this study is robust enough for target coverage, even if there are random SPEs of 1 mm. However, this leads to an increase in the dose to the critical organ located close to the target.

Advances in radiotherapy technology for pediatric cancer patients and roles of medical physicists: COG and SIOP Europe perspectives

Over the last two decades, rapid technological advances have dramatically changed radiation delivery to children with cancer, enabling improved normal-tissue sparing. This article describes recent advances in photon and proton therapy technologies, image-guided patient positioning, motion management, and adaptive therapy that are relevant to pediatric cancer patients. For medical physicists who are at the forefront of realizing the promise of technology, challenges remain with respect to ensuring patient safety as new technologies are implemented with increasing treatment complexity. The contributions of medical physicists to meeting these challenges in daily practice, in the conduct of clinical trials, and in pediatric oncology cooperative groups are highlighted. Representing the perspective of the physics committees of the Children's Oncology Group (COG) and the European Society for Paediatric Oncology (SIOP Europe), this paper provides recommendations regarding the safe delivery of pediatric radiotherapy. Emerging innovations are highlighted to encourage pediatric applications with a view to maximizing the therapeutic ratio.

Practical aspects of the application of helical tomotherapy for craniospinal irradiation

We investigated the practical aspects of the application of craniospinal irradiation using helical tomotherapy (HT-CSI) by evaluating interfractional setup errors and intrafractional movement during each treatment in 83 patients undergoing HT-CSI between January 2014 and December 2018. Interfractional setup errors in each axis (mediolateral; ML, craniocaudal; CC, and anteroposterior; AP) were assessed as differences between pre-treatment megavoltage computed tomography (MVCT) images scanned (zygomatic arch to the C4 spine) and planning CT images. Intrafractional movements were evaluated as the difference between pre-treatment and post-treatment MVCT (T12–L4 spine) images at each fraction. Median interfractional setup error was acceptable in every axis (ML: 1.6 mm, CC: 1.9 mm, AP: 3.1 mm). Seven patients (8.4%) experienced significant intrafractional displacement from 1 to 10 fractions (0.34% for ML, 0.74% for CC, 1.21% for AP). Weight loss grade 1+ during treatment (p = 0.016) was an independent risk factor for significant intrafractional displacement. The risk factor for significant intrafractional movement in pediatric patients was weight loss grade 1+ (p = 0.020), while there was no factor in adults. HT-CSI could be a feasible treatment modality with acceptable setup verification. Inter- and intrafractional errors were acceptable; paying attention to weight loss during treatment is necessary, especially in pediatric patients.

A static beam delivery device for fast scanning proton arc-therapy

Arc-therapy is a dose delivery technique regularly applied in photon radiation therapy, and is currently subject of great interest for proton therapy as well. In this technique, proton beams are aimed at a tumor from different continuous ranges of incident directions (so called 'arcs'). This technique can potentially yield a better dose conformity around the tumor and a very low dose in the surrounding healthy tissue. Currently, proton-arc therapy is performed by rotating a proton gantry around the patient, adapting the normally used dose-delivery method to the arc-specific motion of the gantry. Here we present first results from a feasibility study of the conceptual design of a new static fast beam delivery device/system for proton-arc therapy, which could be used instead of a gantry. In this novel concept, the incident angle of proton beams can be set rapidly by only changing field strengths of small magnets. This device eliminates the motion of the heavy gantry and related hardware. Therefore, a reduction of the total treatment time is expected. In the feasibility study presented here, we concentrate on the concept of the beam transport. Based on several simple, but realistic assumptions and approximations, proton tracking calculations were performed in a 3D magnetic field map, to calculate the beam transport in this device and to investigate and address several beam-optics challenges. We propose and simulate corresponding solutions and discuss their outcomes. To enable the implementation of some usually applied techniques in proton therapy, such as pencil beam scanning, energy modulation and beam shaping, we present and discuss our proposals. Here we present the concept of a new idea to perform fast proton arc-scanning and we report on first results of a feasibility study. Based on these results, we propose several options and next steps in the design.

Pediatric craniospinal irradiation with a short partial-arc VMAT technique for medulloblastoma tumors in dosimetric comparison

Background

This study aimed to contrast four different irradiation methods for pediatric medulloblastoma tumors in a dosimetric comparison regarding planning target volume (PTV) coverage and sparing of organs at risk (OARs).

Methods

In sum 24 treatment plans for 6 pediatric patients were realized. Besides the clinical standard of a 3D-conformal radiotherapy (3D-CRT) treatment plan taken as a reference, volumetric modulated arc therapy (VMAT) treatment plans (“VMAT_AVD” vs. “noAVD” vs. “FullArc”) were optimized and calculated for each patient. For the thoracic and abdominal region, the short partial-arc VMAT_AVD technique uses an arc setup with reduced arc-length by 100°, using posterior and lateral beam entries. The noAVD uses a half 180° (posterior to lateral directions) and the FullArc uses a full 360° arc setup arrangement. The prescription dose was set to 35.2 Gy.

Results

We identified a more conformal dose coverage for PTVs and a better sparing of OARs with used VMAT methods. For VMAT_AVD mean dose reductions in organs at risk can be realized, from 16 to 6.6 Gy, from 27.1 to 8.7 Gy and from 8.0 to 1.9 Gy for the heart, the thyroid and the gonads respectively, compared to the 3D-CRT treatment method. In addition we have found out a superiority of VMAT_AVD compared to the noAVD and FullArc trials with lower exposure to low-dose radiation to the lungs and breasts.

Conclusions

With the short partial-arc VMAT_AVD technique, dose exposures to radiosensitive OARS like the heart, the thyroid or the gonads can be reduced and therefore, maybe the occurrence of late sequelae is less likely. Furthermore the PTV conformity is increased. The advantages of the VMAT_AVD have to be weighed against the potentially risks induced by an increased low dose exposure compared to the 3D-CRT method.

Impact of setup errors on multi-isocenter volumetric modulated arc therapy for craniospinal irradiation

Multi‐isocenter volumetric modulated arc therapy (VMAT) is recommended for craniospinal irradiation (CSI) to smooth the dose distribution in the junction regions relying solely on inverse optimization. However, few studies have measured the dosimetric impact of setup errors on this multi‐isocenter VMAT in the junction areas. The purpose of this study is to evaluate the impact of positional errors during VMAT CSI with two‐dimension (2D) and three‐dimension (3D) dosimetric measurements. A total of 20 patients treated by three‐isocenter VMAT CSI were retrospectively reviewed and analyzed. A 3D diode array ArcCHECK and radiochromic film EBT3 were applied to measure the percentage gamma passing rates (%GPs) and dose distributions in the junction areas between the cranial/upper‐spinal and the upper/lower‐spinal fields with intentionally introduced setup errors of ± 1 mm, ±2 mm, ±3 mm, ±5 mm, and ± 8 mm, respectively. The length and volume of planning target volume (PTV) for these CSI patients ranged from 50.14 to 80.8 cm, and 1572.3 to 2114.5 cm³, respectively. The %GPs for ±3 mm, ±5 mm, and ±8 mm positional errors were around 95%, 90%, and 85%, respectively, in the junction areas. The dosimetric verification results with EBT3 films indicated that cold and hot areas were observed with the increase of introduced setup errors. In conclusion, the dosimetric verification with intentionally introduced setup errors demonstrated that positional errors within 3 mm have a little impact for VMAT CSI, although setup errors should be minimized. Relying on the inverse optimization of VMAT to smooth the dose distribution in the junction areas is feasible for CSI.

Automatic feathering algorithm for VMAT craniospinal irradiation: A comprehensive comparison with other VMAT planning strategies

In craniospinal irradiation, field matching is very sensitive to intrafraction positional uncertainties in cranio-caudal direction, which could lead to severe overdoses/underdoses inside the planning target volume. During the last decade, significant efforts were made to develop volumetric-modulated arc therapy strategies, which were less sensitive to setup uncertainties. In this study, a treatment planning system-integrated method, named automatic feathering (AF) algorithm, was compared against other volumetric-modulated arc therapy strategies. Three patients were retrospectively included. Five different planning techniques were compared, including overlap (O), staggered overlap (SO), gradient optimization (GO), overlap with AF algorithm turned on (O-AF), and staggered overlap with AF algorithm turned on (SO-AF). Three overlapping lengths were considered (5 cm, 7.5 cm, and 10 cm). The middle isocenter was shifted of ±1 mm, ±3 mm, and ±5 mm to simulate setup uncertainties. Plan robustness against simulated uncertainties was evaluated by calculating near maximum and near minimum dose differences between shifted and nonshifted plans (ΔD_2%, ΔD_98%). Dose differences among combinations of techniques and junction lengths were tested using Wilcoxon signed-rank test. Higher ΔD_2% and ΔD_98% were obtained using the overlap technique (ΔD_2% = 15.4%, ΔD_98% = 15.0%). O-AF and SO-AF provided comparable plan robustness to GO technique. Their performance improved significantly for grater overlapping length. For 10-cm overlap and 5-mm shift, GO, O-AF, and SO-AF yielded to the better plan robustness (5.7% < ΔD_2% < 6.0%, 6.1% < ΔD_98% < 7.6%). SO provided an intermediate plan robustness (9.8% < ΔD_2% < 10.8%, 8.9% < ΔD_98% < 10.3%). The addition of AF to the overlap technique significantly improves plan robustness especially if larger overlapping lengths are used. Using the AF algorithm, plans become as robust as plans optimized with more sophisticated and time-consuming approaches (like GO).

Assessment of the results and hematological side effects of 3D conformal and IMRT/ARC therapies delivered during craniospinal irradiation of childhood tumors with a follow-up period of five years

Background

Craniospinal irradiation (CSI) of childhood tumors with the RapidArc technique is a new method of treatment. Our objective was to compare the acute hematological toxicity pattern during 3D conformal radiotherapy with the application of the novel technique.

Methods

Data from patients treated between 2007 and 2014 were collected, and seven patients were identified in both treatment groups. After establishing a general linear model, acute blood toxicity results were obtained using SPSS software. Furthermore, the exposure dose of the organs at risk was compared. Patients were followed for a minimum of 5 years, and progression-free survival and overall survival data were assessed.

Results

After assessment of the laboratory parameters in the two groups, it may be concluded that no significant differences were detected in terms of the mean dose exposures of the normal tissues or the acute hematological side effects during the IMRT/ARC and 3D conformal treatments. Laboratory parameters decreased significantly compared to the baseline values during the treatment weeks. Nevertheless, no significant differences were detected between the two groups. No remarkable differences were confirmed between the two groups regarding the five-year progression-free survival or overall survival, and no signs of serious organ toxicity due to irradiation were observed during the follow-up period in either of the groups.

Conclusion

The RapidArc technique can be used safely even in the treatment of childhood tumors, as the extent of the exposure dose in normal tissues and the amount of acute hematological side effects are not higher with this technique.

Craniospinal irradiation as part of re-irradiation for children with recurrent intracranial ependymoma

BACKGROUND

The goal of this study was to evaluate outcomes in children with relapsed, molecularly characterized intracranial ependymoma treated with or without craniospinal irradiation (CSI) as part of a course of repeat radiation therapy (re-RT).

METHODS

This was a retrospective cohort study of 31 children. Patients with distant relapse received CSI as part of re-RT. For patients with locally recurrent ependymoma, those treated before 2012 were re-irradiated with focal re-RT. In 2012, institutional practice changed to offer CSI, followed by boost re-RT to the site of resected or gross disease.

RESULTS

Median follow-up was 5.5 years. Of 9 patients with distant relapse after initial RT, 2-year freedom from progression (FFP) and overall survival (OS) were 12.5% and 62.5%, respectively. There were 22 patients with local failure after initial RT. In these patients, use of CSI during re-RT was associated with improvement in 5-year FFP (83.3% with CSI vs 15.2% with focal re-RT only, P = 0.030). In the subgroup of patients with infratentorial primary disease, CSI during re-RT also improved 5-year FFP (100% with CSI, 10.0% with focal re-RT only, P = 0.036). Twenty-three patients had known molecular status; all had posterior fossa group A tumors (n = 17) or tumors with a RELA (v-rel avian reticuloendotheliosis viral oncogene homolog A) fusion (n = 6). No patient developed radiation necrosis after fractionated re-RT, though almost all survivors required assistance throughout formal schooling. Five out of 10 long-term survivors have not developed neuroendocrine deficits.

CONCLUSIONS

Re-irradiation with CSI is a safe and effective treatment for children with locally recurrent ependymoma and improves disease control compared with focal re-irradiation, with the benefit most apparent for those with infratentorial primary tumors.

MRI-guided definition of cerebrospinal fluid distribution around cranial and sacral nerves: implications for brain tumors and craniospinal irradiation

Background: The SIOPE-Brain Tumor Group recently published a guideline on craniospinal target volume delineation for highly conformal radiotherapy. In order to spare critical structures like e.g., the lens or cochlea, highly conformal techniques can underdose the cerebrospinal fluid (CSF) in the dural reflections around cranial and sacral nerves. The purpose of this study is to generate evidence for CSF extension within the dural sheaths of the cranial and sacral nerves in order to improve accuracy in target volume delineation.Material and methods: Ten healthy volunteers, age 21 till 41 years, underwent an MRI-scan of the skull-base and sacral plexus. To evaluate CSF extension, cT2-weighted images with fat suppression, low signal to noise ratio and little to no motion-related artifacts were used. Two observers measured the extension of CSF from the inner table of the skull for the cranial nerves, and outside the spinal canal for the sacral nerves.Results: CSF extension (mean distance [95% CI]) was visible within the dural sheaths surrounding the majority of the cranial nerves: optic nerve (40 mm [38-42]), trigeminal nerve (16 mm [15-19]), facial-vestibulocochlear nerve (11 mm [11-12]), glossopharyngeal-vagus-accessory nerve (7 mm [7-9]) and hypoglossal nerve (8 mm [7-9]). No CSF was observed outside the spinal canal at sacral level. No significant difference between both observers was measured.Conclusion: This study generates evidence for significant CSF extension outside the inner table of the skull. Despite the vicinity of the lens and cochlea, we therefore recommend the inclusion of both optic nerves and internal auditory canals in the clinical target volume for craniospinal irradiation when using highly conformal delivery techniques.

Proton versus Photon Radiotherapy for Pediatric Central Nervous System Malignancies: A Systematic Review and Meta-Analysis of Dosimetric Comparison Studies

BACKGROUND

Radiotherapy (RT) plays a fundamental role in the treatment of pediatric central nervous system (CNS) malignancies, but its late sequelae are still a challenging question. Despite developments in modern high-conformal photon techniques and proton beam therapy (PBT) are improving the normal tissues dose-sparing while maintaining satisfactory target coverage, clinical advantages supporting the optimal treatment strategy have to be better evaluated in long-term clinical studies and assessed in further radiobiological analyses. Our analysis aimed to systematically review current knowledge on the dosimetric advantages of PBT in the considered setting, which should be the basis for future specific studies.

MATERIALS AND METHODS

A PubMed and Google Scholar search was conducted in June 2019 to select dosimetric studies comparing photon versus proton RT for pediatric patients affected by CNS tumors. Then, a systematic review and meta-analysis according to the PRISMA statement was performed. Average and standard deviation values of Conformity Index, Homogeneity Index, and mean and maximum doses to intracranial and extracranial organs at risk (OARs) were specifically evaluated for secondary dosimetric comparisons. The standardized mean differences (SMDs) for target parameters and the mean differences (MDs) for OARs were summarized in forest plots (P < 0.05 was considered statistically significant). Publication bias was also assessed by the funnel plot and Egger's regression test.

RESULTS

Among the 88 identified papers, a total of twelve studies were included in the meta-analysis. PBT showed dosimetric advantages in target homogeneity (significant especially in the subgroup comparing PBT and 3D conformal RT), as well as in the dose sparing of almost all analyzed OARs (significantly superior results for brainstem, normal brain, and hippocampal dose constraints and for extracranial OARs parameters, excluding the kidneys). Publication bias was observed for Conformity Index.

CONCLUSION

Our analysis supports the evidence of dosimetric advantages of PBT over photon RT, especially in the dose sparing of normal growing tissues. Confirmations from wider well-designed studies are required.

Cardiotoxicity of mediastinal radiotherapy

Aim

To explore available recent literature related to cardiotoxicity following mediastinal radiation.

Background

Radiotherapy-related heart injury is well documented, with no apparent safety threshold dose. The number of long-term cancer survivors exposed to mediastinal radiotherapy at some point of their treatment is increasing. Heart dosimetric parameters are of great importance in developing a treatment plan, but few data are available regarding radiosensitivity and dose-volume constraints for specific heart structures.

Materials and Methods

In October 2018, we identified articles published after 1990 through a PubMed/MEDLINE database search. The authors examined rough search results and manuscripts not relevant for the topic were excluded. We extracted clinical outcomes following mediastinal radiotherapy of childhood cancers, lymphoma, medulloblastoma, thymic cancers and hematopoietic cell transplantation survivors and evaluated treatment planning data, whenever available.

Results

A total of 1311 manuscripts were identified in our first-round search. Of these manuscripts, only 115 articles, matching our selection criteria, were included.

Conclusions

Studies uniformly show a linear radiation dose-response relationship between mean absorbed dose to the heart (heart-D_mean) and the risk of dying as a result of cardiac disease, particularly when heart-D_mean exceeds 5 Gy. Limited data are available regarding dose-volume predictors for heart substructures and the risk of subsequent cardiac toxicity. An individual patient's cardiotoxicity risk can be modified with advanced treatment planning techniques, including deep inspiration breath hold. Proton therapy is currently showing advantages in improving treatment planning parameters when compared to advanced photon techniques in lymphoma, thymic malignancies, malignant mesothelioma and craniospinal irradiation.

Pineoblastoma in Adults: A Rare Case Successfully Treated with Multimodal Approach Including Craniospinal Irradiation Using Helical Tomotherapy

Pineoblastomas (PBs) are rare and aggressive malignancies of the pineal gland. They are more commonly diagnosed in children between 1-12 years old, and are very rarely diagnosed in adults. For this reason, evidence in literature for adults is scarce and mainly derives from the paediatric practice. For their clinical behaviour and embryonal histology, PBs are often grouped together with medulloblastomas in clinical trials. In this report, we describe an adult PB case who was treated at our institution. We reference the literature to explain the clinical reasoning behind our decision-making process. A 46-year-old male patient was referred to our institution in November 2015 with three months history of headache. Imaging confirmed localised disease of the pineal gland. He underwent surgery which was radical and clinically uncomplicated. Histology showed PB. He then received adjuvant craniospinal radiotherapy with a boost to the tumour bed followed by consolidation chemotherapy. After 36 months follow-up, he remains disease-free without significant toxicities. Surgery followed by craniospinal irradiation and consolidation chemotherapy can be a safe and effective treatment option in adult PBs.

Ultrasonographic and elastographic biometry in adult major salivary glands: a preliminary case-control report

Specifications about the size and stiffness of healthy salivary glands with ultrasound (US) are not available for Asian people. Using a Toshiba Apolio 500 US platform, we determined the size (including anterior-posterior median length, median paramandibular depth dimension, and cranio-caudal height) and hardness of 100 healthy submandibular and parotid glands in volunteers without a history of disease affecting the salivary glands or post-radiation, and compared the dimensions to those of 36 parotid glands and 37 submandibular glands in post-irradiated patients. The dimensions of the parotid and submandibular glands were significantly correlated with body weight. However, the dimension of the parotid glands was not significantly correlated with that of patients with prior radiation; the shear wave velocity (SWV) significantly increased (1.99 m/s versus 2.43 m/s, p-value < 0.01). The dimension of the submandibular glands was significantly correlated with prior radiation, where the SWV also significantly increased (2.32 m/s versus 2.50 m/s, p-values < 0.01). We find that US is a useful tool for assessment of the reference dimensions and hardness of major salivary glands that may be altered by irradiation.

Proton therapy for brain tumours in the area of evidence-based medicine

ADVANCES IN KNOWLEDGE

This review details the indication of brain tumors for proton therapy and give a list of the open prospective trials for these challenging tumors.