Very high-energy electron therapy as light-particle alternative to transmission proton FLASH therapy - An evaluation of dosimetric performances.

PURPOSE: Clinical translation of FLASH-radiotherapy (RT) to deep-seated tumours is still a technological challenge. One proposed solution consists of using ultra-high dose rate transmission proton (TP) beams of about 200-250 MeV to irradiate the tumour with the flat entrance of the proton depth-dose profile. This work evaluates the dosimetric performance of very high-energy electron (VHEE)-based RT (50-250 MeV) as a potential alternative to TP-based RT for the clinical transfer of the FLASH effect. METHODS: Basic physics characteristics of VHEE and TP beams were compared utilizing Monte Carlo simulations in water. A VHEE-enabled research treatment planning system was used to evaluate the plan quality achievable with VHEE beams of different energies, compared to 250 MeV TP beams for a glioblastoma, an oesophagus, and a prostate cancer case. RESULTS: Like TP, VHEE above 100 MeV can treat targets with roughly flat (within ± 20 %) depth-dose distributions. The achievable dosimetric target conformity and adjacent organs-at-risk (OAR) sparing is consequently driven for both modalities by their lateral beam penumbrae. Electron beams of 400[500] MeV match the penumbra of 200[250] MeV TP beams and penumbra is increased for lower electron energies. For the investigated patient cases, VHEE plans with energies of 150 MeV and above achieved a dosimetric plan quality comparable to that of 250 MeV TP plans. For the glioblastoma and the oesophagus case, although having a decreased conformity, even 100 MeV VHEE plans provided a similar target coverage and OAR sparing compared to TP. CONCLUSIONS: VHEE-based FLASH-RT using sufficiently high beam energies may provide a lighter-particle alternative to TP-based FLASH-RT with comparable dosimetric plan quality.

A multicenter study of modified electron beam output calibration.

PURPOSE: This study aims to assess the accuracy of a modified electron beam calibration based on the IAEA TRS-398 and AAPM-TG-51 in multicenter radiotherapy. METHODS: This study was performed using the Elekta and Varian Linear Accelerator electron beams with energies of 4-22 MeV under reference conditions using cylindrical (PTW 30013, IBA FC65-G, and IBA FC65-P) and parallel-plate (PTW 34045, PTW 34001, and IBA PPC-40) chambers. The modified calibration used a cylindrical chamber and an updated k ' Q $k{^{\prime}}_Q$ based on Monte Carlo calculations, whereas TRS-398 and TG-51 used cylindrical and parallel-plate chambers for reference dosimetry. The dose ratio of the modified calibration procedure, TRS-398 and TG-51 were obtained by comparing the dose at the maximum depth of the modified calibration to TRS-398 and TG-51. RESULTS: The study found that all cylindrical chambers' beam quality conversion factors determined with the modified calibration ( k ' Q ) $( {{{k^{\prime}}}_Q} )$ to the TRS-398 and TG-51 vary from 0.994 to 1.003 and 1.000 to 1.010, respectively. The dose ratio of modified/TRS-398cyl and modified/TRS-398parallel-plate, the variation ranges were 0.980-1.014 and 0.981-1.019, while for the counterpart modified/TG-51cyl was found varying between 0.991 and 1.017 and the ratio of modified/TG-51parallel-plate varied in the range of 0.981-1.019. CONCLUSION: This multi-institutional study analyzed a modified calibration procedure utilizing new data for electron beam calibrations at multiple institutions and evaluated existing calibration protocols. Based on observed variations, the current calibration protocols should be updated with detailed metrics on the stability of linac components.

Evaluation of the water-equivalent characteristics of the SP34 plastic phantom for film dosimetry in a clinical linear accelerator.

In this study, some confusing points about electron film dosimetry using white polystyrene suggested by international protocols were verified using a clinical linear accelerator (LINAC). According to international protocol recommendations, ionometric measurements and film dosimetry were performed on an SP34 slab phantom at various electron energies. Scaling factor analysis using ionometric measurements yielded a depth scaling factor of 0.923 and a fluence scaling factor of 1.019 at an electron beam energy of <10 MeV (i.e., R50 < 4.0 g/cm2). It was confirmed that the water-equivalent characteristics were similar because they have values similar to white polystyrene (i.e., depth scaling factor of 0.922 and fluence scaling factor of 1.019) presented in international protocols. Furthermore, percentage depth dose (PDD) curve analysis using film dosimetry showed that when the density thickness of the SP34 slab phantom was assumed to be water-equivalent, it was found to be most similar to the PDD curve measured using an ionization chamber in water as a reference medium. Therefore, we proved that the international protocol recommendation that no correction for measured depth dose is required means that no scaling factor correction for the plastic phantom is necessary. This study confirmed two confusing points that could occur while determining beam characteristics using electron film dosimetry, and it is expected to be used as basic data for future research on clinical LINACs.

Secondary radiation dose modeling in passive scattering and pencil beam scanning very high energy electron (VHEE) radiation therapy.

BACKGROUND: Electrons with kinetic energy up to a few hundred MeV, also called very high energy electrons (VHEE), are currently considered a promising technique for the future of radiation therapy (RT) and in particular ultra-high dose rate (UHDR) therapy. However, the feasibility of a clinical application is still being debated and VHEE therapy remains an active area of research for which the optimal conformal technique is also yet to be determined. PURPOSE: In this work, we will apply two existing formalisms based on analytical Gaussian multiple-Coulomb scattering theory and Monte Carlo (MC) simulations to study and compare the electron and bremsstrahlung photon dose distributions arising from two beam delivery systems (passive scattering with or without a collimator or active scanning). METHODS: We therefore tested the application of analytical and MC models to VHEE beams and assessed their performance and parameterization in the energy range of 6-200 MeV. The optimized electron beam fluence, the bremsstrahlung, an estimation of central-axis and off-axis x-ray dose at the practical range and neutron contributions to the total dose, along with an extended parameterization for the photon dose model were developed, together with a comparison between double scattering (DS) and pencil beam scanning (PBS) techniques. MC simulations were performed with the TOPAS/Geant4 toolkit to verify the dose distributions predicted by the analytical calculations. RESULTS: The results for the clinical energy range (between 6 and 20 MeV) as well as for higher energies (VHEE range between 20 and 200 MeV) and for two treatment field sizes (5 × 5 and 10 × 10 cm2 ) are reported, showing a reasonable agreement with MC simulations with mean differences below 2.1%. The relative contributions of photons generated in the medium or by the scattering system along the central-axis (up to 50% of the total dose) are also illustrated, along with their relative variations with electron energy. CONCLUSIONS: The fast analytical models parametrized in this study allow an estimation of the amount of photons produced behind the practical range by a DS system with an accuracy lower than 3%, providing important information for the eventual design of a VHEE system. The results of this work could support future research on VHEE radiotherapy.

[Basic Knowledge of Neutron: Generation of Neutrons Accompanied with the High-Energy Photon Therapy].

Photo neutrons are generated from high-energy medical X-ray linacs via photo-nuclear reactions with the materials of target and collimator as well as therapeutic X-rays. Such photo neutrons sometimes make unwanted influences and are not negligible for the aspects of radiation protection and radiation control. In this article, fundamental principle of such photo-neutron generation is briefly explained. The side effects induced by the photo neutrons are summarized. In addition, some techniques of the detection and measurement of photo neutrons are introduced.

Application of a portable primary standard level graphite calorimeter for absolute dosimetry in a clinical low-energy passively scattered proton beam.

Objective. A calibration service based on a primary standard calorimeter for the direct determination of absorbed dose for proton beams does not exist. A new Code of Practice (CoP) for reference dosimetry of proton beams is being developed by a working party of the UK Institute of Physics and Engineering in Medicine (IPEM), which will recommend that ionisation chambers are calibrated directly in their clinical beams against the proposed Primary Standard Proton Calorimeter (PSPC) developed at the National Physical Laboratory (NPL). The aim of this work is to report on the use of the NPL PSPC to directly calibrate ionisation chambers in a low-energy passively scattered proton beam following recommendations of the upcoming IPEM CoP.Approach. A comparison between the dose derived using the proposed IPEM CoP and the IAEA TRS-398 protocol was performed, andkQvalues were determined experimentally for three types of chambers. In total, 9 plane-parallel and 3 cylindrical chambers were calibrated using the two protocols for two separate visits.Main results. The ratio of absorbed dose to water obtained with the PSPC and with ionisation chambers applying TRS-398 varied between 0.98 and 1.00, depending on the chamber type. The new procedure based on the PSPC provides a significant improvement in uncertainty where absorbed dose to water measured with a user chamber is reported with an uncertainty of 0.9% (1σ), whereas the TRS-398 protocol reports an uncertainty of 2.0% and 2.3% (1σ) for cylindrical and plane-parallel chambers, respectively. ThekQvalues found agree within uncertainties with those from TRS-398 and Monte Carlo calculations.Significance. The establishment of a primary standard calorimeter for the determination of absorbed dose in proton beams combined with the introduction of the associated calibration service following the IPEM recommendations will reduce the uncertainty and improve consistency in the dose delivered to patients.

Empirical modeling of the percent depth dose for megavoltage photon beams.

INTRODUCTION: This study presents an empirical method to model the high-energy photon beam percent depth dose (PDD) curve by using the home-generated buildup function and tail function (buildup-tail function) in radiation therapy. The modeling parameters n and µ of buildup-tail function can be used to characterize the Collimator Scatter Factor (Sc) either in a square field or in the different individual upper jaw and lower jaw setting separately for individual monitor unit check. METHODS AND MATERIALS: The PDD curves for four high-energy photon beams were modeled by the buildup and tail function in this study. The buildup function was a quadratic function in the form of [Formula: see text] with the main parameter of d (depth in water) and n, while the tail function was in the form of e-µd and was composed by an exponential function with the main parameter of d and µ. The PDD was the product of buildup and tail function, PDD = [Formula: see text]. The PDD of four-photon energies was characterized by the buildup-tail function by adjusting the parameters n and µ. The Sc of 6 MV and 10 MV can then be expressed simply by the modeling parameters n and µ. RESULTS: The main parameters n increases in buildup-tail function when photon energy increased. The physical meaning of the parameter n expresses the beam hardening of photon energy in PDD. The fitting results of parameters n in the buildup function are 0.17, 0.208, 0.495, 1.2 of four-photon energies, 4 MV, 6 MV, 10 MV, 18 MV, respectively. The parameter µ can be treated as attenuation coefficient in tail function and decreases when photon energy increased. The fitting results of parameters µ in the tail function are 0.065, 0.0515, 0.0458, 0.0422 of four-photon energies, 4 MV, 6 MV, 10 MV, 18 MV, respectively. The values of n and µ obtained from the fitted buildup-tail function were applied into an analytical formula of Sc = nE(S)0.63µE to get the collimator to scatter factor Sc for 6 and 10 MV photon beam, while nE, µE, S denotes n, µ at photon energy E of field size S, respectively. The calculated Sc were compared with the measured data and showed agreement at different field sizes to within ±1.5%. CONCLUSIONS: We proposed a model incorporating a two-parameter formula which can improve the fitting accuracy to be better than 1.5% maximum error for describing the PDD in different photon energies used in clinical setting. This model can be used to parameterize the Sc factors for some clinical requirements. The modeling parameters n and µ can be used to predict the Sc in either square field or individual jaws opening asymmetrically for treatment monitor unit double-check in dose calculation. The technique developed in this study can also be used for systematic or random errors in the QA program, thus improves the clinical dose computation accuracy for patient treatment.

Conventional 3D conformal radiotherapy and volumetric modulated arc therapy for cervical cancer: Comparison of clinical results with special consideration of the influence of patient- and treatment-related parameters.

PURPOSE: Intensity-modulated radiotherapy (IMRT) for cervical cancer yields favorable results in terms of oncological outcomes, acute toxicity, and late toxicity. Limited data are available on clinical results with volumetric modulated arc therapy (VMAT). This study's purpose is to compare outcome and toxicity with VMAT to conventional 3D conformal radiotherapy (3DCRT), giving special consideration to the influence of patient- and treatment-related parameters on side effects. MATERIALS AND METHODS: Patients with cervical cancer stage I-IVA underwent radiotherapy alone or chemoradiotherapy using 3DCRT (n = 75) or VMAT (n = 30). Survival endpoints were overall survival, progression-free survival, and locoregional control. The National Cancer Institute Common Terminology Criteria for Adverse Events and the Late Effects of Normal Tissues criteria were used for toxicity assessment. Toxicity and patient- and treatment-related parameters were included in a multivariable model. RESULTS: There were no differences in survival rates between treatment groups. VMAT significantly reduced late small bowel toxicity (OR = 0.10, p = 0.03). Additionally, VMAT was associated with an increased risk of acute urinary toxicity (OR = 2.94, p = 0.01). A low body mass index (BMI; OR = 2.46, p = 0.03) and overall acute toxicity ≥grade 2 (OR = 4.17, p < 0.01) were associated with increased overall late toxicity. CONCLUSION: We demonstrated significant reduction of late small bowel toxicity with VMAT treatment, an improvement in long-term morbidity is conceivable. VMAT-treated patients experienced acute urinary toxicity more frequently. Further analysis of patient- and treatment-related parameters indicates that the close monitoring of patients with low BMI and of patients who experienced relevant acute toxicity during follow-up care could improve late toxicity profiles.

Bronchoplastic Procedure Versus Pneumonectomy After High-dose Radiation for Non-small Cell Lung Cancer.

BACKGROUND: Studies have revealed that salvage surgery after definitive chemoradiotherapy (CRT) for unresectable advanced non-small cell lung cancer improves survival with acceptable surgical adverse events. Few reports exist regarding pneumonectomy or the bronchoplastic procedure in this setting. METHODS: Between 2008 and 2018, 27 patients (21 men; median age, 61 years) underwent salvage surgery after definitive CRT for non-small cell lung cancer. We investigated postoperative short- and long-term outcomes of salvage surgery and aimed to elucidate the feasibility of pneumonectomy or the bronchoplastic procedure. RESULTS: The median radiation dose was 60 Gy. The median period from the last day for irradiation to the operative day was 8.5 months. Pneumonectomy was performed in 9 patients, including 2 carinal resections; lobectomy was performed in 18 patients, including 5 bronchoplasties. Bronchial wrapping was performed in 9 cases (33%), R0 resection was achieved in 24 (89%), and postoperative complications were detected in 16 (59%). Although bronchopleural fistulas were found in only 2 patients who underwent pneumonectomy, arrhythmia was observed more frequently in patients who underwent the bronchoplastic procedure (P = .05). Regarding major complications, no relationship with any factors were found. The 90-day mortality was 0%. The 5-year overall and recurrence-free survival were 63% and 27%, respectively. R0 resection was a good prognostic factor for recurrence-free survival (P = .001). CONCLUSIONS: Perioperative short- and long-term outcomes of salvage surgery after definitive CRT for non-small cell lung cancer were acceptable. Complete resection offered a better recurrence-free survival. The bronchoplastic procedure or pneumonectomy should be considered as an option even after administration of high-dose CRT.

Fatigue following radiotherapy of low-risk early breast cancer - a randomized controlled trial of intraoperative electron radiotherapy versus standard hypofractionated whole-breast radiotherapy: the COSMOPOLITAN trial (NCT03838419).

BACKGROUND: Fatigue is one of the most common and distressing side-effects of breast cancer radiotherapy. According to current guidelines, accelerated partial breast irradiation (APBI) may be considered as an alternative treatment option for women with early-stage low-risk breast cancer. One method for APBI is single-dose intraoperative radiotherapy (IORT) applied directly to the tumor bed during breast conserving surgery (BCS). The COSMOPOLITAN trial therefore aims to analyze the intensity of fatigue following single-shot IORT with electrons (IOERT) compared to conventional hypofractionated whole breast irradiation (WBI) in low risk early breast cancer patients. METHODS: This trial is conducted as a multicenter, prospective, randomized, two-arm phase II study comparing the intensity of fatigue in early-stage breast cancer (cT1cN0cM0, tumor size < 2,5 cm, ER pos. Her2neu neg., age > 50 years) treated either with WBI or APBI after BCS. Secondary outcomes investigated are tumor control, overall survival (OS), disease-free survival (DFS), acute and chronic toxicity, quality of life (QoL) and cosmesis. A total of 202 patients will be randomized into two arms: Patients in arm A will receive WBI (40.05 Gy, 15 fractions) after surgical resection, while patients in arm B will receive IOERT (21 Gy to the 90%-isodose) during BCS. Fatigue will be assessed 12 weeks post surgery with the help of the Functional Assessment of Chronic Illness Therapy (FACIT) Fatigue Scale. DISCUSSION: The present trial aims to evaluate treatment response to compare single-shot intraoperative electron APBI to conventional WBI following BCS in early-stage low risk breast cancer patients. Fatigue is selected as the primary, patient-reported endpoint due its major clinical relevance. TRIAL REGISTRATION: The study is prospectively registered on February 12th, 2019: Clinicaltrials.gov, NCT03838419. "Intraoperative Electron Radiotherapy for Low-risk Early Breast Cancer (COSMOPOLITAN)". STUDY STATUS: Ongoing study. Start of recruitment was December 2019.

Lithium chloride increases sensitivity to photon irradiation treatment in primary mesenchymal colon cancer cells.

Colorectal cancer (CRC) is the third most prevalent type of cancer worldwide. It is also the second most common cause of cancer­associated mortality; it accounted for about 9.2% of all cancer deaths in 2018, most of which were due to resistance to therapy. The main treatment for CRC is surgery, generally associated with chemotherapy, radiation therapy and combination therapy. However, while chemo­radiotherapy kills differentiated cancer cells, mesenchymal stem­like cells are resistant to this treatment, and this can give rise to therapy­resistant tumors. Our previous study isolated T88 primary colon cancer cells from a patient with sporadic colon cancer. These cells exhibited mesenchymal and epithelial features, high levels of epithelial­to­mesenchymal transition transcription factors, and stemness markers. In addition, it was revealed that lithium chloride (LiCl), a specific glycogen synthase kinase (GSK)­3ß inhibitor, induced both the mesenchymal­to­epithelial transition and differentiation, and also reduced cell migration, stemness features and cell plasticity in these primary colon cancer cells. The aim of the present study was to investigate the effect of LiCl treatment on the viability of primary colon cancer cells exposed to 7 Gy delivered by high­energy photon beams, which corresponds to 6 megavolts of energy. To achieve this aim, the viability of irradiated T88 cells was compared with that of irradiated T88 cells pre­treated with LiCl. As expected, it was observed that LiCl sensitized primary colon cancer cells to high­energy photon irradiation treatment. Notably, the decrease in cell viability was greater with combined therapy than with irradiation alone. To explore the molecular basis of this response, the effect of LiCl on the expression of Bax, p53 and Survivin, which are proteins involved in the apoptotic mechanism and in death escape, was analyzed. The present study revealed that LiCl upregulated the expression of pro­apoptotic proteins and downregulated the expression of proteins involved in survival. These effects were enhanced by high­energy photon irradiation, suggesting that LiCl could be used to sensitize colon cancer cells to radiation therapy.

A novel, yet simple MLC-based 3D-crossfire technique for spatially fractionated GRID therapy treatment of deep-seated bulky tumors.

PURPOSE: Treating deep-seated bulky tumors with traditional single-field Cerrobend GRID-blocks has many limitations such as suboptimal target coverage and excessive skin toxicity. Heavy traditional GRID-blocks are a concern for patient safety at various gantry-angles and dosimetric detail is not always available without a GRID template in user's treatment planning system. Herein, we propose a simple, yet clinically useful multileaf collimator (MLC)-based three-dimensional (3D)-crossfire technique to provide sufficient target coverage, reduce skin dose, and potentially escalate tumor dose to deep-seated bulky tumors. MATERIALS/METHODS: Thirteen patients (multiple sites) who underwent conventional single-field cerrobend GRID-block therapy (maximum, 15 Gy in 1 fraction) were re-planned using an MLC-based 3D-crossfire method. Gross tumor volume (GTV) was used to generate a lattice pattern of 10 mm diameter and 20 mm center-to-center mimicking conventional GRID-block using an in-house MATLAB program. For the same prescription, MLC-based 3D-crossfire grid plans were generated using 6-gantry positions (clockwise) at 60° spacing (210°, 270°, 330°, 30°, 90°, 150°, therefore, each gantry angle associated with a complement angle at 180° apart) with differentially-weighted 6 or 18 MV beams in Eclipse. For each gantry, standard Millenium120 (Varian) 5 mm MLC leaves were fit to the grid-pattern with 90° collimator rotation, so that the tunneling dose distribution was achieved. Acuros-based dose was calculated for heterogeneity corrections. Dosimetric parameters evaluated include: mean GTV dose, GTV dose heterogeneities (peak-to-valley dose ratio, PVDR), skin dose and dose to other adjacent critical structures. Additionally, planning time and delivery efficiency was recorded. With 3D-MLC, dose escalation up to 23 Gy was simulated for all patient's plans. RESULTS: All 3D-MLC crossfire GRID plans exhibited excellent target coverage with mean GTV dose of 13.4 ± 0.5 Gy (range: 12.43-14.24 Gy) and mean PVDR of 2.0 ± 0.3 (range: 1.7-2.4). Maximal and dose to 5 cc of skin were 9.7 ± 2.7 Gy (range: 5.4-14.0 Gy) and 6.3 ± 1.8 Gy (range: 4.1-11.1 Gy), on average respectively. Three-dimensional-MLC treatment planning time was about an hour or less. Compared to traditional GRID-block, average beam on time was 20% less, while providing similar overall treatment time. With 3D-MLC plans, tumor dose can be escalated up to 23 Gy while respecting skin dose tolerances. CONCLUSION: The simple MLC-based 3D-crossfire GRID-therapy technique resulted in enhanced target coverage for de-bulking deep-seated bulky tumors, reduced skin toxicity and spare adjacent critical structures. This simple MLC-based approach can be easily adopted by any radiotherapy center. It provides detailed dosimetry and a safe and effective treatment by eliminating the heavy physical GRID-block and could potentially provide same day treatment. Prospective clinical trial with higher tumor-dose to bulky deep-seated tumors is anticipated.

Intraoperative computed tomography imaging for dose calculation in intraoperative electron radiation therapy: Initial clinical observations.

In intraoperative electron radiation therapy (IOERT) the energy of the electron beam is selected under the conventional assumption of water-equivalent tissues at the applicator end. However, the treatment field can deviate from the theoretic flat irradiation surface, thus altering dose profiles. This patient-based study explored the feasibility of acquiring intraoperative computed tomography (CT) studies for calculating three-dimensional dose distributions with two factors not included in the conventional assumption, namely the air gap from the applicator end to the irradiation surface and tissue heterogeneity. In addition, dose distributions under the conventional assumption and from preoperative CT studies (both also updated with intraoperative data) were calculated to explore whether there are other alternatives to intraoperative CT studies that can provide similar dose distributions. The IOERT protocol was modified to incorporate the acquisition of intraoperative CT studies before radiation delivery in six patients. Three studies were not valid to calculate dose distributions due to the presence of metal artefacts. For the remaining three cases, the average gamma pass rates between the doses calculated from intraoperative CT studies and those obtained assuming water-equivalent tissues or from preoperative CT studies were 73.4% and 74.0% respectively. The agreement increased when the air gap was included in the conventional assumption (98.1%) or in the preoperative CT images (98.4%). Therefore, this factor was the one mostly influencing the dose distributions of this study. Our experience has shown that intraoperative CT studies are not recommended when the procedure includes the use of shielding discs or surgical retractors unless metal artefacts are removed. IOERT dose distributions calculated under the conventional assumption or from preoperative CT studies may be inaccurate unless the air gap (which depends on the surface irregularities of the irradiated volume and on the applicator pose) is included in the calculations.

Reference dose determination in 60Co and high-energy radiotherapy photon beams by using Farmer-type cylindrical ionization chambers - an experimental investigation.

Ionization chamber dosimetry is predominantly used for determination of the absorbed dose to water in 60Co and high-energy radiotherapy photon beams. The most widespread ionization chambers employed for absolute or reference dose determinations in reference conditions are the Farmer-type cylindrical ionization chambers. The Farmer-type ionization chambers have a variety of constructions and materials and their responses vary in the radiation beam. Clinical accelerators, in addition to conventional photon beams with flattening-filter, can also deliver flattening-filter-free (FFF) photon beams. The responses of five different Farmer-type cylindrical ionization chambers were experimentally examined with reference to absorbed dose determination in reference conditions when using the International Atomic Energy Agency (IAEA) - American Association of Physicists in Medicine (AAPM) Technical Reports Series no. 483 (TRS-483) and the IAEA TRS-398 dosimetry protocol in the present investigation. The irradiations were performed using 60Co and megavoltage photon beams with 6 MV, 15 MV, 6 MV FFF and 10 MV FFF nominal photon energies. The chamber calibrations were performed at different Secondary Standard Dosimetry Laboratories and are traceable to primary standards at different Primary Standard Dosimetry Laboratories. The chambers were also cross-calibrated at our laboratory using 60Co γ-beam. The variation found in the data regarding the reference dose determination using the various Farmer-type chambers in the photon beams employed was about 1% at maximum. Thus, the selection of the ionization chamber in reference dose determinations may affect the outcomes. The differences in the absorbed dose values were similar in the conventional as well as in the FFF photon beams. For the FFF photon beams the absorbed dose computations were performed using the IAEA-AAPM TRS-483 dosimetry protocol. Two of the ionization chambers used had identical construction but different central electrodes, i.e. graphite versus aluminium. The results obtained using these two chambers show that, in the photon beams examined, the employed correction for the central electrode (p cel ) regarding these two chambers is associated with an inaccuracy which is larger than the calculated uncertainty for this correction. The outcomes found in the present experimental investigation using the various ionization chambers also indicate possible inaccuracy in the employed beam quality correction factors (k Q ) and imply the need for a revision of these factors.

Role of radiation therapy for pediatric upper extremity extraskeletal osteosarcoma: A case series.

BACKGROUND: Extraskeletal osteosarcoma is an extremely rare disease, comprising less than 0.1% of all cancers diagnosed in the United States, of which less than 5% occur in the upper extremities. The management of two cases of pediatric upper extremity extraskeletal osteosarcoma is discussed. CASE DESCRIPTION: Two children initially noticed painless left upper extremity masses at the ages of 16 and 13, respectively. Following a period of several months, both lesions became symptomatic, necessitating operative intervention, which revealed giant cell-rich extraskeletal osteosarcoma; PET staging following gross total resection revealed no residual or metastatic disease in either patient. After extensive discussion with the patients and family, adjuvant chemotherapy was initiated for one patient, and adjuvant radiation therapy was initiated in both patients. CONCLUSIONS: Despite the rarity of these tumors, the importance of radiation therapy has been established by current and ongoing studies such as the Children's Oncology Group study ARST0332. Radiation therapy remains an important component of the multimodality therapy comprising optimal treatment of this disease, despite the relative paucity of long-term outcome data derived from level I evidence.

Evaluation of the efficacy of lipotransfer to manage radiation-induced fibrosis and volume defects in head and neck oncology.

BACKGROUND: Multimodality treatment for head and neck cancer leads to substantial functional and esthetic impairment mainly manifested as radiation-induced skin fibrosis (RIF) in combination with volumetric defects and reduction in neck mobility. This study assessed the impact of lipotransfer as part of secondary surgical procedure(s) in patients treated for head and neck malignancies. METHODS: Retrospective analysis was performed between 2005 and 2016. All patients with a history of head and neck malignancy, multimodal treatment including at least surgery or radiotherapy, and at least 2-year disease-free survival were included. Thirty-eight patients (22 men, 16 women) matched the inclusion criteria. RESULTS: Thirty seven (97%) reported esthetic and functional improvements in their RIF and volumetric defect at follow-up of 32 months. Major improvement in esthetic and functional outcome was reported by 24 (63%) patients and surgeons and minor by 13 patients and surgeons (34%) without causing any complications. Lipotransfer was also found to significantly improve patient's psychological health postoperatively as showed by significant improvements in Derriford Appearance Scale (DAS24), Short Form Health Survey (SF-36), and University of Washington Quality of Life Questionnaire (UW-QOL V4) scores (P < .001). CONCLUSIONS: Lipotransfer is effective for volume restoration and treating scar and RIF from head and neck defects.

A prospective study of health-related quality of life outcomes among men treated for intermediate- and high-risk prostate cancer: the impact of primary and secondary therapies.

INTRODUCTION: To assess the impact of primary and secondary therapies for high- and intermediate-risk prostate cancer on health-related quality of life (HRQoL). MATERIALS AND METHODS: A prospective study was initiated in 2007 at Center for Prostate Disease Research Multicenter National Database sites. Longitudinal patterns in HRQoL from baseline (pre-treatment) to 5 years post-diagnosis were examined for patients with high- and intermediate-risk prostate cancer, treated by radical prostatectomy (RP) or external beam radiation therapy (EBRT). Change in HRQoL was modeled using linear regression models fit with generalized estimating equations. The probability of maintaining HRQoL was compared between patients receiving RP only versus RP with secondary treatment. RESULTS: Of 445 men with high- and intermediate-risk prostate cancer, 228 underwent RP and 143 had EBRT± androgen deprivation therapy (ADT). Fifty received secondary therapy (EBRT and/or ADT or chemotherapy) after RP. RP patients showed a greater decline over time in sexual function and bother and urinary function compared to EBRT±ADT patients. Patients who had secondary therapy after RP were less likely to maintain their HRQoL compared to those who had RP alone. These differences were most pronounced for sexual and hormonal function. CONCLUSIONS: Prostate cancer patients experience significant declines in HRQoL after primary therapy. Additional secondary therapy after RP, in the form of EBRT and/or ADT, appears to be responsible for further deterioration in HRQoL outcomes.

Temporomandibular disorder in head and neck cancer patients undergoing radiotherapy: Clinical findings and patient-reported symptoms.

BACKGROUND: The aim of this study was to investigate how common temporomandibular disorder (TMD) symptoms are among head and neck cancer (HNC) patients before and after oncological treatment. METHODS: Eighty-nine patients with HNC receiving radiotherapy were enrolled in the study. Patients were examined before radiotherapy and at 6 and 12 months after radiotherapy to evaluate the function and tenderness of the temporomandibular jaw and the muscles of mastication as well as the patient-reported symptoms. RESULTS: At 6 months after radiotherapy, there was a large increase in the number of patients reporting problems with opening their mouth, fatigue, stiffness, and pain of the jaw. Sixty-eight percent of the patients had symptoms of TMD before oncological treatment and 94% and 81% had symptoms at the 6- and 12-month follow-up, respectively. CONCLUSION: The signs and symptoms of TMD escalate after radiotherapy, with symptoms peaking at 6 months after radiotherapy. Most commonly, patients suffer from restricted mouth opening, stiffness, fatigue, and pain of the jaw.

PHASER: A platform for clinical translation of FLASH cancer radiotherapy.

Pluridirectional high-energy agile scanning electronic radiotherapy (PHASER) is next-generation medical linac technology for ultra-rapid highly conformal image-guided radiation, fast enough to "freeze" physiological motion, affording improved accuracy, precision, and potentially superior FLASH radiobiological therapeutic index. Designed for compactness, economy, and clinical efficiency, it is also intended to address barriers to global access to curative radiotherapy.

Neutron track length estimator for GATE Monte Carlo dose calculation in radiotherapy.

The out-of-field dose in radiation therapy is a growing concern in regards to the late side-effects and secondary cancer induction. In high-energy x-ray therapy, the secondary neutrons generated through photonuclear reactions in the accelerator are part of this secondary dose. The neutron dose is currently not estimated by the treatment planning system while it appears to be preponderant for distances greater than 50 cm from the isocenter. Monte Carlo simulation has become the gold standard for accurately calculating the neutron dose under specific treatment conditions but the method is also known for having a slow statistical convergence, which makes it difficult to be used on a clinical basis. The neutron track length estimator, a neutron variance reduction technique inspired by the track length estimator method has thus been developped for the first time in the Monte Carlo code GATE to allow a fast computation of the neutron dose in radiotherapy. The details of its implementation, as well as the comparison of its performances against the analog MC method, are presented here. A gain of time from 15 to 400 can be obtained by our method, with a mean difference in the dose calculation of about 1% in comparison with the analog MC method.