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Daugherty EC, Zhang Y, Xiao Z, Mascia AE, Sertorio M, Woo J, McCann C, Russell KJ, Sharma RA, Khuntia D, Bradley JD, Simone CB, Breneman JC, Perentesis JP. FLASH radiotherapy for the treatment of symptomatic bone metastases in the thorax (FAST-02): protocol for a prospective study of a novel radiotherapy approach. Radiat Oncol 2024; 19:34. [PMID: 38475815 PMCID: PMC10935811 DOI: 10.1186/s13014-024-02419-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2023] [Accepted: 02/08/2024] [Indexed: 03/14/2024] Open
Abstract
BACKGROUND FLASH therapy is a treatment technique in which radiation is delivered at ultra-high dose rates (≥ 40 Gy/s). The first-in-human FAST-01 clinical trial demonstrated the clinical feasibility of proton FLASH in the treatment of extremity bone metastases. The objectives of this investigation are to assess the toxicities of treatment and pain relief in study participants with painful thoracic bone metastases treated with FLASH radiotherapy, as well as workflow metrics in a clinical setting. METHODS This single-arm clinical trial is being conducted under an FDA investigational device exemption (IDE) approved for 10 patients with 1-3 painful bone metastases in the thorax, excluding bone metastases in the spine. Treatment will be 8 Gy in a single fraction administered at ≥ 40 Gy/s on a FLASH-enabled proton therapy system delivering a single transmission proton beam. Primary study endpoints are efficacy (pain relief) and safety. Patient questionnaires evaluating pain flare at the treatment site will be completed for 10 consecutive days post-RT. Pain response and adverse events (AEs) will be evaluated on the day of treatment and on day 7, day 15, months 1, 2, 3, 6, 9, and 12, and every 6 months thereafter. The outcomes for clinical workflow feasibility are the occurrence of any device issues as well as time on the treatment table. DISCUSSION This prospective clinical trial will provide clinical data for evaluating the efficacy and safety of proton FLASH for palliation of bony metastases in the thorax. Positive findings will support the further exploration of FLASH radiation for other clinical indications including patient populations treated with curative intent. REGISTRATION ClinicalTrials.gov NCT05524064.
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Affiliation(s)
- E C Daugherty
- Department of Radiation Oncology, University of Cincinnati, Cincinnati, OH, USA
| | - Y Zhang
- Department of Radiation Oncology, University of Cincinnati, Cincinnati, OH, USA
- Cancer and Blood Disease Institute , Cincinnati Children's Hospital , Cincinnati, OH, USA
| | - Z Xiao
- Department of Radiation Oncology, University of Cincinnati, Cincinnati, OH, USA
- Cancer and Blood Disease Institute , Cincinnati Children's Hospital , Cincinnati, OH, USA
| | - A E Mascia
- Department of Radiation Oncology, University of Cincinnati, Cincinnati, OH, USA
- Cancer and Blood Disease Institute , Cincinnati Children's Hospital , Cincinnati, OH, USA
| | - M Sertorio
- Department of Radiation Oncology, University of Cincinnati, Cincinnati, OH, USA
| | - J Woo
- Varian, a Siemens Healthineers Company, Palo Alto, USA
| | - C McCann
- Varian, a Siemens Healthineers Company, Palo Alto, USA
| | - K J Russell
- Varian, a Siemens Healthineers Company, Palo Alto, USA
| | - R A Sharma
- Varian, a Siemens Healthineers Company, Palo Alto, USA
| | - D Khuntia
- Varian, a Siemens Healthineers Company, Palo Alto, USA
| | - J D Bradley
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, USA
| | - C B Simone
- Department of Radiation Oncology, New York Proton Center , New York, NY, USA
| | - J C Breneman
- Department of Radiation Oncology, University of Cincinnati, Cincinnati, OH, USA
| | - J P Perentesis
- Cancer and Blood Disease Institute , Cincinnati Children's Hospital , Cincinnati, OH, USA.
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Chimote AA, Lehn MA, Bhati J, Mascia AE, Sertorio M, Lamba MA, Ionascu D, Tang AL, Langevin SM, Khodoun MV, Wise-Draper TM, Conforti L. Proton Treatment Suppresses Exosome Production in Head and Neck Squamous Cell Carcinoma. Cancers (Basel) 2024; 16:1008. [PMID: 38473367 PMCID: PMC10931005 DOI: 10.3390/cancers16051008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2024] [Revised: 02/23/2024] [Accepted: 02/26/2024] [Indexed: 03/14/2024] Open
Abstract
Proton therapy (PT) is emerging as an effective and less toxic alternative to conventional X-ray-based photon therapy (XRT) for patients with advanced head and neck squamous cell carcinomas (HNSCCs) owing to its clustered dose deposition dosimetric characteristics. For optimal efficacy, cancer therapies, including PT, must elicit a robust anti-tumor response by effector and cytotoxic immune cells in the tumor microenvironment (TME). While tumor-derived exosomes contribute to immune cell suppression in the TME, information on the effects of PT on exosomes and anti-tumor immune responses in HNSCC is not known. In this study, we generated primary HNSCC cells from tumors resected from HNSCC patients, irradiated them with 5 Gy PT or XRT, and isolated exosomes from cell culture supernatants. HNSCC cells exposed to PT produced 75% fewer exosomes than XRT- and non-irradiated HNSCC cells. This effect persisted in proton-irradiated cells for up to five days. Furthermore, we observed that exosomes from proton-irradiated cells were identical in morphology and immunosuppressive effects (suppression of IFN-γ release by peripheral blood mononuclear cells) to those of photon-irradiated cells. Our results suggest that PT limits the suppressive effect of exosomes on cancer immune surveillance by reducing the production of exosomes that can inhibit immune cell function.
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Affiliation(s)
- Ameet A. Chimote
- Division of Nephrology, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45267, USA; (A.A.C.); (J.B.)
| | - Maria A. Lehn
- Division of Hematology-Oncology, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45267, USA; (M.A.L.); (T.M.W.-D.)
| | - Jay Bhati
- Division of Nephrology, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45267, USA; (A.A.C.); (J.B.)
| | - Anthony E. Mascia
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA; (A.E.M.); (M.S.); (M.A.L.); (D.I.)
| | - Mathieu Sertorio
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA; (A.E.M.); (M.S.); (M.A.L.); (D.I.)
| | - Michael A. Lamba
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA; (A.E.M.); (M.S.); (M.A.L.); (D.I.)
| | - Dan Ionascu
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA; (A.E.M.); (M.S.); (M.A.L.); (D.I.)
| | - Alice L. Tang
- Department of Otolarynogology, Head and Neck Surgery, University of Cincinnati College of Medicine, Cincinnati, OH 45267, USA;
| | - Scott M. Langevin
- Larner College of Medicine, University of Vermont, Burlington, VT 05405, USA;
- University of Vermont Cancer Center, Burlington, VT 05405, USA
| | - Marat V. Khodoun
- Division of Rheumatology, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45267, USA;
- Division of Immunobiology, Cincinnati Children’s Hospital Medical Center, Cincinnati, OH 45229, USA
| | - Trisha M. Wise-Draper
- Division of Hematology-Oncology, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45267, USA; (M.A.L.); (T.M.W.-D.)
| | - Laura Conforti
- Division of Nephrology, Department of Internal Medicine, University of Cincinnati, Cincinnati, OH 45267, USA; (A.A.C.); (J.B.)
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MacDonald T, Sackett JJ, Gaskill-Shipley M, Rao R, Chaudhary R, Curry R, Forbes J, Andaluz N, Zuccarello M, Yogendran L, Sengupta S, Struve Iii TD, Vatner RE, Pater LE, Mascia AE, Breneman JC, Wang K. Neurologic Events and Outcomes in Patients Receiving Proton and Photon Reirradiation for High Grade Non-Codeleted Gliomas. Int J Radiat Oncol Biol Phys 2023; 117:e133-e134. [PMID: 37784697 DOI: 10.1016/j.ijrobp.2023.06.936] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/04/2023]
Abstract
PURPOSE/OBJECTIVE(S) Patients undergoing reirradiation (ReRT) for high grade glioma are at risk for tumor progression, pseudoprogression, and radiation necrosis. We investigated factors associated with neurologic events and disease control after re-irradiation with protons and photons at a single academic center. MATERIALS/METHODS We reviewed records and MRIs of patients receiving scanning beam proton (since center opening in 2016) and photon (since 2015) reirradiation in ≥10 fractions for grade 3 anaplastic astrocytoma (AA) and grade 4 glioblastoma (GBM), excluding 1p19q co-deleted oligodendrogliomas and extensive multifocal/leptomeningeal disease. The primary endpoint was time from ReRT to ≥ grade 2 pseudoprogression or radiation necrosis (PsP/RN, grade 2: moderate symptoms requiring outpatient steroids/bevacizumab, grade 3: severe symptoms leading to admission or surgical intervention). Dose was converted to EQD2 using a/b = 3. Cox proportional hazards model was used to calculate survival and time to PsP/RN. RESULTS A total of 53 patients were included (26 protons, 27 photons, median KPS 80). Patients receiving protons had more favorable features. Compared to the photons, the proton group was younger (48 vs. 58) and more likely to have AA (46% vs. 22%) and resection within 3 months (42% vs 26%). The proton group also had a longer interval from prior RT (57 vs. 39 months) and were less likely to receive bevacizumab at reRT (15% vs. 59%). CTV was 130 cc for protons vs 99 cc for photons, and most had active disease at time of ReRT identified on planning MRI (76% protons, 85% photons). Median OS was 10.5 months (14.1 months protons, 8.1 months photons), with time from initial RT the only significant factor on multivariate analysis. Median PFS was 9.4 months (9.8 months protons, 6.2 months photons). 9 patients (18%) had ≥ grade 3 PsP/RN (8 proton, 1 photon) and 21 patients (41%) had ≥ grade 2 PsP/RN (16 proton, 5 photon). Grade 3 events included 1 seizure (photon group), 1 hemorrhage, 1 thalamic stroke, 1 shunt placement, 1 re-resection, and PSP4 4 PsP/RN requiring admission. Protons were associated shorter time to ≥ grade 2 PsP/RN (4 months vs. not reached, p = 0.027). When accounting for bevacizumab use at time of reRT, the association between protons and PsP/RN lost significance but there remained a trend (grade 2, p = 0.095, HR 2.4; grade 3, p = 0.105, HR 5.8). CTV, MGMT status, EQD2, and interval from prior RT were not associated with PsP/RN. CONCLUSION High grade neurologic events were common in patients with predominantly active, unresected high grade gliomas receiving ReRT. Though ascertainment and survival bias are significant limitations, pseudoprogression and necrosis appeared to be more prominent in patients receiving protons. These results contribute to ongoing efforts to both optimize ReRT for high grade glioma and investigate biologic effects of proton therapy.
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Affiliation(s)
- T MacDonald
- Department of Radiation Oncology, University of Cincinnati, Cincinnati, OH
| | - J J Sackett
- Department of Radiation Oncology, University of Cincinnati, Cincinnati, OH
| | | | - R Rao
- Cincinnati Children's Hospital Medical Center, Cincinnati, OH
| | - R Chaudhary
- Division of Oncology, University of Cincinnati, Cincinnati, OH
| | - R Curry
- CTI Clinical Trial and Consulting Services, Covington, KY
| | - J Forbes
- Department of Neurosurgery, University of Cincinnati, Cincinnati, OH
| | - N Andaluz
- Department of Neurosurgery, University of Cincinnati, Cincinnati, OH
| | - M Zuccarello
- Department of Neurosurgery, University of Cincinnati, Cincinnati, OH
| | - L Yogendran
- Department of Neurology, University of Cincinnati, Cincinnati, OH
| | - S Sengupta
- Department of Neurology, University of Cincinnati, Cincinnati, OH
| | - T D Struve Iii
- Department of Radiation Oncology, University of Cincinnati, Cincinnati, OH
| | - R E Vatner
- Department of Radiation Oncology, University of Cincinnati, Cincinnati, OH
| | - L E Pater
- Department of Radiation Oncology, University of Cincinnati, Cincinnati, OH
| | - A E Mascia
- Department of Radiation Oncology, University of Cincinnati, Cincinnati, OH
| | - J C Breneman
- Department of Radiation Oncology, University of Cincinnati, Cincinnati, OH
| | - K Wang
- Department of Radiation Oncology, University of Cincinnati, Cincinnati, OH
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Zou W, Zhang R, Schüler E, Taylor PA, Mascia AE, Diffenderfer ES, Zhao T, Ayan AS, Sharma M, Yu SJ, Lu W, Bosch WR, Tsien C, Surucu M, Pollard-Larkin JM, Schuemann J, Moros EG, Bazalova-Carter M, Gladstone DJ, Li H, Simone CB, Petersson K, Kry SF, Maity A, Loo BW, Dong L, Maxim PG, Xiao Y, Buchsbaum JC. Framework for Quality Assurance of Ultrahigh Dose Rate Clinical Trials Investigating FLASH Effects and Current Technology Gaps. Int J Radiat Oncol Biol Phys 2023; 116:1202-1217. [PMID: 37121362 PMCID: PMC10526970 DOI: 10.1016/j.ijrobp.2023.04.018] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2023] [Revised: 03/28/2023] [Accepted: 04/17/2023] [Indexed: 05/02/2023]
Abstract
FLASH radiation therapy (FLASH-RT), delivered with ultrahigh dose rate (UHDR), may allow patients to be treated with less normal tissue toxicity for a given tumor dose compared with currently used conventional dose rate. Clinical trials are being carried out and are needed to test whether this improved therapeutic ratio can be achieved clinically. During the clinical trials, quality assurance and credentialing of equipment and participating sites, particularly pertaining to UHDR-specific aspects, will be crucial for the validity of the outcomes of such trials. This report represents an initial framework proposed by the NRG Oncology Center for Innovation in Radiation Oncology FLASH working group on quality assurance of potential UHDR clinical trials and reviews current technology gaps to overcome. An important but separate consideration is the appropriate design of trials to most effectively answer clinical and scientific questions about FLASH. This paper begins with an overview of UHDR RT delivery methods. UHDR beam delivery parameters are then covered, with a focus on electron and proton modalities. The definition and control of safe UHDR beam delivery and current and needed dosimetry technologies are reviewed and discussed. System and site credentialing for large, multi-institution trials are reviewed. Quality assurance is then discussed, and new requirements are presented for treatment system standard analysis, patient positioning, and treatment planning. The tables and figures in this paper are meant to serve as reference points as we move toward FLASH-RT clinical trial performance. Some major questions regarding FLASH-RT are discussed, and next steps in this field are proposed. FLASH-RT has potential but is associated with significant risks and complexities. We need to redefine optimization to focus not only on the dose but also on the dose rate in a manner that is robust and understandable and that can be prescribed, validated, and confirmed in real time. Robust patient safety systems and access to treatment data will be critical as FLASH-RT moves into the clinical trials.
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Affiliation(s)
- Wei Zou
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, USA.
| | - Rongxiao Zhang
- Department of Radiation Oncology, Geisel School of Medicine, Dartmouth College, Hanover, NH, USA
| | - Emil Schüler
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Paige A Taylor
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | | | - Eric S Diffenderfer
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, USA
| | - Tianyu Zhao
- Department of Radiation Oncology, Washington University, St. Louis, MO, USA
| | - Ahmet S Ayan
- Department of Radiation Oncology, Ohio State University, Columbus, OH, USA
| | - Manju Sharma
- Department of Radiation Oncology, University of California San Francisco, San Francisco, CA, USA
| | - Shu-Jung Yu
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, USA
| | - Weiguo Lu
- Department of Radiation Oncology, University of Texas Southwestern, Dallas, TX, USA
| | - Walter R Bosch
- Department of Radiation Oncology, Washington University, St. Louis, MO, USA
| | - Christina Tsien
- Department of Radiation Oncology, McGill University Health Center, Montreal, QC, Canada
| | - Murat Surucu
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, USA
| | - Julianne M Pollard-Larkin
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Jan Schuemann
- Department of Radiation Oncology, Massachusetts General Hospital and Harvard Medical School, Boston, MA, USA
| | - Eduardo G Moros
- Department of Radiation Oncology, Moffitt Cancer Center, Tampa, FL, USA
| | | | - David J Gladstone
- Department of Radiation Oncology, Geisel School of Medicine, Dartmouth College, Hanover, NH, USA
| | - Heng Li
- Department of Radiation Oncology, Johns Hopkins University, Baltimore, MD, USA
| | - Charles B Simone
- Department of Radiation Oncology, New York Proton Center, New York, NY, USA
| | - Kristoffer Petersson
- Department of Radiation Oncology, MRC Oxford Institute for Radiation Oncology, University of Oxford, Oxford, UK
| | - Stephen F Kry
- Department of Radiation Physics, The University of Texas MD Anderson Cancer Center, Houston, TX, USA
| | - Amit Maity
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, USA
| | - Billy W Loo
- Department of Radiation Oncology, Stanford University School of Medicine, Stanford, CA, USA
| | - Lei Dong
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, USA
| | - Peter G Maxim
- Department of Radiation Oncology, University of California Irvine, Irvine, CA, USA
| | - Ying Xiao
- Department of Radiation Oncology, University of Pennsylvania, Philadelphia, PA, USA
| | - Jeffrey C Buchsbaum
- Radiation Research Program, Division of Cancer Treatment and Diagnosis, National Cancer Institute, National Institute of Health, Bethesda, MD, USA
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Nelson B, Meier T, Zhang Y, Wang K, Mascia AE, Paquette I, Thompson E, Rafferty J, Snyder J, Olowokure O, Sohal D, Kharofa J. Feasibility Trial of Intensity Modulated Proton Therapy to Reduce Toxicity in Anal Cancer Patients. Am J Clin Oncol 2023; 46:293-299. [PMID: 37088904 DOI: 10.1097/coc.0000000000001007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/25/2023]
Abstract
PURPOSE The purpose of this trial was to assess the patient and physician-reported toxicity in anal cancer patients undergoing definitive chemoradiation with intensity-modulated proton therapy (IMPT). METHODS Patients with stage II and III anal cancer were treated with IMPT. All patients received 2 cycles of 5-fluorouracil and mitomycin concurrently with radiation. Toxicity was assessed at baseline, weekly during chemoradiation, and in follow-up using physician-graded common terminology criteria for adverse events (CTCAE) v 4.0 and PRO-CTCAE. The primary endpoint was to define point estimates and 95% CI for acute ≥ grade 2/3 gastrointestinal (GI), genitourinary (GU), dermatologic, and hematologic toxicity. The proportion of PRO-CTCAE questions scored ≥3 for each domain was compared with the baselinse. The proportion of ≥ grade 2 and ≥ grade 3 toxicities were compared with historic intensity-modulated radiotherapy patients treated on RTOG 0529. RESULTS Fourteen patients were enrolled from 2017 to 2020. Rates of physician-reported GI, GU, dermatologic, and hematologic toxicity were not significantly different between patients treated with IMPT compared with patients treated with intensity-modulated radiotherapy. Rates of patient-reported dermatologic and GU toxicity were low at baseline with a peak at week 6 (91% and 58% PRO-CTCAE items ≥ grade 3, respectively) and normalization to baseline 3 months after IMPT. In contrast, the proportion of high-grade PRO-CTCAE GI scores was 40% at baseline, which persisted through 1-year posttreatment. CONCLUSIONS Clinician-reported toxicity was not improved with IMPT in the context of this underpowered trial. High-grade GI symptoms persisted for 12 months and were similar to baseline. Additional measures are needed to minimize acute and chronic toxicity related to chemoradiation.
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Affiliation(s)
| | | | - Yin Zhang
- Division of Biostatistics and Epidemiology, Cincinnati Children's Hospital Medical Center, Cincinnati, OH
| | | | | | | | | | | | | | | | - Davendra Sohal
- Department of Hematology Oncology, University of Cincinnati
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Mascia AE, Daugherty EC, Breneman JC. FLASH Radiotherapy in a Value-Based Health Care Environment-Reply. JAMA Oncol 2023; 9:727. [PMID: 36951830 DOI: 10.1001/jamaoncol.2023.0134] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/24/2023]
Affiliation(s)
- Anthony E Mascia
- Cancer and Blood Diseases Institute, Cincinnati Children's Hospital, Cincinnati, Ohio
- College of Medicine, Department of Radiation Oncology, University of Cincinnati, Cincinnati, Ohio
| | - Emily C Daugherty
- Cancer and Blood Diseases Institute, Cincinnati Children's Hospital, Cincinnati, Ohio
- College of Medicine, Department of Radiation Oncology, University of Cincinnati, Cincinnati, Ohio
| | - John C Breneman
- Cancer and Blood Diseases Institute, Cincinnati Children's Hospital, Cincinnati, Ohio
- College of Medicine, Department of Radiation Oncology, University of Cincinnati, Cincinnati, Ohio
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Mascia AE, Daugherty EC, Zhang Y, Lee E, Xiao Z, Sertorio M, Woo J, Backus LR, McDonald JM, McCann C, Russell K, Levine L, Sharma RA, Khuntia D, Bradley JD, Simone CB, Perentesis JP, Breneman JC. Proton FLASH Radiotherapy for the Treatment of Symptomatic Bone Metastases: The FAST-01 Nonrandomized Trial. JAMA Oncol 2023; 9:62-69. [PMID: 36273324 PMCID: PMC9589460 DOI: 10.1001/jamaoncol.2022.5843] [Citation(s) in RCA: 62] [Impact Index Per Article: 62.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2022] [Accepted: 09/26/2022] [Indexed: 01/24/2023]
Abstract
Importance To our knowledge, there have been no clinical trials of ultra-high-dose-rate radiotherapy delivered at more than 40 Gy/sec, known as FLASH therapy, nor first-in-human use of proton FLASH. Objectives To assess the clinical workflow feasibility and treatment-related toxic effects of FLASH and pain relief at the treatment sites. Design, Setting, and Participants In the FAST-01 nonrandomized trial, participants treated at Cincinnati Children's/UC Health Proton Therapy Center underwent palliative FLASH radiotherapy to extremity bone metastases. Patients 18 years and older with 1 to 3 painful extremity bone metastases and life expectancies of 2 months or more were eligible. Patients were excluded if they had foot, hand, and wrist metastases; metastases locally treated in the 2 weeks prior; metal implants in the treatment field; known enhanced tissue radiosensitivity; and implanted devices at risk of malfunction with radiotherapy. One of 11 patients who consented was excluded based on eligibility. The end points were evaluated at 3 months posttreatment, and patients were followed up through death or loss to follow-up for toxic effects and pain assessments. Of the 10 included patients, 2 died after the 2-month follow-up but before the 3-month follow-up; 8 participants completed the 3-month evaluation. Data were collected from November 3, 2020, to January 28, 2022, and analyzed from January 28, 2022, to September 1, 2022. Interventions Bone metastases were treated on a FLASH-enabled (≥40 Gy/sec) proton radiotherapy system using a single-transmission proton beam. This is consistent with standard of care using the same prescription (8 Gy in a single fraction) but on a conventional-dose-rate (approximately 0.03 Gy/sec) photon radiotherapy system. Main Outcome and Measures Main outcomes included patient time on the treatment couch, device-related treatment delays, adverse events related to FLASH, patient-reported pain scores, and analgesic use. Results A total of 10 patients (age range, 27-81 years [median age, 63 years]; 5 [50%] male) underwent FLASH radiotherapy at 12 metastatic sites. There were no FLASH-related technical issues or delays. The average (range) time on the treatment couch was 18.9 (11-33) minutes per patient and 15.8 (11-22) minutes per treatment site. Median (range) follow-up was 4.8 (2.3-13.0) months. Adverse events were mild and consistent with conventional radiotherapy. Transient pain flares occurred in 4 of the 12 treated sites (33%). In 8 of the 12 sites (67%) patients reported pain relief, and in 6 of the 12 sites (50%) patients reported a complete response (no pain). Conclusions and Relevance In this nonrandomized trial, clinical workflow metrics, treatment efficacy, and safety data demonstrated that ultra-high-dose-rate proton FLASH radiotherapy was clinically feasible. The treatment efficacy and the profile of adverse events were comparable with those of standard-of-care radiotherapy. These findings support the further exploration of FLASH radiotherapy in patients with cancer. Trial Registration ClinicalTrials.gov Identifier: NCT04592887.
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Affiliation(s)
- Anthony E. Mascia
- Cancer and Blood Diseases Institute, Cincinnati Children’s Hospital, Cincinnati, Ohio
- Department of Radiation Oncology, College of Medicine, University of Cincinnati, Cincinnati, Ohio
| | - Emily C. Daugherty
- Cancer and Blood Diseases Institute, Cincinnati Children’s Hospital, Cincinnati, Ohio
- Department of Radiation Oncology, College of Medicine, University of Cincinnati, Cincinnati, Ohio
| | - Yongbin Zhang
- Cancer and Blood Diseases Institute, Cincinnati Children’s Hospital, Cincinnati, Ohio
- Department of Radiation Oncology, College of Medicine, University of Cincinnati, Cincinnati, Ohio
| | - Eunsin Lee
- Cancer and Blood Diseases Institute, Cincinnati Children’s Hospital, Cincinnati, Ohio
- Department of Radiation Oncology, College of Medicine, University of Cincinnati, Cincinnati, Ohio
| | - Zhiyan Xiao
- Cancer and Blood Diseases Institute, Cincinnati Children’s Hospital, Cincinnati, Ohio
- Department of Radiation Oncology, College of Medicine, University of Cincinnati, Cincinnati, Ohio
| | - Mathieu Sertorio
- Department of Radiation Oncology, College of Medicine, University of Cincinnati, Cincinnati, Ohio
| | - Jennifer Woo
- Varian Medical Systems, Siemens Healthineers, Palo Alto, California
| | - Lori R. Backus
- Cancer and Blood Diseases Institute, Cincinnati Children’s Hospital, Cincinnati, Ohio
| | - Julie M. McDonald
- Cancer and Blood Diseases Institute, Cincinnati Children’s Hospital, Cincinnati, Ohio
| | - Claire McCann
- Varian Medical Systems, Siemens Healthineers, Palo Alto, California
| | - Kenneth Russell
- Varian Medical Systems, Siemens Healthineers, Palo Alto, California
| | - Lisa Levine
- Varian Medical Systems, Siemens Healthineers, Palo Alto, California
| | - Ricky A. Sharma
- Varian Medical Systems, Siemens Healthineers, Palo Alto, California
| | - Dee Khuntia
- Varian Medical Systems, Siemens Healthineers, Palo Alto, California
| | - Jeffrey D. Bradley
- Department of Radiation Oncology, Emory University School of Medicine, Atlanta, Georgia
| | - Charles B. Simone
- Department of Radiation Oncology, New York Proton Center, New York, New York
| | - John P. Perentesis
- Cancer and Blood Diseases Institute, Cincinnati Children’s Hospital, Cincinnati, Ohio
| | - John C. Breneman
- Cancer and Blood Diseases Institute, Cincinnati Children’s Hospital, Cincinnati, Ohio
- Department of Radiation Oncology, College of Medicine, University of Cincinnati, Cincinnati, Ohio
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8
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Williams MT, Sugimoto C, Regan SL, Pitzer EM, Fritz AL, Sertorio M, Mascia AE, Vatner RE, Perentesis JP, Vorhees CV. Cognitive and behavioral effects of whole brain conventional or high dose rate (FLASH) proton irradiation in a neonatal Sprague Dawley rat model. PLoS One 2022; 17:e0274007. [PMID: 36112695 PMCID: PMC9481014 DOI: 10.1371/journal.pone.0274007] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 08/22/2022] [Indexed: 11/18/2022] Open
Abstract
Recent studies suggest that ultra-high dose rates of proton radiation (>40 Gy/s; FLASH) confer less toxicity to exposed healthy tissue and reduce cognitive decline compared with conventional radiation dose rates (~1 Gy/s), but further preclinical data are required to demonstrate this sparing effect. In this study, postnatal day 11 (P11) rats were treated with whole brain irradiation with protons at a total dose of 0, 5, or 8 Gy, comparing a conventional dose rate of 1 Gy/s vs. a FLASH dose rate of 100 Gy/s. Beginning on P64, rats were tested for locomotor activity, acoustic and tactile startle responses (ASR, TSR) with or without prepulses, novel object recognition (NOR; 4-object version), striatal dependent egocentric learning ([configuration A] Cincinnati water maze (CWM-A)), prefrontal dependent working memory (radial water maze (RWM)), hippocampal dependent spatial learning (Morris water maze (MWM)), amygdala dependent conditioned freezing, and the mirror image CWM [configuration B (CWM-B)]. All groups had deficits in the CWM-A procedure. Weight reductions, decreased center ambulation in the open-field, increased latency on day-1 of RWM, and deficits in CWM-B were observed in all irradiated groups, except the 5 Gy FLASH group. ASR and TSR were reduced in the 8 Gy FLASH group and day-2 latencies in the RWM were increased in the FLASH groups compared with controls. There were no effects on prepulse trials of ASR or TSR, NOR, MWM, or conditioned freezing. The results suggest striatal and prefrontal cortex are sensitive regions at P11 to proton irradiation, with reduced toxicity from FLASH at 5 Gy.
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Affiliation(s)
- Michael T. Williams
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Division of Neurology, Cincinnati Children’s Research Foundation, Cincinnati, OH, United States of America
- Cincinnati Children’s/University of Cincinnati Proton Therapy and Research Center, Cincinnati, OH, United States of America
- * E-mail:
| | - Chiho Sugimoto
- Division of Neurology, Cincinnati Children’s Research Foundation, Cincinnati, OH, United States of America
| | - Samantha L. Regan
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Division of Neurology, Cincinnati Children’s Research Foundation, Cincinnati, OH, United States of America
| | - Emily M. Pitzer
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Division of Neurology, Cincinnati Children’s Research Foundation, Cincinnati, OH, United States of America
| | - Adam L. Fritz
- Division of Neurology, Cincinnati Children’s Research Foundation, Cincinnati, OH, United States of America
| | - Mathieu Sertorio
- Cincinnati Children’s/University of Cincinnati Proton Therapy and Research Center, Cincinnati, OH, United States of America
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
| | - Anthony E. Mascia
- Cincinnati Children’s/University of Cincinnati Proton Therapy and Research Center, Cincinnati, OH, United States of America
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
| | - Ralph E. Vatner
- Cincinnati Children’s/University of Cincinnati Proton Therapy and Research Center, Cincinnati, OH, United States of America
- Department of Radiation Oncology, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
| | - John P. Perentesis
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Cincinnati Children’s/University of Cincinnati Proton Therapy and Research Center, Cincinnati, OH, United States of America
- Division of Oncology, Cincinnati Children’s Research Foundation, Cincinnati, OH, United States of America
| | - Charles V. Vorhees
- Department of Pediatrics, University of Cincinnati College of Medicine, Cincinnati, OH, United States of America
- Division of Neurology, Cincinnati Children’s Research Foundation, Cincinnati, OH, United States of America
- Cincinnati Children’s/University of Cincinnati Proton Therapy and Research Center, Cincinnati, OH, United States of America
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9
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Hua CH, Mascia AE, Servalli E, Lomax AJ, Seiersen K, Ulin K. Advances in radiotherapy technology for pediatric cancer patients and roles of medical physicists: COG and SIOP Europe perspectives. Pediatr Blood Cancer 2021; 68 Suppl 2:e28344. [PMID: 33818892 PMCID: PMC8030241 DOI: 10.1002/pbc.28344] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/30/2020] [Revised: 03/27/2020] [Accepted: 04/02/2020] [Indexed: 11/11/2022]
Abstract
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.
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Affiliation(s)
- Chia-ho Hua
- Department of Radiation Oncology, St. Jude Children’s Research Hospital, Memphis, Tennessee, USA
| | - Anthony E. Mascia
- Department of Radiation Oncology, University of Cincinnati, Cincinnati, Ohio, USA
| | - Enrica Servalli
- Department of Radiotherapy, University Medical Center Utrecht, The Netherlands
| | - Antony J. Lomax
- Center for Proton Therapy, Paul Scherrer Institute, PSI Villigen, Switzerland
| | | | - Kenneth Ulin
- Department of Radiation Oncology, University of Massachusetts, Worcester, Massachusetts, USA
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10
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Sertorio M, Perentesis JP, Vatner RE, Mascia AE, Zheng Y, Wells SI. Cancer Cell Metabolism: Implications for X-ray and Particle Radiation Therapy. Int J Part Ther 2018; 5:40-48. [PMID: 31773019 DOI: 10.14338/ijpt-18-00023.1] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2018] [Accepted: 06/21/2018] [Indexed: 01/13/2023] Open
Abstract
Advances in radiation delivery technologies and immunotherapy have improved effective cancer treatments and long-term outcomes. Experimental and clinical trials have demonstrated the benefit of a combination of radiation therapy and immunotherapy for tumor eradication. Despite precise radiation dose delivery that is achievable by particle therapy and benefits from reactivating the antitumor immune response, resistance to both therapeutic strategies is frequently observed in patients. Understanding the biological origins of such resistance will create new opportunities for improved cancer treatment. Cancer metabolism and especially a high rate of aerobic glycolysis leading to overproduction and release of lactate is one such biological process favoring tumor progression and treatment resistance. Because of their known protumor effects, aerobic glycolysis and lactate production are potential targets for increased efficacy of radiation alone or in combination with immunotherapy. In the following review, we present an overview of the interplay of cancer cell lactate metabolism with the tumor microenvironment and immune cells. We discuss how a deeper understanding and careful modulation of lactate metabolism and radiation therapy might exploit this interplay for improved therapeutic outcome.
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Affiliation(s)
- Mathieu Sertorio
- Cancer and Blood Diseases Institute, Cincinnati Children's Hospital, Cincinnati, OH, USA
| | - John P Perentesis
- Cancer and Blood Diseases Institute, Cincinnati Children's Hospital, Cincinnati, OH, USA
| | - Ralph E Vatner
- Division of Immunobiology, Cincinnati Children's Hospital, OH, USA.,Department of Radiation Oncology, University of Cincinnati, Cincinnati, OH, USA
| | - Anthony E Mascia
- Department of Radiation Oncology, University of Cincinnati, Cincinnati, OH, USA
| | - Yi Zheng
- Cancer and Blood Diseases Institute, Cincinnati Children's Hospital, Cincinnati, OH, USA
| | - Susanne I Wells
- Cancer and Blood Diseases Institute, Cincinnati Children's Hospital, Cincinnati, OH, USA
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11
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Farr JB, O'Ryan-Blair A, Jesseph F, Hsi WC, Allgower CE, Mascia AE, Thornton AF, Schreuder AN. Validation of dosimetric field matching accuracy from proton therapy using a robotic patient positioning system. J Appl Clin Med Phys 2010; 11:3015. [PMID: 20592691 PMCID: PMC5719946 DOI: 10.1120/jacmp.v11i2.3015] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2009] [Accepted: 11/30/2009] [Indexed: 11/23/2022] Open
Abstract
Large area, shallow fields are well suited to proton therapy. However, due to beam production limitations, such volumes typically require multiple matched fields. This is problematic due to the relatively narrow beam penumbra at shallow depths compared to electron and photon beams. Therefore, highly accurate dose planning and delivery is required. As the dose delivery includes shifting the patient for matched fields, accuracy at the 1-2 millimeter level in patient positioning is also required. This study investigates the dosimetric accuracy of such proton field matching by an innovative robotic patient positioner system (RPPS). The dosimetric comparisons were made between treatment planning system calculations, radiographic film and ionization chamber measurements. The results indicated good agreement amongst the methods and suggest that proton field matching by a RPPS is accurate and efficient.
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Affiliation(s)
- Jonathan B Farr
- Midwest Proton Radiotherapy Institute, 2425 Milo B. Sampson Lane, Bloomington, Indiana USA.
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12
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Hsi WC, Moyers MF, Nichiporov D, Anferov V, Wolanski M, Allgower CE, Farr JB, Mascia AE, Schreuder AN. Energy spectrum control for modulated proton beams. Med Phys 2009; 36:2297-308. [PMID: 19610318 DOI: 10.1118/1.3132422] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
In proton therapy delivered with range modulated beams, the energy spectrum of protons entering the delivery nozzle can affect the dose uniformity within the target region and the dose gradient around its periphery. For a cyclotron with a fixed extraction energy, a rangeshifter is used to change the energy but this produces increasing energy spreads for decreasing energies. This study investigated the magnitude of the effects of different energy spreads on dose uniformity and distal edge dose gradient and determined the limits for controlling the incident spectrum. A multilayer Faraday cup (MLFC) was calibrated against depth dose curves measured in water for nonmodulated beams with various incident spectra. Depth dose curves were measured in a water phantom and in a multilayer ionization chamber detector for modulated beams using different incident energy spreads. Some nozzle entrance energy spectra can produce unacceptable dose nonuniformities of up to +/-21% over the modulated region. For modulated beams and small beam ranges, the width of the distal penumbra can vary by a factor of 2.5. When the energy spread was controlled within the defined limits, the dose nonuniformity was less than +/-3%. To facilitate understanding of the results, the data were compared to the measured and Monte Carlo calculated data from a variable extraction energy synchrotron which has a narrow spectrum for all energies. Dose uniformity is only maintained within prescription limits when the energy spread is controlled. At low energies, a large spread can be beneficial for extending the energy range at which a single range modulator device can be used. An MLFC can be used as part of a feedback to provide specified energy spreads for different energies.
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Affiliation(s)
- Wen C Hsi
- Midwest Proton Radiotherapy Institute, Bloomington, Indiana 47408 and University Florida Proton Therapy Institute, Jacksonville, Florida 32206, USA.
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13
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Hsi WC, Schreuder AN, Moyers MF, Allgower CE, Farr JB, Mascia AE. Range and modulation dependencies for proton beam dose per monitor unit calculations. Med Phys 2009; 36:634-41. [PMID: 19292004 DOI: 10.1118/1.3056466] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Calculations of dose per monitor unit (D/MU) are required in addition to measurements to increase patient safety in the clinical practice of proton radiotherapy. As in conventional photon and electron therapy, the D/MU depends on several factors. This study focused on obtaining range and modulation dependence factors used in D/MU calculations for the double scattered proton beam line at the Midwest Proton Radiotherapy Institute. Three dependencies on range and one dependency on modulation were found. A carefully selected set of measurements was performed to discern these individual dependencies. Dependencies on range were due to: (1) the stopping power of the protons passing through the monitor chamber; (2) the reduction of proton fluence due to nuclear interactions within the patient; and (3) the variation of proton fluence passing through the monitor chamber due to different source-to-axis distances (SADs) for different beam ranges. Different SADs are produced by reconfigurations of beamline elements to provide different field sizes and ranges. The SAD effect on the D/MU varies smoothly as the beam range is varied, except at the beam range for which the first scatterers are exchanged and relocated to accommodate low and high beam ranges. A geometry factor was devised to model the SAD variation effect on the D/MU. The measured D/MU variation as a function of range can be predicted within 1% using the three modeled dependencies on range. Investigation of modulated beams showed that an analytical formula can predict the D/MU dependency as a function of modulation to within 1.5%. Special attention must be applied when measuring the D/MU dependence on modulation to avoid interplay between range and SAD effects.
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Affiliation(s)
- Wen C Hsi
- Midwest Proton Radiotherapy Institute, Bloomington, Indiana 47408, USA.
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14
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Farr JB, Mascia AE, Hsi WC, Allgower CE, Jesseph F, Schreuder AN, Wolanski M, Nichiporov DF, Anferov V. Clinical characterization of a proton beam continuous uniform scanning system with dose layer stacking. Med Phys 2009; 35:4945-54. [PMID: 19070228 DOI: 10.1118/1.2982248] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
A proton beam delivery system on a gantry with continuous uniform scanning and dose layer stacking at the Midwest Proton Radiotherapy Institute has been commissioned and accepted for clinical use. This paper was motivated by a lack of guidance on the testing and characterization for clinical uniform scanning systems. As such, it describes how these tasks were performed with a uniform scanning beam delivery system. This paper reports the methods used and important dosimetric characteristics of radiation fields produced by the system. The commissioning data include the transverse and longitudinal dose distributions, penumbra, and absolute dose values. Using a 208 MeV cyclotron's proton beam, the system provides field sizes up to 20 and 30 cm in diameter for proton ranges in water up to 27 and 20 cm, respectively. The dose layer stacking method allows for the flexible construction of spread-out Bragg peaks with uniform modulation of up to 15 cm in water, at typical dose rates of 1-3 Gy/min. For measuring relative dose distributions, multielement ion chamber arrays, small-volume ion chambers, and radiographic films were employed. Measurements during the clinical commissioning of the system have shown that the lateral and longitudinal dose uniformity of 2.5% or better can be achieved for all clinically important field sizes and ranges. The measured transverse penumbra widths offer a slight improvement in comparison to those achieved with a double scattering beam spreading technique at the facility. Absolute dose measurements were done using calibrated ion chambers, thermoluminescent and alanine detectors. Dose intercomparisons conducted using various types of detectors traceable to a national standards laboratory indicate that the measured dosimetry data agree with each other within 5%.
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Affiliation(s)
- J B Farr
- Indiana University, Department of Physics, Swain Hall West, Room 117, 727 E. Third St., Bloomington, Indiana 47405, USA.
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15
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Allgower CE, Schreuder AN, Farr JB, Mascia AE. Experiences with an application of industrial robotics for accurate patient positioning in proton radiotherapy. Int J Med Robot 2007; 3:72-81. [PMID: 17441029 DOI: 10.1002/rcs.128] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
BACKGROUND Protons beams deliver targeted radiation doses with greater precision than is possible with electrons or megavoltage X-ray photons, but to retain this advantage, patient positioning systems at proton clinics must meet tighter accuracy requirements. For this and other reasons, robots were incorporated into the treatment room systems at MPRI. METHODS The Midwest Proton Radiotherapy Institute (MPRI) is the first radiotherapy facility in the United States to use commercial robots with six degrees of freedom for patient positioning, rather than a traditional bed with four degrees of freedom. RESULTS This paper outlines the ways in which robots are used at MPRI and attempts to distil insights from the experience of treating over 200 radiotherapy patients with a robotic system from February 2004 to late 2006. CONCLUSIONS The system has performed well, and with great reliability, but there is room for future improvement, especially in ease of use and in reducing the time to get patients into position.
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Affiliation(s)
- C E Allgower
- Medical Physics Department, Midwest Proton Radiotherapy Institute, Bloomington, IN 47408, USA.
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