Proton Beam Therapy Centre Research Articles

PTCOG international survey of practice patterns and trends in utilization of proton therapy for breast cancer

Purpose/objectivesThe indications, techniques, and extent to which proton beam therapy (PBT) is employed for breast cancer are unknown. We seek to determine PBT utilization for breast cancer. Materials/methodsThe Particle Therapy Co-Operative Group (PTCOG) Breast Subcommittee developed an IRB-approved 29-question survey and sent it to breast cancer radiation oncologists at all active PBT centers worldwide in June 2023. Descriptive statistics were used to summarize responses, and comparisons by continent were performed using Fisher’s exact tests. ResultsOf 79 surveys distributed, 28 recipients submitted responses (35 % response rate) representing fifteen U.S., 8 European, and 5 Asian centers (continent response rate 50 %, 38 %, and 18 %, respectively). Overall, 93 % reported treating breast cancer patients with PBT; 13 (50 %) have treated ≥100 breast cancer patients at their center since opening. Most (89 %) have pencil beam scanning technology. Nearly half (46 %) use moderate hypofractionation (15–20 fractions) for regional nodal irradiation and 42 % conventional fractionation (25–30 fractions). More European centers prefer hypofractionation (88 %) vs. Asian (50 %) and U.S. (21 %) centers (p = 0.003). Common patient selection methods were practitioner determination/patient preference (n = 16) and comparative plan evaluation (n = 15). U.S. centers reported the most experience with breast PBT, with 71 % having treated ≥100 breast cancer patients vs. 38 % in Europe and none in Asia (p = 0.001). Of respondent centers, 39 % enrolled ≥75 % of breast PBT patients on a research study. ConclusionUtilization, patient selection methods, and dose-fractionation approaches for breast cancer PBT vary worldwide. These survey data serve as a benchmark from which successor surveys can provide insight on practice pattern evolution.

Clinical Trials Radiographers identifying priority challenges associated with implementing a national programme of clinical trials in the United Kingdom's first proton beam therapy centre.

This article is an evaluation of the current trial processes within a national proton beam therapy (PBT) clinical trial service in the United Kingdom. The work within the article identifies priority challenges associated with the implementation of PBT trials with a view to improving patient trial processes. The nominal group technique (NGT) was used. Five Clinical Trials Radiographers were asked the target question "what are the major challenges when implementing PBT clinical trials and facilitating PBT trial-related activities?" Participants individually and silently listed their challenges to the target question. Following this, group discussion clarified and refined responses. Participants then individually selected five challenges that they deemed most pertinent to the target question, giving a weighted score (out of 10). Individual scores were combined to provide a ranked, weighted order of challenges. Further group discussion identified improvement strategies to the highest scored challenges. After combining lists generated by participants, 59 challenges were identified. Group discussion eliminated 27 responses. Eighteen were merged, resulting in 14 challenges. The two challenges that ranked highest were: (i) lack of initial understanding of the responsibilities of teams and who the relevant stakeholders were, and (ii) that a national PBT service requires the provision of shared care across multi-disciplinary teams and sites. Improvement areas include the development of shared protocols, clarifying stakeholder responsibilities and improving communication between centres to streamline PBT trial processes. This work has identified priority areas requiring development to improve the conduct of a national PBT clinical trials programme. This is the first publication to evaluate current clinical trial processes for the United Kingdom's PBT service.

Working in a UK national proton radiotherapy facility: the therapeutic radiographer perspective

Abstract The first national UK proton beam therapy centre opened at The Christie NHS Foundation Trust in 2018, which alongside University College London Hospitals NHS Foundation Trust (UCLH) proton beam therapy centre, is expected to treat approximately seven-hundred and fifty patients per year at service ramp up. The aim of this editorial is to share with a wider audience the role of a Band 6 proton senior treatment radiographer working in a national NHS service and future developments of the service. Prior to the service being clinical, a range of processes were followed, including the creation of quality documents, departmental training and end-to-end testing, with the first patient receiving treatment in December 2018. Proton senior radiographers are responsible for the delivery of safe and accurate radiotherapy and ensuring a smooth patient pathway, through a multi-collaborative team approach. Although there are key differences between proton and photon radiotherapy, the fundamental aspects, including radiation principles, governance and patient advice are the same. The training package for proton senior radiographers includes an individual local induction as part of the proton education and competency framework, which incorporates practical learning, including clinical supervision and workshops, plus audio-visual presentations and workbooks to complete. Future developments of proton beam therapy include proton arc therapy and flash therapy, alongside educational developments, such as training the future workforce and advanced practice consultant radiographer roles. Shared learning through multi-collaboration of international proton beam therapy centres is crucial to improve care for future service users.

Investigation of the impact of machine operating parameters on beam delivery time and its correlation with treatment plan characteristics for synchrotron-based proton pencil beam spot scanning system.

To investigate the beam delivery time (BDT) reduction due to the improvement of machine parameters for Hitachi synchrotron-based proton PBS system. BDTs for representative treatment plans were calculated to quantitatively estimate the BDT improvement from our 2015 system at Mayo Clinic in Arizona to our system to be implemented in 2025 at Mayo Clinic in Florida, and to a hypothetical future system. To specifically assess how each incremental improvement in the operating parameters reduced the total BDT, for each plan, we simulated the BDT 10,368 times with various settings of the nine different operating parameters. The effect of each operating parameter on BDT reduction and its correlation with treatment plan characteristics were analyzed. The optimal number of multiple energy extraction (MEE) layers per spill for different systems was also investigated. The median (range) decrease in BDT was 60% (56%-70%) from the 2015 to the 2025 system. The following incremental improvement in parameters of the 2015 system for the 2025 system played an important role in this decreased BDT: beam intensity (8 to 20 MU/s), recapture efficiency (50% to 80%), number of MEE layers per spill (4 to 8), scanning magnet preparation and verification time (1.9 to 0.95 msec), and MEE layer switch time (200 to 100 msec). Reducing the total spill change time and scanning magnet preparation and verification time from those of the 2025 system further reduced BDT in the hypothetical future system. 8 MEE layers per spill is optimal for a system with 50% recapture efficiency; 16 MEE layers per spill is optimal for a system with 80% recapture efficiency; and more than 16 MEE layers per spill is beneficial only for a system close to 100% recapture efficiency. We systematically studied the effect of each machine operating parameter on the reduction in total BDT and its correlation with treatment plan characteristics. Our findings will aid new and existing synchrotron-based proton beam therapy centers to make balanced decisions on BDT benefits vs. costs when considering machine upgrade or new system selection.

A Novel Model and Infrastructure for Clinical Outcomes Data Collection and Their Systematic Evaluation for UK Patients Receiving Proton Beam Therapy

AimsTo establish an infrastructure for sustainable, comprehensive data collection and systematic outcomes evaluation for UK patients receiving proton beam therapy (PBT). Materials and methodsA Proton Outcomes Working Group was formed in 2014 to develop a national minimum dataset for PBT patients and to define a clinically integrated informatics solution for data collection. The Christie Proton Beam Therapy Centre formed its Proton Clinical Outcomes Unit in 2018 to collect, curate and analyse outcomes data prospectively for UK-treated patients and retrospectively for UK patients referred abroad for PBT since 2008 via the Proton Overseas Programme (POP). ResultsA single electronic form (eForm) was developed to capture the agreed data, using a data tree approach including conditional logic: data items are requested once, further questions depend on previous answers and are sensitive to tumour site and patient pathway time point. Relevant data automatically populate other forms, saving time, prompting completeness of clinical assessments and ensuring data consistency. Completed eForm data populate the electronic patient record and generate individualised outputs, including consultation letters, treatment summary and surveillance plans, based on organs at risk irradiated, age and sex. All data regarding POP-treated patients are verified and migrated into the system, ensuring that patient data, whether overseas or UK treated, are consistently recorded. The eForm utilises a ‘user friendly’ web portal interface, the Clinical Web Portal, including clickable tables and infographics. Data items are coded to a universally recognised standard comparable with other data systems. Patient-reported outcomes are also integrated, highlighting significant toxicities and prompting a response. Outcomes data can be correlated with dosimetric DICOM data to support radiation dose modelling. ConclusionOutcomes data from both POP-treated and The Christie-treated patients support long-term care, allow evaluation of PBT efficacy and safety, assist future selection of PBT patients and support hypothesis generation for future clinical trials.

Medical Mask Wearing During Treatment for Patients Undergoing Radiotherapy in COVID-19 Pandemic – An Experience of Protocol Setup and Dosimetric Evaluation for Particle/Proton Beam Therapy

BackgroundThe coronavirus disease 2019 (COVID-19) pandemic has caused extreme challenges for the healthcare system. Medical masks have been proven to effectively block disease transmission. Radiotherapeutic departments are at unique risk for disease exposure with the repeated daily treatment schedule. A protocol of mask wearing during daily treatment was established, and the effect of wearing medical masks on dosimetry during proton beam therapy (PBT) was validated.MethodsA department protocol of medical mask wearing was initiated after the COVID-19 pandemic. Medical masks that were made under standardized specification and regulation were obtained for analyses. The physical and dosimetric characteristics of these medical masks were measured by different proton energies using commercialized measurement tools.ResultsPatients and staff were able to adopt the protocol on a weekly basis, and no adverse events were reported. The average physical thickness of a single piece of medical mask was 0.5 mm with a water equivalent thickness (WET) of 0.1 mm.ConclusionOur study revealed that mask wearing for patients undergoing daily radiotherapy is feasible and can provide basic protection for patients and staff. The impact of mask wearing on dosimetry was only 0.1 mm in WET, which has no impact on clinical PBT treatment. A medical mask-wearing policy can be applied safely without dosimetric concerns and should be considered as a standard practice for PBT centers during the COVID-19 pandemic.

US-UK collaboration in Proton therapy: The Proton Overseas Program

In 2008 the National Health Service (NHS) in the United Kingdom (UK) started the Proton Overseas Program (POP). This enabled and still enables eligible UK patients to access high energy Proton Beam Therapy (PBT) overseas, a large majority of which were sent to the United States (US), preceding the opening of the first NHS England PBT center in late 2018. More than 10 years since its inception, we report the long-term outcomes on patient groups who have accessed this program and were treated in the US proton centers. Between 2008 and 2018, 1102 patients with indications eligible for PBT (adhering to approved criteria) were treated in the US. The majority of these were managed at the University of Florida Proton Therapy Institute, Jacksonville, although significant numbers have also been treated at Procure Oklahoma. All cases were of sufficient performance status to travel and were appropriately staged. Patient, tumor, treatment and follow-up data were collated in a centralized database. In light of the establishment of the NHS England PBT centers, the Proton Clinical Outcomes Unit (PCOU) has been simultaneously initiated and developed to systematically monitor this patient cohort as well as standardize and improve prospective outcome data collection for UK PBT patients going forward. Systematic follow-up data was available for 878 patients (79.7% of those treated in the US). Analysis has been conducted on the subgroups <25 vs ≥25 years old (y). After a median follow-up of 34 months (range 6-105), the Local Control (LC) rate for the entire cohort was 81%; by age (<25 y vs ≥ 25 y) LC rates were 82.1% for the younger group vs 74.8% for the older group. For tumors of the central nervous system (CNS), the LC rate was 80% (81.6% < 25 y vs 74.4% ≥25 y). For tumors outside the CNS (referred to as ‘body’ tumors), the LC rate was 82.6% (82.8% in <25 y vs 78.6% in ≥25 y). The data show that LC was highest for craniopharyngioma (90.3%) in the CNS subgroup and for Adult type Sarcomas (85.7%) in the body subgroup. Table 1 illustrates the 1- and 5-years survival estimates (95% Confidence Intervals) for the main subgroups. The outcome of patients treated through the POP compares favorably with that reported in the literature (1). The POP has been successful in facilitating equitable access to PBT abroad for patients with complex needs from across the UK without disadvantaging patient outcomes. It is arguably the largest national PBT access program, drawing equitably from a whole population, with treatment, transport abroad and accommodation funded by the NHS, and has enabled collaborative ties and a strengthening of network between the UK and the US.Tabled 1Abstract 2914; TableTimepointAll< 25, Body≥ 25, Body*< 25, CNS≥ 25, CNS1 year99.2% (98.6-99.8%)98.1% (96.6-99.6%)100% (-)100% (-)99.2% (97.5-100%)5 year88.4% (85.5-91.5%)87.3% (82.7-92.2%)80.0% (51.6-100%)91.4% (87.6-95.3%)81.8% (71.9-93.0%) Open table in a new tab

Survey of clinician opinions on the role of proton beam therapy in Australia and New Zealand.

We surveyed the Australian and New Zealand (ANZ) radiation oncology community to assess their perceptions, understanding and experience of the current role of proton beam therapy (PBT) and the existing referral process to access PBT overseas, ahead of the development of the first PBT centre in Australia. The survey was conducted between September and October 2019 using a 17-question instrument, which was distributed by email to all 632 radiation oncology fellows and trainees listed in the Royal Australian and New Zealand College of Radiologists database. One hundred and one respondents completed the survey, with an overall response rate of 16%. Most respondents were based in Australia (93%), with the majority working in public centres only (59%); 51% were >10years post fellowship and 17% were trainees. Most respondents (76%) reported moderate or high levels of confidence in the role of PBT. Only 28% had previously referred a patient for PBT overseas, with the most common referral indication being chordoma. Of those who had not previously referred a patient, 48% were not convinced about the rationale of PBT over current therapies available locally, 33% were not aware of the referral process, and 24% had concerns about the timeliness of a decision for government-funded PBT abroad. This survey has demonstrated that, although there is reasonable confidence in the role of PBT among ANZ radiation oncologists, there are a number of important aspects of PBT awareness, education and access that need to be developed prior to commencement of PBT in Australia.

Proton beam therapy: perspectives on the National Health Service England clinical service and research programme.

The UK has an important role in the evaluation of proton beam therapy (PBT) and takes its place on the world stage with the opening of the first National Health Service (NHS) PBT centre in Manchester in 2018, and the second in London coming in 2020. Systematic evaluation of the role of PBT is a key objective. By September 2019, 108 patients had started treatment, 60 paediatric, 19 teenagers and young adults and 29 adults. Obtaining robust outcome data is vital, if we are to understand the strengths and weaknesses of current treatment approaches. This is important in demonstrating when PBT will provide an advantage and when it will not, and in quantifying the magnitude of benefit.The UK also has an important part to play in translational PBT research, and building a research capability has always been the vision. We are perfectly placed to perform translational pre-clinical biological and physical experiments in the dedicated research room in Manchester. The nature of DNA damage from proton irradiation is considerably different from X-rays and this needs to be more fully explored. A better understanding is needed of the relative biological effectiveness (RBE) of protons, especially at the end of the Bragg peak, and of the effects on tumour and normal tissue of PBT combined with conventional chemotherapy, targeted drugs and immunomodulatory agents. These experiments can be enhanced by deterministic mathematical models of the molecular and cellular processes of DNA damage response. The fashion of ultra-high dose rate FLASH irradiation also needs to be explored.

A comparison of neck positioning devices for general anaesthetic patients treated at the christie NHS proton beam therapy centre

Keywords: proton beam therapy, patient positioning, neck profile. Introduction and Background: For the treatment of paediatric patients undergoing proton beam therapy (PBT) under general anaesthetic (GA), two different headrests were evaluated with a view to enhancing the potential of a more prominent neck flexion in order to obtain a more stable airway. Method and Materials: Imaging data from 10 patients undergoing GA assisted PBT was used to assess consistency of treatment positioning using the standard (n=5) and neck profile (n=5) headrests. Cone-beam computed tomography (CBCT) data was collected throughout treatment; CBCTs were taken for fractions 1-5 then weekly unless required more frequently. Pearson correlations and student paired t-tests were used to assess translational and rotational set up errors in each of the vertical, longitudinal and lateral directions, as well as the pitch, yaw and roll. Notes on patients’ daily setups were also recorded to ensure we considered any non-data related positioning issues (e.g., complex patient setups). Results: On average 12 CBCTs were available to analyse for each patient (9-17) on the standard headrest, and 18 (9-33) on the neck profile headrest. 100% of patients on standard headrests required a re-setup at some point throughout treatment as opposed to 60% of neck profile headrest patients requiring a re-setup at some point. Pearson test for CBCT translations showed R-values 0.21, 0.54 and 0.45 in the right-left, superior-inferior and anterior-posterior directions respectively. Rotationally R-values were 0.18, 0.28 and 0.40 for pitch, roll and yaw. However, paired t-tests indicated no statistically significant differences between the two types of headrest resulting in p-values 0.40, 0.61 and 0.78 in the right-left, superior-inferior and anterior-posterior directions and 0.25, 0.17 and 0.29 for pitch, roll and yaw. Conclusion and Discussion: Overall, no statistically significant result was found between the two datasets, however practise was changed as a result of this project. The prominent reasons for re-setup in standard headrest patients were airway complications or cervical spine deformation impacting on target volume coverage. As a result of these findings, the neck profile headrests are being used for all GA patients. Further analysis is ongoing to validate these results. Numerical

Investigations on Physical and Biological Range Uncertainties in Krak\'ow Proton Beam Therapy Centre

Physical and biological range uncertainties limit the clinical potential of Proton Beam Therapy (PBT). In this proceedings, we report on two research projects, which we are conducting in parallel and which both tackle the problem of range uncertainties. One aims at developing software tools and the other at developing detector instrumentation. Regarding the first, we report on our development and pre-clinical application of a GPU-accelerated Monte Carlo (MC) simulation toolkit Fred. Concerning the letter, we report on our investigations of plastic scintillator based PET detectors for particle therapy delivery monitoring. We study the feasibility of Jagiellonian-PET detector technology for proton beam therapy range monitoring by means of MC simulations of the $\beta^+$ activity induced in a phantom by proton beams and present preliminary results of PET image reconstruction. Using a GPU-accelerated Monte Carlo simulation toolkit Fred and plastic scintillator based PET detectors we aim to improve patient treatment quality with protons.

An introduction to proton beam therapy.

Radiotherapy is a highly effective anti-cancer treatment commonly used alongside systemic therapies and surgery to achieve long-term cancer-free survival. Conventional radiotherapy uses photon beams to deliver a high dose of radiation to the tumour volume to eradicate cancer cells. This has to be offset against the irradiation of surrounding normal tissues, as increasing this dose causes more treatment-related toxicity. In August 2018, the NHS's first high energy proton beam therapy centre opened at The Christie NHS Foundation Trust in Manchester. A second NHS centre is scheduled to open in 2020 at the University College London Hospitals NHS Trust. Proton beam therapy may offer dosimetric advantages compared to conventional radiotherapy as a result of its characteristic dose deposition - proton beams deliver a comparatively higher proportion of their dose to the target volume relative to normal tissues, without significant exit doses when compared to conventional photon therapy. Therefore proton beam therapy may be indicated for certain tumours situated next to critical organs or in the paediatric population where quality of life and the reduction of secondary effects from radiation are particularly significant. The indications for proton beam therapy and patient outcomes after treatment will be carefully monitored and evaluated in order to provide a robust evidence base for its use.

Clinical Results of Proton Beam Therapy for Esophageal Cancer: Multicenter Retrospective Study in Japan.

There are few reports about the clinical results of proton beam therapy for esophageal cancer in a large population. The purpose of this study was to evaluate the clinical results of proton beam therapy for esophageal cancer in a large population using a multicentered database. Between January 2009 and December 2013, patients newly diagnosed with esophageal cancer and who had received proton beam therapy were retrospectively recruited from a database of four proton beam therapy centers in Japan. Two hundred and two patients (including 90 inoperable patients) fulfilled the inclusion criteria, and 100 patients (49.5%) had stage III/IV cancer (Union for International Cancer Control 8th). The 3-year and 5-year overall survival rate was 66.7% and 56.3%, respectively. The five-year local control rate was 64.4%. There were two patients with grade three pericardial effusion (1%) and a patient with grade three pneumonia (0.5%). No grade 4 or higher cardiopulmonary toxicities were observed (Common Terminology Criteria for Adverse Events version 4.0). This study suggests that proton beam therapy for esophageal cancer was not inferior in efficacy and had lower rates of toxicities in comparison to photon radiotherapy. Therefore, proton beam therapy can serve as an alternate treatment for patients with esophageal cancer.

Proton Facility Economics: Single-Room Centers

ObjectiveWe have previously described the central nature of simple cases for financial feasibility of proton beam therapy centers—especially four- to five-room centers. In the 5 years since that publication, such construction has slowed drastically, and smaller, single-room projects are in vogue. We now seek to show under what circumstances a single-room system is optimally financially viable. Materials and MethodsA “standard” construction cost and debt for a single gantry system of $40 million was presumed, with 75% of the construction funded through standard 20-year financing. We then modeled a statistical analysis, deriving the optimal case mix required daily to cover construction and debt service costs. ResultsWe previously published that a single gantry treating only complex patients would need to apply 85% of its treatment slots simply to service debt, though it would cover its debt treating 4 hours of simple patients. As the business model has changed, debt maintenance, profit and operational costs have somewhat reduced the business case for adding a large number of simple patients. Debt maintenance is possible with as little as 13% of daily patients for a 40% Medicare case mix, but these numbers are critically sensitive to continued patient throughput. ConclusionsEven in a single-room system, reducing overall debt, using tax-exempt financing, and having a case load emphasizing simple, private payer patients is paramount to fiscal health of the facility. Unused capacity is a huge risk if insufficient patients are available.

P291] Comparison of beam model implementation methods for commissioning of Monte Carlo code in proton beam therapy centre

Purpose In proton beam therapy (PBT), Monte Carlo (MC) methods offer more accurate dose recalculation than analytical treatment planning system (TPS) used in clinical routine. The purpose of this work was to implement a PBT centre beam model in MC code. This is essential when employing the code as a support tool for quality assurance procedures and using data from MC simulation as an additional information for the clinical TPS. Furthermore, different beam implementation methods were compared in order to find the most adequate approach to simulate beam source and obtain the best agreement between MC simulations and TPS. Methods Simulations of proton pencil beams in water phantom were performed in order to find MC specific beam parameters that characterize the beam model in the PBT centre. A GPU-accelerated MC code was used, which significantly reduces the dose distribution calculation time. Two beam model implementation methods were considered: (i) a paraxial beam approach and (ii) an emittance model. The paraxial beam approach is determined from depth-dose-distribution (DDD) measurements and TPS calculations in a water phantom. The emittance model additionally accounts for the measurement of beam profiles in air. The beam shape and dose values for single beam simulations using the two methods were compared with TPS, which was used as a reference. Results A perfect agreement in beam range, within binning uncertainty of 0.1 mm, was obtained for single beam DDDs calculated with MC code and TPS comparing both beam model implementation approaches. The simulated lateral beam size fit to TPS reference values for the paraxial beam approach and emittance model differing up to 10% (delta_sigma 0.5 mm). The minor difference of up to 0.2 mm in the beam size was observed between the emittance model and the paraxial beam approach. Conclusions The preliminary results showed that the beam size in the water phantom for the paraxial beam approach, the emittance model and TPS are in good agreement, even though, the emittance model considers actual variation of the beam size in air. For the clinical application these findings must be further verified by MC simulations and experimentally.

Predicting the benefits of proton therapy in lung cancer patients from patient-specific anatomic and pathologic geometry

The magnitude of OAR dose sparing feasible with radiation therapy depends upon the patient-specific arrangement of the target volumes in relation to the OARs. When comparing proton beam therapy (PBT) and photon therapy, the evaluation of PBT benefits is currently achieved via resource-intensive treatment planning, which requires specialized software and clinical expertise typically only available at PBT centers. The purpose of this study is to train and validate knowledge-based plan prediction (KPP) models to estimate these benefits for lung cancer patients, requiring fewer resources and no PBT expertise. Our study used a cohort of locally advanced NSCLC patients, enrolled in a trial that randomized treatment between PBT (36 pts) and IMRT (68 pts). KPP models learn geometric patterns from a database of pre-existing treatment plans, and can then predict the feasible OAR DVHs of a new patient. By training independent KPP models for both PBT and IMRT, the feasible benefits of PBT can be predicted for the new patient. Our KPP methodology split each OAR into subvolumes that characterize the dose falloff and coplanar beams. Models were validated by 5-fold cross-validation, by comparing the predicted OAR DVHs to those of the actual treatment plan. DVHs were predicted for the lung (combined lungs excluding GTV), heart and esophagus. For each predicted and planned DVH, the equivalent uniform dose (EUD) and normal tissue complication probability (NTCP) were computed. The table shows the root-mean-square error of the EUD and NTCP predictions, for both the PBT and IMRT models. It also shows the estimated uncertainty in the predicted benefit. Model accuracy depends upon the OAR type and treatment modality, but no significant signs of bias were observed. Pearson’s correlation coefficient was 84% – 98% for PBT and 81% – 96% for IMRT, demonstrating that the KPP models successfully captured the interpatient variation. We developed KPP models for lung cancer patients treated with PBT and an alternative treatment modality (IMRT). By comparing the two predicted plans for a new patient, the patient-specific benefits of PBT can quickly be estimated with high accuracy. This methodology could enable better-informed referral decisions, improving the cost-effectiveness of this expensive therapy and elevating PBT in the era of precision medicine. It could also estimate the expected benefits at an earlier stage in the clinical workflow, or provide a high-throughput patient pre-selection for model-based trials aiming to measure the higher efficacy of PBT.Abstract 3592Prediction Error in EUD [Gy]Prediction Error in NTCP [%]PBTIMRTBenefitsPBTIMRTBenefitsLung2.02.23.02.94.45.3Heart1.93.54.02.14.24.7Esophagus4.35.16.76.87.810.3 Open table in a new tab

Doing Poorly by Doing Good: The Bottom Line of Proton Therapy for Children

Proton beam therapy (PBT) is the most expensive form of radiation therapy in the United States. An area in which clear advantage has been modeled is the use of PBT for pediatric patients, although no publications deal with practice costs to PBT centers associated with a pediatric focus. Pediatric cases require longer treatment times and more staff members and incur higher supply and device costs. In addition to being more expensive to treat, the pediatric patients at the authors' center also present with Medicaid as their primary insurer at higher rates than adults. At their center, in the past 2 years, pediatric patients (<21 years of age) have constituted 32% of total patients treated. The authors present their cost experience in a PBT environment treating a large number of children. After approval was obtained from the local institutional review board, data relating to patients ≤21 years of age who started treatment during the period between November 1, 2011, and October 31, 2013, were reviewed. Direct expenses of devices and supplies used, billing for anesthesia, staffing, and direct operational costs (proton beam) were calculated to determine the direct cost to treat. Those direct costs were then compared with actual reimbursements received for those treatments. Additionally, gross operating costs per hour and gross average expenses per pediatric patient were calculated, and that cost was then compared with actual reimbursement. The mission to preferentially treat pediatric patients involves accepting a loss for one-third of pediatric patients before allocating any overhead. After averaging gross expenses over total operating hours, 60% of the pediatric patients were found to be treated at a net loss. Given insurance constraints and unique costs associated with the pediatric population, PBT centers devoted to children should not be expected to be markedly profitable. For centers that do choose to accept pediatric patients, those patients must be balanced with patients producing higher net reimbursement.

Proton Beam Therapy and Accountable Care: The Challenges Ahead

Proton beam therapy (PBT) centers have drawn increasing public scrutiny for their high cost. The behavior of such facilities is likely to change under the Affordable Care Act. We modeled how accountable care reform may affect the financial standing of PBT centers and their incentives to treat complex patient cases. We used operational data and publicly listed Medicare rates to model the relationship between financial metrics for PBT center performance and case mix (defined as the percentage of complex cases, such as pediatric central nervous system tumors). Financial metrics included total daily revenues and debt coverage (daily revenues - daily debt payments). Fee-for-service (FFS) and accountable care (ACO) reimbursement scenarios were modeled. Sensitivity analyses were performed around the room time required to treat noncomplex cases: simple (30 minutes), prostate (24 minutes), and short prostate (15 minutes). Sensitivity analyses were also performed for total machine operating time (14, 16, and 18 h/d). Reimbursement under ACOs could reduce daily revenues in PBT centers by up to 32%. The incremental revenue gained by replacing 1 complex case with noncomplex cases was lowest for simple cases and highest for short prostate cases. ACO rates reduced this incremental incentive by 53.2% for simple cases and 41.7% for short prostate cases. To cover daily debt payments after ACO rates were imposed, 26% fewer complex patients were allowable at varying capital costs and interest rates. Only facilities with total machine operating times of 18 hours per day would cover debt payments in all scenarios. Debt-financed PBT centers will face steep challenges to remain financially viable after ACO implementation. Paradoxically, reduced reimbursement for noncomplex cases will require PBT centers to treat more such cases over cases for which PBT has demonstrated superior outcomes. Relative losses will be highest for those facilities focused primarily on treating noncomplex cases.

TH‐D‐BRB‐02: Improving the Accuracy of Monte Carlo Spread‐Out Bragg Peak Treatment Head Models Using Beam Current Modulation Optimization

Purpose: For challenging clinical cases Monte Carlo methods can help to verify the accuracy of proton beam planning results based on the pencil beam algorithm. However the use of Monte Carlo methods as a verification tool requires an accurate model of the proton fields generated in the treatment head. This paper presents a novel approach to improve upon the achievable accuracy of Monte Carlo models of proton beam treatment heads. We will also demonstrate the usefulness of this approach by presenting commissioning results of two treatment head models at our facility. Methods and Materials: The achievable accuracy of our treatment head model was examined by quantifying the impact of uncertainties in material and beam parameters on SOPB dose distributions. A novel approach to improve this accuracy was developed by optimizing the beam current modulation function defined in our Monte Carlo model to produce clinically acceptable SOBP dose distributions. Finally this method was utilized for the commissioning two models of SOBP proton beam treatment heads at our facility. Results: Uncertainty in material density led to the largest impact on the SOBP dose distributions (less than 4%). The impact of mean ionization potential uncertainties was smaller (less than 2%). We did not detect a statistically significant influence of clinically relevant beam energy spreads and spot sizes on the SOBP dose distribution. The optimization of our beam current modulation functions allowed us to fully commission two treatment head models at our facility. Conclusion: Several proton beam therapy centers are now operational or being planned and constructed which promises the future need for Monte Carlo modeling of proton beam therapy treatment heads. The methodology and results presented in this paper will help accommodate the commissioning of new Monte Carlo simulated treatment heads.