Protein Editing using a Concerted Transposition Reaction.

Protein engineering through the chemical or enzymatic ligation of polypeptide fragments has proven enormously powerful for studying countless biochemical processes in vitro. In general, this strategy necessitates a protein folding step following ligation of the unstructured fragments, a requirement that constrains the types of systems amenable to the approach. Here, we report an in vitro strategy that allows internal regions of target proteins to be replaced in a single operation. Conceptually, our system is analogous to a DNA transposition reaction, but employs orthogonal pairs of split inteins to swap out a designated region of a host protein with an exogenous molecular cassette. We show using isotopic labeling experiments that this 'protein transposition' reaction is concerted when the kinetics for the embedded intein pairs are suitably matched. Critically, this feature allows for efficient manipulation of protein primary structure in the context of a native fold. The utility of this method is illustrated using several protein systems including the multisubunit chromatin remodeling complex, ACF, where we also show protein transposition can occur in situ within the cell nucleus. By carrying out a molecular 'cut and paste' on a protein or protein complex under native folding conditions, our approach dramatically expands the scope of protein semisynthesis.

A Prebiotic Diet Containing Galactooligosaccharides and Polydextrose Produces Dynamic and Reproducible Changes in the Gut Microbial Ecosystem in Male Rats.

Despite substantial evidence supporting the efficacy of prebiotics for promoting host health and stress resilience, few experiments present evidence documenting the dynamic changes in microbial ecology and fecal microbially modified metabolites over time. Furthermore, the literature reports a lack of reproducible effects of prebiotics on specific bacteria and bacterial-modified metabolites. The current experiments examined whether consumption of diets enriched in prebiotics (galactooligosaccharides (GOS) and polydextrose (PDX)), compared to a control diet, would consistently impact the gut microbiome and microbially modified bile acids over time and between two research sites. Male Sprague Dawley rats were fed control or prebiotic diets for several weeks, and their gut microbiomes and metabolomes were examined using 16S rRNA gene sequencing and untargeted LC-MS/MS analysis. Dietary prebiotics altered the beta diversity, relative abundance of bacterial genera, and microbially modified bile acids over time. PICRUSt2 analyses identified four inferred functional metabolic pathways modified by the prebiotic diet. Correlational network analyses between inferred metabolic pathways and microbially modified bile acids revealed deoxycholic acid as a potential network hub. All these reported effects were consistent between the two research sites, supporting the conclusion that dietary prebiotics robustly changed the gut microbial ecosystem. Consistent with our previous work demonstrating that GOS/PDX reduces the negative impacts of stressor exposure, we propose that ingesting a diet enriched in prebiotics facilitates the development of a health-promoting gut microbial ecosystem.

Performance and Return to Play After Surgery for Thoracic Outlet Syndrome in Professional Baseball Players: A Matched Cohort Analysis.

BACKGROUND: Thoracic outlet syndrome (TOS) remains a rare diagnosis but is being recognized as a cause of upper extremity dysfunction in professional baseball players. PURPOSE/HYPOTHESIS: The purpose was to determine performance and return-to-play (RTP) outcomes in professional baseball players after surgical treatment of TOS. The hypothesis was that there would be a high RTP rate in professional baseball players after TOS surgery with no statistical differences in performance between pitchers who had TOS surgery and matched controls. STUDY DESIGN: Cohort study; Level of evidence, 3. METHODS: All professional baseball players who underwent surgical treatment of TOS between 2010 and 2017 were identified using the Major League Baseball Health and Injury Tracking System database. Demographic and performance data (before and after surgery) for each player were recorded. Performance variables were then compared between players who underwent TOS surgery and matched controls. The matching criteria were no history of previous surgeries on affected arm, age at time of surgery, throwing side, level of play (Major or Minor League Baseball), and years of experience playing professional baseball. RESULTS: Overall, 52 players underwent surgery for TOS, of whom 46 (88%) were pitchers. The type of TOS was neurogenic in 69% and venous in 29%. One player had arterial TOS. After TOS surgery, 79% of players returned to play at the same or higher level (RTSP) by 9.5 months and played ≥3 years after surgery. No differences were found in RTSP rate based on the type of TOS. No statistical difference was found in RTP rates between major and minor league players. Pitchers had a 76% RTSP, which was similar to the natural attrition for control pitchers (P = .874). After TOS surgery, pitchers saw a decline in several performance metrics, but these declines were not different from those of control pitchers, indicating that the decline in performance after TOS surgery was no faster than is seen in healthy professional pitchers as they age. CONCLUSION: The rate of RTSP after surgery for TOS in professional baseball players was 79%. There was no difference in RTP based on the type of TOS. Pitchers who underwent surgery for TOS had no significant differences in pitching performance metrics after surgery compared with matched controls.

Fundamental Themes in Social-Emotional Learning: A Theoretical Framework for Inclusivity.

Social-emotional learning (SEL) is a rapidly growing field of research that has garnered significant attention in recent years. Each facet of SEL research in fields such as education, mental health, and developmental research has used specific methodologies and terms in their narrow research focus. In education specifically, where the most SEL research has been produced, many frameworks have implementation requirements. The lack of a framework focused on overarching themes without implementation requirements prevents the fields from coming together to compile and compare research and progress to create parent-, adult-, or mental health-specific SEL programs. This paper provides a conceptual analysis of SEL, aimed at clarifying the concept and deconstructing its various facets. This framework is needed to acknowledge the many different terms and skills for the same principle while also narrowing down definitions for clarity. The resulting framework can be used as a basis for future research, practice, and policy discussions in the field.

Plant macrofossil data for 48-0 ka in the USGS North American Packrat Midden Database, version 5.0.

Plant macrofossils from packrat (Neotoma spp.) middens provide direct evidence of past vegetation changes in arid regions of North America. Here we describe the newest version (version 5.0) of the U.S. Geological Survey (USGS) North American Packrat Midden Database. The database contains published and contributed data from 3,331 midden samples collected in southwest Canada, the western United States, and northern Mexico, with samples ranging in age from 48 ka to the present. The database includes original midden-sample macrofossil counts and relative-abundance data along with a standardized relative-abundance scheme that makes it easier to compare macrofossil data across midden-sample sites. In addition to the midden-sample data, this version of the midden database includes calibrated radiocarbon (14C) ages for the midden samples and plant functional type (PFT) assignments for the midden taxa. We also provide World Wildlife Fund ecoregion assignments and climate and bioclimate data for each midden-sample site location. The data are provided in tabular (.xlsx), comma-separated values (.csv), and relational database (.mdb) files.

Quantum gas mixtures and dual-species atom interferometry in space.

The capability to reach ultracold atomic temperatures in compact instruments has recently been extended into space1,2. Ultracold temperatures amplify quantum effects, whereas free fall allows further cooling and longer interactions time with gravity-the final force without a quantum description. On Earth, these devices have produced macroscopic quantum phenomena such as Bose-Einstein condensates (BECs), superfluidity, and strongly interacting quantum gases3. Terrestrial quantum sensors interfering the superposition of two ultracold atomic isotopes have tested the universality of free fall (UFF), a core tenet of Einstein's classical gravitational theory, at the 10-12 level4. In space, cooling the elements needed to explore the rich physics of strong interactions or perform quantum tests of the UFF has remained elusive. Here, using upgraded hardware of the multiuser Cold Atom Lab (CAL) instrument aboard the International Space Station (ISS), we report, to our knowledge, the first simultaneous production of a dual-species BEC in space (formed from 87Rb and 41K), observation of interspecies interactions, as well as the production of 39K ultracold gases. Operating a single laser at a 'magic wavelength' at which Rabi rates of simultaneously applied Bragg pulses are equal, we have further achieved the first spaceborne demonstration of simultaneous atom interferometry with two atomic species (87Rb and 41K). These results are an important step towards quantum tests of UFF in space and will allow scientists to investigate aspects of few-body physics, quantum chemistry and fundamental physics in new regimes without the perturbing asymmetry of gravity.

Supply and Demand for Radiation Oncologists in Canada: Workforce Planning Projections From 2020 to 2040.

PURPOSE: The number of Canadians diagnosed with cancer, and subsequent demand for radiation therapy, are expected to increase over time. This study aimed to update our needs-based workforce planning model to ensure appropriate staffing levels in the future. METHODS AND MATERIALS: The supply of radiation oncologists, by age group, sex, and full-time equivalent status, was projected from 2020 to 2040 using a recursive-aging, input-output model developed with seeding parameters derived from national sources. The demand for radiation oncologists until 2040 was estimated using referral patterns for radiation therapy and consultation workload metrics applied to projected annual cancer incident cases to calculate required full-time equivalent positions. Baseline model parameters were also applied to the 2005-2019 workforce and incident case data to evaluate preprojection supply and demand trends. RESULTS: Preprojection trends for 2005 to 2019 revealed accelerated staffing growth that transitioned from a workforce shortage to a surplus state in 2014 followed by substantial growth slowdown in 2016. The model predicts a transient surplus of radiation oncologists until 2026 followed by a projected deficit in subsequent years. Sensitivity analyses using the plausible range for each parameter continued to favor an undersupply, suggesting a trainee shortage unable to meet workforce expansion needs. Considering possible future declining trends in radiotherapy utilization and workload, calculations to inform corrective efforts in resident numbers resulted in 25 entry positions per year, up from 21 per year currently. Geographic distribution of trainees, relative to workforce and cancer incidence distributions, could be improved with more residency positions in Canadian regions outside Ontario. CONCLUSIONS: Demand for radiation therapy and radiation oncologists in Canada are expected to grow more quickly than future expansion in staffing levels. Our workforce planning model provides evidence for more trainee requirements to inform stakeholders of possible corrective actions to training programs and recruitment. Further research is needed to explore additional strategies to expand capacity and high-quality delivery of radiation therapy to meet the foreseeable increase in Canadian patients with cancer.

Rapid Functional Recovery After Thoracic Outlet Decompression in a Series of Adolescent Athletes With Chronic Atraumatic Shoulder-Girdle Pain, Scapular Winging/Dyskinesis, and Normal Electrodiagnostic Studies.

BACKGROUND: Spontaneous shoulder-girdle pain and scapular winging/dyskinesis can be caused by several neuromuscular disorders identifiable by electrodiagnostic studies (EDX). We describe a group of adolescent athletes with this clinical presentation but normal EDX, followed by later development of neurogenic thoracic outlet syndrome (NTOS). METHODS: We identified patients referred for evaluation of NTOS that had a history of chronic atraumatic shoulder-girdle pain, scapular winging/dyskinesis, and normal EDX. Each was refractory to conservative management and underwent supraclavicular decompression and brachial plexus neurolysis for NTOS. Functional disability was quantified by Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH) scores. RESULTS: There were 5 female patients with a mean age at symptom onset of 14.2 ± 0.4 years, including spontaneous severe pain in the shoulder, scapula, and arm, along with prominent scapular winging/dyskinesis, and normal EDX. Symptoms had persisted for 18.9 ± 4.0 months prior to referral, with pronounced upper extremity disability (mean QuickDASH, 54.6 ± 6.9). By 3 months after surgical treatment for NTOS, all 5 patients experienced near-complete symptom resolution, including scapular winging/dyskinesis, with markedly improved function (mean QuickDASH, 2.2 ± 1.3) and a return to normal activity. CONCLUSIONS: A subset of patients with chronic atraumatic shoulder-girdle pain, scapular winging/dyskinesis, and normal EDX may develop dynamic brachial plexus compression characteristic of NTOS, exhibiting an ischemic "Sunderland-zero" nerve conduction block for which surgical decompression can result in rapid and substantial clinical improvement. The presence of surgically treatable NTOS should be considered for selected patients with long-standing scapular winging/dyskinesis who fail conservative management.

Oral CBD-rich hemp extract modulates sterile inflammation in female and male rats.

Introduction: Cannabidiol (CBD) extract from the cannabis plant has biomedical and nutraceutical potential. Unlike tetrahydrocannabinol (THC), CBD products produce few psychoactive effects and pose little risk for abuse. There is emerging preclinical and clinical evidence that CBD is stress modulatory and may have anti-inflammatory properties. People across the United States legally ingest CBD-rich hemp extracts to manage mental and physical health problems, including stress and inflammation. Preclinical studies have revealed potential mechanisms for these effects; however, the impact of this prior work is diminished because many studies: 1) tested synthetic CBD rather than CBD-rich hemp extracts containing terpenes and/or other cannabinoids thought to enhance therapeutic benefits; 2) administered CBD via injection into the peritoneal cavity or the brain instead of oral ingestion; and 3) failed to examine potential sex differences. To address these gaps in the literature, the following study tested the hypothesis that the voluntary oral ingestion of CBD-rich hemp extract will attenuate the impact of stressor exposure on plasma and tissue inflammatory and stress proteins in females and males. Methods: Adult male and female Sprague Dawley rats (10-15/group) were randomly assigned to be given cereal coated with either vehicle (coconut oil) or CBD-rich hemp extract (L-M0717, CBDrx/Functional Remedies, 20.0 mg/kg). After 7 days, rats were exposed to a well-established acute model of stress (100, 1.5 mA, 5-s, intermittent tail shocks, 90 min total duration) or remained in home cages as non-stressed controls. Results: Stressor exposure induced a robust stress response, i.e., increased plasma corticosterone and blood glucose, and decreased spleen weight (a surrogate measure of sympathetic nervous system activation). Overall, stress-induced increases in inflammatory and stress proteins were lower in females than males, and oral CBD-rich hemp extract constrained these responses in adipose tissue (AT) and mesenteric lymph nodes (MLN). Consistent with previous reports, females had higher levels of stress-evoked corticosterone compared to males, which may have contributed to the constrained inflammatory response measured in females. Discussion: Results from this study suggest that features of the acute stress response are impacted by oral ingestion of CBD-rich hemp extract in female and male rats, and the pattern of changes may be sex and tissue dependent.

Neurotransmission-related gene expression in the frontal pole is altered in subjects with bipolar disorder and schizophrenia.

The frontal pole (Brodmann area 10, BA10) is the largest cytoarchitectonic region of the human cortex, performing complex integrative functions. BA10 undergoes intensive adolescent grey matter pruning prior to the age of onset for bipolar disorder (BP) and schizophrenia (SCHIZ), and its dysfunction is likely to underly aspects of their shared symptomology. In this study, we investigated the role of BA10 neurotransmission-related gene expression in BP and SCHIZ. We performed qPCR to measure the expression of 115 neurotransmission-related targets in control, BP, and SCHIZ postmortem samples (n = 72). We chose this method for its high sensitivity to detect low-level expression. We then strengthened our findings by performing a meta-analysis of publicly released BA10 microarray data (n = 101) and identified sources of convergence with our qPCR results. To improve interpretation, we leveraged the unusually large database of clinical metadata accompanying our samples to explore the relationship between BA10 gene expression, therapeutics, substances of abuse, and symptom profiles, and validated these findings with publicly available datasets. Using these convergent sources of evidence, we identified 20 neurotransmission-related genes that were differentially expressed in BP and SCHIZ in BA10. These results included a large diagnosis-related decrease in two important therapeutic targets with low levels of expression, HTR2B and DRD4, as well as other findings related to dopaminergic, GABAergic and astrocytic function. We also observed that therapeutics may produce a differential expression that opposes diagnosis effects. In contrast, substances of abuse showed similar effects on BA10 gene expression as BP and SCHIZ, potentially amplifying diagnosis-related dysregulation.

Epithelial-intrinsic defects in TGFßR signaling drive local allergic inflammation manifesting as eosinophilic esophagitis.

Allergic diseases are a global health challenge. Individuals harboring loss-of-function variants in transforming growth factor-ß receptor (TGFßR) genes have an increased prevalence of allergic disorders, including eosinophilic esophagitis. Allergic diseases typically localize to mucosal barriers, implicating epithelial dysfunction as a cardinal feature of allergic disease. Here, we describe an essential role for TGFß in the control of tissue-specific immune homeostasis that provides mechanistic insight into these clinical associations. Mice expressing a TGFßR1 loss-of-function variant identified in atopic patients spontaneously develop disease that clinically, immunologically, histologically, and transcriptionally recapitulates eosinophilic esophagitis. In vivo and in vitro, TGFßR1 variant-expressing epithelial cells are hyperproliferative, fail to differentiate properly, and overexpress innate proinflammatory mediators, which persist in the absence of lymphocytes or external allergens. Together, our results support the concept that TGFß plays a fundamental, nonredundant, epithelial cell-intrinsic role in controlling tissue-specific allergic inflammation that is independent of its role in adaptive immunity.

Boutonniere Versus Pseudoboutonniere Deformities: Pathoanatomy, Diagnosis, and Treatment.

Finger injuries involving the proximal interphalangeal (PIP) joint are common, particularly among athletes. Injury severity is often underappreciated at initial presentation and may be dismissed broadly as a "jammed finger" injury. Delayed diagnosis and treatment of certain injuries can have an important impact on the patient's chance of regaining full function. Central slip and PIP volar plate injuries are frequently encountered injuries that, if left untreated, can lead to the permanent loss of function of the proximal interphalangeal joint. Despite the differing mechanisms of these 2 pathologies, volar plate hyperextension injuries often present with a PIP joint flexion contracture and mild distal interphalangeal joint hyperextension deformity. This is similar to a boutonniere deformity seen after an injury to the central slip, and thus, has been referred to as a "pseudo-boutonnière" deformity. Distinguishing these 2 diagnoses is important, as treatment differs, and highlights the importance of thoroughly understanding the anatomy and relevant clinical applications when evaluating PIP joint injuries.

Venographic classification and long-term surgical treatment outcomes for axillary-subclavian vein thrombosis due to venous thoracic outlet syndrome (Paget-Schroetter syndrome).

OBJECTIVE: We assessed the clinical presentation, operative findings, and surgical treatment outcomes for axillary-subclavian vein (AxSCV) thrombosis due to venous thoracic outlet syndrome (VTOS). METHODS: We performed a retrospective, single-center review of 266 patients who had undergone primary surgical treatment of VTOS between 2016 and 2022. The clinical outcomes were compared between the patients in four treatment groups determined by intraoperative venography. RESULTS: Of the 266 patients, 132 were male and 134 were female. All patients had a history of spontaneous arm swelling and idiopathic AxSCV thrombosis, including 25 (9%) with proven pulmonary embolism, at a mean age of 32.1 ± 0.8 years (range, 12-66 years). The timing of clinical presentation was acute (<15 days) for 132 patients (50%), subacute (15-90 days) for 71 (27%), and chronic (>90 days) for 63 patients (24%). Venography with catheter-directed thrombolysis or thrombectomy (CDT) and/or balloon angioplasty had been performed in 188 patients (71%). The median interval between symptom onset and surgery was 78 days. After paraclavicular thoracic outlet decompression and external venolysis, intraoperative venography showed a widely patent AxSCV in 150 patients (56%). However, 26 (10%) had a long chronic AxSCV occlusion with axillary vein inflow insufficient for bypass reconstruction. Patch angioplasty was performed for focal AxSCV stenosis in 55 patients (21%) and bypass graft reconstruction for segmental AxSCV occlusion in 35 (13%). The patients who underwent external venolysis alone (patent or occluded AxSCV; n = 176) had a shorter mean operative time, shorter postoperative length of stay and fewer reoperations and late reinterventions compared with those who underwent AxSCV reconstruction (patch or bypass; n = 90), with no differences in the incidence of overall complications or 30-day readmissions. At a median clinical follow-up of 38.7 months, 246 patients (93%) had no arm swelling, and only 17 (6%) were receiving anticoagulation treatment; 95% of those with a patent AxSCV at the end of surgery were free of arm swelling vs 69% of those with a long chronic AxSCV occlusion (P < .001). The patients who had undergone CDT at the initial diagnosis were 32% less likely to need AxSCV reconstruction at surgery (30% vs 44%; P = .034) and 60% less likely to have arm swelling at follow-up (5% vs 13%; P < .05) vs those who had not undergone CDT. CONCLUSIONS: Paraclavicular decompression, external venolysis, and selective AxSCV reconstruction determined by intraoperative venography findings can provide successful and durable treatment for >90% of all patients with VTOS. Further work is needed to achieve earlier recognition of AxSCV thrombosis, prompt usage of CDT, and even more effective surgical treatment.

Imaging Real-Time Coronary Anatomy Using a Three-Dimensional Electrophysiology Mapping System.

The aim of this study is to evaluate the feasibility of creating fast three-dimensional maps of coronary arteries and to develop a bipolar coronary guidewire in vitro and determine whether it can be localised accurately within the model.A total of five patients were recruited, and EnSite Precision was utilised to create 3D coronary anatomy. A water bath to accommodate a 3D-printed coronary model was developed to test the performance of the bipolar angioplasty wire.Successful guidewire localisation and 3D reconstruction of coronary anatomy were achieved in all the cases. No complications. The bipolar wire was able to collect point clouds, and localisation of the distal tip was excellent when tested in the water bath.Our study demonstrates the feasibility and safety of utilising EAMS to collect coronary anatomy. Real-time tracking with a bipolar catheter is accurate when tested in vitro.

Surgical approaches for thoracic outlet decompression in the treatment of thoracic outlet syndrome.

Thoracic outlet syndrome (TOS) is a controversial and uncommon syndrome. Three different diagnoses can be made based on the compressed structure: arterial TOS, venous TOS, and neurogenic TOS. Diagnosing TOS, especially neurogenic TOS, remains difficult since a single diagnostic tool does not exist. Although this resulted in a lot of confusion, standardization of care and outcome improved daily care practice measures in the last decade. Current treatment algorithms consist of both conservative and surgical treatment approaches, which should be chosen depending on the type of TOS and extend of the complaints. Surgical treatment of TOS is performed via thoracic outlet decompression (TOD). TOD surgery includes complete resection of the first rib (cartilage to cartilage), transection of the scalene muscles and complete neurolysis/venolysis or arteriolysis. Four different approaches can be chosen for TOD surgery: the transaxillary (TA), supraclavicular (SC), paraclavicular (PC), and infraclavicular (IC) approach. The TA, SC, and PC approach can be used for every form of TOS. However, the PC approach is mostly used for treating venous TOS. The IC approach has no role in treating neurogenic or arterial TOS and is only used for venous TOS. Every approach has its own benefits and limitations and literature does not agree on what approach is best. Therefore, the used surgical approach for TOD should be based on the surgeon's preference and experience. The aim of this review is to present an overview of the diagnostic pathway and provide an in-depth description of the surgical approach in each form of TOS.

Variable phenotypes and penetrance between and within different zebrafish ciliary transition zone mutants.

Meckel syndrome, nephronophthisis, Joubert syndrome and Bardet-Biedl syndrome are caused by mutations in proteins that localize to the ciliary transition zone (TZ). The phenotypically distinct syndromes suggest that these TZ proteins have differing functions. However, mutations in a single TZ gene can result in multiple syndromes, suggesting that the phenotype is influenced by modifier genes. We performed a comprehensive analysis of ten zebrafish TZ mutants, including mks1, tmem216, tmem67, rpgrip1l, cc2d2a, b9d2, cep290, tctn1, nphp1 and nphp4, as well as mutants in ift88 and ift172. Our data indicate that variations in phenotypes exist between different TZ mutants, supporting different tissue-specific functions of these TZ genes. Further, we observed phenotypic variations within progeny of a single TZ mutant, reminiscent of multiple disease syndromes being associated with mutations in one gene. In some mutants, the dynamics of the phenotype became complex with transitory phenotypes that are corrected over time. We also demonstrated that multiple-guide-derived CRISPR/Cas9 F0 'crispant' embryos recapitulate zygotic null phenotypes, and rapidly identified ciliary phenotypes in 11 cilia-associated gene candidates (ankfn1, ccdc65, cfap57, fhad1, nme7, pacrg, saxo2, c1orf194, ttc26, zmynd12 and cfap52).

A space-based quantum gas laboratory at picokelvin energy scales.

Ultracold quantum gases are ideal sources for high-precision space-borne sensing as proposed for Earth observation, relativistic geodesy and tests of fundamental physical laws as well as for studying new phenomena in many-body physics during extended free fall. Here we report on experiments with the Cold Atom Lab aboard the International Space Station, where we have achieved exquisite control over the quantum state of single 87Rb Bose-Einstein condensates paving the way for future high-precision measurements. In particular, we have applied fast transport protocols to shuttle the atomic cloud over a millimeter distance with sub-micrometer accuracy and subsequently drastically reduced the total expansion energy to below 100 pK with matter-wave lensing techniques.

Pan-Canadian consensus recommendations for proton beam therapy access in Canada.

PURPOSE: Proton Beam Therapy (PBT)is a treatment option for select cancer patients. It is currently not available in Canada. Assessment and referral processes for out-of-country treatment for eligible patients vary by jurisdiction, leading to variability in access to this treatment for Canadian cancer patients. The purpose of this initiative was to develop a framework document to inform consistent and equitable PBT access for appropriate patients through the creation of pan-Canadian PBT access consensus recommendations. MATERIALS AND METHODS: A modified Delphiprocess was used to develop pan-Canadian recommendations with input from 22 PBT clinical and administrative experts across all provinces, external peer-review by provincial cancer and system partners, and feedback from a targeted community consultation. This was conducted by electronic survey and live discussion. Consensus threshold was set at 70% agreement. RESULTS: Fourconsensus rounds resulted in a final set of 27 recommendations divided into three categories: patient eligibility (n = 9); program level (n = 10); and system level (n = 8). Patient eligibility included: anatomic site (n = 4), patient characteristics (n = 3), clinical efficacy (n = 2). Program level included: regulatory and staff requirements (n = 5), equipment and technologies (n = 4), quality assurance (n = 1). System level included: referral process (n = 5), costing, budget impact and quality adjusted life years (n = 2), eligible patient estimates (n = 1). Recommendations were released nationally in June 2021 and distributed to all 43 cancer programs in Canada. CONCLUSION: A pan-Canadian consensus-building approach was successful in creating an evidence-based, peer-reviewed suite of recommendations thatsupportapplication of consistent clinical criteria to inform treatment options, facility set-up and access to high quality proton therapy.