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Cyanobacteria of the genus Trichodesmium form extensive blooms that supply new N to nutrient-poor marine ecosystems. Yet little is known about what eats Trichodesmium . In this laboratory study, we show that one of the greatest threats to coral reefs, predatory crown-of-thorns starfish (CoTS), Acanthaster sp., completes their larval phase feeding solely on Trichodesmium . We observed Trichodesmium erythraeum CMP1985 in the stomachs of larvae using florescence microscopy and traced the assimilation of nitrogen from labeled trichomes into larval tissues using stable isotopes. Some larvae fed T. erythraeum were morphologically ready to become benthic juveniles after 19 days. Given that Trichodesmium can be food for CoTS, reported increases in Trichodesmium could be a driving factor in the heightened frequency of CoTS population irruptions that have devastated coral reefs in past decades. Future studies could test this through investigating the diets of wild larvae and incorporating Trichodesmium abundance into models of CoTS population dynamics.

Background: We report the results of an international multi-institutional cohort of oligometastatic (OMD) head and neck cancer (HNC) patients treated with SBRT., Methods: Patients with OMD HNC (≤5 metastases) treated with SBRT between 2008 and 2016 at six institutions were included. Treated metastasis control (TMC), progression-free survival (PFS), and overall survival (OS) were analyzed by multivariable analysis (MVA)., Results: Forty-two patients with 84 HNC oligometastases were analyzed. The TMC rate at 1 and 2 years were 80% and 66%, with a median time to recurrence of 10.1 months. The median PFS and OS were 4.7 and 23.3 months. MVA identified a PTV point maximum (BED)10 > 100 Gy as a predictor of improved TMC (HR = 0.31, p = 0.034), and a cumulative PTV > 48 cc as having worse PFS (HR = 2.99, p < 0.001)., Conclusion: Favorable TMC and OS was observed in OMD HNCs treated with SBRT., (© 2023 Wiley Periodicals LLC.)

Purpose: To report clinical outcomes for patients with metastatic disease to the head and neck (HN) treated with stereotactic body radiation therapy (SBRT)., Methods: A retrospective review of patients treated with SBRT to HN sites from 2012 to 2020 was conducted. Treatment indications included the following: oligometastases, oligoprogression, and control a dominant area of progression (DAP). Kaplan-Meier method was used to estimate local control (LC), regional control (RC), overall survival (OS), and progression-free survival (PFS). Univariable (UVA) and multivariable analyses (MVA) were performed. Grade 3-4 acute and late toxicities were reported by the Common Terminology Criteria for Adverse Events v5.0., Results: Fifty-six patients (58 lesions) were analysed with a median follow-up of 16 months. Primary sites included lung (25.0%), kidney (19.6%), breast (19.6%) and other (35.8%). SBRT indications were as follows: oligometastases (42.9%), oligoprogression (19.6%) and local control of a dominant area of progression (37.5%). Most patients received SBRT to a single neck node (n = 47, 81.0%). Median SBRT dose was 40 Gy (range 25-50 Gy) in five fractions, with a median biologically effective dose (BED 10 ) of 72 Gy (range 37.5-100 Gy). One- and 2-year LC and RC rates were 97.6% and 72.7% as well as 100% and 86.7%, respectively. Median OS was 19.2 months (95% [CI] 14.8-69.4), and median PFS was 7.4 months (95% [CI] 5.2-11.9). The 1-year OS and PFS rates for oligometastases, oligoprogression and DAP were 95.8%, 63.6% and 38.1% (p = 0.0039) as well as 56.5%, 27.3% and 19.1% (p = 0.0004), respectively. On MVA, treatment indication and histology were predictive for OS, while indication and prior systemic therapy were predictive for PFS. Cumulative late grade 3 + toxicity rate was 11.3%, without grade 5 events., Conclusion: The use of SBRT for metastatic disease to the HN provided excellent LC rates with low rates of regional failure and an acceptable toxicity profile, highlighting its utility in these patients. Patients with oligometastatic disease had better OS and PFS than others., (© 2024. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Purpose: Advanced practice (AP) in radiation therapy (RT) is being implemented around the globe. In an effort to advance the understanding of the similarities and differences in APRT roles in Ontario, Canada, a community of practice (CoP) sought ways to provide quantitative data on the nature of APRT clinical activities and the frequency with which these activities were being executed., Methods: In 2017, a consensus building project involving 20 APRTs and 14 radiation therapy (RT) department managers in Ontario was completed to establish a mechanism to quantify APRTs' clinical impact. In Round 1 & 2, expert feedback was gathered to generate an Advanced Practice (AP) Activity List. In Round 3: 20 APRTs completed an online survey to assess the importance and applicability of each AP Activity to their role using Likert scale (0-5). A final AP Activity List & Definitions was generated., Results & Discussion: Round 1: Forty-seven AP activities were identified. Round 2: 3/14 RT managers provided 145 feedback statements on Round 1 AP Activity List. The working group used RT managers' feedback to clarify AP activities and definitions, specifically merging 33 unique AP activities to create 11 inclusive AP activities and eliminating 8 activities identified from Round 1. The most inclusive AP activity created was #1 New Patient Consultation, this AP Activity is merged from 7 unique AP activities. Incorporating RT managers' feedback with the internal AP clinical workload lists from 2 Ontario cancer centres resulted in a revised AP Activity List with 20 AP inclusive activities. Round 3: 14/20 APRTs provided Likert scores on this revised list. The most applicable AP activities (mean score) were #16 Technical Consultation (4.0), #15 Contouring Target Volume (3.8) and #2 Planning Consultation (3.8); the least applicable was #18 MR Applicator Assessment (0.9)., Conclusions: This is the first systematic attempt to build consensus on AP clinical activities. Non-clinical APRT activities related to research, education, innovation, and program development were not in the scope of this project. The Final AP Activity List & Definitions serves as a framework that allows standardized and continuous monitoring of AP clinical activities and impact., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Crown Copyright © 2024 Published by Elsevier B.V. on behalf of European Society for Radiotherapy & Oncology.)

The effectiveness of nitrogen removal in wetlands relies heavily on the biological processes that control its removal. Here, we used δ 15 N and δ 18 O of nitrate (NO 3 - ) to assess the presence and the dominance of transformation processes of nitrogen in two urban water treatment wetlands in Victoria, Australia over two rainfall events. Laboratory incubation experiments were undertaken in both light and dark to measure the isotopic fractionation factor of nitrogen assimilation (by periphyton and algae) and benthic denitrification (using bare sediment). Highest isotopic fractionations were observed for nitrogen assimilation by algae and periphyton in the light, 15 ε = -14.6 to -25 ‰ while the 15 ε = -1.5 ‰ in bare sediment, consistent with that of benthic denitrification. Transect water samplings of the wetlands showed different rainfall patterns (discrete versus continuous) affect the removal capability of the wetlands. During the discrete event sampling, the observed 15 ε of NO 3 - (an average of 3.0 to 4.3 ‰) within the wetland falls between the experimental 15 ε of benthic denitrification and assimilation; coinciding with the decrease in NO 3 - concentrations, suggesting that both denitrification and assimilation were important removal pathways. Depletion of δ 15 N-NO 3 - throughout the whole wetland system also suggested the influence of water column nitrification during this time. In contrast, during continuous rain events, no fractionation effect was observed within the wetland and was consistent with limited NO 3 - removal. The difference in fractionation factors within the wetland during different sampling conditions suggested that nitrate removal was highly likely limited by changes in overall nutrient inputs, residence time and water temperature which impeded biological uptake or removal. These highlight that consideration of sampling condition is crucial when assessing the efficacy of a wetland in removing nitrogen., Competing Interests: Declaration of competing interest All authors declare no conflict of interest., (Copyright © 2023 The Authors. Published by Elsevier B.V. All rights reserved.)

In the pursuit of energy and carbon neutrality, nitrogen removal technologies have been developed featuring nitrite (NO 2 - ) accumulation. However, high NO 2 - accumulations are often associated with stimulated greenhouse gas (i.e., nitrous oxide, N 2 O) emissions. Furthermore, the coexistence of free nitrous acid (FNA) formed by NO 2 - and proton (pH) makes the consequence of NO 2 - accumulation on N 2 O emissions complicated. The concurrent three factors, NO 2 - , pH and FNA may play different roles on N 2 O and nitric oxide (NO) emissions simultaneously, which has not been systematically studied. This study aims to decouple the effects of NO 2 - (0-200 mg N/L), pH (6.5-8) and FNA (0-0.15 mg N/L) on the N 2 O and NO production rates and the production pathways by ammonia oxidizing bacteria (AOB), with the use of a series of precisely executed batch tests and isotope site-preference analysis. Results suggested the dominant factors affecting the N 2 O production rate were NO 2 - and FNA concentrations, while pH alone played a relatively insignificant role. The most influential factor shifted from NO 2 - to FNA as FNA concentrations increased from 0 to 0.15 mg N/L. At concentrations below 0.0045 mg HNO 2 -N/L, nitrite rather than FNA played a significant role stimulating N 2 O production at elevated nitrite concentrations. The inhibition effect of FNA emerged with further increase of FNA between 0.0045-0.015 mg HNO 2 -N/L, weakening the promoting effect of increased nitrite. While at concentrations above 0.015 mg HNO 2 -N/L, FNA inhibited N 2 O production especially from nitrifier denitrification pathway with the level of inhibition linearly correlated with the FNA concentration. pH and the nitrite concentration regulated the production pathways, with elevated pH promoting the nitrifier nitrification pathway, while elevated NO 2 - concentrations promoting the nitrifier denitrification pathway. In contrast to N 2 O, NO emission was less susceptible to FNA at concentrations up to 0.015 mg N/L but was stimulated by increasing NO 2 - concentrations. This study, for the first time, distinguished the effects of pH, NO 2 - and FNA on N 2 O and NO production, thereby providing support to the design and operation of novel nitrogen removal systems with NO 2 - accumulation., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Purpose: We investigated the impact of local control (LC) on widespread progression (WSP) and overall survival (OS) in patients treated to all extracranial oligometastases (OMs) at presentation to SBRT in this retrospective review across 6 international centers., Materials/methods: Relationships between LC status of SBRT-directed OMs and OS and WSP (>5 new active/untreated lesions) were explored using Cox and Fine-Gray regression models, adjusting for radioresistant histology and pre-SBRT systemic therapy receipt. The association between LC and dosimetric predictors was analyzed with competing risk regression using death as a competing risk and across a wide range of simulated α/βratios., Results: In total, 1700 OMs in 1033 patients were analyzed, with 25.2% NSCLC, 22.7% colorectal, 12.8% prostate, and 8.1% breast histology. Patients who failed locally in any SBRT-directed OM within 6 mo were at 3.6-fold higher risk of death and 2.7-fold higher risk of WSP compared to those who remained locally-controlled (p < 0.001). Similar associations existed for each duration of LC investigated through 3 yrs post-SBRT. There was no significant difference in risk of WSP or death between patients who failed in a subset of SBRT-treated lesions vs. patients who failed in all lesions. Minimum dose (Dmin) to the GTV/ITV was most predictive of LC when compared to prescription dose, PTV Dmin, and PTV Dmax. Sensitivity analysis for achieving 1-yr LC > 95% found thresholds of 41.2 Gy and 55.2 Gy in 5 fractions for smaller (< 27.7 cc) and larger radioresistant lesions, respectively., Conclusion: This large multinational cohort suggests that the duration of LC following OM-directed SBRT strongly correlates with WSP and OS., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Purpose: Stereotactic Body Radiation Therapy (SBRT) is increasingly applied to treat non-spine bone metastases (NSBM) though data remains limited on this approach. In this retrospective study, we report outcomes and predictors of local failure (LF) and pathological fracture (PF) post-SBRT for NSBM using a mature single-institution database., Methods: Patients with NSBM treated with SBRT between 2011 and 2021 were identified. The primary objective was to assess the rates of radiographic LF. Secondary objectives were to assess the rates of in-field PF, overall survival (OS), and late grade ≥ 3 toxicity. Competing risks analysis was used to assess rates of LF and PF. Univariable regression and multivariable regression (MVR) were performed to investigate predictors of LF and PF., Results: A total of 373 patients with 505 NSBM were included in this study. Median follow-up was 26.5 months. The cumulative incidence of LF at 6, 12, and 24 months were 5.7%, 7.9%, and 12.6%, respectively. The cumulative incidence of PF at 6, 12, and 24 months were 3.8%, 6.1%, and 10.9%, respectively. Lytic NSBM (HR = 2.18; p < 0.01), a lower biologically effective dose (HR = 1.11 per 5 Gy 10 decrease; p = 0.04), and a PTV ≥ 54 cc (HR = 4.32; p < 0.01) predicted for a higher risk of LF on MVR. Lytic NSBM (HR = 3.43; p < 0.01), mixed (lytic/sclerotic) lesions (HR = 2.70; p = 0.04), and rib metastases (HR = 2.68; p < 0.01) predicted for a higher risk of PF on MVR., Conclusion: SBRT is an effective modality to treat NSBM with high rates of radiographic local control with an acceptable rate of PF. We identify predictors of both LF and PF that can serve to inform practice and trial design., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Purpose: With the increasing use of stereotactic body radiation therapy (SBRT) for primary and metastatic cancer, use of multitarget thoracic (MTT) SBRT is rising. Given the limited safety and efficacy data, we report the experience of this strategy from a large academic center., Methods and Materials: Between 2012 and 2021, patients who received SBRT for ≥2 thoracic targets separated by ≤1 year were retrospectively reviewed. The primary endpoint was clinically significant radiation pneumonitis (CSRP) requiring steroids, oxygen, or intubation. Secondary endpoints included local failure (LF), initiation or change of systemic therapy (ICST), progression-free survival, and overall survival. Competing risk analysis was used to evaluate the cumulative incidence of CSRP, LF, and ICST. Univariate and multivariable analyses were performed to look for clinical and dosimetric predictive factors of CSRP and LF., Results: One hundred ninety patients (481 lesions) were treated with MTT SBRT with a median follow-up of 19.7 months. Indications for SBRT were oligometastases (n = 70; 36.8%), oligoprogression (n = 62; 32.6%), curative intent in patients with primary lung cancer (n = 37; 19.5%), and control of dominant areas of metastatic progression (n = 21; 11.0%). The number of irradiated tumors ranged from 2 to 7 and the majority of SBRT courses were delivered simultaneously (88.2%). Overall, 14 patients (7.4%) had CSRP, with 5 cases requiring oxygen. The cumulative incidence of CSRP at 6 and 12 months was 5.3% and 7.6%, respectively. The cumulative incidence of LF at 2 years was 10.5%. The cumulative incidence of ICST at 2 years was 41.1%. Median progression-free survival was 11.8 months and median overall survival was 51.3 months. On multivariable analysis, a higher lung V35 Gy (hazard ratio, 2.59; P = .02) was a statistically significant predictor of CSRP and colorectal histology predicted for higher LF (hazard ratio, 2.12; P = .02)., Conclusions: In one of the largest institutional series of MTT SBRT, rates of CSRP and LF were low. Optimizing plans to lower the lung V35 Gy may decrease the risk of CSRP., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Purpose: Patients with oligometastatic disease (OMD) can experience durable disease control with ablative therapy to all sites of disease. Stereotactic body radiation therapy (SBRT) is an important modality in the management of OMD, although a validated prognostic model for OMD treated with SBRT is currently lacking. The purpose of this study was to develop a prognostic model for overall survival (OS) in patients with OMD treated with SBRT., Methods and Materials: A multi-institutional database of patients with extracranial OMD treated with SBRT was used for model development. The final prognostic model was generated in a training set using recursive partitioning analysis representing 75% of the population. Model performance was evaluated in the reserved test set., Results: The analysis included 1033 patients. The median OS for the entire cohort was 44.2 months (95% confidence interval [CI], 39.2-48.8 months). The variables used in the regression tree, in order of importance, were primary histology, lung-only OMD on presentation, the timing of OMD presentation, and age at the start of SBRT. A full 5-category risk stratification system based on the terminal nodes possessed fair to good discriminative power with a Harrell concordance statistic of 0.683 (95% CI, 0.634-0.731) and a time-dependent area under the receiver operating characteristic curve of 0.709 (95% CI, 0.706-0.711) in the test set, with good calibration. A simplified risk stratification system consisting of 3 risk categories was also proposed for greater ease of use with comparable performance., Conclusions: A clinical prognostic model for OS in patients with extracranial OMD treated with SBRT has been developed and validated., (Copyright © 2021 Elsevier Inc. All rights reserved.)

Purpose: Prolonged survivorship is increasingly observed in patients with oligometastases (OM) treated with stereotactic body radiation therapy (SBRT). The purpose of this study was to study the conditional survival of patients with OM, which can provide more detailed prognostic information over time by considering time already survived., Methods and Materials: A multi-institutional database consisting of 1033 patients with OM (≤5 metastases) treated with SBRT between 2006 and 2017 was analyzed. Conditional overall survival (OS) and progression-free survival (PFS) in 3 years were obtained at multiple time points for all patients and by primary cancer type. Cox regression was used to determine trends in conditional OS and PFS. Changes in the predictors of OS and PFS over time were also determined by multivariable Cox regression., Results: The median follow-up was 24 months (0.3-105 months). Three-year OS and PFS at baseline were 56.7% and 23.2%, respectively. The OS in 3 years conditional on having survived for 3, 6, 12, and 24 months did not significantly change over time (56.7%, 55.4%, 55.8%, and 50.6%, respectively; P = .60). In contrast, the probability of PFS in 3 years conditional on having survived progression-free for 3, 6, 12, and 24 months significantly increased over time (23.6%, 27.3%, 35.1%, and 48.8%, respectively; P < .001). When stratified by primary site, conditional PFS significantly increased over time for patients with colorectal, breast, or kidney cancer. Conditional OS remained stable for patients with non-small cell lung cancer or kidney cancer but significantly decreased over time for patients with prostate, breast, or colorectal cancer. Changes in significant prognostic factors of OS and PFS over time were also observed., Conclusions: Analysis of conditional survival among patients with OM showed that as patients survived longer, their prognosis for further survival remained stable or decreased. However, patients who survived longer without disease progression had increased probability of PFS over time., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Purpose: To evaluate the cumulative incidence of fracture and local failure and associated risk factors after stereotactic body radiation therapy (SBRT) for long bone metastases., Methods and Materials: Data from 111 patients with 114 metastases in the femur, humerus, and tibia treated with SBRT in 7 international centers between October 2011 and February 2021 were retrospectively reviewed and analyzed using a competing risk regression model., Results: The median follow-up was 21 months (range, 6-91 months). All but 1 patient had a Karnofsky performance status ≥70. There were 84 femur (73.7%), 26 humerus (22.8%), and 4 tibia (3.5%) metastases from prostate (45 [39.5%]), breast (22 [19.3%]), lung (15 [13.2%]), kidney (13 [11.4%]), and other (19 [16.6%]) malignancies. Oligometastases accounted for 74.8% of metastases and 28.1% were osteolytic. The most common total doses were 30 to 50 Gy in 5 daily fractions (50.9%). Eight fractures (5 in the femur, 2 in the tibia, and 1 in the humerus) were observed with a median time to fracture of 12 months (range, 0.8-33 months). In 6 out of 8 patients, fracture was not associated with local failure. The cumulative incidence of fracture was 3.5%, 6.1%, and 9.8% at 1, 2, and 3 years, respectively. The cumulative incidence of local failure (9/110 metastases with imaging follow-up) was 5.7%, 7.2%, and 13.5% at 1, 2, and 3 years, respectively. On multivariate analysis, extraosseous disease extension was significantly associated with fracture (P = .001; subhazard ratio, 10.8; 95% confidence interval, 2.8-41.9) and local failure (P = .02; subhazard ratio, 7.9; 95% confidence interval, 1.4-44.7)., Conclusions: SBRT for metastases in long bones achieved high rates of durable local metastasis control without an increased risk of fracture. Similar to spine SBRT, patients with extraosseous disease extension are at higher risk of local failure and fracture., (Copyright © 2022 Elsevier Inc. All rights reserved.)

Sewage sludges are a rich underused source of phosphorus (P) which contributes to environmental degradation, yet if recaptured, could return significant amounts of P to agricultural systems. Hydrothermal carbonisation (HTC) can efficiently recover P, with the added ability to transform P species into potentially more desirable forms for direct application to crops. P dynamics in hydrochars have primarily examined P speciation and chemical extractability as indicators of P bioavailability, but few studies directly evaluate the agronomic effectiveness of hydrochars as P fertilisers. As such, there is a clear need to assess the suitability of hydrochar as a source of bioavailable P in plant systems and the influence of HTC synthesis conditions. Response Surface Modelling of HTC synthesis conditions (pH, temperature and time), revealed initial pH significantly influence P distribution. Mild conditions of 180 °C for 30 min at pH 8.0 maximised P recovery (99%) along with carbon (62%) and nitrogen (43%) in hydrochars. Systematic characterisation of hydrochar P by chemical extraction and P L 2,3 -edge X-ray absorption near edge spectroscopy revealed H 2 O, NaHCO 3 and NaOH- P fractions were significantly (p < 0.05) reduced in all hydrochars, while HCl-P fraction increased with HTC temperatures at pH 7. In contrast, P L 2,3 -edge XANES spectra were remarkably similar in raw sludges and corresponding hydrochars, regardless of HTC temperature or pH, revealing P was predominantly present as ferric phosphate with some hydroxyapatite. Multiple linear regression modelling suggested a significant relationship between chemical extractability and P bioavailability to wheat present in the raw sludges and hydrochars. This research provides further insight into the potential to use hydrothermal treatment for recovery and agricultural reuse of P, the importance of operational conditions on P transformation and the relationship between P speciation and bioavailability. The value of sewage sludge in a more sustainable global P cycle is also highlighted., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Purpose: In recent years, stereotactic body radiotherapy (SBRT) has emerged as an effective treatment for oligometastatic cancers. Here, we report radiation treatment parameters and clinical outcomes for patients with oligometastatic colorectal cancer (CRC) treated with SBRT using a large multi-institutional database., Methods: Patients with extra-cranial oligometastatic CRC (≤5 lesions) treated with SBRT at six large academic cancer centers were included. The primary outcome was local recurrence while secondary outcomes included overall survival (OS) progression free survival, oligo-progression, and widespread progression. Survival outcomes were estimated using the Kaplan-Meier method. Univariable and multivariable analyses were performed to determine the relationship between patient and treatment characteristics and clinical outcomes., Results: We identified 235 patients with a total of 381 oligometastatic CRC lesions. The 1- and 5-year local recurrence rate was 13.6% and 44.3% respectively. The median OS was 49 months with a 2-and 5-year OS of 76.1% and 35.9%, respectively. On multivariable analysis, a BED 10 of ≥120 Gy, and lung versus liver metastases were associated with a reduction in local recurrence. Larger total PTV size (≥17.5 cc) was associated with worse overall survival, progression free survival, and widespread progression., Conclusion: This large multi-institutional analysis found that the use of SBRT for oligometastatic colorectal cancer resulted in favorable overall survival. However, local recurrence is higher than expected for ablative radiation treatment. An increase in BED 10 should be considered if feasible and safe., (Copyright © 2021. Published by Elsevier B.V.)

Introduction: Several studies have demonstrated the psychological impact of the COVID-19 pandemic on health care providers. However, there is little known about how the COVID-19 pandemic has impacted radiation therapists (RTs) in Norway or Canada. The aim of this investigation was to study the psychological impact of working during the COVID-19 pandemic among RTs in Canada and Norway., Methods: Online surveys were administered to a convenience sample of RTs and RT department managers. Approximately 2000 and 300 RTs were invited to participate from Canada and Norway, respectively. The RT survey collected information on demographics, work-related stressors, psychological impact, quality of life, and workplace support programmes. The RT manager survey collected information on departmental changes, patient volumes, staff shortages and redeployment, personal protective equipment, and infection control measures. Descriptive analysis, group comparisons and logistic regression were used to examine the impact of COVID-19 on RTs in the two countries, while open-ended questions were examined through thematic analysis., Results: Work-related stress and anxiety were prevalent among Canadian (n = 155) and Norwegian RTs (n = 124), with Canadian RTs reporting higher levels. Fear of transmission, changes in PPE usage, and changes in staffing were reported as the most frequent work-related stressors. Themes related to working during the pandemic included: generalised anxiety; physical, emotional and cognitive symptoms of stress; and loneliness, as well as negative impact on health and quality of relationships. Survey findings from RT department managers in Canada (n = 12) and Norway (n = 13) suggest that the pandemic had an organisational impact on RT departments due to implemented infection control measures and changes in staffing., Conclusion: The COVID-19 pandemic has led to similar stressors amongst Canadian and Norwegian RTs but relatively higher levels of psychological impact among Canadian RTs. Findings demonstrate the importance of mental health support programmes in the workplace to mitigate the psychological impact of the COVID-19 pandemic on RTs., (© 2021 The Authors. Journal of Medical Radiation Sciences published by John Wiley & Sons Australia, Ltd on behalf of Australian Society of Medical Imaging and Radiation Therapy and New Zealand Institute of Medical Radiation Technology.)