Tuning spatially fractionated radiotherapy dose profiles using the moiré effect.

Spatially Fractionated Radiotherapy (SFRT) has demonstrated promising potential in cancer treatment, combining the advantages of reduced post-radiation effects and enhanced local control rates. Within this paradigm, proton minibeam radiotherapy (pMBRT) was suggested as a new treatment modality, possibly producing superior normal tissue sparing to conventional proton therapy, leading to improvements in patient outcomes. However, an effective and convenient beam generation method for pMBRT, capable of implementing various optimum dose profiles, is essential for its real-world application. Our study investigates the potential of utilizing the moiré effect in a dual collimator system (DCS) to generate pMBRT dose profiles with the flexibility to modify the center-to-center distance (CTC) of the dose distribution in a technically simple way.We employ the Geant4 Monte Carlo simulations tool to demonstrate that the angle between the two collimators of a DCS can significantly impact the dose profile. Varying the DCS angle from 10 ∘ to 50 ∘ we could cover CTC ranging from 11.8 mm to 2.4 mm, respectively. Further investigations reveal the substantial influence of the multi-slit collimator's (MSC) physical parameters on the spatially fractionated dose profile, such as period (CTC), throughput, and spacing between MSCs. These findings highlight opportunities for precision dose profile adjustments tailored to specific clinical scenarios.The DCS capacity for rapid angle adjustments during the energy transition stages of a spot scanning system can facilitate dynamic alterations in the irradiation profile, enhancing dose contrast in normal tissues. Furthermore, its unique attribute of spatially fractionated doses in both lateral directions could potentially improve normal tissue sparing by minimizing irradiated volume. Beyond the realm of pMBRT, the dual MSC system exhibits remarkable versatility, showing compatibility with different types of beams (X-rays and electrons) and applicability across various SFRT modalities.Our study illuminates the dual MSC system's potential as an efficient and adaptable tool in the refinement of pMBRT techniques. By enabling meticulous control over irradiation profiles, this system may expedite advancements in clinical and experimental applications, thereby contributing to the evolution of SFRT strategies.

Introduction of ultra-hypofractionation in breast cancer: Implications for costs and resource use.

PURPOSE: A shift towards (ultra-)hypofractionated breast irradiation can have important implications for the practice of contemporary radiation oncology. This paper presents a systematic analysis of the impact of different fractionation schedules on multiple key performance indicators, namely resource use, costs, work times, throughput and waiting times. MATERIALS AND METHODS: Time-driven activity-based costing (TD-ABC) is applied to calculate the costs and resources consumed where the perspective of the radiotherapy department in adopted. Three fractionation regimens are considered: ultra-hypofractionation (5 x 5.2 Gy, UHF), moderate hypofractionation (15 x 2.67 Gy, HF) and conventional fractionation (25 x 2 Gy, CF). Subsequently, a discrete event simulation (DES) model of the radiotherapy care pathway is developed and scenarios are compared in which the following factors are varied: distribution of fractionation regimens, patient volume and operating hours. RESULTS: The application of (U)HF can permit radiotherapy departments to reduce the use of scarce resources, realise work time and cost savings, increase throughput and reduce waiting times. The financial advantages of (U)HF are, however, reduced in cases of excess capacity and cost savings may therefore be limited in the short-term. Moreover, although an extension of operating hours has favourable effects on throughput and waiting times, it may also reduce cost differences between fractionation schedules by increasing the capacity of resources. CONCLUSION: By providing an in-depth analysis of the consequences associated with a shift towards (U)HF in breast cancer, the present study demonstrates how a DES model based on TD-ABC costing can assist radiotherapy professionals in making data-driven decisions.

A Systematic Review of the Economic Burden of Proton Therapy in Head and Neck Cancer.

BACKGROUND: Radiation therapy is used to treat head and neck cancer (HNC) patients. Proton beam therapy (PBT) is one of the newer treatment options. This systematic review will describe the cost and cost-effectiveness of PBT compared with other first-line treatment options based on available literature and provide a better understanding of its usage in HNC in the future. METHODS: This systematic review was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Systematic searches were conducted in PUBMED, EMBASE and SCOPUS till February 2022. Original pharmacoeconomic articles written in English that considered PBT for HNC were included; the title, abstract and full text of the search items were screened. The included studies were critically appraised using the Drummond Checklist followed by data extraction. RESULTS: Eight of the ten included studies were of good quality; most were cost-effectiveness or cost comparison studies and used the Markov model and lifetime horizon. The dominant comparator was intensity-modulated radiotherapy. The willingness to pay threshold ranged from $30,828 to $150,000 per QALY. The incremental cost-effectiveness ratio (ICER) was between $4,436.1 and $695,000 per QALY. In HNC patients with human papillomavirus infection, the ICER was lower ($288,000/QALY) from the payer's perspective, but much higher ($390,000/QALY) from the societal perspective. CONCLUSION: Our systematic review showed that appropriate patient selection can make PBT cost-effective. HPV-associated tumors can be cost-effectively treated with PBT. From the payer's perspective, PBT is a cost-effective treatment option. In younger patients, PBT can result in lesser incidence of adverse effects, and hence, can reduce the subsequent need for long-term supportive care. Lower fractionation schedules can also make PBT a cost-effective treatment.

Increasing Use of Shorter-Course Radiotherapy for Prostate Cancer.

Importance: Randomized clinical trials have demonstrated the noninferiority of shorter radiotherapy (RT) courses (termed hypofractionation) compared with longer RT courses in patients with localized prostate cancer. Although shorter courses are associated with cost-effectiveness, convenience, and expanded RT access, their adoption remains variable. Objective: To identify the current practice patterns of external beam RT for prostate cancer in the US. Design, Setting, and Participants: This cohort study obtained data from the National Cancer Database, which collects hospital registry data from more than 1500 accredited US facilities on approximately 72% of US patients with cancer. Patients were included in the sample if they had localized prostate adenocarcinoma that was diagnosed between 2004 and 2020 and underwent external beam RT with curative intent. Analyses were conducted between February and March 2023. Exposures: Radiotherapy schedules, which were categorized as ultrahypofractionation (≤7 fractions), moderate hypofractionation (20-30 fractions), and conventional fractionation (31-50 fractions). Main Outcomes and Measures: Longitudinal pattern in RT fractionation schedule was the primary outcome. Multivariable logistic regression was performed to evaluate the variables associated with shorter RT courses. Covariables included age, National Comprehensive Cancer Network risk group, rurality, race, facility location, facility type, median income, insurance type or status, and Charlson-Deyo Comorbidity Index. Results: A total of 313 062 patients with localized prostate cancer (mean [SD] age, 68.8 [7.7] years) were included in the analysis. There was a temporal pattern of decline in the proportion of patients who received conventional fractionation, from 76.0% in 2004 to 36.6% in 2020 (P for trend <.001). From 2004 to 2020, use of moderate hypofractionation increased from 22.0% to 45.0% (P for trend <.001), and use of ultrahypofractionation increased from 2.0% to 18.3% (P for trend <.001). By 2020, the most common RT schedule was ultrahypofractionation for patients in the low-risk group and moderate hypofractionation for patients in the intermediate-risk group. On multivariable analysis, treatment at a community cancer program (compared with academic or research program; odds ratio [OR], 0.54 [95% CI, 0.52-0.56]; P < .001), Medicaid insurance (compared with Medicare; OR, 1.49 [95% CI, 1.41-1.57]; P < .001), Black race (compared with White race; OR, 0.90 [95% CI, 0.87-0.92]; P < .001), and higher median income (compared with lower median income; OR, 1.28 [95% CI, 1.25-1.31]; P < .001) were associated with receipt of shorter courses of RT. Conclusions and Relevance: Results of this cohort study showed an increase in the use of shorter courses of RT for prostate cancer from 2004 to 2020; a number of social determinants of health appeared to be associated with reduced adoption of shorter treatment courses. Realignment of reimbursement models may be necessary to enable broader adoption of ultrahypofractionation to support technology acquisition costs.

Monocrystalline diamond detector for online monitoring during synchrotron microbeam radiotherapy.

Microbeam radiation therapy (MRT) is a radiotherapy technique combining spatial fractionation of the dose distribution on a micrometric scale, X-rays in the 50-500 keV range and dose rates up to 16 × 103 Gy s-1. Nowadays, in vivo dosimetry remains a challenge due to the ultra-high radiation fluxes involved and the need for high-spatial-resolution detectors. The aim here was to develop a striped diamond portal detector enabling online microbeam monitoring during synchrotron MRT treatments. The detector, a 550 µm bulk monocrystalline diamond, is an eight-strip device, of height 3 mm, width 178 µm and with 60 µm spaced strips, surrounded by a guard ring. An eight-channel ASIC circuit for charge integration and digitization has been designed and tested. Characterization tests were performed at the ID17 biomedical beamline of the European Synchrotron Radiation Facility (ESRF). The detector measured direct and attenuated microbeams as well as interbeam fluxes with a precision level of 1%. Tests on phantoms (RW3 and anthropomorphic head phantoms) were performed and compared with simulations. Synchrotron radiation measurements were performed on an RW3 phantom for strips facing a microbeam and for strips facing an interbeam area. A 2% difference between experiments and simulations was found. In more complex geometries, a preliminary study showed that the absolute differences between simulated and recorded transmitted beams were within 2%. Obtained results showed the feasibility of performing MRT portal monitoring using a microstriped diamond detector. Online dosimetric measurements are currently ongoing during clinical veterinary trials at ESRF, and the next 153-strip detector prototype, covering the entire irradiation field, is being finalized at our institution.

Cost-effectiveness of hypofractionated versus conventional fractionated radiotherapy for the treatment of men with early glottic cancer: a study in the Brazilian public and private health system.

BACKGROUND: This study aims to evaluate whether hypofractionated radiotherapy (HYPOFRT) is a cost-effective strategy than conventional fractionated radiotherapy (CFRT) for early-stage glottic cancer (ESGC) in the Brazilian public and private health systems. METHODS: Adopting the perspective of the Brazilian public and private health system as the payer, a Markov model with a lifetime horizon was built to delineate the health states for a cohort of 65-year-old men after with ESGC treated with either HYPOFRT or CFRT. Probabilities of controlled disease, local failure, distant metastasis, and death and utilities scores were extracted from randomized clinical trials. Costs were based on the public and private health system reimbursement values. RESULTS: In the base case scenario, for both the public and private health systems, HYPOFRT dominated CFRT, being more effective and less costly, with a negative ICER of R$264.32 per quality-adjusted life-year (QALY) (public health system) and a negative ICER of R$2870.69/ QALY (private health system). The ICER was most sensitive to the probability of local failure, controlled disease, and salvage treatment costs. For the probabilistic sensitivity analysis, the cost-effectiveness acceptability curve indicates that there is a probability of 99.99% of HYPOFRT being cost-effective considering a willingness-to-pay threshold of R$2,000 ($905.39) per QALY (public sector) and willingness-to-pay threshold of R$16,000 ($7243.10) per QALY (private sector). The results were robust in deterministic and probabilistic sensitivity analyses. CONCLUSIONS: Considering a threshold of R$ 40,000 per QALY, HYPOFRT was cost-effective compared to CFRT for ESGC in the Brazilian public health system. The Net Monetary Benefit (NMB) is approximately 2,4 times (public health system) and 5,2 (private health system) higher for HYPOFRT than CFRT, which could open the opportunity of incorporating new technologies.

Risk assessment, surveillance, and nonpharmaceutical prevention of acute radiation dermatitis: results of a multicentric survey among the German-speaking radiation oncology community.

PURPOSE: Radiation dermatitis (RD) represents one of the most frequent side effects in radiotherapy (RT). Despite technical progress, mild and moderate RD still affects major subsets of patients and identification and management of patients with a high risk of severe RD is essential. We sought to characterize surveillance and nonpharmaceutical preventive management of RD in German-speaking hospitals and private centers. METHODS: We conducted a survey on RD among German-speaking radiation oncologists inquiring for their evaluation of risk factors, assessment methods, and nonpharmaceutical preventive management of RD. RESULTS: A total of 244 health professionals from public and private institutions in Germany, Austria, and Switzerland participated in the survey. RT-dependent factors were deemed most relevant for RD onset followed by lifestyle factors, emphasizing the impact of treatment conceptualization and patient education. While a broad majority of 92.8% assess RD at least once during RT, 59.0% of participants report RD at least partially arbitrarily and 17.4% stated to classify RD severity solely arbitrarily. 83.7% of all participants were unaware of patient-reported outcomes (PROs). Consensus exists on some lifestyle recommendations like avoidance of sun exposure (98.7%), hot baths (95.1%), and mechanical irritation (91.8%) under RT, while deodorant use (63.4% not at all, 22.1% with restrictions) or application of skin lotion (15.1% disapproval) remain controversial and are not recommended by guidelines or evidence-based practices. CONCLUSION: Identification of patients at an increased risk of RD and subsequent implementation of adequate preventive measures remain relevant and challenging aspects of clinical routines. Consensus exists on several risk factors and nonpharmaceutical prevention recommendations, while RT-dependent risk factors, e.g., the fractionation scheme, or hygienic measures like deodorant use remain controversial. Surveillance is widely lacking methodology and objectivity. Intensifying outreach in the radiation oncology community is needed to improve practice patterns.

Hypofractionation and SABR: 25 years of evolution in medical physics and a glimpse of the future.

As we were invited to write an article for celebrating the 50th Anniversary of Medical Physics journal, on something historically significant, commemorative, and exciting happening in the past decades, the first idea came to our mind is the fascinating radiotherapy paradigm shift from conventional fractionation to hypofractionation and stereotactic ablative radiotherapy (SABR). It is historically and clinically significant since as we all know this RT treatment revolution not only reduces treatment duration for patients, but also improves tumor control and cancer treatment outcomes. It is also commemorative and exciting for us medical physicists since the technology development in medical physics has been the main driver for the success of this treatment regimen which requires high precision and accuracy throughout the entire treatment planning and delivery. This article provides an overview of the technological development and clinical trials evolvement in the past 25 years for hypofractionation and SABR, with an outlook to the future improvement.

Is ultra-hypo-fractionated radiotherapy more cost-effective relative to conventional fractionation in treatment of prostate cancer? A cost-utility analysis alongside a randomized HYPO-RT-PC trial.

BACKGROUND: Economic evidence for comparing low fraction with ultra-hypo fractionated (UHF) radiation therapy in the treatment of intermediate-to-high-risk prostate cancer (PC) is lacking, especially in Europe. This study presents an economic evaluation performed alongside an ongoing clinical trial. AIM: To investigate up to 6 years' follow-up whether conventional fractionation (CF, 78.0 Gy in 39 fractions, 5 days per week for 8 weeks) is more cost-effective than UHF (42.7 Gy in 7 fractions, 3 days per week for 2.5 weeks inclusive of 2 weekends) radiotherapy in treatment for patients with intermediate-to-high-risk PC. METHOD: HYPO-RT-PC trial is an open-label, randomized, multicenter (10 in Sweden; 2 in Denmark) phase-3 trial. Patients from Sweden (CF 434; UHF 445) were included in this study. The trial database was linked to the National Patient Registry (NPR). Costs for inpatient/non-primary outpatient care for each episode were retrieved. For calculating Quality-adjusted life years (QALYs), the EORTC QLQ-C30 questionnaire was mapped to the EQ-5D-3L index. Multivariable regression analyses were used to compare the difference in costs and QALYs, adjusting for age and baseline costs, and health status. The confidence interval for the difference in costs, QALYs and incremental cost-effectiveness ratio effectiveness ratio (ICER) was estimated by the bootstrap percentile method. RESULTS: No significant differences were found in ICER between the two arms after 6 years of follow-up. CONCLUSION: The current study did not support that the ultra-hypo-fractionated treatment was more cost-effective than the conventional fraction treatment up to the sixth year of the trial.

FRAME-Monte Carlo model for evaluation of the stable isotope mixing and fractionation.

Bayesian stable isotope mixing models are widely used in geochemical and ecological studies for partitioning sources that contribute to various mixtures. However, none of the existing tools allows accounting for the influence of processes other than mixing, especially stable isotope fractionation. Bridging this gap, new software for the stable isotope Fractionation And Mixing Evaluation (FRAME) has been developed with a user-friendly graphical interface (malewick.github.io/frame). This calculation tool allows simultaneous sources partitioning and fractionation progress determination based on the stable isotope composition of sources/substrates and mixture/products. The mathematical algorithm applies the Markov-Chain Monte Carlo model to estimate the contribution of individual sources and processes, as well as the probability distributions of the calculated results. The performance of FRAME was comprehensively tested and practical applications of this modelling tool are presented with simple theoretical examples and stable isotope case studies for nitrates, nitrites, water and nitrous oxide. The open mathematical design, featuring custom distributions of source isotope signatures, allows for the implementation of additional processes that alternate the characteristics of the final mixture and its application for various range of studies.

Variable and fixed costs in NHS radiotherapy; consequences for increasing hypo fractionation.

BACKGROUND/PURPOSE: The increased use of hypofractionated radiotherapy changes department activity. While expected to be cost-effective, departments' fixed costs may impede savings. Understanding radiotherapy's cost-drivers, to what extent these are fixed and consequences of reducing activity can help to inform reimbursement strategies. MATERIAL/METHODS: We estimate the cost of radiotherapy provision, using time-driven activity-based costing, for five bone metastases treatment strategies, in a large NHS provider. We compare these estimations to reimbursement tariff and assess their breakdown by cost types: fixed (buildings), semi-fixed (staff, linear accelerators) and variable (materials) costs. Sensitivity analyses assess the cost-drivers and impact of reducing departmental activity on the costs of remaining treatments, with varying disinvestment assumptions. RESULTS: The estimated radiotherapy cost for bone metastases ranges from 430.95€ (single fraction) to 4240.76€ (45 Gy in 25#). Provider costs align closely with NHS reimbursement, except for the stereotactic ablative body radiotherapy (SABR) strategy (tariff exceeding by 15.3%). Semi-fixed staff costs account for 28.1-39.7% and fixed/semi-fixed equipment/space costs 38.5-54.8% of provider costs. Departmental activity is the biggest cost-driver; reduction in activity increasing cost, predominantly in fractionated treatments. Decommissioning linear accelerators ameliorates this, although can only be realised at equipment capacity thresholds. CONCLUSION: Hypofractionation is less burdensome to patients and long-term offers a cost-efficient mechanism to treat an increasing number of patients within existing capacity. As a large majority of treatment costs are fixed/semi-fixed, disinvestment is complex, within the life expectancy of a linac, imbalances between demand and capacity will result in higher treatment costs. With a per-fraction reimbursement, this may disincentivise delivery of hypofractionated treatments.

Assessment of predictive indicators of acute gastrointestinal toxicity using in vivo transmission images.

PURPOSE: For pelvic and abdominal treatments, excess dose to the bowel can result in acute toxicities. Current estimates of bowel toxicity are based on pre-treatment dose-volume histogram data. However, the actual dose the bowel receives depends on interfraction variations, such as patient anatomy changes. We propose a method to model bowel toxicities, incorporating in vivo patient information using transit electronic portal imaging device (EPID) images. METHODS AND MATERIALS: For 63 patients treated to the lower thorax, abdomen, or pelvis on the Varian Halcyon, weekly chart review was performed to obtain incidences of grade 2 or higher toxicity, RTOG scale. Twenty patients presented with acute gastrointestinal (GI) toxicity. All patients were treated with conventional fractionation. For each treatment plan, the absolute volume dose-volume histogram of the bowel was exported and analyzed. Additionally, for each fraction of treatment, in vivo EPID images were collected and used to estimate the change in radiation transmission during the course of treatment. A logistic model was used to test correlations between acute GI toxicity and bowel dosimetric parameters as well as metrics obtained from in vivo image measurements. After performing the fit to the in vivo EPID data, the bootstrap resampling method was used to create confidence intervals. In vivo EPID image metrics from an additional 42 patients treated to the lower thorax, abdomen, or pelvis were used to validate the logistic model fit. RESULTS: The incidence of toxicity versus the volume of 40 Gy to the bowel space was fitted with a logistic function, which was superior to an average model (p < 0.0001) and agrees with previously published models. For the initial in vivo EPID data, the incidence of toxicity versus the sum of in vivo transmission measurements showed marginal significance after 15 fractions (p = 0.10) of treatment and a significance of p = 0.038 is seen at the 20th fraction, when compared to an average model. For the validation data set, the logistic model of the in vivo transmission measurement after 20 fractions was superior to the average model (p = 0.043), with the model falling within the 68% confidence interval of the fit of the initial data set. CONCLUSIONS: Dose-volume constraints to reduce the incidence of acute GI toxicity have been validated. The presented novel EPID transmission-based metric can be used to identify GI toxicity as patients progress through treatment.

The efficiency of 18F-FDG-PET/CT in the assessment of tumor response to preoperative chemoradiation therapy for locally recurrent rectal cancer.

BACKGROUND: Locally recurrent rectal cancer (LRRC) remains a major problem after curative resection of primary rectal cancer. A noninvasive, prognostic biomarker with which to accurately evaluate disease status and assess the treatment response is critically needed to optimize treatment plans. This study assesses the effectiveness of PET/CT evaluation of preoperative chemoradiation therapy (CRT) in patients with LRRC. METHODS: Since 2004, we have been performing preoperative CRT to improve local tumor control and survival. Between 2004 and 2013, 40 patients with LRRC underwent preoperative CRT (radiation: 50 Gy/25 fractions; chemotherapy: irinotecan plus UFT [tegafur and uracil]/leucovorin) and radical surgery, and underwent 18F-FDG-PET/CT before and 3 weeks after the completion of CRT. The maximum standardized uptake values (SUVmax) of the pre-CRT scan (Pre-SUV) and the post-CRT scan (Post-SUV) were measured. The predictive value of the 18F-FDG-PET and CT/MRI response assessments was evaluated. RESULTS: The mean Pre-SUV was significantly higher than the Post-SUV (8.2 ± 6.1, vs. 3.8 ± 4.0; P < 0.0001). Following CRT, 17/40 patients (42.5%) were classified as responders according to the Mandard tumor regression grade (TRG1-2). The mean Post-SUV was significantly lower in responders than in nonresponders (2.0 ± 1.7 vs. 5.1 ± 3.9; P = 0.0038). Pathological response was not correlated with the response as evaluated by CT (P > 0.9999) or MRI (P > 0.9999). Multivariate regression analysis identified Post-SUV as an independent predictor of local re-recurrence-free survival (P = 0.0383) and for overall survival (P = 0.0195). CONCLUSIONS: PET/CT is useful in assessing tumor response to preoperative CRT for LRRC and predicting prognosis after surgery.

Practical considerations for prostate hypofractionation in the developing world.

External beam radiotherapy is an effective curative treatment option for localized prostate cancer, the most common cancer in men worldwide. However, conventionally fractionated courses of curative external beam radiotherapy are usually 8-9 weeks long, resulting in a substantial burden to patients and the health-care system. This problem is exacerbated in low-income and middle-income countries where health-care resources might be scarce and patient funds limited. Trials have shown a clinical equipoise between hypofractionated schedules of radiotherapy and conventionally fractionated treatments, with the advantage of drastically shortening treatment durations with the use of hypofractionation. The hypofractionated schedules are supported by modern consensus guidelines for implementation in clinical practice. Furthermore, several economic evaluations have shown improved cost effectiveness of hypofractionated therapy compared with conventional schedules. However, these techniques demand complex infrastructure and advanced personnel training. Thus, a number of practical considerations must be borne in mind when implementing hypofractionation in low-income and middle-income countries, but the potential gain in the treatment of this patient population is substantial.

Early health economic analysis of 1.5 T MRI-guided radiotherapy for localized prostate cancer: Decision analytic modelling.

BACKGROUND AND PURPOSE: 1.5 Tesla magnetic resonance imaging radiotherapy linear accelerator (MR-Linac) is gaining interest for treatment of localized prostate cancer. Clinical evidence is lacking and it therefore remains uncertain whether MR-Linac is cost-effective. An early health economic analysis was performed to calculate the necessary relative reduction in complications and the maximum price of MR-Linac (5 fractions) to be cost-effective compared to 5, 20 and 39 fractionation schedules of external beam radiotherapy (EBRT) and low-dose-rate (LDR) brachytherapy. MATERIALS AND METHODS: A state transition model was developed for men with localized prostate cancer. Complication rates such as grade ≥2 urinary, grade ≥2 bowel and sexual complications, and utilities were based on systematic literature searches. Costs were estimated from a Dutch healthcare perspective. Threshold analyses were performed to identify the thresholds of complications and costs for MR-Linac to be cost-effective, while holding other outcomes such as biochemical progression and mortality constant. One-way sensitivity analyses were performed to outline uncertainty outcomes. RESULTS: At €6460 per patient, no reductions in complications were needed to consider MR-Linac cost-effective compared to EBRT 20 and 39 fractions. Compared to EBRT 5 fractions and LDR brachytherapy, MR-Linac was found to be cost-effective when complications are relatively reduced by 54% and 66% respectively. Results are highly sensitive to the utilities of urinary, bowel and sexual complications and the probability of biochemical progression. CONCLUSIONS: MR-Linac is found to be cost-effective compared to 20 and 39 fractions EBRT at baseline. For MR-Linac to become cost-effective over 5 fractions EBRT and LDR brachytherapy, it has to reduce complications substantially or be offered at lower costs.

Cost-effectiveness of postmastectomy hypofractionated radiation therapy vs conventional fractionated radiation therapy for high-risk breast cancer.

BACKGROUND: The phase 3 NCT00793962 trial demonstrated that postmastectomy hypofractionated radiation therapy (HFRT) was noninferior to conventional fractionated radiation therapy (CFRT) in patients with high-risk breast cancer. This study assessed the cost-effectiveness of postmastectomy HFRT vs CFRT based on the NCT00793962 trial. METHODS: A Markov model was adopted to synthesize the medical costs and health benefits of patients with high-risk breast cancer based on data from the NCT00793962 trial. Main outcomes were discounted lifetime costs, quality-adjusted life-years (QALYs), and incremental cost-effectiveness ratio (ICER). We employed a time-dependent horizon from Chinese, French and USA payer perspectives. Model robustness was evaluated with one-way and probabilistic sensitivity analyses. RESULTS: Patients receiving CFRT versus HFRT gained an incremental 0.0163 QALYs, 0.0118 QALYs and 0.0028 QALYs; meanwhile an incremental cost of $2351.92, $4978.34 and $8812.70 from Chinese, French and USA payer perspectives, respectively. Thus CFRT versus HFRT yielded an ICER of $144,281.47, $420,636.10 and $3,187,955.76 per QALY from Chinese, French and USA payer perspectives, respectively. HFRT could maintain a trend of >50% probabilities of cost-effectiveness below a willingness-to-pay (WTP) of $178,882.00 in China, while HFRT was dominant relative to CFRT, regardless of the WTP values in France and the USA. Sensitivity analyses indicated that the ICERs were most sensitive to the parameters of overall survival after radiotherapy. CONCLUSIONS: Postmastectomy HFRT could be used as a cost-effective substitute for CFRT in patients with high-risk breast cancer and should be considered in appropriately selected patients.

Irradiator Commissioning and Dosimetry for Assessment of LQ α and ß Parameters, Radiation Dosing Schema, and in vivo Dose Deposition.

Radiation dosimetry is critical in the accurate delivery and reproducibility of radiation schemes in preclinical models for high translational relevance. Prior to performing any in vitro or in vivo experiments, the specific dose output for the irradiator and individual experimental designs must be assessed. Using an ionization chamber, electrometer, and solid water setup, the dose output of wide fields at isocenter can be determined. Using a similar setup with radiochromic films in the place of the ionization chamber, dose rates for smaller fields at different depths can also be determined. In vitro clonogenic survival assays of cancer cells in response to radiation treatment are inexpensive experiments that provide a measure of inherent radio-sensitivity of cell lines by fitting these data with the traditional linear-quadratic model. Model parameters estimated from these assays, combined with the principles of biologic effective doses, allows one to develop varying fractionation schedules for radiation treatment that provide equivalent effective doses in tumor-bearing animal experiments. This is an important factor to consider and correct for in comparing in vivo radiation therapy schedules to eliminate potential confounding of results due to variance in the delivered effective doses. Taken together, this article provides a general method for dose output verification preclinical animal and cabinet irradiators, in vitro assessment of radio-sensitivity, and verification of radiation delivery in small living organisms.

Assessment of Simulated SARS-CoV-2 Infection and Mortality Risk Associated With Radiation Therapy Among Patients in 8 Randomized Clinical Trials.

Importance: During the COVID-19 pandemic, cancer therapy may put patients at risk of SARS-CoV-2 infection and mortality. The impacts of proposed alternatives on reducing infection risk are unknown. Objective: To investigate how the COVID-19 pandemic is associated with the risks and benefits of standard radiation therapy (RT). Design, Setting, and Participants: This comparative effectiveness study used estimated individual patient-level data extracted from published Kaplan-Meier survival figures from 8 randomized clinical trials across oncology from 1993 to 2014 that evaluated the inclusion of RT or compared different RT fractionation regimens. Included trials were Dutch TME and TROG 01.04 examining rectal cancer; CALGB 9343, OCOG hypofractionation trial, FAST-Forward, and NSABP B-39 examining early stage breast cancer, and CHHiP and HYPO-RT-PC examining prostate cancer. Risk of SARS-CoV-2 infection and mortality associated with receipt of RT in the treatment arms were simulated and trials were reanalyzed. Data were analyzed between April 1, 2020, and June 30, 2020. Exposures: COVID-19 risk associated with treatment was simulated across different pandemic scenarios, varying infection risk per fractions (IRFs) and case fatality rates (CFRs). Main Outcomes and Measures: Overall survival was evaluated using Cox proportional hazards modeling under different pandemic scenarios. Results: Estimated IPLD from a total of 14 170 patients were included in the simulations. In scenarios with low COVID-19-associated risks (IRF, 0.5%; CFR, 5%), fractionation was not significantly associated with outcomes. In locally advanced rectal cancer, short-course RT was associated with better outcomes than long-course chemoradiation (TROG 01.04) and was associated with similar outcomes as RT omission (Dutch TME) in most settings (eg, TROG 01.04 median HR, 0.66 [95% CI, 0.46-0.96]; Dutch TME median HR, 0.91 [95% CI, 0.80-1.03] in a scenario with IRF 5% and CFR 20%). Moderate hypofractionation in early stage breast cancer (OCOG hypofractionation trial) and prostate cancer (CHHiP) was not associated with survival benefits in the setting of COVID-19 (eg, OCOG hypofractionation trial median HR, 0.89 [95% CI, 0.74-1.06]; CHHiP median HR, 0.87 [95% CI, 0.75-1.01] under high-risk scenario with IRF 10% and CFR 30%). More aggressive hypofractionation (FAST-Forward, HYPO-RT-PC) and accelerated partial breast irradiation (NSABP B-39) were associated with improved survival in higher risk scenarios (eg, FAST-Forward median HR, 0.58 [95% CI, 0.49-0.68]; HYPO-RT-PC median HR, 0.60 [95% CI, 0.48-0.75] under scenario with IRF 10% and CFR 30%). Conclusions and Relevance: In this comparative effectiveness study of data from 8 clinical trials of patients receiving radiation therapy to simulate COVID-19 risk and mortality rates, treatment modification was not associated with altered risk from COVID-19 in lower-risk scenarios and was only associated with decreased mortality in very high COVID-19-risk scenarios. This model, which can be adapted to dynamic changes in COVID-19 risk, provides a flexible, quantitative approach to assess the potential impact of treatment modifications and supports the continued delivery of standard evidence-based care with appropriate precautions against COVID-19.

Assessment of Toxic Effects Associated With Dose-Fractionated Radiotherapy Among Patients With Cancer and Comorbid Collagen Vascular Disease.

Importance: The adoption of alternative fractionated radiotherapy regimens for the treatment of patients with cancer and comorbid collagen vascular disease (CVD) is controversial among oncologists because of concerns about potentially severe toxic effects; however, the association between fractionated radiotherapy and toxic effects in the modern era has not been well studied. Objective: To compare acute and late toxic effects among patients with cancer and comorbid CVD who received dose-fractionated radiotherapy. Design, Setting, and Participants: This retrospective cohort study examined 197 adult patients with cancer and CVD who received radiotherapy at a single-institution tertiary academic center over a 12-year period (February 1, 2007, to April 30, 2019), with a median follow-up of 23 months (range, 0-108 months). Data were analyzed from February 1 to August 31, 2020. Exposures: Three dose-fractionated radiotherapy regimens: conventional fractionation (CF; ≤2 Gy per fraction), moderate hypofractionation (MH; >2 Gy to <5 Gy per fraction), and ultrahypofractionation (UH; ≥5 Gy per fraction). Main Outcomes and Measures: The main outcomes were the incidence and severity of acute and late radiotherapy-associated toxic effects, which were assessed separately by dose-fractionation regimen. Toxic effects occurring within 90 days after radiotherapy completion were considered acute, and toxic effects occurring after that 90-day period were considered late. Secondary goals were to identify covariates associated with toxic effects and to characterize the incidence of CVD symptom flares (defined as worsening clinical symptoms and/or worsening results [transient or permanent] on associated blood tests compared with baseline, as documented by managing physicians) after radiotherapy. Results: Of 197 patients with cancer and comorbid CVD (mean [SD] age, 69 [12] years; 134 women [68.0%]; and 149 White participants [75.6%]), 80 patients (40.6%) received CF radiotherapy, 55 patients (27.9%) received MH radiotherapy, and 62 patients (31.5%) received UH radiotherapy. The most common CVD diagnoses were rheumatoid arthritis (74 patients [37.6%]), psoriasis (54 patients [27.4%]), systemic lupus erythematosus (34 patients [17.3%]), and scleroderma (8 patients [4.1%]). The most common radiotherapy sites were the breast (48 patients [24.4%]), thorax (25 patients [12.7%]), central nervous system (24 patients [12.2%]), and prostate (23 patients [11.7%]). Data on acute toxic effects were available for 188 patients (95.4%) and missing for 9 patients (4.6%). Data on late toxic effects were available for 142 patients (72.1%) and missing for 55 patients (27.9%). Over 12 years, the unadjusted incidences of severe acute toxic effects associated with CF, MH, and UH radiotherapy were 5.4% (95% CI, 0.3%-10.5%), 7.4% (95% CI, 0.4%-14.4%), and 1.7% (95% CI, 0%-5.0%), respectively. The incidences of severe late toxic effects associated with CF, MH, and UH radiotherapy were 8.3% (95% CI, 1.3%-15.3%), 0%, and 2.2% (95% CI, 0%-6.4%), respectively. No significant associations were found between severe acute or late toxic effects by dose fractionation regimen. In the multivariable analysis, MH radiotherapy was associated with a lower likelihood of developing late toxic effects (odds ratio [OR], 0.21; 95% CI, 0.05-0.83; P = .03) compared with CF radiotherapy. Those who received UH radiotherapy had a lower likelihood of experiencing late toxic effects (OR, 0.22; 95% CI, 0.04-1.21; P = .08). A total of 19 of 80 patients (23.8%), 15 of 55 patients (27.3%), and 10 of 62 patients (16.1%) experienced CVD symptom flares after receiving CF, MH, and UH radiotherapy, respectively (P = .33). Conclusions and Relevance: In this study, the incidences of unadjusted severe toxic effects over 12 years were less than 10% and were not significantly associated with dose fractionation. When clinically indicated, patients with cancer and comorbid CVD may not require immediate exclusion from the receipt of currently used hypofractionated radiotherapy regimens.