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PURPOSE: The European Society on Breast Imaging has recommended supplemental magnetic resonance imaging (MRI) every two to four years for women with mammographically dense breasts. This may not be feasible in many screening programs. Also, the European Commission Initiative on Breast Cancer suggests not implementing screening with MRI. By analyzing interval cancers and time from screening to diagnosis by density, we present alternative screening strategies for women with dense breasts. METHODS: Our BreastScreen Norway cohort included 508 536 screening examinations, including 3125 screen-detected and 945 interval breast cancers. Time from screening to interval cancer was stratified by density measured by an automated software and classified into Volpara Density Grades (VDGs) 1–4. Examinations with volumetric density ≤3.4% were categorized as VDG1, 3.5%–7.4% as VDG2, 7.5%–15.4% as VDG3, and ≥15.5% as VDG4. Interval cancer rates were also determined by continuous density measures. RESULTS: Median time from screening to interval cancer was 496 (IQR: 391–587) days for VDG1, 500 (IQR: 350–616) for VDG2, 482 (IQR: 309–595) for VDG3 and 427 (IQR: 266–577) for VDG4. A total of 35.9% of the interval cancers among VDG4 were detected within the first year of the biennial screening interval. For VDG2, 26.3% were detected within the first year. The highest annual interval cancer rate (2.7 per 1000 examinations) was observed for VDG4 in the second year of the biennial interval. CONCLUSIONS: Annual screening of women with extremely dense breasts may reduce the interval cancer rate and increase program-wide sensitivity, especially in settings where supplemental MRI screening is not feasible.

PurposeThe aim of this study was to develop a prioritization strategy for scheduling immediate screening mammographic interpretation and possible diagnostic evaluation.MethodsA population-based cohort with screening mammograms performed from 2012 to 2020 at 126 radiology facilities from 7Breast Cancer Surveillance Consortium registries was identified. Classification trees identified combinations of clinical history (age, BI-RADS® density, time since prior mammogram, history of false-positive recall or biopsy result), screening modality (digital mammography, digital breast tomosynthesis), and facility characteristics (profit status, location, screening volume, practice type, academic affiliation) that grouped screening mammograms by recall rate, with ≥12/100 considered high and ≥16/100 very high. An efficiency ratio was estimated as the percentage of recalls divided by the percentage of mammograms.ResultsThe study cohort included 2,674,051 screening mammograms in 925,777 women, with 235,569 recalls. The most important predictor of recall was time since prior mammogram, followed by age, history of false-positive recall, breast density, history of benign biopsy, and screening modality. Recall rates were very high for baseline mammograms (21.3/100; 95% confidence interval, 19.7-23.0) and high for women with ≥5 years since prior mammogram (15.1/100; 95% confidence interval, 14.3-16.1). The 9.2% of mammograms in subgroups with very high and high recall rates accounted for 19.2% of recalls, an efficiency ratio of 2.1 compared with a random approach. Adding women

BACKGROUND: Artificial intelligence (AI) may improve cancer detection and risk prediction during mammography screening, but radiologists' preferences regarding its characteristics and implementation are unknown. PURPOSE: To quantify how different attributes of AI-based cancer detection and risk prediction tools affect radiologists' intentions to use AI during screening mammography interpretation. MATERIALS AND METHODS: Through qualitative interviews with radiologists, we identified five primary attributes for AI-based breast cancer detection and four for breast cancer risk prediction. We developed a discrete choice experiment based on these attributes and invited 150 US-based radiologists to participate. Each respondent made eight choices for each tool between three alternatives: two hypothetical AI-based tools versus screening without AI. We analyzed samplewide preferences using random parameters logit models and identified subgroups with latent class models. RESULTS: Respondents (n = 66; 44% response rate) were from six diverse practice settings across eight states. Radiologists were more interested in AI for cancer detection when sensitivity and specificity were balanced (94% sensitivity with

The practice leaders shared common concerns with different approaches in the immediate and longer terms. By the time this information is available to the reader, the projections for the disease burden and the recovery will have changed again. Already, some states and institutions are reporting a plateau in COVID-19 cases, and non-COVID-related admissions are on the rise. Nevertheless, the practice-level maneuvers to manage extraordinary conditions remain salient as we, collectively, will be systemically stressed again. Heeding these lessons may lessen the impact of second waves of regional COVID-19 infections and future pandemics.

Objective We conducted a national survey to understand the impact of state-level density reporting laws on women’s level of density risk awareness and their engagement in conversations with providers regarding supplemental screening. Methods In all, 1,500 US women aged 40 to 74 years who obtained a mammogram within 2 years were surveyed in February 2018. The sampling design yielded 300 respondents in each of five groups categorized based on density reporting law features. Women were asked about their breast density-related knowledge, importance of being notified, and sources of information and if conversations with providers regarding density and supplemental screening occurred. Survey results were compared across groups and between women residing in states with versus without density laws. Results The majority of respondents in all groups felt that it is important for women to know their breast density type (range, 85%-90%). Women were most likely informed of breast density type by a health care provider (range, 68%-72%), followed by the mammography result letter (range, 48%-68%), and then a radiologist (range, 46%-61%). Women from states with a density law were significantly more likely to have learned of their breast tissue type from a mammogram results letter (60% versus 48%, P = .011) and discuss supplemental screening (67% versus 53%, respectively; P = .008) than women from states without a law. Conclusion State-level density reporting laws are associated with increased breast density awareness and increased likelihood of conversations between women and their providers regarding supplemental screening.

Purpose/Objective(s) There are multiple technical approaches for stereotactic radiosurgery (SRS) delivery to multiple brain metastases, including single-isocenter (SIT) and multiple-isocenter (MIT) techniques. SIT is increasing employed to streamline treatment planning and delivery in the setting of multiple brain metastases such that a single radiosurgery plan is generated to treat all metastases simultaneously, rather than generating and delivering separate plans for each metastasis. In this study, we compare clinical outcomes using a single-isocenter versus multiple-isocenter approaches for treating multiple brain metastases amenable to single fraction radiosurgery. Materials/Methods This is a single-institution, retrospective review of patients treated from 2017-2019 with intact brain metastases treated using a SIT or MIT with linear accelerator-based SRS. The typical prescription dose was 18 Gy in 1 fraction prescribed to the 80-90% isodose line. Time from end of treatment to local failure or radionecrosis (RN) for each lesion was recorded. On the per-lesion basis, local control (LC) and freedom-from-radionecrosis (FFR), were estimated with Kaplan Meier method and compared between SIT and MIT group via log-rank test. Evidence of RN was defined as radiographic evidence of cerebral edema surrounding a treated lesion with associated clinical symptoms. Multivariable analysis using Cox proportional-hazard regression was used to establish potential predictors for RN, and significance assessed by Likelihood ratio test. Results 104 patients with a total of 437 metastases (80% supratentorial and 20% infratentorial) were included. 232 lesions were treated with a SIT approach, ranging from 2-13 (median 5) intact metastases treated per treatment course. Median radiographic follow up time was 6.4 months for SIT lesions and 10.7 months for MIT lesions. Primary malignancies included non-small cell lung cancer (n = 41), breast cancer (n = 33), melanoma (n = 14), gastrointestinal cancer (n = 6), head and neck cancer (n = 5), and kidney cancer (n = 5). On a per-lesion basis, 6-month LC was 97% for SIT and 99% for MIT (P = 0.12). On a per-lesion basis, 6-month FFR was 96% for SIT and 96% for MIT (P = 0.81). Fourteen patients developed symptomatic RN leading to steroid treatment in 7 patients, laser interstitial thermal therapy in 2 patients, anti-VEGF therapy in 3 patients, and continued observation in 2 patients. The only multivariable predictor for developing RN was increasing PTV size (HR 1.76, P Conclusion These data indicate high rates of LC and low rates of RN for both MIT and SIT for SRS. Efficient and effective treatment planning and delivery for the treatment of multiple metastases with a single isocenter improves the clinical feasibility of delivering initial and subsequent radiosurgery courses for patients, allowing for optimal integration with systemic therapy in patients with metastatic disease. Author Disclosure J. Deng: Employee; UCLA.M.K. Li: None. R.R. Savjani: Research Grant; ASTRO-Varian Research Training Fellowship. F. Chu: None. S.E. Tenn: Research Grant; Brain Lab. Honoraria; Brain Lab. C. Lee: Stock; Varian Medical Systems. N. Agazaryan: Honoraria; Brainlab and Novalis Accreditation. Consultant; Brainlab and Novalis Accreditation. expert panel member; Brainlab and Novalis Accreditation. I. Yang: Consultant; Baxter, Brain Lab. R. Everson: None. W. Kim: None. N. Pouratian: Research Grant and Speaker; Brain Lab. A.U. Kishan: None. R.K. Chin: None. M.L. Steinberg: None. T.B. Kaprealian: Research Grant and Honoraria; Brain Lab. J.V. Hegde: Research Grant; Soylent.

Rationale and Objectives We examined female representation on editorial boards of four prominent radiology journals. We compared editorial board representation to female academic radiology career advancement and the proportion of female authorship in three journals over four decades. Methods We collected data on the gender of editorial board members as listed on mastheads of Radiology, American Journal of Roentgenology (AJR), Academic Radiology, and the Journal of the American College of Radiology in 5-year intervals plus the most recent year available (1973–2017), and the gender of their editors-in-chief for all years since each journal's inception. We compared Radiology, AJR, and Academic Radiology data to published data on gender of the journals' authors, all US medical students, and academic radiologists over time. Results Gender was determined for 171 editors-in-chief (100%) and 2139 (100%) editorial board members listed in the selected journals for each of the study years. The proportion of women on editorial boards increased from 1.4% (1 of 69) in 1978 to 18.8% (73 of 388) in 2013 (P Conclusions Female representation on editorial boards has increased over time, but still lags behind increases seen in female first authorship in radiology journals and radiology faculty appointments over the last four decades. There was no female editor-in-chief during the study period.

Breast density (BD) is an independent risk factor for breast cancer and reduces the sensitivity of mammography. The enactment of BD legislation in a majority of states in the USA mandating notification of risks associated with BD directly to women undergoing mammography has catapulted interest in BD among women, physicians, and policymakers. We therefore report a descriptive review of the evidence on the impact of enactment of BD legislation. Based on 22 eligible studies, we identified four broad themes of research: studies of the impact on screening rates, most showing increased utilisation of supplemental screening; studies exploring the effect on women, radiologists, or primary physicians (reporting heterogeneous effects on knowledge, awareness, perceptions, attitudes and behaviour; and changes in practice); few studies assessing the population impact (effect on screening outcomes or breast cancer stage); and studies of costs highlighting the economic burden from supplemental screening. Given that many of the studies were retrospective single institution studies (comparing pre- and post-legislation) or small surveys with a paucity of population-level studies, we highlight areas meriting additional research. The information described in this review can inform research priorities where BD legislation has been introduced and can be used to guide world-wide policy or practice decisions where BD legislation may be under debate or contemplation.

The approach to breast cancer screening has changed over time from a general approach to a more personalized, risk-based approach. Women with dense breasts, one of the most prevalent risk factors, are now being informed that they are at increased risk of developing breast cancer and should consider supplemental screening beyond mammography. This article reviews the current evidence regarding the impact of breast density relative to other known risk factors, the evidence regarding supplemental screening for women with dense breasts, supplemental screening options, and recommendations for physicians having shared decision-making discussions with women who have dense breasts.

Purpose This study aims to determine whether radiologists who perform well in screening also perform well in interpreting diagnostic mammography. Materials and methods We evaluated the accuracy of 468 radiologists interpreting 2,234,947 screening and 196,164 diagnostic mammograms. Adjusting for site, radiologist, and patient characteristics, we identified radiologists with performance in the highest tertile and compared to those with lower performance. Results A moderate correlation was noted for radiologists' accuracy when interpreting screening versus their accuracy on diagnostic examinations: sensitivity (r spearman =0.51, 95% CI: 0.22, 0.80; P =.0006) and specificity (r spearman =0.40, 95% CI: 0.30, 0.49; P Conclusion Different educational approaches to screening and diagnostic imaging should be considered.

Emerging imaging technologies, including digital breast tomosynthesis, have the potential to transform breast cancer screening. However, the rapid adoption of these new technologies outpaces the evidence of their clinical and cost-effectiveness. The authors describe the forces driving the rapid diffusion of tomosynthesis into clinical practice, comparing it with the rapid diffusion of digital mammography shortly after its introduction. They outline the potential positive and negative effects that adoption can have on imaging workflow and describe the practice management challenges when incorporating tomosynthesis. The authors also provide recommendations for collecting evidence supporting the development of policies and best practices.

Rationale and Objectives Our objective was to evaluate the frequency with which patients viewed their online radiology reports in relation to clinical and laboratory notes and identify sociodemographic factors associated with report viewing. Method and Materials We conducted a cross-sectional study of 129,419 patients who had online patient portal access in our large health system in 2014. We determined whether patients viewed their radiology reports, laboratory reports, and clinical notes. We also collected patient sociodemographic information including gender, age, primary spoken language, race/ethnicity, and insurance status. We performed multivariate analyses to determine significant associations between viewing of radiology reports and viewing of other types of clinical reports and patient characteristics. Results Of 61,131 patients with at least one radiology report available, 31,308 (51.2%) viewed them. Patients who also viewed laboratory reports or clinical notes were significantly more likely to view their radiology reports (P Conclusion More than half of patients with access to online radiology reports viewed them, with higher viewing rates associated with viewing other types of reports and lower rates associated with characteristics of traditionally underserved patient populations.

In the U.S., guidelines recommend that women continue mammography screening until at least age 74, but recent evidence suggests declining screening rates in older women. We estimated adherence to screening mammography and multilevel factors associated with adherence in a longitudinal cohort of older women. Women aged 66–75 years receiving screening mammography within the Breast Cancer Surveillance Consortium were linked to Medicare claims (2005–2010). Claims data identified baseline adherence, defined as receiving subsequent mammography within approximately 2 years, and length of time adherent to guidelines. Characteristics associated with adherence were investigated using logistic and Cox proportional hazards regression models. Analyses were stratified by age to investigate variation in relationships between patient factors and adherence. Among 49,775 women, 89% were adherent at baseline. Among women 66–70 years, those with less than a high school education were more likely to be non-adherent at baseline (odds ratio [OR] 1.96; 95% confidence interval [CI] 1.65–2.33) and remain adherent for less time (hazard ratio [HR] 1.41; 95% CI 1.11–1.80) compared to women with a college degree. Women with ≥ 1 versus no Charlson co-morbidities were more likely to be non-adherent at baseline (OR 1.46; 95% CI 1.31–1.62) and remain adherent for less time (HR 1.44; 95% CI 1.24–1.66). Women aged 71–75 had lower adherence overall, but factors associated with non-adherence were similar. In summary, adherence to guidelines is high among Medicare-enrolled women in the U.S. receiving screening mammography. Efforts are needed to ensure that vulnerable populations attain these same high levels of adherence.

Breast cancer screening is used to identify women with asymptomatic cancer with the goal of enabling women to undergo less invasive treatments that lead to better outcomes, ideally at earlier stages before the cancer progresses. There are important considerations for who should be screened, how often women should be screened, and with which imaging modality (or modalities). Ultimately, clinicians need to help women understand the benefits and risks of breast cancer screening in order to make informed decisions.

There is increasing interest in the potential benefits and harms of screening ultrasound to supplement mammographic screening of women with dense breast tissue. We review the current evidence regarding adjunctive screening breast ultrasound (US) and provide a summary for clinicians who counsel patients with dense breasts. We conducted a comprehensive literature review of published clinical trials and observational cohort studies assessing the efficacy of screening handheld US (HHUS) and automated breast US (ABUS) to supplement mammography among women with dense breasts. From a total of 189 peer-reviewed publications on the performance of screening US, 12 studies were relevant to our analysis. The reporting of breast cancer risk factors varied across studies; however, the study populations tended to be at greater than average risk for developing breast cancer. There is consistent evidence that adjunctive screening US detects more invasive cancers compared to mammography alone, but there is currently no evidence of associated long-term breast cancer mortality reduction. The studies also collectively found that US was associated with an additional 11.7–106.6 biopsies/1,000 examinations (Median 52.2), and detected an additional 0.3–7.7 cancers/1,000 examinations (Median 4.2). The associated number of unnecessary breast biopsies resulting from adjunct US screening exceeds that observed with screening mammography alone by approximately 5-fold. Adjunctive screening with ultrasound should also be considered in the context of screening mammography. It is important for clinicians to be aware that improvements in cancer detection in mammographically dense breasts have been achieved with the transition from film to digital mammography, reducing a limitation of film mammography. Clinicians should discuss breast density as one of several important breast cancer risk factors, consider the potential harms of adjunctive screening, and arrive at a shared decision consistent with each woman’s preferences and values.

The creation of the Patient-Centered Outcomes Research Trust Fund and the Patient-Centered Outcomes Research Institute (PCORI) through the Patient Protection and Affordable Care Act of 2010 presents new opportunities for funding patient-centered comparative effectiveness research (CER) in radiology. We provide an overview of the evolution of federal funding and priorities for CER with a focus on radiology-related priority topics over the last two decades, and discuss the funding processes and methodological standards outlined by PCORI. We introduce key paradigm shifts in research methodology that will be required on the part of radiology health services researchers to obtain competitive federal grant funding in patient-centered outcomes research. These paradigm shifts include direct engagement of patients and other stakeholders at every stage of the research process, from initial conception to dissemination of results. We will also discuss the increasing use of mixed methods and novel trial designs. One of these trial designs, the pragmatic trial, has the potential to be readily applied to evaluating the effectiveness of diagnostic imaging procedures and imaging-based interventions among diverse patient populations in real-world settings.

With widespread adoption of web portals and unfettered patient access to online radiology reports, these previous end products are quickly becoming springboards for direct radiologist-patient interactions, further increasing the value proposition for radiologists in an era of patient-centered care. Here, we provide a real-world scenario demonstrating a teachable moment on how imaging examination reporting in the digital era is expanding the radiologist's role in patient consultation.

Because benign biopsies resulting from false-positive mammographic findings are a known harm of breast cancer screening, physicians and test manufacturers are searching for ways to reduce their frequency. The aim of this study was to estimate potential costs and consequences associated with using an adjunct diagnostic test for triaging women with suspicious mammographic findings before biopsy.A decision model was developed to compare the use of an adjunct test before biopsy to the current standard of care for suspicious mammographic findings. The decision analysis was performed from the perspective of a national health payer, with a 1-year time horizon among women representative of the US screening population aged 40 to 79 years. Three primary outcomes were assessed: (1) incremental costs, (2) number of benign biopsies avoided, and (3) number of missed opportunities for diagnosing cancer per million women screened. Input parameters were obtained from the medical literature and expert opinion. Sensitivity analyses were performed to evaluate the effects of uncertainty in parameter estimates.The base-case analysis demonstrated that the use of an adjunct diagnostic test with 95% sensitivity, 75% specificity, and a cost of $1,000 would eliminate 8,127 unnecessary breast biopsies per million women screened. However, this would cost the US health care system an additional $6,462,977 and result in 255 missed opportunities for diagnosing cancer per million women screened.The addition of an adjunct test for triaging women for breast biopsy after abnormal findings on screening mammography would likely eliminate many unnecessary biopsies but also increase overall health care costs. This exploratory analysis highlights the fact that mammography remains a relatively inexpensive and effective breast cancer screening and diagnostic modality.

The ACR Education Center's Breast MR With Guided Biopsy course is designed to provide radiologists with an intensive, hands-on experience in interpreting breast MR. The aim of this study was to describe radiologists' performance in breast MR interpretation by case clinical indication, lesion type, and BI-RADS(®) assessment to inform future educational efforts.Data from 16 consecutive courses held from 2009 to 2012 at the ACR Education Center were analyzed. For each MR case, the clinical indication (screening vs diagnostic), background parenchymal enhancement, and lesion type (mass vs nonmass enhancement) were recorded. Participant case BI-RADS assessments were categorized as either correct or incorrect in relation to expert-opinion BI-RADS assessments. Participants' interpretive accuracy on the basis of study indication, lesion type, and background parenchymal enhancement is reported.Data from 745 course participants over 3 years were analyzed. Of the 96 MR cases included in the analysis, 58% (n = 50) were indicated for screening and 42% (n = 46) for diagnostic purposes. Participants provided correct BI-RADS assessments for 79% of screening cases (32,399 of 41,249) and 74% of diagnostic cases (20,888 of 28,106). Participants more accurately assessed screening compared with diagnostic MR cases (P.0001) and masses compared with nonmass enhancement (P.0001). There was no statistically significant difference in performance on the basis of background parenchymal enhancement.Practicing radiologists perform more accurately on screening compared with diagnostic MR and when evaluating masses as opposed to areas of nonmass enhancement. Future case-based breast MR education efforts should emphasize strategies for interpreting diagnostic breast MR cases and evaluating nonmass enhancement.

Merely suggesting that radiologists answer the call to bolster and secure the future of their own specialty has not resulted in increased activism. Therefore, the ACR Commission on Human Resources has developed a definition for the concept of citizenship in radiology and explicit descriptions of the activities associated with it. Furthermore, the authors introduce a methodology for the measurement and valuation of individual radiologists' contributions to group practices and to the specialty as a whole. These measures can in turn be used to promote, acknowledge, recognize, and incentivize citizenship activity among radiologists at the local, regional, and national levels.

Because radiology has historically not measured its added value to patient care and thus not communicated it in easily understood terms to all stakeholders, the specialty must correct this to prepare for the eventual transition from the current fee-for-service payment schedule to new value-based reimbursement systems. Given the increasing risk for marginalization, radiologists need to engage clinicians and managers to map the processes and associated costs of episodes of patient care to identify areas for providing and improving integrated diagnostic information and to measure the value thereof. In such time-driven, activity-based costing practices, radiologists should highlight how proper investments in the information generated by imaging and how radiologists' associated consultative and coordination of services can save greater resources downstream, especially in the nonrenewable resource of physician time, an increasingly scarce health care resource. Using physician time in the most efficient way will be a key element for decreasing health care costs at the aggregate level. Therefore, expressing radiology's contribution in terms of downstream physician time saved is a metric that can be easily understood by all stakeholders. In a conceptual framework centered on value, the specialty of radiology must focus more on its most important product, actionable information, rather than on imaging technologies themselves. Information, unlike imaging technologies, does not depreciate with time but rather increases in value the more it is used.

Plus ca change, plus c’est la meme chose. The Patient Protection and Affordable Care Act fundamentally shifts priorities for US health care, with an increased focus on preventive medicine, in which screening asymptomatic individuals will identify the most deadly and costly of diseases, including cancer and cardiovascular disease, at their earliest stages, when intervention can decrease both patient mortality and the higher costs of treating advanced disease. Given tremendous technological advances over the past decade, radiology now stands to take on a higher profile and central role in US population-based screening. Nevertheless, if history serves us well, imaging-based screening will continue to be met with a host of controversies and challenges. Furthermore, both the Affordable Care Act and programs to comply with its requirements may lead to unintended consequences. No other US preventive medicine topic generates more controversy and emotional charge as breast cancer screening. The heavily debated revised recommendations from the US Preventive Services Task Force (USPSTF) in 2009 for biennial mammography starting at 50 years of age, rather than annual mammography starting at age 40, is just one example of the historically complex interpretation of the available evidence linking image-based screening to long-term patient outcomes. Reducing the divisiveness requires representation of all stakeholders, giving voice to the myriad points of view. Some of the most powerful and influential voices are those of patients. The advocacy group Are You Dense has spearheaded state-level and national-level legislation to mandate that patients with dense breasts on mammography be directly informed about their increased risk for developing breast cancer. This special issue begins with an overview of the state of these density reporting legislative efforts across the United States by Dehkordy and Carlos [1] .W ith a unique perspective on the matter, Cappello [2] ,t he founder and president of Are You Dense, accounts both her personal and professional journeys in seeing her density reporting legislative goals come to fruition. Smith [3], the cofounder of the Research Advocacy Network, provides a contrasting perspective as both a patient and a patient advocate, highlighting

Cultural competence is touted as a strategy for minimizing health disparities by creating an equitable health care system for every patient, regardless of race, ethnicity, or culture. 1 Over the last several decades, such an effort has taken root in the breast cancer community with a specific aim of ensuring access to effective screening, diagnostic, and therapeutic tools for all women. Breast cancer mortality has been reduced significantly by advances in imaging-based detection and more effective chemotherapies. Nevertheless, African American women continue to have a higher incidence of and mortality rates from early-onset breast cancer compared to Caucasian women. 2 Now, advances in the field of genetics promise to again revolutionize and individualize breast cancer diagnosis and treatment. However, with this promise are also renewed concerns about the possibility of increasing health disparities.

table rotations, collimator angle and photon beam energy have been investigated. Results: VMAT plans with ±45 degree collimator rotations required on average 38% less monitor units compared to plans with no collimator rotations and 20% less monitor units than plans with ±22.5 degree rotations. Plans with ±45 degree collimator rotations provided more homogeneous dose distribution with an average of 6% less maximal dose. VMAT plans with two arcs provided improved conformality and homogeneity with an average of 3% lower maximal dose compared to single arc plans. However, increasingthe number of arcsto threedid not provideany significantimprovement. Introductionof±5 and±10degree table rotations between arcs did not result in any significant dosimetric improvements. The selection of photon beam energy between 6MV and 10MV did not provide any notable dosimetric differences either. Conclusions: Thefinalselectionoftheprotocolincludes twocoplanar10MV RapidArcs with±45degreecollimatorrotations.This prospective clinical trial is designed to deliver 5 fractions of 8 Gy with the prescription dose covering the 95% of the planning target volume. The beam-on time for eachof the coplanar arcs is approximately 2 minutes.For the purpose ofintrafraction motionmanagement, two Rapid Arcs are further split to 4 half arcs with approximately one minute treatment time for each segment. The patient is stereoscopicallyimagedandrepositionedifnecessaryusingExacTracpriortothedeliveryofeacharc.Additionally,CBCTisobtained prior to eachfractionforthe purposesof confirmationofExacTracpositioningand volumetric evaluation of bladderand rectalfilling.