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Purpose: This guideline provides evidence-based recommendations on appropriate indications and techniques for partial breast irradiation (PBI) for patients with early-stage invasive breast cancer and ductal carcinoma in situ., Methods: ASTRO convened a task force to address 4 key questions focused on the appropriate indications and techniques for PBI as an alternative to whole breast irradiation (WBI) to result in similar rates of ipsilateral breast recurrence (IBR) and toxicity outcomes. Also addressed were aspects related to the technical delivery of PBI, including dose-fractionation regimens, target volumes, and treatment parameters for different PBI techniques. The guideline is based on a systematic review provided by the Agency for Healthcare Research and Quality. Recommendations were created using a predefined consensus-building methodology and system for grading evidence quality and recommendation strength., Results: PBI delivered using 3-dimensional conformal radiation therapy, intensity modulated radiation therapy, multicatheter brachytherapy, and single-entry brachytherapy results in similar IBR as WBI with long-term follow-up. Some patient characteristics and tumor features were underrepresented in the randomized controlled trials, making it difficult to fully define IBR risks for patients with these features. Appropriate dose-fractionation regimens, target volume delineation, and treatment planning parameters for delivery of PBI are outlined. Intraoperative radiation therapy alone is associated with a higher IBR rate compared with WBI. A daily or every-other-day external beam PBI regimen is preferred over twice-daily regimens due to late toxicity concerns., Conclusions: Based on published data, the ASTRO task force has proposed recommendations to inform best clinical practices on the use of PBI., Competing Interests: Disclosures All task force members’ disclosure statements were reviewed before being invited and were shared with other task force members throughout the guideline's development. Those disclosures are published within this guideline. Where potential conflicts were detected, remedial measures to address them were taken. Bethany Anderson: American Board of Radiology (ABR) (board examiner), Brachytherapy Journal (section editor), Clinical Breast Cancer Journal (associate editor), International Journal of Radiation Oncology, Biology, Physics (breast section associate editor), School of Breast Oncology (honoraria); Douglas Arthur: Advanced Radiation Therapy (consultant); Jose Bazan: ABR (board examiner), ASTRO VA Breast Panel (honoraria), International Journal of Radiation Oncology, Biology, Physics (breast section associate editor), Intraop Medical (institutional research); Jennifer Bellon: American Board of Radiology (ABR) (oral exam chair-ended 8/2023), Leidos Pharmaceutical (honoraria), National Cancer Institute (NCI) (research; BOLD task force on breast cancer co-chair), Oncoclinicas (honoraria), PER (honoraria), Prosigna (research), UpToDate (honoraria), Varian (honoraria); Charlotte Coles: Breast Cancer Now (research), Cancer Research UK (research), Lancet Breast Cancer Commission (chair), National Institutes of Health and Care Research (NIHR) (research; IMPORT LOW trial chief investigator); Naamit Gerber: Accuray (advisory board-ended 10/2023), Invus Group (consultant), John Theurer Cancer Center (consultant), Mount Sinai Icahn School of Medicine (honoraria-ended 8/2022), PreludeDX (research); Leonard Kim: American Associations of Physicists in Medicine (subcommittee/working group chair), ABR (board examiner), Elekta (MR-Linac Consortium, institutional representative), The Greeley Company (consultant-ended 5/2022); Christine Laronga (Society of Surgical Oncology [SSO]representative): SSO Breast Disease Site (chair), UpToDate (section editor); Janice Lyons (Chair): ABR (board examiner), Primum (consultant); Icro Meattini: Accuray, Eli Lily, Ipsen, Novartis, Pfizer, Seagen (all advisory board); Elizabeth Nichols: ABR (board examiner), Applied Radiation Oncology (editorial board), Xcision (research, co-chair); Lori Pierce (American Society of Clinical Oncology [ASCO] representative): ASCO (board chair), Breast Cancer Research Foundation (advisory board and travel), BMS Foundation DCIDCP National Advisory Committee (advisory board and travel), Damon Runyon Cancer Research Foundation (board of directors and travel), Exact Sciences (consultant), Michigan Radiation Oncology Quality Consortium (director), PER Educational Symposium (speakers bureau and travel), UpToDate (editor); Matthew Poppe: Agency for Healthcare Research and Quality (technical expert), Alliance for Breast Clinical Trials in Oncology (vice chair), Alliance for Breast Clinical Trials Local Regional Working Group (chair), Mevion (honoraria and travel-ended 3/2022), NIH (research), NIH/NCI (research-PI), PEEL Therapeutics (stock), UpToDate (editor); Simona Shaitelman (Vice Chair): Alpha Tau Medical (research-ended 2022), Artios Pharma (research-ended 2022), Becton, Dickinson & Co (consultant), Brachytherapy Journal (editorial board), Elekta (MR-Linac Consortium, institutional representative), Emerson Collective Foundation (research), Exact Sciences (research), NIH (research-ended 8/2023), TAE Life Sciences (research); Patti Spears (patient representative): Pfizer (advocate advisory care committee member-ended 12/2022); Shaveta Vinayak (ASCO representative): OncoSec Biotech (research and consultant), Pfizer, Puma Biotech, Seattle Genetics (all research); Timothy Whelan: Exact Sciences (research). Lisa Bradfield and Madeera Kathpal (Guideline Subcommittee representative) reported no disclosures., (Copyright © 2023 American Society for Radiation Oncology. Published by Elsevier Inc. All rights reserved.)

Purpose: With most patients now living long after their breast cancer diagnosis, minimizing long-term side effects of breast cancer treatment, such as reducing late cardiac and pulmonary side effects of radiation therapy (RT), is particularly important. It is now possible to use an electromagnetic tracking system to allow real-time tracking of chest wall (CW) position during the delivery of RT. Here, we report our experience using electromagnetic surface transponders as an added measure of CW position during deep inspiration breath hold (DIBH)., Methods and Materials: We conducted a single-institution institutional review board-approved retrospective review of 15 female left-sided breast cancer patients treated between July 2012 and June 2013 with conventional whole breast radiation. We compared daily port films with treatment planning digitally reconstructed radiographs to establish daily setup accuracy, then used Calypso tracings to compare the position of the CW during the daily port film with the position of the CW during that day's treatment to determine the reproducibility of the breath hold position. Finally, we created competing treatment plans not using DIBH and used a paired t test to compare mean heart (MH) and left anterior descending (LAD) coronary artery dose between the 2 techniques., Results: Mean total error (inter- and intrafraction) was dominated by interfraction error and was greatest in the longitudinal direction with a mean of 2.13 mm and 2 standard deviations of 8.2 mm. DIBH significantly reduced MH and LAD dose versus free breathing plans (MH, 1.26 Gy vs 2.84 Gy, P ≤ .001; LAD, 5.49 Gy vs 18.15 Gy, P ≤ .001)., Conclusions: This study demonstrates that DIBH with electromagnetic confirmation of CW position is feasible, and allows potential improvement in the accurate delivery of adjuvant RT therapy for breast cancer., (Published by Elsevier Inc.)

The relative contribution of endothelial vasodilating factors to acetylcholine (ACh)-mediated vasodilation in the forearm cutaneous microcirculation is unclear. The aims of this study were to investigate the contributions of prostanoids and cutaneous C fibers to basal cutaneous blood flow (CuBF) and ACh-mediated vasodilation. ACh was iontophoresed into the forearm, and cutaneous perfusion was measured by laser-Doppler flowmetry. To inhibit the production of prostanoids, four doses of acetylsalicylic acid (ASA; 81, 648, 972, and 1,944 mg) were administered orally. Cutaneous nerve fibers were blocked with topical anesthesia. Cyclooxygenase inhibition did not change basal CuBF or endothelium-mediated vasodilation to ACh. In contrast, ASA (972 and 1,944 mg) significantly reduced the C-fiber-mediated axon reflex in a dose-dependent fashion. Blockade of C-fiber function significantly reduced axon reflex-mediated vasodilation but did not affect basal CuBF or endothelium-dependent vasodilation. The findings suggest that prostanoids do not contribute significantly to basal CuBF or endothelium-dependent vasodilation in the forearm microcirculation. In contrast, prostanoids are mediators of the ACh-provoked axon reflex.