AAPM medical physics practice guideline 13.a: HDR brachytherapy, part A.

The American Association of Physicists in Medicine (AAPM) is a nonprofit professional society whose primary purposes are to advance the science, education, and professional practice of medical physics. The AAPM has more than 8000 members and is the principal organization of medical physicists in the United States. The AAPM will periodically define new practice guidelines for medical physics practice to help advance the science of medical physics and to improve the quality of service to patients throughout the United States. Existing medical physics practice guidelines (MPPGs) will be reviewed for the purpose of revision or renewal, as appropriate, on their fifth anniversary or sooner. Each medical physics practice guideline represents a policy statement by the AAPM, has undergone a thorough consensus process in which it has been subjected to extensive review, and requires the approval of the Professional Council. The medical physics practice guidelines recognize that the safe and effective use of diagnostic and therapeutic radiology requires specific training, skills, and techniques, as described in each document. Reproduction or modification of the published practice guidelines and technical standards by those entities not providing these services is not authorized. The following terms are used in the AAPM practice guidelines: (1) Must and must not: Used to indicate that adherence to the recommendation is considered necessary to conform to this practice guideline. (2) Should and should not: Used to indicate a prudent practice to which exceptions may occasionally be made in appropriate circumstances. Approved by AAPM's Executive Committee April 28, 2022.

Salvage resection plus cesium-131 brachytherapy durably controls post-SRS recurrent brain metastases.

BACKGROUND: Salvage of recurrent previously irradiated brain metastases (rBrM) is a significant challenge. Resection without adjuvant re-irradiation is associated with a high local failure rate, while reirradiation only partially reduces failure but is associated with greater radiation necrosis risk. Salvage resection plus Cs131 brachytherapy may offer dosimetric and biologic advantages including improved local control versus observation, with reduced normal brain dose versus re-irradiation, however data are limited. METHODS: A prospective registry of consecutive patients with post-stereotactic radiosurgery (SRS) rBrM undergoing resection plus implantation of collagen-matrix embedded Cs131 seeds (GammaTile, GT Medical Technologies) prescribed to 60 Gy at 5 mm from the cavity was analyzed. RESULTS: Twenty patients underwent 24 operations with Cs131 implantation in 25 tumor cavities. Median maximum preoperative diameter was 3.0 cm (range 1.1-6.3). Gross- or near-total resection was achieved in 80% of lesions. A median of 16 Cs131 seeds (range 6-30), with a median air-kerma strength of 3.5 U/seed were implanted. There was one postoperative wound dehiscence. With median follow-up of 1.6 years for survivors, two tumors recurred (one in-field, one marginal) resulting in 8.4% 1-year progression incidence (95%CI = 0.0-19.9). Radiographic seed settling was identified in 7/25 cavities (28%) 1.9-11.7 months post-implantation, with 1 case of distant migration (4%), without clinical sequelae. There were 8 cases of radiation necrosis, of which 4 were symptomatic. CONCLUSIONS: With > 1.5 years of follow-up, intraoperative brachytherapy with commercially available Cs131 implants was associated with favorable local control and toxicity profiles. Weak correlation between preoperative tumor geometry and implanted tiles highlights a need to optimize planning criteria.

Commissioning considerations for the Bravos high-dose-rate afterloader: Towards improving treatment delivery accuracy.

BACKGROUND AND PURPOSE: The upgrade of major equipment can be disruptive to clinical operations and introduce risk as policy and procedures need to adapt to new technical possibilities and constraints. We describe here the transition from GammaMedPlus-iX to Bravos in a busy brachytherapy clinic, involving four afterloaders across two sites. MATERIAL AND METHODS: Our clinic employs three high-dose-rate remote afterloaders in four dedicated treatment vaults at the main site and a fourth afterloader at a regional location. Of more than 600 new HDR treatment plans performed annually, most are planned and treated intraoperatively. Most treatments are for prostate cancer, followed by GYN, intraoperative brachytherapy, GI, and other sites. Applicators used include vendor-provided applicators as well as third party applicators and in-house 3D-printed devices to provide interstitial, intracavitary, intraluminal, and surface treatments. All applicators were commissioned according to recommended guidelines. The choice of tolerances and the design of new procedures were informed by current guidelines and leveraged new HDR afterloader functionalities. A review of clinical operations in the 4 months postupgrade was conducted to evaluate the feasibility of new tolerances and the effectiveness of new procedures. RESULTS: The procedures outlined improved and standardized afterloader QA and treatment protocols with clear actionable steps for staff to follow to ensure treatments are delivered as planned. Re-commissioning of applicators yielded results similar to those previously reported by other investigators. A review of initial treatment data revealed that in one case, due to the implementation of tight tolerances, obstruction near the tip of the channel was detected and corrected prior to treatment. It confirms that the implementation of the tolerances adopted is feasible and effective in flagging treatment deviations. CONCLUSION: Enhanced procedures and QA processes were implemented successfully. We established clear actionable steps to follow by staff to ensure that treatments are delivered accurately.

AAPM Task Group 334: A guidance document to using radiotherapy immobilization devices and accessories in an MR environment.

Use of magnetic resonance (MR) imaging in radiation therapy has increased substantially in recent years as more radiotherapy centers are having MR simulators installed, requesting more time on clinical diagnostic MR systems, or even treating with combination MR linear accelerator (MR-linac) systems. With this increased use, to ensure the most accurate integration of images into radiotherapy (RT), RT immobilization devices and accessories must be able to be used safely in the MR environment and produce minimal perturbations. The determination of the safety profile and considerations often falls to the medical physicist or other support staff members who at a minimum should be a Level 2 personnel as per the ACR. The purpose of this guidance document will be to help guide the user in making determinations on MR Safety labeling (i.e., MR Safe, Conditional, or Unsafe) including standard testing, and verification of image quality, when using RT immobilization devices and accessories in an MR environment.

Extended Follow-Up Outcomes from Pooled Prospective Studies Evaluating Efficacy of Interstitial Alpha Radionuclide Treatment for Skin and Head and Neck Cancers.

The initial favorable efficacy and safety profile for Alpha DaRT have been demonstrated (NCT04377360); however, the longer-term safety and durability of the treatment are unknown. This pooled analysis of four prospective trials evaluated the long-term safety and efficacy of Alpha DaRT for the treatment of head and neck or skin tumors. A total of 81 lesions in 71 patients were treated across six international institutions, with a median follow-up of 14.1 months (range: 2-51 months). Alpha DaRT sources were delivered via a percutaneous interstitial technique and placed to irradiate the tumor volume with the margin. The sources were removed two to three weeks following implantation. A complete response was observed in 89% of treated lesions (n = 72) and a partial response in 10% (n = 8). The two-year actuarial local recurrence-free survival was 77% [95% CI 63-87]. Variables, including recurrent versus non-recurrent lesions, baseline tumor size, or histology, did not impact long-term outcomes. Twenty-seven percent of patients developed related acute grade 2 or higher toxicities, which resolved with conservative measures. No grade 2 or higher late toxicities were observed. These data support the favorable safety profile of Alpha DaRT, which is currently being explored in a pivotal US trial.

Feasibility and Safety of Diffusing Alpha-Emitter Radiation Therapy for Recurrent or Unresectable Skin Cancers.

Importance: Patients with recurrent or unresectable skin cancers have limited treatment options. Diffusing alpha-emitter radiation therapy (DaRT), a novel solid tumor management strategy using alpha-particle interstitial brachytherapy, may address this challenge. Objective: To evaluate the feasibility and safety of using DaRT to manage recurrent or unresectable skin cancers. Design, Setting, and Participants: This prospective cohort study of patients who received a 2-week to 3-week treatment course and were followed up for 24 weeks after treatment during 2021 and 2022 at 2 sites in the US. Patients with malignant skin tumors or soft tissue tumors were recruited if they had limited treatment options for tumors recurrent after prior surgery or external beam radiotherapy or unresectable tumors. Intervention: Patients underwent DaRT to deliver a physical dose of 10 Gy (equivalent weighted dose of 200 CGE) to the tumor. Main Outcomes and Measures: Feasibility of the DaRT procedure was evaluated based on the ability of investigators to successfully deliver radiation to the tumor. Patients were followed up for adverse events (AEs) for 24 weeks and for tumor response by physicians' physical examination and imaging 12 weeks after device removal. Results: This study included 10 participants with recurrent or unresectable skin cancer (median [IQR] age, 72 [68-75] years; 6 males [60%]; 4 females [40%]). Six patients (60%) had recurrent disease, and 4 (40%) had tumors that were deemed unresectable. Tumors were located on the nose, chin, eyelid, scalp, neck, trunk, and extremities. Median (range) tumor volume before treatment was 2.1 cm3 (0.65-12.65 cm3). The mean (SD) prescription dose coverage of the gross tumor volume was 91% (2.8%) with all tumors having coverage of 85% or more. No device-related grade 3 AEs were noted. Common AEs were grade 1 to 2 erythema, edema, and pruritus. At 12 weeks following treatment, there was a 100% complete response rate. Nine of 10 complete responses (90%) were confirmed by CT imaging. Conclusions and Relevance: This cohort study suggests the feasibility and preliminary safety of DaRT in the management of recurrent or unresectable skin cancers. The favorable safety profile and high response rates are promising. A US trial for marketing approval based on this pilot study is under way. Trial Registration: ClinicalTrials.gov Identifier: NCT04377360.

Protocol for the measurement of the absorbed dose rate to water for a planar 32P beta emitting brachytherapy source: A multi-institutional validation.

PURPOSE: This is a multi-institutional report on inter-observer and inter-instrument variation in the calibration of the absorbed dose rate for a planar 32P beta emitting brachytherapy source. Measurement accuracy is essential since the dose profile is steep and the source is used for the treatment of tumors that are located in close proximity to healthy nervous system structures. METHODS AND MATERIALS: An RIC-100 32P source was calibrated by three institutions using their own equipment and following their standard procedures. The first institution calibrated the source with an electron diode and EBT3 film. The second institution used an electron diode. The third institution used HD810 film. Additionally, each institution was asked to calibrate the source using an electron diode and procedure that was shared among all institutions and shipped along with the radiation source. The dose rate was reported in units of cGy*min-1 at a water equivalent depth of 1 mm. RESULTS: Close agreement was observed in the measurements from different users and equipment. The variation across all diode detectors and institutions had a standard deviation of 1.8% and maximum difference of 4.6%. The observed variation among two different diode systems used within the same institution had a mean difference of 1.6% and a maximum variation of 1.8%. The variations among film and diode systems used within the same institution had a mean difference of 2.9% and a maximum variation of 4.3% CONCLUSIONS: The absorbed dose rate measurement protocol of the planar beta-emitting 32P source permits consistent dosimetry across three institutions and five different electron diode and radiochromic film systems. The methodologies presented herein should enable measurement consistency among other clinical users, which will help ensure high quality patient treatments and outcomes analysis.

Safety practices and opportunities for improvement in brachytherapy: A patient safety practices survey of the American Brachytherapy Society membership.

PURPOSE: Safe delivery of brachytherapy and establishing a safety culture are critical in high-quality brachytherapy. The American Brachytherapy Society (ABS) Quality and Safety Committee surveyed members regarding brachytherapy services offered, safety practices during treatment, quality assurance procedures, and needs to develop safety and training materials. METHODS AND MATERIALS: A 22-item survey was sent to ABS membership in early 2019 to physicians, physicists, therapists, nurses, and administrators. Participation was voluntary. Responses were summarized with descriptive statistics and relative frequency distributions. RESULTS: There were 103 unique responses. Approximately one in three was attending physicians and one in three attending physicists. Most were in practice >10 years. A total of 94% and 50% performed gynecologic and prostate brachytherapy, respectively. Ninety-one percent performed two-identification patient verification before treatment. Eighty-six percent performed a time-out. Ninety-five percent had an incident reporting or learning system, but only 71% regularly reviewed incidents. Half reviewed safety practices within the last year. Twenty percent reported they were somewhat or not satisfied with department safety culture, but 92% of respondents were interested in improving safety culture. Most reported time, communication, and staffing as barriers to improving safety. Most respondents desired safety-oriented webinars, self-assessment modules, learning modules, or checklists endorsed by the ABS to improve safety practice. CONCLUSIONS: Most but not all practices use standards and quality assurance procedures in line with society recommendations. There is a need to heighten safety culture at many departments and to shift resources (e.g., time or staffing) to improve safety practice. There is a desire for society guidance to improve brachytherapy safety practices. This is the first survey to assess safety practice patterns among a national sample of radiation oncologists with expertise in brachytherapy.

The American Brachytherapy society consensus statement for skin brachytherapy.

PURPOSE: Keratinocyte carcinoma (KC, previously nonmelanoma skin cancer) represents the most common cancer worldwide. While surgical treatment is commonly utilized, various radiation therapy techniques are available including external beam and brachytherapy. As such, the American Brachytherapy Society has created an updated consensus statement regarding the use of brachytherapy in the treatment of KCs. METHODS: Physicians and physicists with expertise in skin cancer and brachytherapy created a consensus statement for appropriate patient selection, data, dosimetry, and utilization of skin brachytherapy and techniques based on a literature search and clinical experience. RESULTS: Guidelines for patient selection, evaluation, and dose/fractionation schedules to optimize outcomes for patients with KC undergoing brachytherapy are presented. Studies of electronic brachytherapy are emerging, although limited long-term data or comparative data are available. Radionuclide-based brachytherapy represents an appropriate option for patients with small KCs with multiple techniques available. CONCLUSIONS: Skin brachytherapy represents a standard of care option for appropriately selected patients with KC. Radionuclide-based brachytherapy represents a well-established technique; however, the current recommendation is that electronic brachytherapy be used for KC on prospective clinical trial or registry because of a paucity of mature data.