American Society for Therapeutic Radiology and Oncology (ASTRO) Emerging Technology Committee Report on Electronic Brachytherapy

doi:10.1016/j.ijrobp.2009.10.068

International Journal of Radiation OncologyBiologyPhysics

Volume 76, Issue 4, 15 March 2010, Pages 963-972

https://doi.org/10.1016/j.ijrobp.2009.10.068 Get rights and content

The development of novel technologies for the safe and effective delivery of radiation is critical to advancing the field of radiation oncology. The Emerging Technology Committee of the American Society for Therapeutic Radiology and Oncology appointed a Task Group within its Evaluation Subcommittee to evaluate new electronic brachytherapy methods that are being developed for, or are already in, clinical use. The Task Group evaluated two devices, the Axxent Electronic Brachytherapy System by Xoft, Inc. (Fremont, CA), and the Intrabeam Photon Radiosurgery Device by Carl Zeiss Surgical (Oberkochen, Germany). These devices are designed to deliver electronically generated radiation, and because of their relatively low energy output, they do not fall under existing regulatory scrutiny of radioactive sources that are used for conventional radioisotope brachytherapy. This report provides a descriptive overview of the technologies, current and future projected applications, comparison of competing technologies, potential impact, and potential safety issues. The full Emerging Technology Committee report is available on the American Society for Therapeutic Radiology and Oncology Web site.

Section snippets

Problem Definition

The use of intraoperative radiotherapy (IORT) has a long history in radiation oncology, primarily to deliver single large fractions or a “boost” dose directly in situ, allowing for increased dose delivery and decreased normal tissue exposure (1). Preclinical studies in animals, combined with experience in humans, have provided guidance for safe and effective use of this approach in general.

Intraoperative radiotherapy using electrons has been the favored approach over orthovoltage beams because

Description of the Technology

There are currently two systems that fit the category of EBT. The first is the Axxent Electronic Brachytherapy System (Xoft Inc., Fremont, CA), a system of devices used for delivery of low-energy radiation at an HDR. The second, the Zeiss Intrabeam (Carl Zeiss Surgical, Oberkochen, Germany), is a mobile photon radiosurgery system (PRS) that procures a miniature electron beam–driven X-ray source.

Present scope of use for Xoft Axxent

The date of approval for marketing of the device by the FDA was December 22, 2005 (K050843). At this time, the scope of the FDA's approved usage has been restricted to postoperative breast cancer treatment. As stated by the FDA, “The Xoft Axxent Electronic Brachytherapy System is intended to provide brachytherapy when the physician chooses to deliver intracavitary or interstitial radiation to the surgical margins following lumpectomy for breast cancer.”

After FDA approval, Xoft initiated a

Present status of product marketing

The Breast Center at the WellStar Kennestone Hospital in Marietta, Georgia, was the first to use the Xoft Axxent brachytherapy system to treat patients. Other physicians have adopted the technology and are serving in educational roles with the company. Physicians at Dallas Breast Center, Dallas, Texas, led an industry-sponsored symposium entitled “The Role of the Surgeon in Electronic Brachytherapy of the Breast” at the annual ASBS meeting in Phoenix, Arizona, in May 2007 to discuss best

Evaluation/Summary of Results of Existing Studies

Mature clinical data specifically using the Xoft device have not been published. However, a number of small-scale industry-sponsored studies have addressed the characteristics of the produced radiation, safety considerations related to the device, and feasibility of the device for clinical use. More specifically, several issues were addressed including relative biological effectiveness (RBE) of radiation of an HDR and low energy, dose distributions obtained with a variable energy source,

Identification, Analysis, and Evaluation of Consequences of Non-Use

Advantages of EBT over existing technologies are as yet unproven in terms of efficacy or patient outcomes. Viable and tested treatment methods are available for the intraoperative environment and include electron beam IORT and HDR. In addition, treatment for accelerated partial-breast irradiation (APBI) is also currently available in the form of external beam radiotherapy and via various HDR brachytherapy techniques. The aforementioned modalities require licensed, qualified, authorized

Possible Impact

The impact of clinical use of EBT could be far-reaching and, if used properly, has potential to benefit patients. However, if applied improperly in an unregulated environment, use could potentially cause harm. As was noted in the technical sections of this report, EBT is currently an unregulated treatment delivery modality for cancer therapy, with minimal clinical data available from small single-institution studies, none with significant follow-up. The EBT devices currently commercially

Emerging Technology Committee note

Assignment of this project to the Task Group was made on March 27, 2007, and data collection for preparation of the full report available on the ASTRO Web site and this condensed version was closed on January 1, 2008. Clinical, physics, or biology data and regulatory revisions available after that date are not included in this review.

This document was prepared by the Emerging Technology Committee (ETC) of the American Society for Radiation Oncology.

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Before initiation of this evaluation project,

Acknowledgment

The Task Group and Emerging Technology Committee wish to acknowledge the assistance of Subir Nag, M.D., in preparation of portions of this document.

References (15)

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Targeted intraoperative radiotherapy (TARGIT) yields very low recurrence rates when given as a boost
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General rationale and historical perspective of intraoperative irradiation

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Cited by (46)

Clinical perspectives on dosimetry in molecular radiotherapy
2023, Physica Medica
Molecular radiotherapy is the use of systemically administered unsealed radioactive sources to treat cancer. Theragnostics is the term used to describe paired radiopharmaceuticals localising to a specific target, one optimised for imaging, the other for therapy. For many decades, molecular radiotherapy has developed empirically. Standard administered activity schedules have been used without the prior estimation of the resulting tumour radiation absorbed dose by theragnostic imaging, or its subsequent measurement by serial scanning. This pragmatic approach has benefited many patients, however others who should have benefited have failed to do so as the radiation absorbed dose in the tumour was suboptimal. The accurate prediction and measurement of tumour and organ at risk radiation absorbed doses allows treatment to be personalised, and offers the prospect of improved clinical outcomes. To deliver this for all molecular radiotherapy patients would require not only a significant financial investment in equipment and skilled personnel, but also a change in attitude of those who believe that simple – or simplistic – schedules are easier to deliver, and that accurate dosimetry is too much trouble. Further clinical studies are required to demonstrate beyond doubt that the advantages of individualised treatment planning outweigh the inconvenience, and that the expense is justified by enhanced results.
Outcomes of intraoperative radiotherapy for early-stage breast cancer: Experience from a multidisciplinary breast oncology program
2020, American Journal of Surgery
Citation Excerpt :
Delivery of this single APBI dose of radiation directly into the operative field is thought to be radiobiologically similar to conventional EBRT dosing of 50 Gy in 2 Gy fractions, thereby decreasing the total treatment duration. It also targets the area of the breast with the greatest risk of recurrence and decreases incidental dose to adjacent normal tissues significantly decreasing the risk of pneumonitis, cardiac disease and poor cosmetic outcome typically associated with external beam radiation.6–8 The TARGIT-A trial, was a prospective, international, multicenter, randomized non-inferiority trial which compared IORT with EBRT.
Intraoperative radiotherapy (IORT) was implemented at our institution for early stage breast cancer patients including those with geographic or medical co-morbidity limitations to whole breast radiation therapy (WBRT).
Retrospective review of patients (n = 127) who underwent IORT from 2009 to 2016 for breast cancer. Demographics, pathology, toxicity, and recurrences were ascertained.
The median age was 67 years (interquartile range: 62–73). At median follow-up (49.6 months), 5 patients (4%) had ipsilateral breast tumor recurrence with median time to recurrence of 36.8 months. Acute and late grade ≥3 skin toxicities were observed in 3.1% and 4.7% of patients, respectively. A subset (n = 7) who received prior ipsilateral WBRT was found to have no subsequent local recurrence, one case of acute grade 3 skin toxicity, and no late toxicity.
IORT is a safe and effective alternative to whole breast radiotherapy, and serves as a suitable alternative to completion mastectomy in locally recurrent breast cancer.
Evaluation of impact of an external breast shield (FlexiShield) in electronic brachytherapy for breast IORT: A phantom study
2017, Brachytherapy
Citation Excerpt :
Electronic brachytherapy (eBT) is an emerging technology in which a miniaturized X-ray source is used to generate low-energy photons with a peak voltage of up to 120 kVp by the definition of the latest American College of Radiology and the American Brachytherapy Society practice parameter (1). Currently, two different types of spherical applicators are used in eBT for breast intraoperative radiation therapy (IORT): an inflatable balloon applicator for the Xoft Axxent eBT system (iCAD, Inc., San Jose, CA) and a solid applicator used in the INTRABEAM system (Carl Zeiss Meditec, Inc., Oberkochen, Germany) (2). In the Axxent eBT system, a flexible tungsten-impregnated external shield (FlexiShield [FS]; iCAD, Inc.) is placed over breast surface to minimize radiation to other organs and reduce dose to personnel.
To investigate Axxent (iCAD, Inc., San Jose, CA) electronic brachytherapy balloon deformation and its dosimetric impact because of an external flexible shield (FlexiShield [FS]; iCAD, Inc.).
Prostheses breast tissue phantom overlaid three spherical balloon applicators to simulate three clinical scenarios depending on minimum skin-to-balloon surface spacing (SS): balloon with SS of 2 cm, 1 cm, and balloon with 1 cm SS and touching the chest wall. Two sets of megavoltage CT (MVCT) scans were obtained with or without FS for 15 different sizes of balloons. For 45 pairs of MVCT scans, balloon deformation was measured in superior–inferior (d_SI) dimension on coronal and sagittal planes and anterior–posterior (d_AP) and lateral (d_LAT) dimensions on the equatorial plane of balloon. SS was also compared. A treatment plan was made on each MVCT scan. Doses at four balloon surface points and skin were compared. Conformity index value was also compared to evaluate three-dimensional dose distribution. Clinically, 20 Gy was prescribed to the surface of balloon.
Balloon deformation was observed with compression in SI and AP dimensions and expansion in lateral dimension. Average SI compression was 0.5 mm. Average d_Lat - d_AP was 2.4 mm, which resulted in elevated point doses at AP dimension by 10.8% of prescribed dose and reduced point doses at lateral dimension by 4.6%. FS decreased SS by 1.8 mm, increasing skin dose by 1.2 Gy, on average. Conformity index value was decreased from 0.922 to 0.908, on average.
This phantom study demonstrates that use of skin shielding during breast intraoperative radiation therapy can cause balloon deformation and SS reduction, resulting in dosimetric changes that are disregarded in current practice.
Targeted radiotherapy enhancement during electronic brachytherapy of accelerated partial breast irradiation (APBI) using controlled release of gold nanoparticles
2015, Physica Medica
Citation Excerpt :
Such a new approach has potential to help reduce long-term adverse outcomes on toxicity (e.g. telangiectasia) and cosmesis. When the 50 kVp Xoft device is chosen for brachytherapy APBI following BCS, the balloon applicator is inserted into the lumpectomy cavity and the irradiation can be performed twice a day for 5–7 days [14]. Here, we propose to deliver GNPs via in-situ release from a GNP-loaded polymer film that is coated on the surface of the balloon applicator (Fig. 1a).
Several studies have demonstrated low rates of local recurrence with brachytherapy-based accelerated partial breast irradiation (APBI). However, long-term outcomes on toxicity (e.g. telangiectasia) and cosmesis remain a major concern. The purpose of this study is to investigate the dosimetric feasibility of using targeted non-toxic radiosensitizing gold nanoparticles (GNPs) for localized dose enhancement to the planning target volume (PTV) during electronic brachytherapy APBI while reducing normal tissue toxicity. We propose to incorporate GNPs into a micrometer-thick polymer film on the surface of routinely used lumpectomy balloon applicators and provide subsequent treatment using a 50 kVp Xoft device. An experimentally determined diffusion coefficient was used to determine space-time customizable distribution of GNPs for feasible in-vivo concentrations of 7 mg/g and 43 mg/g. An analytical approach from previously published work was employed to estimate the dose enhancement due to GNPs as a function of distance up to 1 cm from the lumpectomy cavity surface. Clinically significant dose enhancement values of at least 1.2, due to 2 nm GNPs, were found at 1 cm away from the lumpectomy cavity wall when using electronic brachytherapy APBI. Higher customizable dose enhancement was also achieved at other distances as a function of nanoparticle size. Our preliminary results suggest that significant dose enhancement can be achieved to residual tumor cells targeted with GNPs during APBI with electronic brachytherapy.
Dosimetric comparison of the INTRABEAM and Axxent for intraoperative breast radiotherapy
2020, Brachytherapy
Citation Excerpt :
Radiotherapy can be delivered postoperatively with linear accelerators, high-dose-rate (HDR) brachytherapy using Ir-192, or intraoperatively using electronic brachytherapy (eBT) sources. At the moment, there are two eBT systems for breast intraoperative radiotherapy (IORT): Zeiss INTRABEAM (Carl Zeiss Surgical, AJ, Jena Germany) and Xoft Axxent (Xoft Inc is a subsidiary of iCad Inc., San Jose, CA) (2). The INTRABEAM system generates an isotropic distribution of radiation at the tip of a rigid needle-like probe and a rigid spherical applicator and is used to irradiate the lumpectomy cavity (3).
Breast intraoperative radiotherapy with electronic brachytherapy (eBT) sources, such as the Zeiss INTRABEAM and the Xoft Axxent, are used to treat the lumpectomy cavity using a stationary or a stepped 50 kVp X-ray source, respectively. For three comparable applicator sizes with volume differences <11%, we compare the dosimetry using clinical planning data.
A dosimetric comparison between the INTRABEAM and Axxent to the proximal 1.0 cm of tissue surrounding the applicator is performed using dose–volume parameters (DVPs): V₉₀, V₈₀, V₅₀, D_min, and Homogeneity Index (HI); HI was calculated as D_max/D_min. The dose–volume histograms of the INTRABEAM and Axxent were computed with measured percent depth dose data and with TG-43 parameters, respectively. The skin dose of 0.7–1.0 cm from the applicator surface was also computed.
The mean DVPs were 5.5 ± 0.8% V₉₀, 12.1 ± 1.5% V₈₀, 47.5 ± 5.8% V₅₀, 6.4 ± 0.6 Gy D_min, and 3.2 ± 0.3 HI for the INTRABEAM applicators compared with 7.4 ± 0.3% V₉₀, 14.7 ± 0.8% V₈₀, 55.2 ± 4.7% V₅₀, 4.0 ± 0.6 Gy D_min, and 6.4 ± 1.1 HI for the Axxent applicators. INTRABEAM skin doses ranged from 7.7 to 9.0 Gy at 0.7 cm to 5.5–6.8 Gy at 1.0 cm, whereas Axxent skin doses ranged from 10.7 to 13.0 Gy at 0.7 cm to 7.8 to 9.3 Gy at 1.0 cm.
We demonstrated ±5% comparable dosimetric coverage for tissue ≤0.5 cm from the cavity and higher skin dose for Axxent plans. The DVPs increased with applicator size and with stepped treatment delivery.
Breast intraoperative radiotherapy: A review of available modalities, dedicated machines and treatment procedure
2019, Journal of Radiotherapy in Practice

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: Conflict of interest: none.

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ReportAmerican Society for Therapeutic Radiology and Oncology (ASTRO) Emerging Technology Committee Report on Electronic Brachytherapy

Section snippets

Problem Definition

Description of the Technology

Present scope of use for Xoft Axxent

Present status of product marketing

Evaluation/Summary of Results of Existing Studies

Identification, Analysis, and Evaluation of Consequences of Non-Use

Possible Impact

Emerging Technology Committee note

Acknowledgment

Int J Radiat Oncol Biol Phys

Intraoperative radiation therapy

J Clin Oncol

General rationale and historical perspective of intraoperative irradiation

Report
American Society for Therapeutic Radiology and Oncology (ASTRO) Emerging Technology Committee Report on Electronic Brachytherapy