A clinician details the development of the electronic brachytherapy field and the design and engineering aspects that make the technology unique.
Rakesh Patel, MD
High-dose rate electronic brachytherapy systems have a wide range of applicator sizes, allowing the radiation to precisely target cancer cells while sparing healthy tissue.
Each year in the United States, clinicians treat more than 5.4 million cases of nonmelanoma skin cancer (NMSC), including basal cell carcinoma (BCC) and squamous cell carcinoma (SCC). Rates of NMSC have increased dramatically in recent years, highlighting the need for advanced treatment options to improve patient care. In the treatment of NMSC, clinicians now have a range of options to consider, each of which presents important considerations for both patients and the clinicians who treat them.
Mohs micrographic dermatologic surgery is widely considered to be the standard of care for NMSC. The technique is positioned as an alternative to excision, electrodessication, cryosurgery, and traditional radiation therapy. In multiple clinical studies, Mohs surgery has been shown to be a safe and effective treatment option for many patients. One potential disadvantage is that Mohs can result in disfigurement depending on the size and location of the tumor. In some cases, patients may require corrective plastic surgery procedures, resulting in additional costs and an increased risk of infection or other complications.
Brachytherapy, which conventionally delivers radiation by temporarily placing radioactive sources in or near the tumor site, is another treatment option that has been used to treat NMSC for decades. It is also supported by extensive clinical research that demonstrates positive long-term outcomes for appropriate patients. In recent years, clinicians have adopted a high-dose rate (HDR) electronic brachytherapy (eBx) technology as a cutting-edge, targeted treatment option for NMSC. This option involves use of radiation from a low-energy electronic X-ray source rather than a radionuclide-based source. This non-radioactive therapy applies a precise dose of radiation directly to the cancerous site, reducing the risk of damage to surrounding healthy tissue.
According to a recent meta-analysis published in the Journal of Contemporary Brachytherapy, HDR eBx is shown to offer excellent or good clinical results for most patients in the treatment of NMSC. Researchers examined results from 10 separate studies collectively involving treatment of 1870 patients with nearly 2000 lesions and found HDR eBx resulted in a 97% local control rate and excellent or good clinical results in approximately 95% of cases. Another study of HDR eBx, published in the Journal of Clinical and Aesthetic Dermatology, reviewed data involving treatment of 1822 NMSC lesions from 2009 to 2014 in patients ages 52 to 104 years old. At between four and 16 months HDR eBx patients showed a recurrence rate of less than 1% with excellent cosmetic results.
In addition to data reinforcing both safety and efficacy, HDR eBx also offers some important advantages that can help to improve quality of care and streamline services for medical practices. In a recent survey, radiation oncologists indicated that they prefer eBx over traditional external beam radiation therapy (EBRT) based on factors including shorter treatment course (eBx typically requires eight fractions twice weekly, compared to EBRT which requires daily fractions of radiation for up to six weeks), conformality of treatment for irregular or curved targets for patients with lesions in challenging anatomical locations including the ear, nose, scalp, neck, shin, and elbow, and shallow dose deposition that targets cancer cells while limiting exposure to surrounding healthy tissue and organs.
When delivering eBx, clinicians prepare the lesion with a flexible shield that is customized to fit around the target area and protect adjacent healthy tissues. The miniaturized X-ray source is placed in the applicator and energized to deliver radiation for a prescribed amount of time. When the treatment is complete, the X-ray source is turned off. Clinicians can choose from a wide range of skin-specific applicators (10mm, 20mm, 35mm, and 50mm), allowing for more flexibility in treating different sized lesions.
The system can be easily transported from room to room and can be used in any clinical setting, including an outpatient clinic office, hospital or cancer center, under the direction of a supervising physician. As a result, this treatment option can be readily available to any patients for whom it might be appropriate. The radiation process is also simplified.
The technology uses a flexible clamp and a lightweight, direct contact applicator that can be precisely positioned to the target lesion. It is designed to deliver a homogenous dose over 90% of the target area. This feature allows clinicians to precisely target therapy to within 1mm of the desired target lesion and deliver the radiation dose over a smaller area. Treatment is isotope-free (non-radioactive) and uses low voltage energy (50kV) that requires minimal shielding of the patient and allows medical professionals to remain in the room during the procedure, which is often a comfort to patients.
These and other benefits of eBx can be attributed in part to the unique design and engineering aspects of the technology.
Rakesh Patel, MD, is a radiation oncologist and medical director of the Department of Radiation Oncology at Good Samaritan Hospital in Los Gatos, CA and is a member of the Xoft Scientific Advisory Board.
[Image courtesy of XOFT, A SUBSIDIARY OF iCAD, INC.]