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Electronic Brachytherapy for Nonmelanoma Skin Cancer

Stegman, Lauren D. MD, PhD, DABR

doi: 10.1097/01.COT.0000516752.51518.13
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Rates of nonmelanoma skin cancer (NMSC), including basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), have risen to epidemic levels in recent years (JAMA Dermatol 2015;151(10):1081-1086, Semin Cutuan Med Surg 2011;30(1):3-5).

Given that approximately 3 million Americans are diagnosed with NMSC each year and almost half of those who live to age 65 will have BCC or SCC at least once, it is essential for clinicians to continually review and assess emerging advances in treatment that have the potential to improve patient comfort and outcomes.

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Standard Treatments

Mohs micrographic dermatologic surgery is considered the standard-of-care for treatment of NMSC. The technique has become widely adopted as an alternative to excision, electrodessication, cryosurgery, and traditional radiation therapy.

However, despite its prevalence and clinical efficacy, it can result in serious disfigurement depending on size and anatomical location of a tumor. In severe cases, some patients may require corrective plastic surgery procedures following Mohs surgery, resulting in additional costs and an increased risk for potential infections or complications.

Radiation therapy is another treatment option that has been used for decades for treatment of NMSC. High-quality data from a randomized controlled trial of radiotherapy versus Mohs are not yet available; however, most experts agree that tumor control rates are generally equivalent to surgery.

Recent retrospective reviews and two meta-analyses have reported 5-year local control rates above 90 percent for both BCC and SCC (Int J Dermatol 2005;44(6):513-517, J Dtsch Dermatol Ges 2006;4(2):124-130, Int J Radiat Oncol Biol Phys 2000;47(1):95-102). These data validate guidelines from the National Comprehensive Cancer Network (NCCN) that include radiation therapy as a reasonable alternative to surgery for many patients.

The best candidates are patients with lesions in anatomically challenging locations (ear, nose, scalp, neck, shin, elbow), patients who may have trouble with wound healing, patients who are on anticoagulants, or those with medical comorbidities that may preclude them from surgery.

The traditional methods of offering radiation therapy for skin cancer can be cumbersome for both providers and patients and have contributed to limitations in its use. First, traditional brachytherapy, orthovoltage, and electron beam treatment machines require a significant capital investment in equipment and shielded treatment vaults.

Second, these treatments often require custom-made shielding devices, bolus, a special material placed on the skin over the lesion to ensure delivery of the full treatment dose to the skin surface and help minimize the dose delivered with the subcutaneous tissues, and special immobilization devices.

These can be time-consuming for the treatment team to make and can be uncomfortable for the patient to wear during treatments. Moreover, these modalities require the patient be in the treatment room alone for 10-20 minutes for each treatment session. Finally, most traditional radiation treatment regimens consist of 15-33 treatment sessions over 4-7 weeks, which can be logistically difficult.

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Electronic Brachytherapy

In 2009, a new method of delivering radiotherapy for NMSC was introduced called high-dose rate (HDR) electronic brachytherapy (eBx). It uses a miniaturized electronic X-ray source rather than a radionuclide-based source.

Practical advantages for providers include less capital investment, no required special shielding of the treatment room, a mobile treatment platform without worries about protecting a radioactive source, and a streamlined system of applicators that do not require bolus and facilitate treatment delivery.

Patients appreciate that members of the treatment team may remain with them in the treatment room during the treatment. This is reassuring and allows the use of less-restrictive immobilization devices. No bolus is needed, which also likely increases patient comfort. An additional advantage is that the very rapid dose fall off below the skin allows more radiation to be given in each session, which generally shortens the total number of treatment sessions to 8-10 doses in most eBx treatment regimens.

Several recent surveys have demonstrated that eBx is well-rated by both patients and doctors. In one study, a majority of patients surveyed between 32 and 73 months after treatment said that eBx did not hinder their daily activities and they were satisfied with how well the modality worked. Patients unanimously agreed the treatment was convenient, and most patients said they would recommend the treatment to a friend with NMSC (Int J Radiat Oncol Biol Phys 2000;47(1):95-102). In a survey of doctors, the majority reported they prefer eBx over traditional external beam radiation therapy due to its shorter treatment course, conformality of treatment for irregular or curved targets, and shallow dose deposition (Brachytherapy 2016; doi:10.1016/j.brachy.2016.10.006).

eBx for the treatment of NMSC is both painless and non-invasive, and can offer many patient benefits including added convenience, fewer treatments compared to traditional radiotherapy, and excellent clinical results. It can be delivered on an outpatient basis in a dermatologist's office, hospital, or cancer center under the direction of a supervising physician. A growing body of evidence supports the use of eBx for NMSC patients who meet specific selection criteria. Research on the use of this modality has been conducted by leading clinicians and positive clinical results have been presented at important medical meetings and published in leading peer-reviewed journals.

In my clinical practice, we recently introduced technology to offer eBx to appropriate patients. The entire system is mobile and can be wheeled easily from room to room. In addition, radiation from an electronic source rather than a radionuclide-based source reduces the need for a shielded vault to protect health care professionals from repeat exposure to radiation. The technology is FDA-cleared for the treatment of cancer anywhere in the body, including eBx for NMSC, making it a cost-effective investment for medical practices that treat different types of cancers.

While NCCN guidelines still suggest that the standard-of-care in treatment of NMSC is surgery and eBx does not yet have the long-term follow-up data of other radiation modalities, the significant level of clinical data showing that eBx treatment is safe and effective positions it well to be an increasingly utilized option for patients. As with the use of all medical technologies, decisions regarding the use of eBx to treat NMSC should be made by treating physicians in close consultation with the patient.

LAUREN D. STEGMAN, MD, PHD, DABR, is Medical Director for Radiation Oncology at Palo Verde Cancer Center, Scottsdale, Ariz.

Copyright © 2017 Wolters Kluwer Health, Inc. All rights reserved.
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