Image-Guided Superficial Radiation Therapy (SRT) for Skin Cancer | A Mohs Surgeon’s Perspective

For decades, Mohs Micrographic Surgery has proved to be the gold standard for the treatment of primary, as well as recurrent, skin cancers of the head and neck, where its tissue-sparing utility has allowed for superior outcomes in areas of complex regional anatomy and great functional importance, such as the eyelid, mucosal lip and nasal rim. Offering cure rates up to 99% for primary tumors, ACMS Fellowship-trained and Board-Certified surgeons are trained to microscopically analyze the full extent of the surgical margin of cancers in difficult anatomic areas, often overlying important nerves and muscles of facial expression. Mohs minimizes postoperative wound depth where stakes are particularly high: e.g., skin cancers overlying vital motor nerves on the dorsal hand; and on the lower legs where the skin cancer burden can be particularly high, and where wounds can sometimes take months to heal.

In recent years, many of my patients have asked about Superficial Radiation Therapy, or “SRT”. Perhaps they have read about it after doing a Google search on treatment options for their skin cancer; or perhaps their friend recommended this treatment based on a positive personal experience. SRT is an X-ray based treatment, requiring multiple patient visits for the non-surgical treatment of skin cancers. Interestingly, “SRT” has become almost vernacular among dermatologists and Mohs surgeons, not because it bears the approval or endorsement by the American College of Mohs Surgery or the American Academy of Dermatology, but because it is such a popular and attractive option to patients.

The recent popularity and appeal of SRT results largely from its widescale promotion by the companies and entities/practices that benefit from its distribution or implementation. Certainly, a procedure that requires no cutting, scarring, or postsurgical downtime or wound healing would be an obvious win-win—or at least that’s what SRT distributors or practices with SRT devices would lead you to believe.

But there is a glaringly obvious and deceptively dangerous omission in this glamorous and alleged “cutting edge and innovative technology”. First of all, radiation therapy is nothing new to medicine, nor is it in any way innovative in the specific realm of cutaneous oncology. As a Mohs surgeon, I routinely work with radiation oncologists for the delivery of adjuvant radiation therapy (XRT), or brachytherapy, even after obtaining clear surgical margins, for certain tumors that exhibit aggressive microscopic features intraoperatively. Fortunately, adjuvant XRT is only necessary for a small minority of Mohs surgery patients, but can further improve overall outcomes when used appropriately.

Secondly, what about outcomes and recurrence rates compared to Mohs micrographic surgery. Remember, though SRT requires no downtime, scars or wound healing, there is no pathologic confirmation—in the form of a microscopic assessment—or pathology report, that the margins are clear. Margin control—a microscopic assessment of the edges of the skin cancer—is the uniquely salient advantage of Mohs microscopic surgery—distinguishing it from all of the other surgical and nonsurgical treatment options.

SRT now has an “image-guided” functionality on newer devices, that seems like it would be a plausible surrogate for margin control….but is it truly? Well, I’m sure it would depend on who you asked. SRT distributors and practices would probably staunchly applause the latest and greatest technological achievement. But any Mohs surgeon—without even having to extract their own intrinsic biases—as well as any doctor who has graduated from any reputable medical institution, for that matter, is taught at the inception of his or her training that tissue trumps imaging in all cases. Period. The end.

But…Not so fast…Why are doctors—even dermatologists—advocating this unsupported procedure without any long-term data in the literature? Probably because they are focused on keeping their patients happy while using an expensive device that generates a lot of revenue for their practice without having to refer the patient to a trained Mohs surgeon. So…if you are a dermatologist or health care provider in an underserved area where skin cancer is epidemic and Mohs surgeons are sparse…this seems like a great, dare I say noble, investment.

In addition to the disparity in recurrence rates for both BCC and SCC (showing vast superiority of Mohs surgery), pay close attention to the statements from the AAD and NCCN—which identify SRT as a second-line treatment reserved only for non-surgical patients. This statement, offers a similar approach for the management of skin cancers in older patients with underlying dementia or multiple comorbid health problems making Mohs surgery an unsafe or impossible option. However, these scenarios which absolutely do happen, occur extremely infrequently and are referred for primary XRT with a well-trained Radiation oncologist, who—unlike SRT—use different machines that deliver targeted, superficial treatments over multiple sessions with customized settings and different billing codes.

So why is SRT now promoted as a novel innovative breakthrough? Unfortunately, I believe it is because of the lucrative billing codes associated with SRT, the widespread appeal that has resulted from SRT promotion by nonmedical corporations who profit from its utilization, and the revenue generated by private practices that offer SRT. As shown in the table, the alleged safe and appealing, and hassle-free nonsurgical option is not being promoted because of its superiority in efficacy…not because of literature which garners any long-term data…not even that it is more cost-effective.

As an ACMS fellowship-trained and Board-Certified dermatologist, Mohs surgeon and cutaneous oncologist having now practiced for almost 15 years, I’m sort of outraged by all of this. Mostly, because I hate that capitalism has intruded into a realm where it should not be—medicine. And I hate that innocent patients will be misled and that in the years following SRT treatments, new, more aggressive cancers could emerge due to the radiation exposure, which…you guessed it…just like the sun, is a risk factor for skin cancers.

What do I mean by this? I mean that choosing SRT to treat small, well-defined tumors in sun-exposed areas is (1) completely unnecessary, (2) vastly increases the number of required appointments, (3) is more costly when compared to Mohs micrographic surgery, (4) is unsupported by the AAD and ACMS, and (5) introduces radiation exposure to surrounding sun-damaged skin that is already vulnerable. So how is this even appealing?

Well, it’s certainly not appealing to me as a Mohs surgeon…I’ve been specializing in the comprehensive treatment of skin cancers in a wide range of patient types and unique clinical scenarios for years. And I am not looking forward to yet another unique clinical scenario that will inevitably pop up in the next couple of years, when we as Mohs surgeons begin to see more aggressive, more frequent skin cancers appearing in treatment fields of previous SRT.

It’s important for the community to understand that Mohs surgeons do not use the Mohs technique for all skin cancers, and the appropriateness of Mohs surgery is not arbitrary. Whether it’s a first-time treatment of a newly-diagnosed basal cell carcinoma on the nasal tip of a 29 year old female patient before her upcoming wedding (yikes!), or the treatment of the 78th basal cell carcinoma in a 92 year old fisherman who has lived a full life on the sunny lowcountry coast, we offer multiple options for all of our patients, but are guided by a well-respected protocol, established by The American College of Mohs Surgery (ACMS), called “Appropriate Use Criteria”, which is a score that is numerically generated for each cancer on which Mohs is considered. The AUC score is based on a variety of histologic and clinical factors including: cancer subtype, specific anatomic location, tumor size and clinical indicators of aggressive tumor behavior (e.g., rapid growth, underlying history of organ transplant or immunocompromise…or…previous history of regional radiation therapy in the area).

That’s right…according to the ACMS’s AUC, now all patients with history of SRT will be considered high-risk because of an unnecessary, expensive, unsupported and substandard procedure that is now becoming widespread. I am fearful most, not about what is theoretically possible, but what we don’t know…because we have no long-term data.

After years of data analysis, numbers-crunching and countless peer-reviewed publications in the literature, Mohs offers the highest cure rate and produces the smallest cancer-free defect, with the smallest amount of normal tissue sacrificed, and pathologic proof that the cancer is gone. Both the American Academy of Dermatology and the National Comprehensive Cancer Network have issued statements relegating SRT to a second-line treatment option, and reserved for patients who are not surgical candidates. And yet, machines are being sold to practices all over the country, and recommending its use indiscriminately.

It has been my honor and privilege to care for our community at May River Dermatology and take pride in my specialty of Mohs surgery and Cutaneous Oncologist. As such, this article comes from genuine concern for our community, my commitment and sincere belief in Mohs surgery as the gold standard for skin cancer treatment, and my intention to keep our community informed and healthy.