Feel Like a Human Whack-a-Mole Game? You Might Need Field Therapy.

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The president of The Skin Cancer Foundation explains why some people get multiple skin cancers in one area, why that is so frustrating and what you can do about it.

By Deborah S. Sarnoff, MD

Many people develop a high concentration of sun damage, precancers and/or skin cancers in a particular area, or “field,” of the face or body. Doctors call this “field cancerization,” but during my training at NYU with dermatologic surgeon Perry Robins, MD (founder of The Skin Cancer Foundation), he called it the patient’s “tinderbox.” I like that connotation of something that is easily ignited or inflamed.

Field cancerization may have a genetic component or be linked to a very bad sunburn from years earlier. Your tinderbox could also be triggered by the way your body is built or by repetitive activities that expose an area of your body to ultraviolet (UV) radiation from the sun. For example, if your lower lip protrudes, that can be like a little shelf that gathers UV rays every time you walk outside. A man with a bald spot or shaved head, who also doesn’t use sunscreen or wear a hat regularly, may develop one or more skin cancers in that area. If your left ear is exposed from driving to work in the sun every day (damaging UVA rays can penetrate glass), that could be your tinderbox. Indoor tanning could also target an area.

In addition, your field, or tinderbox, may have precancerous patches called actinic keratoses (AKs). These precancers can develop over time into squamous cell carcinomas (SCCs). I recently saw a patient who had previously been treated for several SCCs on his lower lip. Later he developed a lump in his neck. A needle biopsy of the lymph node in his neck showed that the SCC had spread beyond the lip and metastasized. That can be life-threatening.

It is important to treat any biopsy-proven skin cancers or clearly delineated AKs. Following that, it’s helpful to examine the area of skin around the treated site. If there are any visible or palpable precancerous spots, your dermatologist might treat them with freezing, scraping or burning. But in a tinderbox area, there may be also be normal-appearing skin between these precancerous spots, with microscopic damage you can’t see but that could lead to precancers or skin cancers. That’s why it is so important to treat the whole tinderbox area (this is also called field therapy or field treatment).

Some patients who have had several skin cancer surgeries in one area feel demoralized. They say to me, “Doc, we just got that one down and now a new one’s popping up. It’s like playing whack-a-mole. What’s going on?” If you practice good prevention and see a dermatologist for field treatment, you have a good chance of fewer problems popping up!

WHAT YOU CAN DO:

• Protect Yourself from the Sun: This is of utmost importance to minimize future skin damage to your tinderbox area and stop future precancers and skin cancers. That means sunscreen and SPF 15+ lip balm (reapplied every two hours), protective clothing, a hat and UV-blocking sunglasses. I counsel my patients about being consistent and diligent about sun protection every day, especially in their tinderbox area. Yale dermatologic surgeon Sean R. Christensen, MD, PhD, spoke about this at a medical conference in 2016: “Any treatment directed at field cancer needs to occur in combination with rigorous sun protection. There are data to show that sun protection alone can decrease the formation of new skin cancers. It’s a zero-risk therapy.”

YOUR DOCTOR MAY SUGGEST:

• A Nutritional Supplement: Nicotinamide (also called niacinamide), a form of vitamin B3, may help prevent new precancers and skin cancers in people with field cancerization. Both oral and topical nicotinamide help bolster the immune system’s ability to repair DNA damage in the skin from exposure to UV radiation. If you’re at high risk, ask your dermatologist about dosage and if this preventive therapy is right for you.
• Topical Treatments: A prescription topical cream, gel or solution, such as 5-fluorouracil, imiquimod or tirbanibulin can treat visible and invisible lesions in a tinderbox area. These medications can cause a forceful reaction in the sun-damaged cells, but that strong reaction works to reduce the precancers so they don’t develop further. The topical options have different intensities and time frames, from a few days to several weeks, and they make your skin more sensitive to the sun. Repeated cycles of treatment may be required after one or two years. 
• Photodynamic Therapy: For this treatment, known as PDT, a topical agent is applied to the skin and commonly left on for about one to three hours to make the skin sensitive to light. Then it’s washed off. The light-sensitive area of skin, when exposed to either blue or red light (both cleared by the FDA) or a pulsed-dye laser, absorbs the light and produces oxygen, causing a toxic effect that destroys the precancers in the tinderbox area. Recovery may take several days for redness and peeling to calm down, and you must protect the treated area from sun exposure while healing.
• Laser Therapy: Fractional laser resurfacing utilizes a laser to make microscopic holes in the skin, which helps to vaporize the damaged top layer of the skin. Patients may need a series of treatments for field cancerization, because a single treatment may not get rid of all the damage. The downtime for this may take three to 10 days for redness and scabbing to heal. It’s crucial to protect the treated skin from the sun afterward.
• Oral Medication: A vitamin A derivative, such as acitretin or isotretinoin (primarily used to treat severe acne), is an option for patients at highest risk for developing SCCs. It’s a type of chemoprevention that may help prevent future skin cancers. Speak to your doctor about the possible side effects. Some high-risk patients may benefit from a combination of topical treatment and oral medication.

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Deborah S. Sarnoff, MD, is a clinical professor of dermatology in the Ronald O. Perelman Department of Dermatology at NYU School of Medicine. Cofounder and codirector of Cosmetique Dermatology, Laser & Plastic Surgery LLP in Manhattan and Long Island, Dr. Sarnoff is also president of The Skin Cancer Foundation.

This article was first published in the 2019 issue of The Skin Cancer Foundation Journal.