Certain psoriasis therapies contribute to the development of skin cancers, while other treatments protect against skin cancers, and still others have not been shown to increase or reduce skin cancers.
“Since the description of psoriasis, it has been known that sun exposure makes the disease better, but it also causes skin cancers,” says Mark Lebwohl, M.D., a professor and chair of the Department of Dermatology at the Icahn School of Medicine at Mount Sinai in New York City.
In an interview with Dermatology Times, following his presentation on psoriasis at the American Academy of Dermatology (AAD) annual meeting in March, Dr. Lebwohl also notes that when broadband ultraviolet (UV) phototherapy was introduced, “by chance, it omitted most wavelengths under 300 nm, which happen to be the wavelengths that are the most carcinogenic.”
A 25-year review published in the Archives of Dermatology in 1981 reported no increase in skin cancers among patients with psoriasis and atopic dermatitis who were treated with broadband UVB phototherapy.
“You would expect narrowband UVB would be even safer that broadband,” Dr. Lebwohl says. “At least so far, it appears that narrowband UVB does not contribute to skin cancer. Nonetheless, in patients who are cancer-prone, we are cautious about the use of phototherapy.”
On the other hand, PUVA (photochemotherapy) causes a dramatic increase in squamous cell carcinomas, and after many years, an increase in malignant melanomas.
The oral therapy first used for psoriasis was methotrexate.
“Now that we have access to registry data, it appears that the drug does cause an increase in skin cancers, specifically squamous cell carcinoma,” Dr. Lebwohl says.
The transplant drug cyclosporine, which was subsequently introduced for the treatment of psoriasis, “definitely causes an increase in skin cancers,” Dr. Lebwohl adds.
An Australian study published in the journal Transplantation in 1996 found that among kidney transplant patients treated with cyclosporine, the most common cause of death was metastatic squamous cell carcinoma of the skin.
“For transplant candidates who stay on cyclosporine, the frequency of skin cancers keeps rising year after year,” Dr. Lebwohl says. “In fact, in patients who have been on immunosuppressive transplant medication for 20 years, the frequency of squamous cell carcinoma of the skin approaches 50%.”
The next drug introduced to treat psoriasis was the precursor to acitretin, called etretinate.
“That drug has actually been shown to be clearly protective against the development of skin cancers,” Dr. Lebwohl conveys. “Thus, in a patient prone to acquiring basal cells and squamous cells, taking acitretin results in many fewer skin cancers. But once the patient stops taking the retinoid, the skin cancer count rebounds.”