The psoriasis-cancer link
Having psoriasis may increase the risk of getting certain cancers. But researchers aren't sure why.
By Heather Johnson Durocher
Editor's note: This is the second in a series of Psoriasis Advance articles about health risks associated with psoriasis. The first article, in the Summer 2009 issue, discussed overall health risks. This and future articles will look at individual health conditions (doctors call them co-morbidities) associated with psoriasis.
Psoriasis patients, particularly those dealing with chronically severe forms of the skin disease, are at a higher risk of also having certain types of cancer, according to recent findings.
Both the skin cancer known as squamous cell carcinoma and lymphoma, a cancer that affects the immune system, are health risks some psoriasis patients face, according to a study published last year in the Journal of the American Academy of Dermatology (JAAD).
"Our review found that people with more severe cases of psoriasis appear to have an increased incidence of psoriatic arthritis, cardiovascular disease, hypertension, diabetes, cancer, depression, obesity and even other immune-related conditions such as Crohn's disease," said Dr. Alexa Kimball, one of the study's researchers who serves as vice chair of dermatology at Massachusetts General Hospital and is an associate professor at Harvard Medical School. She's also a member of the National Psoriasis Foundation Medical Board.
The risk of certain cancers has troubled the psoriasis community in recent years, said Dr. Ken Gordon, a dermatologist at Evanston Northwestern Healthcare in Skokie, Ill., and also a Psoriasis Foundation Medical Board member.
"The concern we all have is primarily lymphoma, and that's still controversial," Gordon said.
Cause is unclear
Controversial because, while studies like the one published in JAAD have linked a higher risk of lymphoma in patients with severe psoriasis, the actual cause of the cancer remains unclear.
Researchers have hypothesized that the increased rate may be due to the following:
Psoriasis leads to increased T-cell activity because it is a disease that affects the immune system. (T cells are white blood cells in the immune system that fight infections and foreign materials.)
Newer treatments that suppress the immune system (immunosuppressants) may be independent risk factors for developing malignancies.
Or the combination of immunosuppressants and the disease itself may lead to the increased rate.
"We don't know which one is exactly right," said Gordon, who believes long-term studies of psoriasis patients are needed before a definite determination can be made.
"We need better information on the diseases—that's our problem right now. There are some efforts. There is a registry to look at psoriasis patients that is being evaluated. But it's still not as good as registries for rheumatoid arthritis."
Even so, some psoriasis treatments have been linked to a higher risk for cancer. For example, a treatment called PUVA—ultraviolet light A used with a light-sensitive drug called psoralen—is the most clear-cut psoriasis treatment associated with developing cancer, said Dr. Mark Lebwohl, dermatology chairman of the Mount Sinai School of Medicine in New York and the chairman of the National Psoriasis Foundation Medical Board.
There also are some studies showing biologics used to treat psoriasis might be linked to lymphoma and squamous cell carcinoma. It's been known for some time that TNF-alpha blockers are associated with an increase in certain kinds of lymphoma, Lebwohl said. (TNF-alpha blockers suppress a protein in the immune system called tumor necrosis factor-alpha, which is believed to play a role in the development of psoriasis.)
"TNF blockers are the only ones that stop the destruction of the joints (in psoriatic arthritis)," he said. "Other treatments don't do that. When I have patients who will benefit from (a TNF blocker), a patient who has significant psoriatic arthritis for instance, I warn them about the risk of developing lymphomas."
Talking openly with your dermatologist about your psoriasis and your overall health is an important first step in ensuring good health, experts said. Specific to cancer risks, Kimball suggests following the recommended routine health screenings for cancers and avoiding high-risk behaviors that increase the risk of developing some cancers, such as smoking, alcohol abuse and intentional sun exposure.
"That must be a high priority for psoriasis patients who may be at an increased risk for these potentially life-threatening diseases," she said.
Learn more about cancer risks by visiting:
Psoriasis Drugs Carry New Cancer Warnings
Prescription drugs that block the action of proteins in the immune system called tumor necrosis factor (TNF)—which are believed to play a role in developing psoriasis—must carry updated warning labels with information that TNF blockers may cause leukemia and other cancers in children and adolescents.
The warning will be included on these FDA-approved drugs, commonly used to treat psoriasis and/or psoriatic arthritis: Remicade (generic name infliximab), Enbrel (etanercept), Humira (adalimumab) and Simponi (golimumab).
The FDA imposed the new rule after a safety review indentified 48 cancers in children and adolescents who were prescribed TNF blockers. The FDA acknowledged that it cannot definitively state that these drugs caused the cancers, but also said it could not rule out the possibility.
The agency advises doctors and patients to discuss the risks and benefits of the drugs and to watch for early signs of cancer.