Psoriasis May Increase Cancer Risk
Three-Fold Rate of Lymphoma Noted in Those with Skin Condition
Nov. 17, 2003 -- Having psoriasis could triple the risk of developing a group of cancers that affect the lymph nodes, a new study shows.
In reviewing medical records of nearly 108,000 people living in England, researchers from the University of Pennsylvania note that those with the itchy, scaly skin condition called psoriasis developed lymphoma cancers three times more often than their similarly aged peers without psoriasis. All the patients studied were at least age 65, and included 2,700 with psoriasis.
Still, the three-fold increased rate of lymphoma translates to only 12 additional cases for every 10,000 people with psoriasis. The skin condition affects about 5 million Americans.
"While 12 cases per 10,000 patients is an important number when you're talking about cancer, people shouldn't think they will get lymphoma just because they have psoriasis," says researcher David J. Margolis, MD, PhD. "The risk is still relatively low."
But his new research backs previous studies, including at least one other by Margolis, that suggest people with psoriasis -- among the so-called autoimmune diseases that also include rheumatoid arthritis, lupus and multiple sclerosis -- face a measurably higher risk of lymphomas, which are grouped together as non-Hodgkin's and Hodgkin's lymphomas. They are cancers of the lymphatic system, part of the body's immune system.
"In past studies I've done, we saw maybe a two-fold increased risk for anyone with psoriasis compared to the general population -- even in younger patients," says Margolis, a longtime investigator on the link between cancer and psoriasis. "But the rates were three to four times higher in those getting psoriasis medications."
His new study, published in the November issue of Archives of Dermatology, is the latest to help scientists better understand whether the increased risk of lymphoma stems from the psoriasis itself or from use of some medications employed to treat severe cases.
"The problem is that it is hard to know if people with immunological disease -- and that's what psoriasis is -- are predisposed to an immunological cancer like lymphoma," Margolis tells WebMD. "We know that people with rheumatoid arthritis are, so it makes sense that people with psoriasis also are."
With psoriasis, the immune system sends faulty signals to speed up the growth cycle in skin cells, resulting in new skin cells developing over existing ones and causing the tell-tale patches of thickened, red and scaly plaques that typically develop on the torso, arms or legs.
Drugs used to treat severe psoriasis such as methotrexate, Neoral, and Sandimmune suppress the immune system and thus increase the risk of infection as well as cancer.
But Margolis found that the risk of lymphoma was the same in psoriasis patients whether or not they were receiving the immune suppressing drug methotrexate.