Psoriatic arthritis does not raise risk of cancer

NEW YORK (Reuters Health) - Overall, people who suffer from psoriatic arthritis do not appear to have a higher risk of cancer compared to the general population, according to a new study.

Psoriasis is a condition linked to an overactive immune system that causes inflamed, scaly red patches on the elbows, knees, scalp, and trunk. In some cases, psoriasis causes arthritis symptoms, such as swollen, stiff, or painful joints.

"The associations between rheumatic disease, psoriasis, immunosuppressive medication, and malignancy remain enigmatic," note Dr. Dafna D. Gladman, of the University of Toronto, Ontario, Canada, and colleagues in a report in the medical journal Arthritis and Rheumatism.

To investigate further, they analyzed 665 patients who were followed from 1978 to 2004 at the University of Toronto Psoriatic Arthritis Clinic. Altogether, 68 (10.2 percent) developed a malignancy, including breast cancer (20.6 percent), lung cancer (13.2 percent), and prostate cancer (8.8 percent).

When Gladman's team compared the rates of first malignancy in their patients with rates in the general population, they found that psoriatic arthritis patients were not at increased risk for developing cancer.

However, the presence of malignancy was predicted by more severe psoriatic arthritis, suggesting that the "burden of disease" is a risk for the development of cancer in patients with psoriatic arthritis, Gladman told Reuters Health.

"The fact that more inflammation is associated with the development of cancer in patients with psoriatic arthritis suggests that these patients need to be treated aggressively to turn off inflammation," she advised. "We already know from our previous studies that inflammation leads to joint damage and excess mortality, now we see that it may also predispose patients to cancer."

SOURCE: Arthritis and Rheumatism, January 2008.