Inflammatory polyarthritis ups risk of lymphoma

NEW YORK, May 6 (Reuters) The risk of lymphoma (cancer of the blood) appears to be more than twice as high in people with inflammatory polyarthritis relative to that seen in the general population, UK researchers report. Inflammatory polyarthritis is a form of rheumatoid arthritis involving two or more joints.

There are conflicting data on the association between rheumatoid arthritis and lymphoma and the possible influence of arthritis treatments that suppress the immune system, Dr Alan J Silman of The Medical School, Manchester and colleagues note.

To investigate further, the researchers conducted a prospective cohort study involving 2105 patients with new-onset inflammatory polyarthritis.

Over a median of 8.4 years, there were 11 cases of non-Hodgkin's lymphoma -- cancer involving the lymph nodes. Six of these cases were large B-cell lymphoma -- the most common type of lymph node cancer in adults.

Individuals with inflammatory polyarthritis were 2.4 times more likely to have lymphoma than the general population.

The incidence was higher in patients with rheumatoid arthritis and those who reported taking disease modifying anti-rheumatic drugs. The highest risk was seen in patients treated with methotrexate.

These data, the researchers point out, ''stress the need for an appropriate control cohort for comparison of the long term adverse of novel drugs for rheumatic diseases.'' Reuters DKS GC0933