Rheumatoid Arthritis Inflammation Associated with Lymphoma Cancer - Drug Treatments Did Not Increase Risk of Epstein Bar Virus Positive Lymphoma

February 27th 2006

Rheumatoid Arthritis

Scientists have known about a link between rheumatoid arthritis (RA) and a higher risk of lymphoma for sometime. They were unsure whether it was due to the drugs or the condition. Now it appears the culprit is the condition. A study associates chronic, severe inflammation with the increased risk of cancer.

Swedish researchers have conducted the largest investigation concerning the link between RA and lymphoma. The statistical analysis revealed risk ratios for lymphoma for three different levels of overall disease activity. They assessed RA according to the duration and how swollen and tender joint were.

The researchers analyzed the medical records and case histories of 378 RA patients afflicted with malignant lymphoma between 1964 and 1995. They compared this to 378 individually matched lymphoma-free control subjects. None of the patients received anti-TNF (tumor necrosis factor) blocker therapy.

In the group with medium RA activity they found an 8-fold increase in the risk of lymphoma. The patients with high RA activity had a 70-fold increased risk of lymphoma. According to the researchers, there was “increased risks of lymphoma associated with pronounced, irreversible joint damage in the hands, feet, and knees documented in the last year before lymphoma diagnosis.”

Patients that received frequent corticosteroid injections in inflamed joints had a substantially reduced risk of contracting lymphoma. According to the researchers, this indicates “a possible lymphoma-protective role of potent anti-inflammatory drugs.”

Earlier research from France showed a increased risk of Epstein-Barr virus (EBV) positive lymphomas associated with the popular drug methotrexate (MTX). The Swedish researchers found no increased lymphoma risk associated with the use of MTX and other DMARDs (disease-modifying antirheumatic drugs). Nor was there an increased cancer risk from NSAIDs (nonsteroidal anti-inflammatory drugs), aspirin or steroids.

The researchers did find an increased cancer risk due to the use of azathioprine (AZA), which is not regarded as a traditional DMARD for RA and rarely used in current treatment. This was the only drug that showed an increased lymphoma risk associated with its use.

The research is featured in the March 2006 issue of Arthritis & Rheumatism. Since lymphoma risk is strongly associated with exceptionally severe and longstanding RA activity, aggressive treatment may reduce the risk by reducing cumulative inflammation. The lead author Dr. Lars Klareskog of Karolinska University Hospital in Stockholm said “from a drug safety perspective, our results provide background data that should be considered essential for the evaluation of lymphoma risk following therapy with TNF blockers, for example, as well as other new drugs."