With the goal of determining which patients with RA are at greatest risk for developing lymphoma, Baecklund looked at a registry of almost 75,000 patients with RA. Within this population, 52 percent were classified as having a moderate level of RA, meaning that between six and 20 joints were affected by their disease, and 23 percent were classified as having severe RA, affecting more than 20 joints and seriously limiting their physical abilities. Additionally, 378 had been diagnosed with a malignant form of lymphoma between 1964 and 1995.
Comparing those RA patients who were diagnosed with malignant lymphoma to those that did not, Baecklund noted that those with a low degree RA had the lowest risk of developing lymphoma, while those with a moderate level of RA had seven times the risk. Those patients with the highest level of RA had 71 times the risk of developing this cancer.
"The risk of lymphoma is substantially increased in a subset of patients with RA: those with very severe disease," wrote Baecklund.
More importantly, the team found no connection between many standard RA treatments and the development of lymphoma. The study included such RA treatment as methotrexate, anti-malarial agents, oral steroids, non-steroidal anti-inflammatory drugs (NSAIDs) and aspirin.
Whelan, however, notes that newer treatments, such as anti-TNF alpha drugs, may still have some connection to the development of lymphoma.
"I think the evidence at this time suggests that methotrexate is very safe," Whelan said, "TNF inhibitors may marginally increase risk."
Additionally, no studies have yet been completed to determine if RA treatment can reduce the risk of developing lymphoma. "My sense is that this is a likely outcome," said Whelan.
No matter what causes the connection between RA and lymphoma, it is important for patients with moderate or severe RA to understand the link between RA and lymphoma and to speak with their doctor about options to help them lower this risk.