RA and lymphoma risk: A critical link?

A history of cancer is not a major risk factor for rheumatoid arthritis (RA), but there is an increased lymphoma risk after RA diagnosis. Shared susceptibility and common risk factors probably do not provide a major explanation, but there may be a critical link between the RA disease or its management and subsequent lymphoma risk.

Hellgren and coworkers studied records from 6745 patients enrolled in the Early Arthritis Register who were cross-linked with entries in the Swedish Cancer Registry. Study participants were matched with controls from the general population.

At the time of RA diagnosis, 5.3% of the patients with RA and 6.7% of the general population controls had a history of cancer. In the time after RA diagnosis, 19 lymphomas occurred in the patients with RA, compared with 53 lymphomas in the population controls. In addition to a 75% overall increase, there was a trend toward increasing relative risks during the first 10 years after the diagnosis of RA.

The authors noted that a history of cancer is not more common in patients with newly diagnosed RA than in the general population, suggesting that RA onset after cancer diagnosis reflects chance, not causality.