MAUI, HAWAII – The incidence of lymphoma in patients with RA appears to have been dropping during the past 2 decades – and for rheumatologists, that’s news you can use.

Dr. John J. Cush (left) and Dr. Arthur Kavanaugh

“I think this is encouraging data about where we’re headed with therapy. And it’s encouraging data for your patients, that maybe more effective therapies can lead to a lower risk of cancer,” John J. Cush, MD, commented at the 2019 Rheumatology Winter Clinical Symposium.

“Patients are always worried about cancer,” observed symposium director Arthur Kavanaugh, MD. “I think this is very useful data to bring to a discussion with patients.”

The study they highlighted was presented at the 2018 annual meeting of the American College of Rheumatology by Namrata Singh, MD, of the University of Iowa, Iowa City and coinvestigators from Veterans Affairs medical centers around the country. They analyzed the incidence of lymphomas as well as all-site cancers in 50,870 men with RA in the national VA health care system during 2001-2015 and compared the rates with the background rates in the general U.S. population as captured in the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) program.

The key finding: While the standardized incidence ratio for the development of lymphoma in the RA patients during 2001-2005 was 190% greater than in the SEER population, the SIR dropped to 1.6 in 2006-2010 and stayed low in 2011-2015.

“These are the only data I’m aware of that say maybe lymphomas are becoming less frequent among RA patients,” said Dr. Kavanaugh, professor of medicine at the University of California, San Diego.

Historically, RA has been associated with roughly a 100% increased risk of lymphoma. The source of the increased risk has been a matter of controversy: Is it the result of immunostimulation triggered by high RA disease activity, or a side effect of the drugs employed in treatment of the disease? The clear implication of the VA study is that it’s all about disease activity.

“The lymphoma rate is higher early in the use of our new therapies, in 2001-2005, because the patients who went on TNF [tumor necrosis factor] inhibitors then had the most disease activity. But with time, patients are getting those treatments earlier. Does this [lower lymphoma rate] reflect a change in the practice of rheumatology? I think it does,” according to Dr. Cush, professor of medicine and rheumatology at Baylor University Medical Center, Dallas.

Dr. Kavanaugh agreed. “Now, if we’re treating early and treating to target, we should see less lymphomas than we did back in the day.”

The rate of cancers at all sites in the VA RA patients has been going down as well, with the SIR dropping from 1.8 in 2001-2005 to close to 1, the background rate in the general population.

“What’s great about this study is this is a large data set. You really can’t compare an RA population on and off treatment. The right comparison is to a normal population – and SEER accounts for something like 14% of the U.S. population,” Dr. Cush said.

Previous support for the notion that the increased lymphoma risk associated with RA was a function of disease activity came from a Swedish study of 378 RA patients in the prebiologic era who developed lymphoma and a matched cohort of 378 others without lymphoma. The investigators found that patients with moderate overall RA disease activity were at a 700% increased risk of lymphoma, compared with those with low overall disease activity, and that patients with high RA disease activity were at a 6,900% increased risk (Arthritis Rheum. 2006 Mar;54[3]:692-701). But that was a cross-sectional study, whereas the VA study examined trends over time.

The VA RA cohort had a mean age of 64 years. About 60% were current or ex-smokers, 65% were positive for rheumatoid factor, and 62% were positive for anticyclic citrullinated peptide.

Dr. Kavanaugh said that, because of the potential for referral bias in the VA study, he’s eager to see the findings reproduced in another data set.

Both Dr. Cush and Dr. Kavanaugh reported serving as a consultant to and/or receiving research funding from numerous pharmaceutical companies.

bjancin@mdedge.com

Lymphoma rate in RA patients is falling