WEDNESDAY, Sept. 7 (HealthDay News) -- Treating rheumatoid arthritis (RA) patients with tumor necrosis factor (TNF) inhibitors appears to increase their risk of developing skin cancer, a new review of prior research indicates.

However, TNF inhibitors, which include infliximab (Remicade), adalimunab (Humira), and etanercept (Enbrel), do not appear to boost the risk for developing other forms of cancer, the researchers added.

The findings stem from an analysis of 21 previous studies conducted between 1998 and 2010, as well as eight study summaries that had been presented at research conferences during the same timeframe. All the studies had focused on the potential for cancer risk in association with the use of standard TNF inhibitors.

"This systematic review and meta analysis provides reassurance to physicians and patients that the treatment of [rheumatoid arthritis] with TNF inhibitors does not increase the risk of malignancy, particularly lymphoma," the French study team said in a news release from Annals of the Rheumatic Diseases, which published the report in its current online issue.

"However, it does appear to increase the risk of skin cancer, including melanoma," added the French team, led by Prof. Xavier Mariette from Paris-Sud University's rheumatology service in Ile de France.

The authors noted that RA has previously been shown to increase the risk for developing certain types of cancer, including both lung cancer and lymphoma, while decreasing the risk for other cancers, including bowel and breast.

However, the question of TNF inhibitor treatments as a cancer risk has remained a subject of debate.

The current review looked at a collection of studies involving a total of more than 40,000 patients. The researchers estimate that, spread across a population that large, this translates to about 150,000 cumulative years of exposure to TNF inhibitor drugs.

Seven of the studies indicated no notable risk increase for any type of cancer associated with the use of TNF meds. Another two long-term studies similarly suggested that while RA patients who had previously had cancer faced a higher likelihood for a second bout, TNF treatments alone posed no additional cancer risk.

But four other studies collectively demonstrated that TNF inhibitors boosted the risk for non-melanoma skin cancer by 45 percent. And another two studies suggested that the RA treatment raised the specific risk for developing melanoma by nearly 80 percent.

Dr. W. Hayes Wilson, chief of rheumatology at Piedmont Hospital in Atlanta, said the findings should help guide physicians on potential RA treatment complications.

"I don't think this is particularly surprising, given that there's long been a concern about cancer risk in the back of our minds," he noted. "And, in fac,t this is somewhat reassuring on the front of solid cancers that there's nothing to be alarmed about."

"But while we can perhaps now put aside our worries about other types of cancers, this does give us some indication that we need to be vigilant when it comes to skin cancer," Wilson added. "And we certainly need to have a high index of suspicion if a patient has a skin abnormality, and make certain that they see their dermatologist."

More information

For more on rheumatoid arthritis, visit the National Institutes of Arthritis and Musculoskeleta...nd Skin Diseases.