IMMUNOTHERAPY-INDUCED ARTHRITIS

Immune checkpoint inhibitors, the most important innovation in cancer treatment in the past decade, have improved survival in many types of cancer and are a godsend to thousands of people who are diagnosed with the disease, says Dr. Cappelli. “But five or so years ago, rheumatologists started getting calls from oncologists saying their patients were complaining of joint pain. As we started seeing more of these patients, we realized they had one thing in common: They were being treated with immunotherapy.”

Immune checkpoint inhibitors are designed to rev up the immune system so it’s better able to fight cancer. But in some people, it over-activates the system and begins attacking healthy tissue, including joint tissue. In some patients who develop immunotherapy-induced arthritis, the joint inflammation doesn’t go away even after they stop the drugs.

When Dr. Cappelli and her colleagues at Johns Hopkins followed 60 patients who developed inflammatory arthritis while taking immune checkpoint inhibitors, 70 percent still had active arthritis three months after stopping the medication; some still had the disease two years later. “ Inflammatory arthritis was more likely to last longer in those who’d been on immune checkpoint inhibitors longer,” she says.

Rheumatologists treat this newest form of arthritis with some of the same anti-inflammatories they use for other forms of inflammatory arthritis. But it’s a delicate balance, says Dr. Cappelli: “We don’t want to turn down cancer patients’ immune systems too much, because immune checkpoint inhibitors success in fighting cancer is their ability to turn the immune system up. We need to find a way to encourage the immune system to attack patients’ cancer, not their joints.