Most checkpoint inhibitor–induced rheumatic complications in cancer patients can be treated successfully with corticosteroids, albeit often at considerably higher doses than rheumatologists typically use in managing rheumatoid arthritis, Eric M. Ruderman, MD, observed at the 2021 Rheumatology Winter Clinical Symposium.
Dr. Eric M. Ruderman
“In RA, we’re all used to the idea that 5 or 10 mg of corticosteroids per day can make a tremendous difference. That’s not always the case here. Patients who develop rheumatic immunotherapy-related adverse events often require 20-30 mg/day to get symptoms under control,” according to Dr. Ruderman, professor of medicine (rheumatology) at Northwestern University, Chicago.
This may be in part because oncologists typically don’t refer affected patients to rheumatologists early on. Guidelines from the National Comprehensive Cancer Network and other oncology groups suggest referral only once a patient develops grade 3 immunotherapy-related rheumatic adverse events, meaning the symptoms significantly impair daily activities, he explained.
Checkpoint inhibitors, which induce T-cell activation to fight the patient’s malignancy, can produce a plethora of off-target effects. These adverse events may involve the skin, heart, lungs, kidneys, eyes, blood, GI tract, and endocrine organs. The drugs also can cause rheumatic or neurologic complications. The most common of these adverse events are colitis and rash. Next most common are arthritis and arthralgia. Rheumatic side effects are most common as a consequence of immunotherapy using a CTLA4 (cytotoxic T-lymphocyte-associated protein 4) inhibitor, but can also occur in association with programmed cell death protein 1 (PD-1) inhibitors and PD-ligand 1 inhibitors. Arthritis and other rheumatic adverse events are more common in patients undergoing combination therapy.
Some form of frank inflammatory arthritis occurs in 5%-10% of cancer patients undergoing checkpoint inhibitor therapy. This can manifest as an RA-like polyarthritis, spondyloarthritis, polymyalgia rheumatica, necrotizing myositis, or vasculitis. Arthralgia occurs in up to 40% of treated patients.
This immunotherapy-related arthritis is typically more inflammatory than RA. It also has a much more abrupt onset. It is usually seronegative and has no gender predisposition, and the limited available evidence to date suggests there is no increased risk of this complication in checkpoint inhibitor–treated patients with a history of prior rheumatic disease, according to Dr. Ruderman.
Delayed onset and resolution of rheumatologic immune-related adverse events
“Onset and resolution of rheumatologic adverse events with immunotherapy may be delayed. This is an important point: While skin rash and colitis often show up pretty early in the course of immunotherapy, some of the arthritic events can happen later. They can actually continue after the immunotherapy is stopped,” the rheumatologist said.
Indeed, a retrospective nationwide Canadian study of 117 patients at nine academic centers who developed 136 rheumatic immune-related adverse events in conjunction with cancer immunotherapy found that the mean time to the first such event was 6.8 months into checkpoint inhibitor therapy. The most common rheumatic complication was symmetric polyarthritis, affecting 45 patients. Other rheumatologic immune-related complications included polymyalgia rheumatica in 17 patients, noninflammatory musculoskeletal symptoms in 18, and myositis in 9.
Seventy-six patients were treated with prednisone for a mean of 8.4 months at a maximum dose of 60 mg/day. Forty-two moved up the treatment ladder to conventional synthetic disease-modifying antirheumatic drugs (csDMARDs) to manage their symptoms. Only two patients required escalation to biologic therapy. A reassuring finding in this relatively small study was that treatment of the patients’ rheumatic complications didn’t appear to worsen the tumor response to immunotherapy: Twenty-three patients experienced tumor progression prior to treatment of their rheumatic disorder, and 14 did so following treatment.