Get ready for cancer immunotherapy-induced rheumatic diseases

SNOWMASS, COLO. – Physicians can expect to encounter more and more patients with inflammatory arthritis and other rheumatic adverse events induced by immune checkpoint inhibitors as a result of anticipated exponential growth in the use of these drugs to treat an expanding list of cancers, Clifton O. Bingham III, MD, said at the Winter Rheumatology Symposium sponsored by the American College of Rheumatology.

These cancer immunotherapy–induced rheumatic diseases may superficially look like the classic forms of familiar autoimmune diseases, but they have highly atypical features that will affect treatment decisions.

“What we’ve seen consistently is that the normal doses of prednisone we would use to treat an inflammatory arthritis are really ineffective in most of these patients. We’ve had to use super doses – up to 120 mg/day – for initial control, and then 7.5-40 mg daily for maintenance of response,” according to Dr. Bingham, professor of medicine and director of the Johns Hopkins Arthritis Center in Baltimore.

To date, only limited data from case series are available on rheumatic IRAEs. There are no prospective patient registries logging accurate data on the incidence of these rheumatic adverse events among cancer patients treated with immune checkpoint inhibitors (ICIs). These IRAEs, which lie at the intersection of rheumatology and oncology, are of special interest to Dr. Bingham – he and his coinvestigators have published five articles on the topic over the course of a single year.

In a wide-ranging talk at the symposium, he touched on the phenotypic spectrum of rheumatologic IRAEs, his conviction that they are greatly underdiagnosed, why physicians can expect to encounter them much more frequently, rheumatologic IRAE treatment issues, and the risks of prescribing ICIs in patients with known preexisting rheumatologic disease.
 

Rheumatologic IRAE presentations

Inflammatory arthritis is the most common form of rheumatologic IRAE, followed by sicca syndrome. At the Johns Hopkins Arthritis Center, Dr. Bingham and his coworkers have 25 well-characterized patients with inflammatory arthritis resulting from an ICI, only 1 of whom is HLA-B27-positive.

“Also, just one is autoantibody-positive, even though they all look for all the world as though they have rheumatoid arthritis,” the rheumatologist observed.

This ICI-induced inflammatory arthritis initially presents most commonly in the midsize and large joints – knees, ankles, elbows – then expands to include small joints such as the wrists, proximal interphalangeal joints, and the metacarpophalangeal joints.

Notably, the Hopkins group also has three patients with classic reactive arthritis marked by conjunctivitis, urethritis, arthritis, and dactylitis.

“I don’t know about you, but, in our general rheumatology practice, we see maybe one case of reactive arthritis in several years, so this is something that has struck us as really quite interesting,” said Dr. Bingham, who is also director of research in the division of rheumatology at Johns Hopkins.

The arthritis center is also managing a group of patients with ICI-induced sicca syndrome, which is uniformly extremely severe and treatment resistant, as well as a couple of patients with myositis IRAE, one with polymyalgia rheumatica, and two with crystal disease that is highly inflammatory in nature, difficult to treat, and includes an inflammatory polyarthritis component not typical in patients with crystal arthritis.
 

Why physicians will see more rheumatologic IRAEs

ICIs have dramatically transformed the treatment of selected advanced-stage cancers. For example, whereas patients with metastatic melanoma historically had a 2-year survival rate of 5%, combination therapy with the ICIs ipilimumab (Yervoy) and nivolumab (Opdivo) resulted in a 60% rate of partial or complete remission in a landmark clinical trial.

The basis of cancer immunotherapy is the discovery that, in order for cancer cells to thrive, they emit blocking signals that downregulate the native ability of T cells to recognize and kill them. This is true for both solid tumors and hematologic malignancies. The ICIs inhibit these blocking signals, which include cytotoxic T-lymphocyte–associated protein 4 (CTLA4), programmed death-1 (PD-1), and programmed death ligand-1 (PDL-1), thereby freeing up the T cells for tumor fighting.

Because of the nonspecific mechanism of this T-cell activation, however, ICIs have, as their main toxicities, T-cell–mediated autoimmune inflammatory tissue damage, which gets lumped under the umbrella term IRAEs. It can affect almost every organ system. Skin rashes are the most common, colitis second. Other commonly encountered IRAEs include thyroiditis, hypophysitis, hepatitis, peripheral neuropathy, and pneumonitis.

In addition to the four currently approved ICIs – ipilimumab, nivolumab, pembrolizumab (Keytruda), and atezolizumab (Tecentriq) – investigational ICIs targeting CTLA4, PD-1, and/or PDL-1 are in development. Plus, new ICIs targeting other blocking signals, including lymphocyte activation gene-3, CD137, and T-cell immunoglobulin and mucin domain-3, are now in clinical trials.

Clinical trials aimed at expanding the indications of existing ICIs and using ICIs in earlier-stage cancers in an effort to improve rates of lasting remission are also underway.

All told, probably at least 400 clinical trials of ICIs are ongoing worldwide, the rheumatologist estimated.

“More people will be exposed to these drugs, and we’ll see more and more of these rheumatologic IRAEs,” Dr. Bingham predicted.