Immune checkpoint inhibitor-induced inflammatory arthritis: a single center review
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INTRODUCTION: Immune checkpoint inhibitors are a new form of immunotherapy that has transformed the treatment landscape for an ever-increasing number of malignancies. While these medications utilize and enhance the immune system to treat malignancies, they can also have significant side effects, termed immune related adverse events, that in many ways resemble autoimmune disease states. One such example is inflammatory arthritis, which has been found to resemble a number of different presentations, including rheumatoid arthritis and seronegative spondyloarthropathies. In addition to these traditional inflammatory arthritis phenotypes, worsening of pre-existing arthritis is another subgroup of inflammatory arthritis that has previously not been considered in this population. Furthermore, while the effects of these autoimmune arthropathies on functionality is well-documented, it is not known whether there is a significant effect on functionality in patients that experience immune checkpoint inhibitor-induced arthritis. Given that patient reported outcomes are a validated and routinely utilized measure of functionality and quality of life, the Health Assessment Questionnaire, pain visual analogue scale and Patient Global Assessment were used to measure these outcomes following diagnosis. Our aim here is to explore the subtypes of inflammatory arthritis that result from this type of treatment and its overall effect on functionality and quality of life. METHODS: This study was a retrospective review of patients at one academic center who experienced an inflammatory arthritis resulting from immune checkpoint inhibition and required a referral to a rheumatologist for further work-up. Patients were evaluated in clinic at which time they also completed a Health Assessment Questionnaire as part of standard of care. Once patients were evaluated, their inflammatory arthritis was classified based on which clinical arthritis that it matched most closely, including polymyalgia rheumatica, rheumatoid arthritis, seronegative spondyloarthritis, or an exacerbation or osteoarthritis. Other demographic information such as gender, age, and race were also collected. Patient questionnaires were scored and compared to the type of inflammatory arthritis to assess for any correlations. RESULTS: We found 30 patients that had an inflammatory arthritis resulting from immune checkpoint inhibition, with 12 having a polyarthritis similar to rheumatoid arthritis, 11 patients having osteoarthritis exacerbation, 4 patients with a polymyalgia rheumatica arthritis phenotype and 3 patients with a spondyloarthopathy. In terms of the patient reported outcomes, the overall score was 0.57 ± 0.47, indicating that there was little effect of these arthropathies on overall functionality. The pain visual analogue scale had an average score of 41.8 ± 31.4 mm and the Patient Global Assessment had an overall score of 25.6 ± 26.7 mm. DISCUSSION: The overall results suggest that the inflammatory arthritis phenotypes do not significantly impact the functionality or quality of life of most patients who experience this side effect. Given that the use of immune checkpoint inhibitors will continue to grow, the overall need to better understand the resulting arthritis presentations is key. This is perhaps most true for those with pre-existing osteoarthritis, given the widespread nature of the disease in the general population and the prominence of the exacerbation as seen in our cohort.