Why Painful Arthritis May Return More Severely After Immunotherapy, Study Finds - Video

Painful arthritis can return repeatedly in cancer patients following immunotherapy, and scientists may have discovered why. A new study suggests that immune memory plays an important role in recurring joint inflammation, with immune cells from earlier episodes becoming reactivated and triggering subsequent arthritis flares.

Published in Cancer Immunology Research, the study conducted by researchers at The University of Texas MD Anderson Cancer Center and Yale University investigated the immune mechanisms responsible for recurrent inflammatory arthritis following cancer immunotherapy.

Immune checkpoint inhibitors are widely used cancer treatments that stimulate the immune system to recognise and destroy tumour cells. However, these therapies can sometimes trigger immune-related complications, including inflammatory arthritis characterised by joint pain, swelling and stiffness.

Approximately 20% to 50% of patients who develop immunotherapy-associated arthritis experience recurring flares, with symptoms sometimes persisting long after cancer treatment has stopped.

To investigate these recurrent episodes, researchers examined joint fluid samples collected from six patients during their initial arthritis flare and a subsequent recurrence.

The findings revealed two distinct immune cell populations present during both episodes: inflammatory CD8 T cells and specialised CD4 T cells expressing PD-1 and CXCL13 markers.

Researchers observed that these immune cells became more active during recurrent flares, producing increased levels of inflammatory signalling molecules that could intensify joint inflammation.

Interestingly, regulatory T cells, which normally suppress excessive immune responses, also began producing inflammatory molecules during subsequent episodes.

The analysis further identified increased communication between inflammatory immune cells within affected joints, suggesting a more coordinated immune response during recurrent arthritis.

Researchers proposed that these persistent immune cell populations may act through an immune memory mechanism, reactivating inflammation rather than generating entirely new immune responses.

The discovery could eventually help identify patients at risk of recurrent arthritis and support the development of targeted treatments.

REFERENCE: Synat Keam, et al.; Immune Hallmarks of Recurrent Immune Checkpoint Inhibitor–Mediated Inflammatory Arthritis. Cancer Immunology Research, 2026; 14 (10): 1653 DOI: 10.1158/2326-6066.CIR-25-1639