Do you consider new onset autoimmune disease (e.g. seronegative rheumatoid arthritis) a few months after completing immunotherapy for cancer to be an immune-related adverse effect to the immunotherapy?  

Yes, if there is no other features that suggest there is another etiology for the event. Immune-related adverse events (irAEs) can present after immunotherapy is stopped for at least one year and potentially longer. Consensus guidance (Naidoo et al., PMID 37001909) discusses delayed onset irAEs. If ...