How would you approach management of a patient who develops squamous cell skin cancer while on abatacept?

I would discontinue abatacept. Several studies now have reported an increased risk of squamous cell cancer/non-melanoma skin cancers in patients on abatacept (Wadstrom et al., PMID 28975211, Simon et al., PMID 37932010) and in someone who actually develops this malignancy on the drug, I would hesitate to continue it. If rituximab is still an option for the patient and RA disease activity warrants a biologic, I would lean towards initiating rituximab.

If the patient was well controlled on Abatacept, I would discuss with the patient either continuing this medication with close follow up with Dermatology, vs change to a different medication with the risk of poorer efficacy and other potential side effects.

In general, Abatacept has a lower risk of serious side effects than other biologics or JAKs. (Ther Adv in MSK disease V15, 2023), (Arthr Res Ther 2023 25 105). The Simon article referenced above, suggests no difference between Abatacept and other "biologics" in regard to skin cancers.

The patient likely has already been on a TNF (or there is a comorbidity that prevented its usage).

Since the pandemic, Rituximab has moved further down on my list of biologic choices.