How would you manage a patient with anal squamous cell carcinoma and 5 FU induced coronary vasospasm 36 hours after starting definitive chemoradiation?

I would seek the assistance of an oncocardiologist, if available. Did the patient develop EKG changes? Troponin leak?

For coronary vasospasm induced by 5FU, there is a range of severity and risk. Given that this patient only requires a second dose of 5FU, I would see if there were any possibility of...

I'm not sure if this is helpful to you in this situation, but in a different GI cancer, I was pleased to learn recently that it is the infusional 5 FU that causes vasospasm that is also seen with capecitabine; bolus 5 FU may be safe to use. See the reference below:

Safety and tolerability of the bol...

If the cancer is early staged or non bulky, consider forgoing further 5FU and finish with mitomycin as planned and slightly higher radiation boost dose. If the cancer is bulky/advanced stage, I would change the regimen to perhaps carbo/tax. Both options would allow a safe alternative.