Would you recommend adjuvant therapy for a patient with intraheptic cholangiocarcinoma with an isolated metastasis who has undergone complete surgical resection and is NED?

Given M1 disease, I would absolutely give adjuvant therapy. Data is of course strongest with 6 months of Capecitabine, but given that you could consider this patient metastatic, it would not be wrong to give 6 months of gem/cis. I would also absolutely profile with NGS, to be prepared for recurrence...

I would consider this patient oligometastatic, and I would give Gem/Cis and follow with scans, CA 19/9 then gradually, I would drop the cisplatin after 4-6 cycles.

This way, I don't lose the opportunity to aggressively control the disease. This depends, of course, on his/her PS, age, and other fact...

With M1 disease, I am unsure about starting “adjuvant” therapy in an asymptomatic patient. An alternative approach might be close observation initially, with chemotherapy at the time of disease recurrence.

I completely agree with @Dr. First Last. The question is when you will treat (sooner rather than later), not whether. Recurrence is virtually certain. NGS sequencing here may be the most important aspect of the care.

6 months: Cisplatin/Gemcitabine

I would get NGS and then, offer appropriate therapy.