12 months free of disease with clear CT scans: What is next?

My husband has been clear of disease for 12 months with clear CT scans. The cancer disappeared after 12 sessions of chemo which the oncologist described as a miracle. He was diagnosed with stage four, mets to liver, however mets disappeared after 3 chemo sessions, he was not a candidate for surgery.
The CA19 market has been rising over the past 4 months, last result marker of 500 - a further CT and MRI later this month …..Oncologist states she will not act in CA19 marker alone. My husband is active, eating well and maintaining weight and feeling very well - we are a little concerned and wondered if anyone has the same experience
Thanks for any info