If I can offer some small advice. Get a CTDNA (cancer tumor DNA) test done. It's relatively new and some insurances may not cover it. (not sure about other countries). In addition to the CEA blood work, the CTDNA test can predict recurrence about 9 months earlier. My doctor was willing to order it and it was fully covered. In fact Signatara, (a CTDNA test provider) told me they are covering the cost even if private insurance fails to, as long as a doctor ordered the test. I'm sure it is part of their marketing campaign to expand awareness.
In short it provides either earlier warning or greater peace of mind.