I very often get that test as well as the CA 27-29. Especially when I was on chemo as my CA 27-29 was often up over 100! That unnerved me, but my onc said that number was a reflection of the chemo (I also had Navelbine as one drug) WORKING, and not necessarily a sign that the cancer was on the march. I now run between 19 - 24 and am NED, taking herceptin and zometa for maintenance.
Right now my CEA is .9ng/mL and normal range is less than 5.0. The other test is 22U/mL with 0 - 37 as normal range.
Try to take you mind off this as your oncologist is probably right, especially if you just had those good test results.