These single point cutoff values on biomarkers are easily improved by your individual data series.
e.g. if CEA preop is 3.2 with a subsequent pathological staging, and a few weeks after curative surgery, CEA is 1.1, then that high/low biomarker range is far more useful than statistical cutoffs alone. Several points at a value or on a trend, are desirable.
Likewise, for many people, they could profitably do this pre-op/postop baseline for several common biomarkers like CA199, LDH, AFP, quantitative D-dimer and others that I've mentioned. Inflammation markers like ESR and hsCRP help identify inflammation effects in your blood data and potentially could help minor adjustments. You are potentially adding extra life chances with improved data series. Even if your current onc today can't read the data well, it can be useful to others, life saving later, even years later. We make decisions partly based on early blood data from 5-6 years ago. I curse about the blood data not taken then because of uninforming, -ed medical advice that has required me to dig it out myself, slowly.
My personal belief is that most oncologists have not invested the time to develop skill with these markers for CRC patients, that conventional chemo or RT disrupts many biomarkers' series during and for a while after treatment, might alarm people over chemo itself, are historically pessimistic about futility of more treatments, are poor at controlling inflammation sources, and are unwilling to buck outside influences (cost managers, ASCO, insurers, etc).
Some of us with experimental backgrounds, like SamT, have added anti-inflammatories and mild immune therapies, along with high frequency and intensive bloodwork to self-identify and solve deadly problems that normally evade timely therapeutic response. Continuous, lower dose chemo backbones like ADAPT (daily capecitabine + celecoxib) may help yield less noisy blood data too.
Should I insist on an additional CEA count, or is he right that it doesn't really matter much at the levels I'm already at?
Although statistics for your cancer pathology are favorable, safety is to consider the fraction that do recur. Bloodwork matters to catch problems early and to identify successful treatments. These blood data are best kept together on a spreadsheet. If you don't want to confront the doctor, it is possible to order it yourself, like at Life Extension. Personally, I prefer to consult doctors that can contribute or at least follow the story.
watchful, active caregiver for stage IVb CC since early 2010. immuno"Chemo forever," for mCRC