BEFORE we go quoting specific ranges people ... please know that there are different monitoring methodologies.
Ask your own Onc and make sure the lab reports "normal" ranges for the particular methodology they use.... they sometimes vary with age/gender/smoker vs non-smoker and other existing comorbidities ( infection or inflammation anywhere BUTT especially in the chest )
..... THEN discuss any discrepancies or questions with the Onc, 'cos they should know the specifics of your wife's situation.
sometimes trends are more significant than actual values, especially if all values are in the "normal" range
I am Stage IV and my CEA was NEVER above the lab "normal" range
The Onc's first response should be :
do a follow up CEA at about 4 weeks to confirm the increase,
look for anomalies,
assess for complicating factors,
check for lab error,
consider alternate / ancillary blood work or imaging .. etc.