High CEA
A raised CEA level can be associated with certain cancers—particularly gastrointestinal malignancies—note thattumour markers lack specificity, meaning elevated CEA can also occur in benign conditions and is not diagnostic of cancer. High CEA is most useful in monitoring patients with known malignancy rather than detecting disease.

Low or Normal CEA
A normal or low CEA level does not rule out cancer, as tumour markers may be normal in early-stage disease or in some patients even with advanced malignancy. Note that tumour markers have limited sensitivity, so low values cannot exclude malignancy