In a retrospective study published in 2007, Machens and Dralleused multivariate analysis in 150 patients preoperatively and studied specific biomarkers including CEA in the treatment of MTC, concluding that elevated CEA levels indicate advanced disease, larger primary tumor size, possible extra-thyroid expansion and distant metastases. This evidence concerns the gene CEACAM5 and medullary thyroid gland carcinoma.