BOSTON – The ratio of serum calcitonin to the serum level of carcinoembryonic antigen in patients with medullary thyroid cancer can predict which patients have a better chance for survival following thyroidectomy, based on retrospective findings from 164 presurgical patients at one U.S. center.
A lower serum calcitonin–to–serum carcinoembryonic antigen (CEA) ratio following thyroidectomy is a second marker of good postsurgical survival, Tania Jaber, MD, said at the World Congress on Thyroid Cancer.
Although Dr. Jaber cautioned that these findings are preliminary and need validation in prospective studies run in different patient populations, the association she and her coworkers at MD Anderson Cancer Center found was compelling enough to convince them to begin measuring the calcitonin-to-CEA ratio routinely in medullary thyroid cancer patients and use the results in counseling patients.“Patients want to know whether surgery will cure them, and we have had no prognostic markers to predict this. Depending on the ratio, we can now tell patients whether or not they have a good chance of cure,” said Dr. Jaber, an endocrinological oncologist at MD Anderson in Houston. “Surgery remains the standard of care, so the ratio does not affect the decision of whether to undergo surgery, but it helps patients know what to expect” after surgery, she said in an interview.
“If their ratio is favorable it can be reassuring, and if their ratio is unfavorable it helps set expectations. We are also studying whether the ratio can be a marker for the need for systemic therapy following surgery. Right now, our prognostic tools for medullary thyroid cancer are very limited, so any additional information we can give patients based on their calcitonin-to-CEA ratio is very valuable.”
Her study included 164 patients treated at MD Anderson who had their serum drawn before thyroidectomy, and 187 patients with specimens taken 3-9 months after surgery. Median patient follow-up after surgery was 5 years. Calcitonin levels were measured as pg/mL and CEA levels as ng/mL; despite this difference in unit size the researchers calculated the ratios by a direct numerical comparison that ignored the units.
Among the preoperative patients and specifically among those with a low serum CEA level of less than 25 ng/ML a calcitonin-to-CEA ratio of less than 43 had the best survival rate, Dr. Jaber reported. Among preoperative patients with a CEA level of 25 ng/mL or greater a ratio of less than 18 flagged patients with the best survival rate following thyroidectomy.
Among postoperative patients the ratios that linked with better survival also depended on the CEA level. In patients with a low postoperative CEA a ratio of less than 149 linked with better survival. In patients with a high CEA level a ratio of less than 12 linked with better postoperative survival.
mzoler@frontlinemedcom.com
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