Calcitonin-negative (Ct-negative) medullary thyroid carcinoma (MTC) is a rare form of the disease which appears to have a good prognosis for most patients according to a study published in Frontiers in Endocrinology.

Of the 312 patients with MTC included in the study, only 24 were found to be Ct-negative yielding an incidence of just under 8%. Previous studies had estimated incidence ranges from .83% to 12.0% of MTC cases. The authors attributed the range potentially to differences in detection reagents and methods.

Read more about MTC prognosis


Continue Reading

Lymph node metastasis is much less likely to appear in Ct-negative patients compared to Ct-positive patients with none of the Ct-negative patients experiencing lymph node metastasis compared to 47.9% of the Ct-positive patients.

All of the Ct-negative patients also only had a single focus with no cases of concurrent papillary thyroid carcinoma (PTC) or other malignant tumors. In comparison, 20 patients had multiple tumor foci and 30 had PTC in the Ct-positive group. No cases of RET gene mutations or familial MTC were detected in the Ct-negative group compared to 6 RET mutations and 1 familial MTC case in the Ct-positive group.

The extent of surgery was also statistically different between the 2 groups (P <.001) with all Ct-positive patients receiving total thyroidectomy with central neck dissection compared to only 7 of the 24 Ct-negative patients (29.2%). The remaining 17 Ct-negative patients only required a unilateral lobectomy with central neck dissection. Lateral neck dissections were also required in 88 of the Ct-positive cases (30.6%) but in none of the Ct-negative cases.

The rate of excellent response after treatment, as defined as a status of undetectable levels of Ct and no evidence of structural disease, was much higher in the Ct-negative patients, as well. Excellent response was achieved in 91.7% of the Ct-negative patients compared to 34.7% in the Ct-positive group (P <.001). An excellent response rate of 100% was achieved in 100% of the female Ct-negative patients (20 out of 20) compared to only a 50% rate in the male patients (2 out of 4).

“This study found that, compared to typical MTC, Ct-negative MTC tended to have limited capacity of lymph node metastasis and proliferation, and a good prognosis independent of the operation extent. However, male patients might require more aggressive treatment,” the authors said.

Reference

Yue W, Zhang Y. Oncologic outcomes of calcitonin-negative medullary thyroid carcinoma. Front Endocrinol. Published online November 23, 2022. doi:10.3389/fendo.2022.1025629