Long-term outcome of “prophylactic therapy” for familial medullary thyroid cancer

Utility of serum thyroglobulin measurements after prophylactic thyroidectomy in patients with hereditary medullary thyroid cancer

INTRODUCTION

Prophylactic thyroidectomy can be curative for patients with hereditary medullary thyroid cancer (MTC) caused by RET proto-oncogene mutations. Calcitonin is a sensitive tumor marker used to follow patients. We suggest that thyroglobulin (Tg) levels should also be monitored postoperatively in these patients.

METHODS

We reviewed patients with RET mutations who underwent prophylactic thyroidectomy between 1981 and 2011 at an academic endocrine surgery center. Patients were excluded if they had no postoperative Tg levels recorded.

RESULTS

Of the 22 patients who underwent prophylactic thyroidectomy, 14 were included in the final analysis. The average age at thyroidectomy was 9.8 years (range, 4-29). Tg levels were detectable 1.5 months to 31 years postoperatively in 11 patients (79%), all of whom were <15 years old at thyroidectomy. Median thyroid-stimulating hormone (TSH) was 2.5 mIU/L and 13.4 mIU/L in patients with undetectable and detectable Tg, respectively. Of those with detectable Tg, 5 had cervical ultrasonographic examination: Two showed no residual tissue in the thyroid bed, and 3 showed remnant thyroid tissue.

CONCLUSION

Tg levels can identify patients with remnant thyroid tissue after prophylactic thyroidectomy. Ultrasonography can determine whether thyroid tissue remains posterolaterally that is at risk of MTC recurrence. Maintaining normal TSH may prevent growth of remaining thyroid follicular cells.

Hereditary medullary thyroid carcinoma: the management dilemma

Hereditary medullary thyroid carcinoma (hereditary MTC) is a rare malignancy, accounting for 25-30% of all MTC. It occurs as part of multiple endocrine neoplasia type 2 (MEN 2). Autosomal dominant gain-of-function mutations in the RET proto-oncogene is the cause of the disease, in which the common mutations are codons 609, 611, 618, 620, 630, 634 and 918. In recent years, the spectrum of RET gene mutations has changed. The classical mutations reduced, whereas the less aggressive mutations increased. Hereditary MTC is a time-dependent disease. Stages of the disorder at diagnosis can significantly influence survival rates. Based on the genotype-phenotype, RET mutations have been classified into four risk levels by American Thyroid Association (ATA) at 2009. The classification system guides the hereditary MTC management, including risk assessment, biochemical screenings and surgical intervention. Though the application of genetic testing and codon-specific phenotypes in hereditary MTC diagnosis is effective with high accuracy, there are some difficulties in implementing RET gene testing as a routine for MTC diagnosis. And most of carriers with RET mutations did not undergo thyroidectomy at the age recommended by the ATA guidelines. The aim of the study is to review the hereditary MTC and discuss the management dilemma.

Sonographic Findings of Medullary Thyroid Carcinoma Leading to Diagnosis of Multiple Endocrine Neoplasia Type 2a during Pregnancy

Multiple endocrine neoplasia (MEN) type 2a (Sipple's syndrome) is characterized by medullary thyroid carcinoma and pheochromocytoma, and in a smaller percentage of cases, multiglandular parathyroid hyperplasia. This autosomal-dominant syndrome is due to a mutation in the rearranged during transfection (RET) proto-oncogene located on chromosome 10cen-10q11.2 and rarely complicates pregnancy. We present an unusual case in a patient with an enlarged thyroid with sonographic findings characteristic of thyroid cancer, which led to diagnosis and subsequent management of RET proto-oncogene-positive MEN type 2a complicating pregnancy.

Dual PET/CT with (18)F-DOPA and (18)F-FDG in metastatic medullary thyroid carcinoma and rapidly increasing calcitonin levels: Comparison with conventional imaging

BACKGROUND

To evaluate the role of a multi-imaging PET with (18)F-DOPA and (18)F-FDG in comparison with conventional imaging (CI) in recurrent medullary thyroid carcinoma (MTC).

METHODS

18 MTC patients who had thyroidectomy were included; they presented with elevated and rapidly increasing calcitonin levels during follow up. CI had revealed metastatic deposits in 9 patients. Patients were referred to us for a PET/CT with (18)F-DOPA and (18)F-FDG. Histologic/cytologic confirmation of recurrent MTC was obtained in at least one PET-positive lesion in all patients.

RESULTS

Foci of abnormal uptake were observed in 15 patients at (18)F-DOPA and in 11 at (18)F-FDG; 8 patients showed the same number of positive lesions with both tracers, 2 showed more lesions on (18)F-FDG, 1 was positive at (18)F-FDG alone and 5 at (18)F-DOPA alone. In 3 patients with a DOPA-positive loco-regional relapse a re-operation with curative intent was offered. SUV(max) values were higher for (18)F-FDG compared to (18)F-DOPA (mean 12.7+/-4.1 vs. 5.5+/-2.1, p<0.05). Calcitonin was higher in PET-positive patients compared to PET negative ones, while no significant differences were observed between (18)F-DOPA and (18)F-FDG positive patients.

CONCLUSIONS

In MTC patients with rapidly increasing calcitonin levels during follow up, (18)F-DOPA has a good sensitivity and a complementary role with (18)F-FDG PET/CT in detecting metastatic deposits. In our experience, the sensitivity of a multi-imaging (18)F-DOPA &(18)F-FDG PET/CT approach is greater than that obtained with CI. The higher SUV(max) values found with (18)F-FDG in some patients may reflect more aggressive tumors.