Medullary carcinoma of the thyroid: management of persistent hypercalcitonaemia utilizing [99mTc] (v) dimercaptosuccinic acid scintigraphy

Delivery of diagnostic agents for gamma-imaging

The administration of radiolabeled compounds with gamma-emitting radionuclides allows real time pursuit of in vivo behavior of the compounds by external counting of the radioactivity. If the compounds possess a specific localization mechanism to target tissue, the image reflects the specific function of the target. This technique has widely been applied in diagnostic nuclear medicine combined with appropriate radionuclides for clinical use. Two strategies have been developed to design radiolabeled compounds for targeted imaging. One constitutes tethering radiolabeled compounds to carrier molecules that possess specific localization mechanisms to target tissue. Another approach constitutes chemical design of radiolabeled compounds, especially metallic compounds, that possess specific localization characteristics to the target per se. In this manuscript, progress of chemical design of radiolabeled compounds for targeted imaging is briefly reviewed. Emphasis is laid on chemical design of radiolabeled antibodies for targeted imaging.

Medullary Thyroid Cancer

BACKGROUND: Medullary thyroid cancer, a tumor of the parafollicular C cells, accounts for approximately 10% of all thyroid malignancies. An estimated 75% of cases are sporadic, and the remaining 25% are familial. METHODS: The author reviews the clinical features and diagnostic tests for this entity, as well as the surgical treatment of recurrent or persistent medullary carcinoma. RESULTS: Sporadic medullary thyroid cancer typically presents as an isolated unilateral mass. Familial tumors tend to be multifocal and bilateral. In patients with multiple endocrine neoplasia type 2A, pheochromocytomas and parathyroid hyperplasia also may develop. Care is taken to avoid operating on a patient with occult pheochromocytoma. Total thyroidectomy and central lymph node dissection are the keys for successful surgical treatment. CONCLUSIONS: Surgery is the cornerstone of treatment for medullary carcinoma of the thyroid. Genetic testing using the ret oncogene allows identification of individuals who are at risk for the disease or those with early-stage disease.

Detection of cervical metastases of thyroid medullary carcinoma by MoAb anti-CEA scintigraphy and immunohistochemistry

Four patients with medullary thyroid carcinoma (MTC) were examined using anti-carcinoembryonic antigen (CEA) scintigraphy. Two patients had positive and two normal scintigraphic findings, although all the patients had elevated blood test markers (calcitonin or CEA). One patient with clinical suspicion of MTC metastases had only a faintly positive anti-CEA image, although single-photon emission tomographic scanning was used to increase the sensitivity and resolution of the method. Therefore, digital image processing of the planar images was performed to obtain more detailed information. The analysis revealed distinct accumulation of the activity at the right side of the neck at 20 h post administration. The specificity of the antibody binding in the malignant cells was confirmed after surgery by immunohistochemical staining of the tumour specimens for CEA. Both conventional and confocal laser scanning microscopy revealed distinct positive staining, indicating that the results obtained from the anti-CEA scanning showed specific binding of the labelled antibody in the neoplastic tissue.

Surgical management and follow-up of medullary thyroid carcinoma

Between 1977 and 1990 we operated on 33 patients with medullary thyroid carcinoma. We performed total thyroidectomy in 31 patients and central node dissection and/or lateral modified node dissection in 21 patients (63.3%). Two patients underwent radiotherapy after subtotal resection and tracheostomy. No perioperative death occurred. Twenty-five patients were followed (mean follow-up, 63.8 months) and 8 others were unavailable for follow-up. Three patients (1 with multiple endocrine neoplasia type IIB, 2 sporadic with distant metastases) died of their disease at 12, 18 and 36 months after initial operation. Of the remaining 22 patients, 4 with stage II disease were normocalcitoninemic even with pentagastrin stimulation, following total thyroidectomy and bilateral modified neck dissection and central node dissection. Eighteen other patients continued to have elevated calcitonin levels postoperatively. Only 10 patients with known cervical metastatic disease were reoperated upon. We performed extensive node dissection in all. In addition we resected recurrent tumor from the thyroid bed in 4 patients. Despite these extensive reoperations no patient became normocalcitoninemic. At the completion of the study (December 1991), 22 of the 25 patients followed were alive: 4 patients with normal calcitonin levels, baseline and after pentagastrin stimulation, and 18 with persistent mildly elevated calcitonin levels but no other evidence of disease. Our experience supports a very aggressive surgical approach at the time of the first operation for patients with medullary thyroid carcinoma. A lesser operation usually resulted in residual medullary thyroid carcinoma in the neck. We demonstrate the difficulty of achieving a cure by reoperation once the tumor becomes demonstrable by localization studies.

Medullary thyroid cancer

Medullary thyroid cancer is a tumor of the thyroid C cells that occurs in sporadic and hereditary clinical settings. Genetic testing of at-risk individuals is available and has been applied to patient management. Plasma calcitonin levels are a very sensitive marker for the presence of disease. Surgery offers the best hope for cure and also is an effective modality for managing metastatic and recurrent disease.

Medullary thyroid carcinoma

Medullary thyroid carcinoma accounts for 5-10 per cent of thyroid malignancies and occurs sporadically, and in three familial settings with autosomal dominant inheritance. Calcitonin, a 32 amino acid 3.5-kDa protein, is a biochemical marker of the tumour. Serum levels correlate with disease burden. Treatment initiated by screening allows disease removal at a premalignant phase: C cell hyperplasia. Genetic linkage studies locate the multiple endocrine neoplasia type 2A gene near the centromere of chromosome 10. Flanking genetic markers may allow polymorphic probes to examine DNA from a once-only blood sample to identify affected individuals. At what age thyroidectomy should be carried out in these patients is unclear.

Long-term course of patients with persistent hypercalcitoninemia after apparent curative primary surgery for medullary thyroid carcinoma

Thirty-one patients with persistent hypercalcitoninemia after seemingly adequate primary operation for medullary thyroid carcinoma (MTC) were followed for a mean period of 11.9 years after operation. Ten patients had sporadic MTC and the remaining patients were members of families with multiple endocrine neoplasia (MEN)--either MEN 2A (15 patients) or MEN 2B (six patients). Overall 5- and 10-year survival rates were 90% and 86%, respectively. Only four patients died at the completion of the study: two of MTC and two of unrelated causes. Eleven patients (35.5%) underwent surgical re-exploration after demonstration of recurrent disease clinically or radiologically. In no patient did the calcitonin level return to normal after re-exploration. The presence of more than three metastatic nodes at the time of initial operation was a statistically significant (p = 0.003) predictor for disease recurrence. Factors approaching statistical significance were patients younger than age 35 (p = 0.06) and the percentage of cells in the S phase of cell division (0.07). This data supports a conservative surgical philosophy in the management of the patient with persistent hypercalcitoninemia after resection of MTC.