Discordance between plasma calcitonin and tumor-cell mass in medullary thyroid carcinoma

Other markers of medullary thyroid cancer, not only calcitonin

BACKGROUND

Medullary thyroid cancer (MTC) is a rare neuroendocrine tumor originating from parafollicular C-cells. It represents 2% of all thyroid malignancies and 0.4-1.4% of all thyroid nodules. MTC has a variable clinical course, with complete remission often difficult to achieve. An early diagnosis is still crucial in MTC management, enabling a radical surgical treatment, the only chance for curing the patient. Calcitonin (Ct) is a very sensitive MTC tumor marker in patients with thyroid nodules, although Ct-negative MTCs have been described, but not all clinical guidelines recommend the Ct routine measurement in thyroid nodules because of the absolute low prevalence of MTC in the general population and the consequent scarce positive predictive value of Ct. Moreover, the specificity of moderately high Ct levels is not high. Thus, the scientific community has been investigating the possible role of other tumor markers for MTC diagnosis and prognosis.

AIM OF THE REVIEW

The present review is an attempt to summarize the knowledge available today on the role of other serum markers for MTC alternative to Ct.

CONCLUSIONS

At present, literature data does not seem solid enough yet to establish effective flowcharts in evaluating a thyroid nodule for MTC, involving alternative serum markers, particularly in cases of moderately high CT levels. MTC is a rare diagnosis in thyroid nodules, and this makes the evaluation of any tumor serum marker accuracy problematic. More extensive and prospective studies are needed to shed more light on this intriguing challenge.

Medical Treatment of Neuroendocrine Tumors

Background

Tumors of the neuroendocrine system are characterized by amine precursor uptake and decarboxylation, and they represent a heterogeneous group of carcinomas including carcinoids, islet cell carcinomas of the pancreas, medullary thyroid carcinomas and Merkel cell carcinomas. Their similar cytochemical and ultrastructural properties sustain the hypothesis of a common embryologic origin within the neural crest. Many of these tumors grow slowly, and reducing tumor burden represents the treatment of choice. However, when surgery is not feasible, medical treatment has to be considered. Therapeutic approaches in metastatic disease often do not consider the different biologic behaviors of these neoplasms. Moreover, efficacy of the treatment is associated with lack of a clear definition of the type of response: objective, symptomatic or biochemical.

Methods

In this review we have analyzed the different medical approaches used in the treatment of neuroendocrine tumors in an attempt to define their precise role in the different neoplasms.

Results

In carcinoid tumors, immunotherapy and the somatostatin analogue can be efficaciously used for the control of carcinoid syndrome. For inhibition of tumor growth, chemotherapy should be used only in patients with rapidly progressive disease, and the results are still unsatisfactory.

Conclusions

Although all these tumors appear to have similar cytochemical properties, the responsiveness of the various neoplasms is very different. In the future, a specific treatment modality and a clear definition of the type of response (objective, symptomatic or biochemical) need to be defined for each type of neuroendocrine tumor.

Medullary thyroid cancer treated by capecitabine

Medullary thyroid carcinoma with distant metastases is generally incurable, with 20% overall survival at 10 years. The treatment goal is palliative. Chemotherapy has a limited role, with low response rates and high toxicities with the different regimens. Here, we report the case of 64-year-old man with metastatic medullary thyroid carcinoma in progression after primary treatment with cisplatin-doxorubicin. The patient received capecitabine 2000 mg/m total per day x 14 days followed by 1-week rest. He received 41 cycles, and presented prolonged and objective tumor response (30 months), without any toxicity.

Reoperation in metastasizing medullary thyroid carcinoma: is a tumor stage-oriented approach justified?

BACKGROUND

Lymph node metastases (LNM) are very often found in medullary thyroid carcinoma. After primary therapy, elevated levels of calcitonin are measurable in many patients. Because of the low sensitivity and specificity of diagnostic tools to detect micrometastases, the question remains whether an extended lymphadenectomy improves the chance of cure and whether this approach should be tumor stage oriented.

METHODS

We analyzed the results of 36 patients with medullary thyroid carcinoma consecutively reoperated from 1988 to 1996, performing microdissection of all four locoregional lymph node compartments.

RESULTS

Pathologic tumor stage (pT) category was classified as pT1, n = 3; pT2 n = 22; pT3, n = 6; and pT4, n = 5. LNM were found in 34 patients (94%). The cervicocentral compartment contained LNM in 85%, the cervicolateral compartments in 41% to 54%, and the upper mediastinum in 36%. Patients with different pT category did not differ in the rate of LNM. Ipsilateral cervicolateral LNM were found in 50% to 71% and contralateral cervicolateral LNM in 14% to 40%. Nine (35%) of 26 patients without distant metastases were biochemically cured. In 10 patients (38%) calcitonin level decreased more than 50%.

CONCLUSIONS

LNM were almost always (94%) found in patients who have elevated calcitonin levels after primary therapy. In patients without distant metastases, four-compartment lymphadenectomy gives a chance of cure in 35%. A tumor stage-oriented approach does not seem to be justified.

Polyamines regulate human medullary thyroid carcinoma TT-cell proliferation and secretion of calcitonin and calcitonin gene-related peptide

The significance of polyamines for the neoplastic proliferation and secretion of calcitonin (CT) and calcitonin-gene-related peptide (CGRP) by the human medullary thyroid carcinoma TT cell line was investigated. TT cells were cultured in vitro for 6 days with or without additions of pathway inhibitors of polyamine biosynthetic enzymes. Treatment of the cells with 1 mM of the specific L-ornithine decarboxylase (ODC) inhibitor DL-alpha-difluoromethylornithine (DFMO) resulted in a 97% decrease in ODC activity, lowered contents of putrescine (96%) and spermidine (85%) and cell proliferation rates (90%) along with a compensatory 15-fold increase in S-adenosyl-L-methionine decarboxylase (SAMDC) activity. DFMO treatment also led to a decrease in cellular content of CT (33%) and CGRP (26%), while the drug enhanced secretion of CT (31%) but depressed that of CGRP (26%), and elevated the ratio of CT to CGRP secreted into the medium by 74%. Ethylglyoxal bis(guanylhydrazone) (EGBG), a SAMDC inhibitor, at 100 microM evoked a similar reduction of cell proliferation and lowered the content of spermine by 81%. Furthermore, EGBG treatment caused a 34-fold increase in ODC activity and a subsequent 35-fold build-up of putrescine, but also seemed to stabilize SAMDC as evidenced by a highly enhanced SAMDC activity (approximately 200-fold) during enzyme assays in the absence of the inhibitor. EGBG exposure resulted in an increase in cellular CT content (110%) and secretion of the hormone (82%), while not affecting CGRP content or release.2+ EGBG effects were partially counteracted by DFMO.(ABSTRACT TRUNCATED AT 250 WORDS)

Prognostic value of N-myc immunoreactivity in medullary thyroid carcinoma

BACKGROUND

The analysis of N-myc expression in some neuroendocrine tumors has been reported to provide prognostic information. To the authors' knowledge, no attempts have been made thus far to correlate N-myc expression with the clinical outcome of medullary thyroid carcinoma (MTC).

METHODS

N-myc gene product immunoreactivity was evaluated in 34 patients with MTC with long term follow-up, using the OA-11-803 polyclonal antiserum. The results were related to patient age and sex, sporadic or familial disease, tumor size, stage, growth rate (as determined by proliferating cell nuclear antigen [PCNA] immunostaining), and to clinical outcome.

RESULTS

Patients harboring tumors with greater than 10% neoplastic cells immunoreactive to the N-myc antiserum (58% of the cases investigated) had significantly greater tumor size (P = 0.031) than patients with fewer or no N-myc immunoreactive cells. Deregulated expression of N-myc protein in tumor cells was not due to gene amplification, as demonstrated by multiplex polymerase chain reaction (PCR). In univariate analysis, patients with more than 10% immunoreactive neoplastic cells showed a significantly shorter disease free survival than did the remaining patients (P = 0.002). Among the other clinicopathologic parameters evaluated, male sex (P = 0.039) and sporadic disease (P = 0.035) also were associated with shorter disease free survival. In multivariate analysis, N-myc immunoreactivity (P = 0.039) and male sex (p = 0.050) retained a significant correlation with poor prognosis.

CONCLUSIONS

Our results suggest that immunoreactivity to the N-myc antiserum, but not tumor growth fraction as evaluated by PCNA immunostaining, is a novel and useful adjunct to predict clinical behavior of MTC.

Compartment-oriented microdissection of regional lymph nodes in medullary thyroid carcinoma

Lymph node metastases have been proven to be the main prognostic factor in medullary thyroid carcinoma (MTC). This retrospective study was undertaken to evaluate the efficiency of two surgical techniques of regional lymph node dissection with regard to the normalization of pentagastrin-stimulated serum calcitonin level and patient survival: selective lymphadenectomy, i.e., the excision of macroscopically or microscopically involved lymph nodes, versus a systematic lymphadenectomy performed by the new technique of a compartment-oriented microdissection. From 1970 to 1990, 82 patients with sporadic (n = 57) and hereditary (n = 25) MTC underwent a total of 142 operations including 63 selective lymphadenectomies and, since 1986, 35 systematic lymphadenectomies. The study revealed that in node-positive MTC the rate of interventions with a postoperative normalization of pentagastrin-stimulated serum calcitonin was higher after systematic lymphadenectomy (29.2%) than after selective lymphadenectomy (8.5%) (P < 0.01). The rate of patients undergoing repeat surgery due to a recurrence of MTC was 48% after selective lymphadenectomy and 10% after systematic lymphadenectomy. Survival was significantly better for patients after systematic versus selective lymphadenectomy (P < 0.005). This study thus emphasizes that systematic lymphadenectomy, using the technique of a compartment-oriented microdissection of cervicomediastinal lymph nodes, represents the preferred surgical treatment as well as the optimum technique in primary as well as secondary node-positive MTC.

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.

The calcitonin gene peptides: biology and clinical relevance

The calcitonin/CGRP multigene complex encodes a family of peptides: calcitonin, its C-terminal flanking peptide, katacalcin, and a third novel peptide, calcitonin gene-related peptide (CGRP). The 32-amino acid peptide calcitonin inhibits the osteoclast, thereby conserving skeletal mass during periods of potential calcium lack, such as pregnancy, growth, and lactation. This hormonal role is emphasized by observations that lower circulating calcitonin levels are associated with bone loss and that calcitonin replacement prevents further bone loss. Structurally, CGRP resembles calcitonin and has been implicated in neuromodulation and in the physiological regulation of blood flow. Here we review the molecular genetics, structure, and function of the calcitonin-gene peptides as analyzed in the laboratory and focus on more recent clinical studies relating to disorders and therapeutics.

Multiple endocrine neoplasia

The MEN syndromes continue to be the focus of considerable interest and research. Since successful treatment requires early diagnosis, proper screening and follow-up of patients at risk is important. In the individual at risk for developing MEN IIa, annual screening should include measurement of the basal and stimulated plasma CT levels, and determination of plasma levels of calcium, PTH, and CEA. Twenty-four hour urine excretion rates of norepinephrine, epinephrine, metanephrine, dopamine, and VMA should also be obtained. It is our recommendation that this screening be continued through the third decade of life. Patients having thyroidectomy for MTC need to be tested annually for recurrent MTC and the development of adrenal medullary disease. All patients at risk for developing MEN IIb should be evaluated in a similar fashion. Recently, several groups using DNA linkage analysis have mapped the gene for MEN IIa to chromosome 10, although the exact location of the gene is yet to be determined. Preliminary linkage studies have mapped the gene for MEN I to chromosome 11. The identification of the genes for MEN I and MEN II will greatly simplify the diagnosis of the disease and perhaps also the therapy of affected patients.

Introduction of v-Ha-ras oncogene induces differentiation of cultured human medullary thyroid carcinoma cells

Medullary thyroid carcinoma (MTC) is an endocrine tumor of the thyroid C cells that expresses high levels of the neuroendocrine peptide hormone calcitonin. During tumor progression in the host, there is an apparent loss of differentiation in MTC cells that involves a consistent decrease in calcitonin content of the tumor cells associated with decreased expression of the calcitonin gene and/or changes in a mRNA alternative-processing pattern away from that characteristic of the parent thyroid C cell. We now report that introduction of the viral Harvey ras (v-Ha-ras) oncogene into cultured human MTC cells can reverse such changes in gene expression and can induce endocrine differentiation of the tumor cells. The expression of v-Ha-ras is associated with decreased cellular proliferation and DNA synthesis. There is a marked increase in the number of cytoplasmic secretory granules that are a classic feature of differentiated thyroid C cells. v-Ha-ras expression induces increased expression of the calcitonin gene and the processing of the primary gene transcript is shifted to favor calcitonin mRNA rather than calcitonin-gene-related peptide (CGRP) mRNA production. These studies with cultured human MTC cells provide a model system to study the role of Ha-ras and related genes in neuroendocrine differentiation. The findings suggest an important approach for identifying genes in solid tumors whose altered expression may play a role in the impaired maturational capacity characteristic of cancer cells during tumor progression.

Calcitonin gene-related peptide and calcitonin in medullary thyroid carcinoma

We have investigated the levels of serum calcitonin and calcitonin-gene related peptide (CGRP) in 35 patients with well-documented medullary thyroid carcinoma (MTC). Immunohistochemical investigations for calcitonin and CGRP have been performed on tumour tissue from 9 patients to clarify the cellular pattern of production. In four patients with aggressive disease, serum calcitonin and CGRP values have been monitored in relation to progression of disease after surgery. All 35 patients with MTC have elevated calcitonin and 26 elevated CGRP levels. Generally calcitonin values were found to be higher than those of CGRP, although the ratio of the two peptides varied from patient to patient. The immunohistochemical investigations corresponded with these findings, generally showing diffuse staining for calcitonin in MTC tumour-cells and only a small number of CGRP positive cells. Calcitonin and CGRP are produced by alternative processing of the common precursor gene transcript. Our results suggest that absolute values of either calcitonin or CGRP in serum have no direct relationship to aggressiveness of disease. Thus whilst serum CGRP measurements appear to be a useful additional marker for the disease, they can be considered to be only a useful adjunct to serum calcitonin as a marker for tumour progression.

Medullary carcinoma of the thyroid. An immunocytochemical and histochemical study of 25 cases using eight separate markers

The current study was undertaken on 25 cases of thyroid medullary carcinoma to compare the diagnostic value of calcitonin with other peptides including PDN-21, the C-terminal flanking peptide of human calcitonin within the calcitonin precursor, and calcitonin gene-related peptide, CGRP. Antiserum raised to chromogranin, an acidic protein of 68,000 daltons, was also used to compare its diagnostic value as a general marker for neuroendocrine neoplasia with neuron-specific enolase (NSE) and Grimelius' argyrophil silver staining. Immunocytochemistry was performed using the peroxidase-antiperoxidase method at the light microscopic level and the immunogold staining procedure at the ultrastructural level. All tumors were reactive to calcitonin and CGRP antisera, whereas PDN-21 was present in 23 cases. It was also found that these peptides were colocalized in the majority of C-cells. The intensity and specificity of CGRP and PDN-21 immunoreaction was comparable to and in some cases even better than that obtained with calcitonin antiserum. In the majority of tumors, somatostatin and bombesin immunoreactivity was either absent, weak, or variable in intensity and distribution. The current study thus demonstrates that together with calcitonin, PDN and, in particular, CGRP antisera may be applied to corroborate immunocytochemical diagnosis in medullary carcinoma of the thyroid. With regard to general neuroendocrine markers, Grimelius' and chromogranin provided the most consistent results. NSE isoenzyme immunoreactivity, on the other hand, was more variable, probably reflecting the metabolic state of the tumor cells.

Tumor markers: value and limitations in the management of cancer patients

Sixteen tumor markers are reviewed, and measured to the ideal: produced by the tumor cell alone absent in health and in benign disease present in all patients with a given malignancy level in the blood representative of tumor mass detectable in occult disease. The only marker that approaches the ideal is human chorionic gonadotropin (HCG) in gestational trophoblastic tumors. In this malignancy, the HCG level suggests the diagnosis and stage, confirms response to therapy, and predicts relapse. The three most widely used and intensely studied tumor markers are carcinoembryonic antigen (CEA), alphafetoprotein (AFP), and HCG. CEA cannot be used in screening for cancer, but in carcinoma of the colon its elevation preoperatively increases the likelihood of advanced disease and postoperative recurrence. Postoperatively, elevated titers are often but not invariably associated with recurrent disease. AFP and HCG are useful in the management of nonseminomatous germ cell testicular tumors. Like CEA, they cannot be used for screening. They are more likely to be increased with advancing stage, and after therapy rising levels almost always mean recurrent disease. Some markers are valuable in specific circumstances, such as calcitonin in screening for familial medullary carcinoma of the thyroid. In multiple myeloma, immunoglobulins are useful in determining the tumor mass and response to therapy. In neuroblastoma, catecholamine metabolites are useful primarily in making the diagnosis. In some malignancies, the absence of effective therapy lowers the value of the marker, as for AFP in hepatoma. The remaining markers are too unreliable or too little studied to be useful in the management of an individual patient with cancer. The purpose of this paper is to provide the clinician with an understanding of the limitations of the present tumor markers that will lead to wiser use of the tests, and to provide standards to which future tumor markers should be measured.

The insidious development of symptomatic secondary hormone syndromes in patients with malignant endocrine tumors

Endocrine tumors may produce secondary or "ectopic" hormones that cause paraneoplastic syndromes. Such syndromes may be confused with more common complications related to a patient's tumor, and thus escape detection and appropriate treatment. The secondary hormone secretion responsible for these syndromes often occurs late in the course of such diseases and presents in an insidious manner. Two patients are presented that illustrate these points. The first, a woman with medullary carcinoma of the thyroid (MCT), developed a syndrome secondary to ACTH secretion that was confused initially with the changes caused by the massive diarrhea that accompanies MCT. The second, a man with malignant glucagonoma, is the first with this disease to have developed symptomatic hyperinsulinemia as a late complication. We stress the clinical courses of these patients and note that treatment of these syndromes may improve the quality of patients' lives.

Relationship of tissue carcinoembryonic antigen and calcitonin to tumor virulence in medullary thyroid carcinoma. An immunohistochemical study in early, localized, and virulent disseminated stages of disease

The distribution of carcinoembryonic antigen (CEA) and its relationship to calcitonin in early, localized, and disseminated (virulent) medullary thyroid carcinoma (MTC) have been studied using immunoperoxidase methods. Carcinoembryonic antigen can be demonstrated within C-cells through all stages of progression of MTC. In early disease (C-cell hyperplasia and microscopic carcinoma), CEA, and calcitonin have a similar distribution, being present in virtually every cell. Likewise, calcitonin and CEA have a similar, homogeneous distribution among cells in gross medullary carcinoma confined to the thyroid region. In both primary and metastatic tumors from patients with virulent, disseminated disease there is an inverse relationship between calcitonin and CEA distribution such that CEA expression is retained and frequently present in the greatest amounts in cells which have poor or absent staining for calcitonin, and present in the least amounts where cellular staining for calcitonin is greatest. It is postulated that in MTC expression of CEA (a marker for early epithelial differentiation), in the face of loss of calcitonin (a marker for terminal differentiation/cellular maturity), may reflect a degree of maturation block in tumors from patients with aggressive disease.

Relation of doubling time of plasma calcitonin levels to prognosis and recurrence of medullary thyroid carcinoma

Plasma calcitonin (CT) levels were measured serially in 54 patients surgically treated for medullary thyroid carcinoma. Patients with postoperative basal CT levels higher than 1 ng/ml measured within 1 month after surgery had a higher recurrence rate than those with lower CT levels (p less than 0.002). Patients with postoperative basal CT levels higher than 2 ng/ml had a lower survival rate than those with lower CT levels (p less than 0.01). However, preoperative basal CT levels had no significant correlation with life expectancy or recurrence during the present observation period. Serial measurements in 23 patients with elevated postoperative CT levels showed exponential increases in basal CT levels in 19 patients (p less than 0.05 in nine patients, 0.05 less than p less than 0.1 in four patients) and slight decreases in four (p less than 0.05 in one patient). Doubling time of CT levels calculated from the regression line in each patient showed the highest correlation with 3-year survival, recurrence within 5 years, and time interval between surgery and clinical recurrence of the tumor, allowing quantitative prediction of the prognosis.

The values of calcitonin and carcinoembryonic antigen in the treatment and management of nonfamilial medullary thyroid carcinoma

Thirty-one patients were studied to evaluate the prognostic value of both calcitonin (CT) and CEA levels determined after the initial treatment in medullary thyroid carcinoma (MTC). Twenty-seven patients were evaluated three to nine months after initial treatment and four others afterwards. The CT and CEA levels were significantly higher and the survival rate lower in the eight patients with residual clinical disease as compared to the 19 patients in complete clinical remission. In patients in complete clinical remission, 11 had elevated CT level after treatment, and all had initial lymph node involvement. Five of these 11 relapsed and one died. None of the eight patients with normal CT levels after treatment relapsed. CEA levels were always abnormally high when patients relapsed. Fourteen patients in complete remission with high CT levels were followed for more than four years. Six had normal CEA levels and no relapse was observed. Eight of the 14 had pathological CEA levels and six of eight relapsed: five of these six patients presented CEA elevation from six to 36 months before the clinical relapse. In two of these six patients, a venous catheterization sampling method demonstrated infra clinical local recurrence. In two patients with liver metastases, the time course changes of CT and CEA levels were different and CEA appeared to be a more sensitive tumor marker than CT. These data are consistent with previous data concerning the values and limits of CT level for the management of MTC. Furthermore, this study demonstrates the prognostic significance of CEA determination in MTC. CEA appears to be a sensitive selective tumor marker capable of defining a high-risk subgroup.

The detection and evaluation of human tumor metastases

Many biochemical indices are purported to have clinical utility in the detection and management of neoplasia. Experience gained during the past decade tends to indicate their having a more important role in the detection and monitoring of metastases than of the primary lesion. From this present review of some of the commoner human tumours, it is concluded that such marker substances are important adjuncts in the management of germ cell and certain endocrine and endocrine-related tumours. The carcinoembryonic antigen (CEA) provides a marker for many gastrointestinal cancers, but there are no presently available substances with clinical usefulness for either breast or lung neoplasms. Alternative approaches to the detection of metastases are also presented. The particular use of antibody probes at an immunohistochemical level has been claimed to be able to detect micrometastastic disease in bone marrow or tumour-related monoclonal antibody probes may have application to other cancers in the future.

Ectopic adrenocorticotrophic (ACTH) syndrome and small cell carcinoma of the lung-assessment of clinical implications in patients on combination chemotherapy

Small cell carcinoma of the lung is the tumor most commonly associated with ectopic ACTH production and hypercortisolism. The relationship between this paraneoplastic endocrine syndrome and the clinical course of the tumor is examined in this review of patients with the ectopic ACTH syndrome and small cell carcinoma seen at The Johns Hopkins Oncology Center between 1973 and 1979. Five of 157 (3.2%) patients with small cell carcinoma were clinically diagnosed as having the ectopic ACTH syndrome. The onset of this endocrine syndrome appeared to coincide with a more aggressive phase of the course of small cell carcinoma. Further analysis of these cases suggests that the development of the ectopic ACTH syndrome may reflect changes in cell populations within the tumor and/or alterations in tumor behavior with time and perhaps with the effects of drug therapy.

Management of hereditary medullary thyroid carcinoma

In this paper we have briefly outlined our views on the management of hereditary MTC. We have stressed the fact that although many patients with the usual form of disease have an indolent clinical course there exists a population of patients who may be at risk for widely disseminated virulent tumour. Also, some patients can have marked invasion of adjacent tissues in the cervical region from localized tumour. Hence it seems rational to attempt removal of the primary tumour prior to the development of regional or distant metastases. The role of the combined calcium-pentagastrin provocative test to identify patients with preclinical disease has been outlined. The only definitive treatment for the disease is total thyroidectomy with resection of adjacent cervical nodes. Many patients who are treated at a time when the disease has become clinically detectable will have residual tumour or recurrence as indicated by abnormal calcitonin levels in the blood. Since most of these patients seem to take an indolent clinical course, it is suggested that they should not be treated with radiation therapy and/or chemotherapy, even though residual MTC is known to be present. Even in patients with advanced stages of MTC, the use of chemotherapy and radiation therapy has not been encouraging. However, some aspects of the management of patients with aggressive disease are discussed. Finally, the lack of features to predict which patients may have a poor prognosis is outlined and some new approaches to defining such parameters are discussed.

ACTH-secreting medullary carcinoma of the thyroid: monitoring of clinical course with calcitonin and cortisol assays and immunohistochemical studies

The clinical course of a patient with Cushing's syndrome secondary to metastatic medullary carcinoma of the thyroid was documented with serial calcitonin and cortisol assays and tumor immunohistochemistry studies. Cortisol levels were originally markedly elevated but returned to normal after total thyroidectomy. These levels rose again when the patient developed liver metastases but normalized during chemotherapy, never to rise again despite the appearance of cervical lymph node metastasis. Calcitonin levels remained elevated throughout the course. The original tumor was composed of two cell lines: one containing both calcitonin and ACTH and another containing only calcitonin-reacting cells. However, the cervical metastasis showed a marked decrease in both cell lines with fever than 1% of cells reacting to ACTH, and only 25% to calcitonin. The almost total disappearance of ACTH-reacting cells may have been therapeutically induced or may represent a consequence of tumor progression.

Testing for disorders of calcium metabolism

Assays of serum immunoreactive parathyroid hormone are clinically useful in the differential diagnosis of hypercalcaemic states and in the assessment of the severity of parathyroid bone disease in uraemic patients. Serum immunoreactive calcitonin measurements are essential in the investigation of individuals who might be suffering from medullary carcinoma, and such measurements may be used in the detection of metastases. Serum 25-hydroxyvitamin D assays are useful in patients receiving pharmacological doses of vitamin D, to monitor patient compliance and to prevent the occurrence of vitamin D intoxication. Low values in patients with renal failure and in patients with malabsorption and highly suggestive of the presence of osteomalacia. The measurement of serum levels of dihydroxylated vitamin D metabolites is currently of doubtful clinical relevance, though such measurements may become useful in monitoring patients receiving these compounds therapeutically.