Early treatment of hereditary medullary thyroid carcinoma after attribution of multiple endocrine neoplasia type 2 gene carrier status by screening for ret gene mutations

Different outcomes in sporadic versus familial medullary thyroid cancer

BACKGROUND

Medullary thyroid carcinoma (MTC) has varying clinical course with familial cases (fMTC) diagnosed earlier than sporadic MTC (spMTC).

METHODS

A total of 273 MTCs (familial: n = 110 [40.3%], males: 38.5%) were followed for 1-35 years (median 5.0 years). Fifty one of the familial cases were operated because of positive findings at genetic screening. Disease extent at diagnosis and follow-up was recorded.

RESULTS

Mean age at diagnosis was: fMTC = 33.85 ± 16.5 years (range 4-74) and spMTC = 52.6 ± 14.0 years (range 16-81, P < .001). This difference remained when genetic screening cases were excluded. fMTCs had more frequently multifocality, smaller size, and more favorable stage at diagnosis (stages I and II: 60.9% vs 47.9%, stage III: 30.0% vs 23.9%, stage IV: 9.1% vs 28.9%, P = .01). fMTC had lower preoperative and postoperative calcitonin, more frequently remission (59.1% vs 47.2%) and less frequently progressive disease (8.2% vs 35.0%, P < .001). After excluding genetic screening cases, no difference in stage at diagnosis was observed. Outcome was more favorable in fMTC compared to sporadic (P = .002); the 10-year probability of lack of progression of disease differed significantly between fMTCs and spMTCs (86.4% vs 65.0%, P < .001).

CONCLUSION

After excluding genetic screening cases, although stage at diagnosis is similar, disease outcome remains worse in sporadic compared to fMTCs.

A comprehensive overview of the role of the RET proto-oncogene in thyroid carcinoma

The rearranged during transfection (RET) proto-oncogene was identified in 1985 and, very soon thereafter, a rearrangement named RET/PTC was discovered in papillary thyroid carcinoma (PTC). After this discovery, other RET rearrangements were found in PTCs, particularly in those induced by radiation. For many years, it was thought that these genetic alterations only occurred in PTC, but, in the past couple of years, some RET/PTC rearrangements have been found in other human tumours. 5 years after the discovery of RET/PTC rearrangements in PTC, activating point mutations in the RET proto-oncogene were discovered in both hereditary and sporadic forms of medullary thyroid carcinoma (MTC). In contrast to the alterations found in PTC, the activation of RET in MTC is mainly due to activating point mutations. Interestingly, in the past year, RET rearrangements that were different to those described in PTC were observed in sporadic MTC. The identification of RET mutations is relevant to the early diagnosis of hereditary MTC and the prognosis of sporadic MTC. The diagnostic and prognostic role of the RET/PTC rearrangements in PTC is less relevant but still important in patient management, particularly for deciding if a targeted therapy should be initiated. In this Review, we discuss the pathogenic, diagnostic and prognostic roles of the RET proto-oncogene in both PTC and MTC.

Surgical approach to medullary thyroid cancer

Medullary thyroid cancer (MTC) compromises 3-5% of all thyroid cancers and arises from parafollicular or calcitonin-producing C cells. It may be sporadic (75% of cases), or may occur as a manifestation of either the hereditary syndrome Multiple Endocrine Neoplasia type 2 (MEN 2A or MEN 2B) (25% of cases), or rarely as an isolated familial syndrome (FMTC). Complete surgical resection comprising in most cases total thyroidectomy with central lymph node dissection at an early stage of the disease is the only potential cure for MTC. The familial form of the disease, MEN-2A occupies a unique place in surgical history, having been the first disease where surgical removal of an affected organ was undertaken before the development of malignancy, solely on the basis of genetic testing. Total thyroidectomy prior to the development of invasive cancer completely avoids an otherwise lethal malignancy. Timing of prophylactic surgery is based on models that utilise genotype-phenotype correlations, which have now been stratified into three risk groups based on the specific codon involved. MTC should be followed with postoperative serial serum calcitonin levels to survey for persistent or recurrent disease as indicated by detectable levels. The challenge however, if calcitonin levels are increased, is to find the source of its production. The first localisation technique recommended would be ultrasound of the neck, since there is a high frequency of local recurrence and cervical node metastasis, followed by a total body CT scan and bone scintigraphy.

Initial surgical management of thyroid cancer

The rapid increase in the rate of papillary thyroid cancer is likely caused by improved surveillance. A significant trend toward total thyroidectomy for low-risk differentiated thyroid cancer is present in the United States after a paradigm shift from treatment of macroscopic disease to the treatment of macroscopic and microscopic disease by increasingly sensitive tests. Compelling arguments for thyroid lobectomy and total thyroidectomy for low-risk thyroid cancer remain. The relatively small number of deaths from thyroid cancer, the small number of clinical thyroid cancers, and the huge number of incidental thyroid cancers are indicative of how little we understand the biology of this disease. Clinical medicine awaits biologic markers to refine treatment recommendations.

The Role of Prophylactic Surgery in Cancer Prevention

BACKGROUND

Since the human genome has been sequenced many mysteries of cell biology have been unravelled, thereby clarifying the pathogenesis of several diseases, particularly cancer. In members of kindreds with certain hereditary diseases, it is now possible early in life to predict with great certainty whether or not a family member has inherited the mutated allele causing the disease. In hereditary malignancies this has been particularly important, because in affected family members there is the possibility of removing the organ destined to develop cancer before malignancy develops or while it is in situ. At first consideration, it would appear that "prophylactic surgery" would have a place in many hereditary malignancies; however, the procedure has applicability only if certain criteria are met: (1) the genetic mutation causing the hereditary malignancy must have a very high penetrance and be expressed regardless of environmental factors; (2) there must be a highly reliable test to identify patients who have inherited the mutated gene; (3) the organ must be removed with minimal morbidity and virtually no mortality; (4) there must be a suitable replacement for the function of the removed organ; and (5) there must be a reliable method of determining over time that the patient has been cured by "prophylactic surgery."

CONCLUSIONS

In this monograph we review several hereditary malignancies and consider those where prophylactic surgery might be useful. As we learn, there are various barriers to performing the procedure in many common hereditary cancer syndromes. The archetype disease syndromes, which meet each of the five criteria mentioned above and where prophylactic surgery is most useful, are the type 2 multiple endocrine neoplasia (MEN) syndromes: MEN2A, MEN2B, and the related familial medullary thyroid carcinoma. An additional benefit of the Human Genome Project, has been the development of pharmacologic and biologic compounds that block the metabolic pathway(s) activated by specific genetic mutations. Many of these compounds have shown efficacy in patients with locally advanced or metastatic cancers, and there is the likelihood that they will prove beneficial in preventing the outgrowth of malignant cells in patients destined to develop a hereditary cancer.

ASCO/SSO review of current role of risk-reducing surgery in common hereditary cancer syndromes

BACKGROUND

A significant portion of cancers are accounted for by a heritable component, which has increasingly been linked to mutations in specific genes. Clinical interventions have been formulated for mutation carriers within affected families. The primary interventions for mutation carriers of highly penetrant syndromes are surgical.

METHODS

The American Society of Clinical Oncology and the Society of Surgical Oncology formed a task force charged with presenting an educational symposium on surgical management of hereditary cancer syndromes at annual society meetings, and this resulted in a position paper on this topic. The content of both the symposium and the position paper was developed as a consensus statement.

RESULTS

This article addresses hereditary breast, colorectal, ovarian/endometrial, and multiple endocrine neoplasias. A brief introduction on the genetics and natural history of each disease is provided, followed by detailed descriptions of modern surgical approaches, clinical and genetic indications, timing of prophylactic surgery, and the efficacy of surgery (when known). Although several recent reviews have addressed the role of genetic testing for cancer susceptibility, this article focuses on the issues surrounding surgical technique, timing, and indications for surgical prophylaxis.

CONCLUSIONS

Risk-reducing surgical treatment of hereditary cancer is a complex undertaking. It requires a clear understanding of the natural history of the disease, realistic appreciation of the potential benefits and risks of these procedures in potentially otherwise healthy individuals, and the long-term sequelae of such interventions, as well as the individual patient's and family's perceptions of surgical risk and anticipated benefit.

ASCO/SSO review of current role of risk-reducing surgery in common hereditary cancer syndromes

Although the etiology of solid cancers is multifactorial, with environmental and genetic factors playing a variable role, a significant portion of the burden of cancer is accounted for by a heritable component. Increasingly, the heritable component of cancer predispositions has been linked to mutations in specific genes, and clinical interventions have been formulated for mutation carriers within affected families. The primary interventions for mutations carriers for highly penetrant syndromes such as multiple endocrine neoplasias, familial adenomatous polyposis, hereditary nonpolyposis colon cancer, and hereditary breast and ovarian cancer syndromes are primarily surgical. For that reason, the American Society of Clinical Oncology (ASCO) and the Society of Surgical Oncology (SSO) have undertaken an educational effort within the oncology community. A joint ASCO/SSO Task Force was charged with presenting an educational symposium on the surgical management of hereditary cancer syndromes at the annual ASCO and SSO meetings, resulting in an educational position article on this topic. Both the content of the symposium and the article were developed as a consensus statement by the Task Force, with the intent of summarizing the current standard of care. This article is divided into four sections addressing breast, colorectal, ovarian and endometrial cancers, and multiple endocrine neoplasia. For each, a brief introduction on the genetics and natural history of the disease is provided, followed by a detailed description of modern surgical approaches, including a description of the clinical and genetic indications and timing of prophylactic surgery, and the efficacy of prophylactic surgery when known. Although a number of recent reviews have addressed the role of genetic testing for cancer susceptibility, including the richly illustrated Cancer Genetics and Cancer Predisposition Testing curriculum by the ASCO Cancer Genetics Working Group (available through http://www.asco.org), this article focuses on the issues surrounding the why, how, and when of surgical prophylaxis for inherited forms of cancer. This is a complex process, which requires a clear understanding of the natural history of the disease and variance of penetrance, a realistic appreciation of the potential benefit and risk of a risk-reducing procedure in a potentially otherwise healthy individual, the long-term sequelae of such surgical intervention, as well as the individual patient and family's perception of surgical risk and anticipated benefit.

Video-assisted central compartment lymphadenectomy in a patient with a positive RET oncogene: initial experience

BACKGROUND

Prophylactic surgery for patients carrying a positive RET proto-oncogene proved to be highly effective in curing those likely to experience the development of a medullary carcinoma. Video-assisted procedures have been proved feasible for central compartment dissection.

METHODS

A total of 15 patients (7 men and 8 women) with a positive RET proto-oncogene underwent total thyroidectomy and central compartment lymphadenectomy via a video-assisted approach. The mean age of the patients was 32.5 years. The echographically estimated mean volume was 10.3 ml, and the mean diameter of the main nodule was 8.8 mm. Preoperative ultrasound showed an absence of lateral neck lymph node involvement in all cases. No drain was used. Direct laryngoscopy was performed in all cases 1 month after surgery.

RESULTS

The mean operative time was 67.3 min. A transient hypoparathyroidism occurred in one patient, and a permanent hypoparathyroidism occurred in another patient. No laryngeal nerve palsy was present. All the patients were discharged on postoperative day 1. Histology showed a medullary carcinoma in 10 patients and diffuse C-cell hyperplasia in 5 patients. The mean number of lymph nodes removed was 5.1. None of these nodes proved to be metastatic. Calcitonin levels were undetectable in all six patients who had a follow-up period longer than 1 year.

CONCLUSION

Video-assisted central compartment lymphadenectomy was proved to be effective and safe. The procedure demonstrated a complication rate comparable with that for the conventional procedure, a better cosmetic outcome, and less postoperative pain. Although the video-assisted access proved to be a valid option for the treatment of patients carrying a positive RET proto-oncogene, a greater number of cases with a longer follow-up period is necessary to estimate the impact of the video-assisted approach on central neck lymphadenectomy.

Medullary Thyroid Cancer

The goal in managing patients who have MTC is to detect and surgically remove disease at an early stage. Tumor marker-based biochemical screening and DNA-based genetic screening have created the opportunity for effective prophylactic surgery in patients at risk for hereditary MTC. Complete surgical resection is critical for cure because cervical reoperation for persistent or recurrent disease benefits only select patients. With the advent of therapies that target the RET-activated pathways, new hope may be emerging for patients who have locally advanced or metastatic disease.

Familial neuroendocrine tumor syndromes: from genetics to clinical practice

Thanks to recent developments in molecular biology and cancer genetics, genetic testing has become widely available and useful in several kinds of familial tumor syndrome. However, the impact of genetic testing on medical management is not always straightforward. Clinicians have to consider the psychological impact and ethical complexities of communicating hereditary cancer risk information to families. This review notes some points on genetic counseling before and after genetic testing for familial neuroendocrine tumor syndromes.

Video assisted prophylactic thyroidectomy and central compartment nodes clearance in two RET gene mutation adult carriers

Activating point mutations of RET gene have been demonstrated to be causative of the familial form of medullary thyroid cancer (MTC), both isolated (FMTC) and associated to other endocrine neoplasia [multiple endocrine neoplasia (MEN) 2A and 2B]. In RET gene mutation carriers, who are prone to developing MTC, prophylactic thyroidectomy is recommended to obtain their definitive cure. The simultaneous excision of the central node compartment is mandatory when the stimulation pentagastrin test for serum calcitonin is positive. Although the minimally invasive video assisted thyroidectomy (MIVAT) is nowadays currently adopted in many centers, it has never been employed for the prophylactic thyroidectomy of RET gene mutation carriers. The fear of obtaining an incomplete lymphadenectomy of the central compartment was the main reason for this reluctance. Since RET gene mutation carriers have often normal thyroid volume and, if involved, small lymph nodes, they indeed represent the best candidates to this approach especially when considering that they are usually young and concerned about the cosmetic results and the period of hospitalization. The excellent results obtained by MIVAT in the last few years induced us to propose this procedure together with a central compartment lymphadenectomy to 2 RET gene mutation carriers recently found by genetic screening. As assessed by a negative pentagastrin stimulation test performed after 6 months from the MIVAT, they were definitively cured without any surgical complication with the exception of a transient hypoparathyroidism. They showed a great satisfaction for both the cosmetic results and the very short period of hospitalization, thus supporting the idea that MIVAT can be used in association with the central node dissection for the prophylactic treatment of RET mutation gene carriers whose thyroid volume is still normal.

Medullary thyroid carcinoma: results of a standardized surgical approach in a contemporary series of 80 consecutive patients

BACKGROUND

The surgical management and follow-up strategy in patients with medullary thyroid carcinoma (MTC) remain controversial because of the lack of data on the natural history of these tumors and their patterns of progression.

METHODS

We reviewed the records of all patients who underwent a cervical operation for MTC between 1991 and 2002. Compartment-oriented surgery (COS) was performed to minimize the risk of cervical recurrence.

RESULTS

We identified 92 consecutive patients who underwent a cervical operation for MTC: 80 had invasive MTC, and 12 had C-cell hyperplasia after prophylactic thyroidectomy for familial MTC. Ten (13%) of the 80 patients with invasive MTC presented with distant metastases and underwent COS to achieve local-regional control; cervical recurrence developed in none, but three have died of MTC. The remaining 70 patients underwent COS for primary (n=23) or recurrent (n=47) MTC. Disease recurred in 18 (26%) of these 70 patients at a median follow-up of 35 months, with 10 (14%) of the recurrences being cervical. Recurrent disease was associated with a basal calcitonin level of >250 pg/mL in all but four patients, two of whom showed tumor dedifferentiation. In contrast, only 5 (11%) patients without evidence of recurrence had basal calcitonin levels of >250 pg/mL at last follow-up.

CONCLUSIONS

Complete COS minimizes cervical recurrence. Radiographic evidence of recurrent disease is unlikely when the calcitonin level is < or =250 pg/mL. These data could be used to develop a logical, cost-effective treatment and follow-up strategy for patients with MTC.

[Multiple endocrine neoplasias. Recent advances in clinical and genetic diagnosis]

PURPOSE

Multiple endocrine neoplasias (MEN) are autosomal dominant inherited syndromes characterized by the association of different glandular lesions in several members of the same kindred. The main clinical features of MEN 1 include primary hyperparathyroidism, pancreatic islet cell tumors and pituitary adenomas; less common features are adrenal adenomas, thymic and bronchial carcinoid tumors, lipomas and various cutaneous lesions. The MEN 2 syndromes (MEN 2A, MEN 2B and familial medullary thyroid carcinomas) are characterized by high penetrance of medullary thyroid carcinoma and differ in their variable expression of pheochromocytoma, hyperparathyroidism and other clinical features.

CURRENT KNOWLEDGE AND KEY POINTS

MEN 1 tumor suppressor gene encodes a nuclear protein, menin, which interacts with different regulation transcription factors. The MEN 2 syndromes are caused by germ-line mutations of the RET proto-oncogene, which encodes a transmembrane tyrosine kinase. Genetic testing for mutations in these 2 genes allows identification of individuals predisposed to the disease, early diagnosis, and clinical and therapeutic management.

FUTURE PROSPECTS AND PROJECTS

Fundamental approach will allow a best comprehension of physiopathogenic mechanisms of these disorders and the improvement of therapeutic management.

Acceptable age for prophylactic surgery in children with multiple endocrine neoplasia type 2a

AIMS

Germline mutated RET proto-oncogene, causing multiple endocrine neoplasia (MEN)-2a syndrome is the indication for prophylactic total thyroidectomy. Literature regarding the risk and the extent of early surgical intervention is scarce and the optimum age for surgery is still controversial. To optimize management in these young children we evaluate our experience and results.

PATIENTS AND METHODS

From 1990 to 2001 preventive total thyroidectomy was performed in 13 MEN-2a gene carriers (4 boys and 9 girls; median age 7 (4-14) years). Preoperative assessment, surgical procedure, pathological examination, postoperative complications and treatment results were studied.

RESULTS

Surgery existed of a total thyroidectomy alone (n=3) in children with normal basal calcitonin and in combination with tracheo-esophageal exploration (n=6) or central compartment dissection (n=4) in case of abnormal calcitonin levels. Eight children presented with medullary thyroid cancer (MTC), three (median: 5 (4-12) years) with microscopic MTC and five (median 6 (4-14) years) with frank invasive MTC. Four of these five patients were younger than 6 years. Except for long-lasting hypoparathyroidism in one patient there were no complications. At a median follow-up of 6.5 years all patients are disease free.

CONCLUSION

MTC in RET mutated MEN-2a gene carriers in childhood are found at the age of 4 years. Therefore, DNA testing should be done preferably before that age. Preventive surgery can be performed safely at that age and may be limited to total thyroidectomy when baseline calcitonin levels are normal.

Prophylactic thyroidectomy in multiple endocrine neoplasia: the impact of molecular mechanisms of RET proto-oncogene

BACKGROUND

Multiple endocrine neoplasia (MEN) type 2, a cancer syndrome inherited in the dominant fashion, is defined by the occurrence of medullary thyroid carcinoma (MTC), either as a singular lesion (familial medullary thyroid carcinoma, FMTC) or with the variable expression of pheochromocytoma, hyperparathyroidism (MEN 2A), ganglioneuromas, buccal neuromas and Marfanoid-like phenotype (MEN 2B).

DISCUSSION

Germline mutations of the RET proto-oncogene, localized on chromosome 10q11.2, have been identified as the underlying genetic cause of the disorder. In the majority of patients with MEN 2A/FMTC missense mutations at exon 10 or exon 11 are identifiable. Cysteine to arginine exchange at codon 634 is the mutation most frequently found. In MEN 2B approximately 95% of patients present with a mutation at codon 918 (exon 16). Additionally, less frequent mutations in other codons have been found in both syndromes. The DNA-based genotype analysis enables the identification of gene carriers at risk of developing MTC and offer them prophylactic thyroidectomy prior to development of any thyroid pathologies. Prophylactic surgery is generally recommended for MEN 2A/FMTC gene carriers at the age of 4-6 years. Due to the aggressiveness of the MEN 2B syndrome gene carriers should be operated by the age of 1 year. Presumably some less virulent mutations allow postponement of the prophylactic treatment to the second to fourth decade of life.

CONCLUSIONS

Compared to standard presymptomatic biochemical screening, genetic testing and consecutive prophylactic treatment contribute to better outcome of individuals at risk for MTC.

Medullary thyroid carcinoma: Genetic screening and prophylactic thyroidectomies

Medullary thyroid carcinoma (MTC) occurs sporadically or is inherited as a characteristic component of MEN 2A, MEN 2B and familial MTC. Germ/line point mutations in RET proto/onkogene are responsible for tumor arise and inheritance. Genetic screening provides information of these RET mutations in family members even before pathologic changes of C-cells progress to MTC. The aim of our study was to identify carriers of RET gene mutations in our patients with MTC and their kindred. Surgical therapy was based on genetic testing results and clinical features. Prophylactic thyroid surgery was the subject of interest. From 1969-2002 105 patients with MTC (88 families), were treated and/or diagnosed at the institute of Oncology Ljubljana, Slovenia. Genetic testing was so performed in 58/88 MTC index patients (24 males (16 - 93y) and 34 females (23 -77y)) and their 50 kindred, aged 8 - 67y. Twentyfive/50 kindred were from affected families. Germline mutations of RET proto-onkogene were found in 12/58 (20, 6%) MTC index patients - 2 males (16 and 65 y) and 10 females (23-55y, median 36y) and in 14/25 kindred from 12 affected families - 5 males aged 18-57 years (median 21) and 9 females aged 12-54 years (median 41) but were absent in 11/25 kindred. Genetic screening results indicate thyroid surgery in all 14 kindred; also MTC was clinically suspected or diagnosed in 11/14 patients and 3/14 were candidates for prophylactic thyroidectomy. Total thyroidectomy with central neck dissection was the minimal surgical procedure. Prophylactic thyroidectomy based on genetic testing results allows earlier diagnosis and treatment of patients, even before pathologic changes of C-cells occur. Patient?s age and codon mutation influence the timing of surgery and even it?s extend.

Prophylactic thyroidectomy in MEN 2A syndrome: experience in a single center

BACKGROUND

Genetic study of the RET proto-oncogene has modified the management, treatment, and prognosis of medullary thyroid carcinoma (MTC), multiple endocrine neoplasia 2A (MEN 2A), for patients with less advanced tumor stages. Classically, the diagnosis was based on an increase in basal and poststimulus peak calcitonin (bCT and pCT). Prophylactic thyroidectomy, based on results of genetic testing, may reduce recurrences in MTC.

STUDY DESIGN

Of 82 MTC (MEN 2A) patients genetically diagnosed and surgically treated at our center, 22 received a prophylactic thyroidectomy (RET +, bCT and pCT with normal values and asymptomatic). We analyzed age, gender, phenotype, RET mutation, cervical ultrasound, laboratory tests (bCT, pCT, and CEA), surgery, histologic data, TNM, and followup.

RESULTS

The 22 patients belonged to 8 families with MTC (MEN 2A). Mean age was 15.2 years (range 5 to 36 years). The RET mutation in 21 patients was Cys-->Tyr and in the remaining patient both in codon 634 in exon 11. The median values of bCT and pCT were 38 pg/mL (range < 15 to 75 pg/mL) and 148.5 pg/mL (range < 15 to 250 pg/mL), respectively. Total thyroidectomy was performed in 8 patients (age < or = 10 years) and associated central neck dissection in 14 patients (age> 10 years). Histologic study showed 7 C-cell hyperplasias and 15 MTCs (8 bilateral); the median size was 0.2 cm (range < 0.1 to 0.7cm); 1 patient had metastatic adenopathies. According to TNM, 7 were stage 0, 14 were stage I, and 1 was stage III. Postsurgery bCT and pCT values were normal in all patients, with a curative rate of 100%. MTC patients compared with C-cell hyperplasia patients were older on average, had higher mean bCT, mean pCT, and mean CEA.

CONCLUSIONS

Prophylactic thyroidectomy based on genetic testing allows identification and treatment of patients at an early stage of the disease and decreases recurrence rates. pCT values above the upper limit of normal may be markers for the presence of MTC and should be considered in selecting operative procedures for these patients.

Prognostic factors in well-differentiated follicular-derived carcinoma and medullary thyroid carcinoma

This paper reviews both clinicopathologic and biological factors in differentiated thyroid carcinoma of follicular and C-cell derivation. The value of specific histological parameters including tumor subtypes, vascular invasion as predictors of prognosis in these tumors is discussed and the pertinent literature reviewed. The utility of ploidy analysis and immunohistochemical assessment of hormonal and tumor markers are described. Current information on biological and molecular markers that may be helpful in predicting behavior is discussed. The commonly used staging systems for thyroid cancer are briefly described.

Molecular influences in thyroid and parathyroid surgery

Recent progress in molecular biology and genetics has made a major impact on the management of patients with multiple endocrine neoplasia syndromes MEN-1 and MEN-2. The understanding of the mechanisms involved in inherited thyroid and parathyroid tumours also offered valuable answers for other models of neoplasia. In addition, parathyroid surgery has witnessed rapid progress, from the cloning of the calcium receptor to the development of calcimimetics, a new class of drugs that could shift the management of hyperparathyroidism from surgical intervention to medical treatment. Laboratory techniques initially designed for research are more and more being used for clinical diagnosis. For example, the use of the polymerase chain reaction is currently being evaluated in the early diagnosis of metastatic thyroid carcinoma by identifying specific gene products in the local lymph nodes. This chapter attempts to convince the reader that molecular biology is no longer restricted to the laboratory but has an increasing impact on clinical decisions to which an endocrine surgeon is exposed.

Current approaches and perspectives in the therapy of medullary thyroid carcinoma

BACKGROUND

Medullary thyroid carcinoma (MTC) is a neuroendocrine tumor derived from parafollicular cells. At present, surgery is the most important treatment for MTC.

METHODS

We describe the current approaches of MTC treatment (surgery, chemotherapy, radiation therapy, and biologic therapy).

RESULTS

MTC is currently approached surgically in the main part through total thyroidectomy and compartment-oriented microdissection of cervicomediastinal lymph nodes. Substitutive l-thyroxine administration together with close clinical monitoring and the measurement of basal and stimulated serum calcitonin are subsequently performed. Radiotherapy and chemotherapy play a marginal role in advanced MTC. Recently, it has been found that somatostatin analogs and type I interferon are able to control the neuroendocrine symptoms induced by advanced MTC and that they provide clinical benefit by improving the lifestyle of these patients.

CONCLUSION

Although these agents are poorly active in inducing a shrinkage in tumor mass, the combined use of different biologic agents and cytotoxic drugs needs to be explored in advanced MTC. However, at present, surgery is the only curative treatment for MTC.

Familial medullary thyroid carcinoma (FMTC). Study of one family (treatment criteria)

AIM

The nosology of familial medullary thyroid carcinoma (FMTC) has been described as a distinct pathology, genetically determined and with autosomal dominant transmission with a gene penetrance of almost 100%. The diagnosis of this morbid condition can be made if at least four members of the same family are affected by calcitonin-secreting C-cell carcinoma.

METHODS AND RESULTS

We report the analysis of a family in which FMTC was diagnosed between 1993 and 1998. Of the five patients we confirmed as being affected by FMTC, we were able to perform a prophylactic thyroidectomy in only one case. The high possibility of lymph-node metastasis at the time of clinical diagnosis (52-75%), and the high morbidity and radio-chemo-resistance to adjuvant therapies, indicate total thyroidectomy with central lymph-node dissection.

CONCLUSION

It appears that preventive lymphadenectomy does not substantially improve survival, while pre-clinical diagnosis is of greater importance than surgery in improving survival and preventing recurrence. Total preventive thyroidectomy has been recommended in all carriers of ret genetic defects, even in families at risk with mutations of the 618 or 620 codon, because the penetrance of FMTC approaches 100%, and a 100% accordance between presence of the disease and gene carrier status is reported. This procedure would therefore represent the only possibility of achieving a 100% cure in subjects affected by familial medullary thyroid carcinoma.

[Usefulness of RET proto-oncogene in the diagnosis of hereditary-type medullary carcinoma of the thyroid. Correlation with surgical findings]

In about 25% of cases medullary thyroid carcinoma (MTC) is hereditary. In this group is possible to detect germline point mutations of the RET proto-oncogene in about 95% of the studied cases. The purpose of the present paper is to confirm the value of the RET in the screening of the hereditary MTC. We studied 43 subjects at risk for a Multiple Endocrine Neoplasia Type 2A Syndrome. RET analysis was positive for MEN 2A in 22 subjects. Fifteen of the 22 have undergone a total thyroidectomy at our facility. Histopathological study of the surgical specimens confirmed the presence of a MTC in all the cases. According with our experience. RET analysis is a 100% sensitive and specific method of hereditary MTC screening, and we think it has obvious advantages over the calcitonin tests in technical, economic and ethic aspects.

Parents' responses to disclosure of genetic test results of their children

The psychological reactions of 22 parental couples and 3 single parents were investigated after disclosure of genetic test results of their children. The children were tested for the early-onset, monogenetic cancer disorder multiple endocrine neoplasia type 2. Participants came from 13 different families and were aged between 28 and 47 years. Parents who were informed that their child was a gene carrier reacted with resignation, showed moderate to high levels of test-related and general anxiety, but few psychological complaints. Daily activities were disturbed in 43% of the parents with carrier-children. There was little disruption of the parents' future perspective, apart from some socioeconomic disadvantages and increased parental concern for the carrier-children. Most parents with carrier-children showed restraint with respect to short-term prophylactic treatment. Parents with favorable test results showed significantly less anxiety and no disturbance in their daily activities. They did not, however, seem to be reassured by the DNA test result. These parents questioned the reliability of the DNA test, wanted confirmation of the test results, and were eager to continue screening of their noncarrier children. Parents, especially those with a lower level of education and/or a pessimistic view of the future, were distressed by unfavorable test results. Additional counseling is advised to prevent parents of carrier-children worrying unnecessarily, or parents with children in whom the disease gene was not found being not reassured. Am. J. Med. Genet. 94:316-323, 2000.

RET proto-oncogene mutations in thyroid carcinomas: clinical relevance

Different forms of RET mutations are found in papillary and medullary thyroid carcinomas. Rearrangements with other genes (RET/PTC oncogene) play a causative role in a significant proportion of papillary thyroid carcinomas. In this case, several factors influence the frequency and the type of RET/PTC, such as exposure to radiation, age and histological variant of the papillary tumor. On the other hand, the presence of the mutation does not seem to influence the biological behavior of the tumor or its response to conventional treatment modalities. In the setting of medullary thyroid cancer, germline RET point-mutations are implicated in the pathogenesis of virtually all hereditary forms and somatic point-mutations in nearly half of the sporadic forms. The clinical impact of this finding is that family members at-risk of hereditary MTC may be screened by genetic analysis, to distinguish those carrying or not-carrying the mutation. The last can be reassured on their status and relieved from further follow-up. Those with the mutation may be treated at a pre-clinical stage of the disease or even before the disease is started. The present review is focused on the clinical implication of RET gene mutations in thyroid cancer patients.

Medullary carcinoma of the thyroid

Medullary thyroid cancer (MTC) is a distinct C-cell tumor of the thyroid. We review the oncogenesis and management of both sporadic tumors and those tumors arising as part of specific inherited syndromes. The RET proto-oncogene plays a role in the development of inherited forms of MTC and has become important in the clinical management of patients and their families. The recognition of the high rate of regional nodal involvement has led to lymphadenectomy being strongly considered for patients undergoing thyroidectomy for MTC.

Presymptomatic detection and treatment of Japanese carriers of the multiple endocrine neoplasia type 2A gene

DNA extracted from the peripheral blood leukocytes of 36 members of five families with multiple endocrine neoplasia (MEN) type 2A was analyzed for mutations of exons 10, 11, 13, 14, and 16 of the RET proto-oncogene by nonisotopic polymerase chain reaction-single-strand conformation polymorphism analysis and automated DNA sequencing. Germline mutations were found in all 9 of the affected individuals and in 6 of the 27 individuals of unknown status. A 70-year-old man who had been completely asymptomatic before genetic diagnosis underwent left adrenalectomy and total thyroidectomy, and was found to have pheochromocytoma and multifocal micromedullary thyroid carcinoma (MTC). A 32-year-old man and a 15-year-old boy, with elevated calcitonin levels detected by the C-cell-stimulation test, but no evident thyroid tumor, underwent total thyroidectomy. Histopathological diagnosis revealed multiple micro MTCs. A 7-year-old girl without evidence of a thyroid tumor or an elevated calcitonin level is being followed up. The remaining two subjects with an evident thyroid tumor and elevated calcitonin levels refused surgery. These results suggest that genetic screening for MEN type 2 afflicted family members can facilitate the presymptomatic detection of gene carriers. Thus, we must carefully evaluate whether immediate prophylactic total thyroidectomy is indicated for gene carriers of MEN 2A without an evident thyroid tumor or elevated calcitonin levels.

[Medullary cancer of the thyroid]

INTRODUCTION

Medullary thyroid carcinoma is a rare disease which originates from the secretion of calcitonin by thyroid parafollicular cells. Sporadic (75%) and inherited (25%) forms of the disease are encountered. Familial forms (termed multiple endocrine neoplasia type IIa, IIb, or familial medullary thyroid carcinoma) may or may not be associated with other endocrinopathies such as pheochromocytoma and/or hyperparathyroidism.

CURRENT KNOWLEDGE AND KEY POINTS

Circulating forms of calcitonin, a marker of the disease, are heterogeneous in blood, thus explaining why assays lead to different results according to the method used.

FUTURE PROSPECT AND PROJECTS

Family screening is much easier, as germ line mutations of the proto-oncogene RET have recently been identified in inherited forms of the disease. Treatment includes extensive surgery. This, and prophylactic thyroidectomy in gene carriers, is discussed. Prognosis is much better nowadays, but precise follow-up has to be instituted.

Different mutations of the RET gene cause different human tumoral diseases

The RET gene encodes a tyrosine kinase receptor for neurotrophic molecules. RET is a conceptually valuable example of how different mutations of a single gene may cause different diseases. Gene rearrangements activate the oncogenic potential of RET in human thyroid papillary carcinomas. On the other side, different point mutations activate RET in familial multiple endocrine neoplasia syndromes. Finally, inactivating mutations of RET can be present in Hirschsprung's disease patients. The detailed knowledge of the specific RET mutations responsible for human tumors provides relevant tools for the clinical management of these diseases. Moreover, the recent discovery of the growth factors which in vivo stimulate its signaling may shed new light on the role played by RET in the development and differentiation of the central and peripheral nervous system.

Current perspectives in the surgery of multiple endocrine neoplasias

Multiple endocrine neoplasia is an uncommon but fascinating condition. In this review we examine the multifaceted presentations, the diagnostic challenges and different management strategies for various syndromes. This is an attempt to share our knowledge and experience towards achieving better outcomes in the management of the diseases.

Genotype-phenotype correlation of patients with multiple endocrine neoplasia type 2 in Japan

BACKGROUND

Multiple endocrine neoplasia type 2 (MEN 2) is a hereditary syndrome characterized by medullary thyroid carcinoma (MTC), pheochromocytoma and hyperparathyroidism. MEN 2 is caused predominantly by germ-line mutations of the RET proto-oncogene. This study aimed to clarify the genotype-phenotype correlation in MEN 2 patients in Japan in order to modify the clinical management according to the genotype.

METHODS

Constitutive DNA of 64 MEN 2 patients (48 kindreds) were searched for mutations at exons 10, 11, 13, 14 and 16 of the RET proto-oncogene using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP), direct sequencing and restriction enzyme digestion. The clinical characteristics of the patients were obtained from a previous nationwide questionnaire survey.

RESULTS

Overall, 62 (96.9%) out of 64 patients had a germ-line point mutation at the hot spots. MTC and pheochromocytoma occurred equally in every genotype except C630S. Specific genotype had a correlation between tumor size and age at the operation for MTC or extent of MTC, i.e. C618S developed late onset type of MTC as compared with that of C634R, C634Y and M918T. Small MTC in C634R may be less aggressive than those in C634Y and M918T.

CONCLUSIONS

DNA testing has good clinical implications for the management of patients with MEN 2 and the timing and operative procedures of thyroidectomy can be modified according to the genotype.

Analysis of RET proto-oncogene abnormalities in patients with MEN 2A, MEN 2B, familial or sporadic medullary thyroid carcinoma

Medullary thyroid carcinoma (MTC) may occur either as a sporadic or familial (FMTC) disease. Multiple endocrine neoplasia (MEN) type 2, inherited as an autosomal dominant disease, is characterized by coexistence of MTC with other endocrine neoplasia. Activating mutations of the RET proto-oncogene, involving the somatic or the germinal cell lineage, are found in both inherited and acquired forms. In this study, RET mutations were screened in 47 individuals either affected by MTC or belonging to families with hereditary MTC. Exons 10, 11, 13, 14, 15 and 16 of the RET gene were amplified by polymerase chain reaction and examined by DNA sequence and/or restriction enzyme analysis to detect mutations in purified amplicons. Six MEN 2A families with a germline mutation at codon 634, one FMTC family carrying a mutation at codon 618 and two MEN 2B families with a mutation at codon 918 were identified. In affected members of a MEN 2A family no known RET mutations were observed. Besides, we identified a germline mutation in a patient with apparently sporadic MTC and in two out of three sons, indicating the presence of a sporadic misclassified familial disease. In all of the families examined we were able to distinguish the affected vs unaffected (not at risk) members. A somatic mutation of codon 918 was detected in three out of ten patients with apparently sporadic MTC.

Seventeen-year-long follow-up of a family affected by type 2A multiple endocrine neoplasia (MEN 2A)

This paper reports the results of a 17-year-long follow-up covering 17 members of a family affected by multiple endocrine neoplasia (MEN) type 2A, first diagnosed in 1980. This family is enrolled in our screening program. The thyroid, parathyroid and adrenal glands of the family members were investigated using the most sophisticated and sensitive techniques which have become available during this period, and their DNA was genetically tested for detecting RET mutations. Thanks to the combination of these two approaches it was possible to confirm the diagnosis in the members concerned from the genetic point of view, and to achieve an early diagnosis in the young members of the last generation before the clinical onset of the disease. The detection of a RET mutation also prompted a prophylactic thyroidectomy in a four year-old boy, in a pre-tumoral stage of the disease. Lastly, evidence is provided that genetic analysis of the DNA of the chorionic villi can be carried out as a prenatal test during routine amniocentesis.

Clinical uses of gut peptides

OBJECTIVE

The authors review clinical applications of gut-derived peptides as diagnostic and therapeutic agents.

SUMMARY BACKGROUND DATA

An increasing number of gut peptides have been evaluated for clinical use. Earlier uses as diagnostic agents have been complemented more recently by increasing application of gut peptides as therapeutic agents.

METHOD

The authors conducted a literature review.

RESULTS

Current experience with clinical use of gut peptides is described. Initial clinical applications focused on using secretomotor effects of gut peptides in diagnostic tests, many of which have now fallen into disuse. More recently, attention has been directed toward harnessing these secretomotor effects for therapeutic use in a variety of disorders, and also using the trophic effects of gut peptides to modulate gut mucosal growth in benign and malignant disease. Gut peptides have been evaluated in a variety of other clinical situations including use as adjuncts to imaging techniques, and modification of behaviors such as feeding and panic disorder.

CONCLUSIONS

Gut peptides have been used successfully in an increasing variety of clinical conditions. Further refinements in analogue and antagonist design are likely to lead to even more selective agents that may have important clinical applications. Further studies are needed to identity and evaluate these new agents.