Long-Term Survivorship in Multiple Endocrine Neoplasia Type 2B Diagnosed Before and in the New Millennium

Abstract

Context

Recent long-term outcomes and survival data are lacking for patients with multiple endocrine neoplasia type 2B (MEN2B).

Objectives

To analyze long-term MEN2B outcomes and define prognostic factors.

Design, Setting, and Participants

Retrospective comparative study of 75 patients with MEN2B from two German tertiary referral centers. Patients diagnosed and treated before and after 2000 were compared for demographic, biochemical, surgical, and outcome parameters.

Intervention

Surgery.

Main Outcome measure

Long-term survival.

Results

We identified seven familial and 68 de novo cases of MEN2B; 61 exhibited the RET M918T genotype (2 others exhibited A883F and E768D/L790T mutations). Surgery was performed at a mean age of 16.4 ± 11.2 years. The tumor stages at diagnosis for 71 patients were stage I, 15%; stage II, 6%; stage III, 35%; and stage IV, 44%. The mean follow-up was 9.6 ± 9.0 years. The outcomes were 15 (20%) cured, 9 (12%) with minimal residual disease, 19 (25%) with metastatic disease, and 10 (13%) unknown. Medullary thyroid cancer (MTC) caused 22 deaths (29%) 7.3 ± 6.2 years after diagnosis (mean age, 22.9 ± 10.7 years). The overall survival rates at 5, 10, and 20 years were 85%, 74%, and 58%, respectively. After 2000 (vs before 2000), significantly more patients had stage I and II (32% vs 11%) and more were cured (43% vs 20%), with a higher survival trend (P = 0.058). The only prognostic factor was tumor stage at diagnosis.

Conclusions

Patients with MEN2B developed MTC at an early age with wide ranging aggressiveness, but the outcome was generally better after 2000 than before 2000.

Multiple endocrine neoplasia 2B (MEN2B) is a rare endocrine tumor syndrome associated with the early onset of medullary thyroid cancer (MTC), the development of pheochromocytoma in approximately 50% of patients, and a distinct physical appearance that develops in childhood (1, 2). The incidence of MEN2B was recently estimated at 1.65 to 1.4 per 1 million live births annually. MEN2B is an orphan disease, and not all physicians are familiar with it (3–5). The hallmarks of MEN2B are mucosal neuromas of the tongue, lips, and inner eyelids and an inability to cry tears (6, 7). Neuromas can also occur anywhere along the gastrointestinal tract (intestinal ganglioneuromatosis). This condition leads to loss of normal bowel tone, distension, segmental dilatation, and megacolon (8). Intestinal involvement usually presents early in childhood with abdominal pain and constipation, before other extrathyroidal manifestations are perceived (9). In MEN2B, MTC is a very early event that occurs in the first year of life; the classic MEN2B phenotype often evolves over time during childhood. Consequently, the diagnosis of MEN2B is often delayed until after MTC has become regionally advanced or metastatic (10).

MEN2B is caused by germline mutations in the proto-oncogene known as RET (“rearranged during transfection”). In 95% to 98% of patients with MEN2B, a mutation in RET codon 918 causes a single amino acid substitution of a threonine for the normal methionine (M918T). Other mutations associated with MEN2B include an alanine to phenylalanine mutation at codon 883 (A883F) (11, 12) and, rarely, tandem mutations (13, 14). In most cases, RET mutations occur de novo. Therefore, most patients with MEN2B lack a family history of the disease, which could alert physicians to the need for early genetic testing and prophylactic thyroidectomy.

Patients with MEN2B have high risk of early MTC development; the youngest patient with histologically proven MTC was 9 weeks old (15). Recently, the American Thyroid Association (ATA) guidelines have recommended that prophylactic thyroidectomy should be performed in patients with MEN2B as early as possible, preferably during the first year of life (1), owing to the narrow window of opportunity for curative thyroidectomy. For patients diagnosed later in childhood, lymph node metastases are almost always present, and the cure rate decreases.

MTC is the main prognostic factor for MEN2B. MTC can be found in virtually all patients during the first year of life. The survival of patients with MEN2B is markedly lower than that of the normal population; among patients with MEN2B, the most common cause of death is MTC. Currently, for MEN2B, long-term follow-up protocols and outcomes are poorly defined. The present study was undertaken to evaluate the changes in diagnosis, treatment, and survival that have occurred within the past 50 years in a large series of 75 patients with MEN2B.

Patients and Methods

Patients

The present retrospective study included 75 patients with the MEN2B phenotype, diagnosed from 1966 to 2016, using the definition provided by the ATA guidelines (1) and histological evidence that confirmed the presence of MTC. Patients were treated at two tertiary referral centers: the surgical center at the University of Halle-Wittenberg and the specialized Endocrine Practice and Molecular Laboratory, Heidelberg. Data were retrieved from hospital records and patient medical records, with additional information given by patients, their parents, and primary care doctors using a standardized case report form. We also retrieved information on the epidemiological, clinical, biochemical, and imaging test results, surgical procedure findings, and follow-up findings. Starting in 1996, genetic testing became available. All patients or their parents provided written informed consent for genetic analyses and other clinical procedures. Care was provided in accordance with the state-of-the-art clinical and therapeutic protocols in place at the time of diagnosis (1, 16). The ethics committee of the University of Heidelberg approved the study protocol (approval no. S-003/2015).

Methods

All laboratory tests and imaging procedures were performed as a part of routine care using standard commercial tests. MEN2B was diagnosed by genetic analysis of the RET gene, with mutations found in 63 patients. Thirteen patients born between 1941 and 1970 had died before RET testing was available; thus, MEN2B had been diagnosed by phenotype alone. For patients born from 1971 to 2014, MEN2B was diagnosed by both phenotype and genotype.

Tumor stages were defined according to the American Joint Committee on Cancer TNM classification (17). Further classifications of the prognostic groups were based on the 2015 revised ATA guidelines for the management of MTC (1). At the final follow-up visit, patients were stratified into four groups according to the response to therapy: cured, biochemical evidence of the cure, with undetectable calcitonin (Ctn); minimal residual disease, detectable Ctn but no structurally identifiable disease; metastasis, structurally identifiable disease; and death, cancer-related death from progressive MTC (18).

Pheochromocytoma was diagnosed in 26 patients. The diagnosis was determined by evidence of increased 24-hour urine fractionated metanephrines, normetanephrines (or vanillylmandelic acid, before 1999), and/or plasma free metanephrine/normetanephrine levels and positive imaging results (computed tomography or magnetic resonance imaging).

To describe the changes in diagnosis, therapy, and outcomes during the past 50 years, we assigned patients to one of two groups, according to whether their diagnosis and treatment of MTC/MEN2B was before 2000 (1966 to 1999; n = 40) or after 2000 (2000 to 2016; n = 35). The two groups were compared for demographic, biochemical, surgical, and outcome parameters.

Statistical analysis

Continuous data are presented as the mean ± standard deviation and range. Categorical data are presented as the absolute and relative frequencies. Between-group differences were calculated using a two-sample t test for continuous data or the χ² test for categorical data. Analyses were performed with patients grouped by the era of diagnosis (early vs recent). MTC and pheochromocytoma penetrance and MTC survival were illustrated with cumulative incidence functions. Different tumor stages were compared using a log-rank test. All statistical analyses were descriptive and were performed using SAS, version 9.4 for Windows.

Results

Patient demographic data

Our cohort comprised 75 patients (33 males and 42 females) with an established MEN2B diagnosis (Table 1). Seven patients belonged to four kindreds (Supplemental Table 1), and 68 patients had no family history. RET analyses were unavailable for 12 patients, all with the phenotypic appearance of MEN2B and histologically proven MTC. The distribution of RET mutations was as follows: 61 patients with RET M918T, 1 patient with RET A883F (12), and 1 patient with a tandem mutation E768D/L790T. This tandem mutation was found in a mother and son. The mother was cured of MTC and had pheochromocytoma. The son had a slowly growing metastasizing MTC, which developed over 23 years.

Table 1.

Characteristics and Clinical Outcomes for 75 Patients With MEN2B Stratified by Year of Diagnosis (1966 to 1999, n = 40; and 2000 to 2016, n = 35)

Variable	All Patients	Before New Millennium (1966–1999)	In New Millennium (2000–2016)	P Value (t Test)
Patients, n	75	40	35
Sex				0.33
Male	32	15	17
Female	43	25	18
Mutated RET, n				0.262
Codon 918	61	26	35
Codon A883F	1	1	—
Codon E768D/L790T	1	1	—
Unknown	12	12	—
Index cases (de novo), n	68	37	31
Familial cases, n	7	3	4	0.133
Age at thyroidectomy for MTC, y
Mean ± SD	16.4 ± 11.2	18.2 ± 11.5	14.3 ± 10.7
Range	0.1–58	3–58	0.1–40
Tumor stage, n (%)				0.0265
I	11 (15.5)	2 (5.4)	9 (26.5)
II	4 (5.6)	2 (5.4)	2 (5.9)
III	25 (35.2)	18 (48.7)	7 (20.6)
IV	31 (43.7)	15 (40.5)	16 (47.1)
No information	4	3	1
Follow-up after diagnosis MTC, y	9.6 ± 9.0	12.6 ± 10.6	6.2 ± 5.1	0.0014
Age at end of study, y	26.3 ± 14.0	31.3 ± 14.1	20.5 ± 11.6	0.0005
Outcome, n (%)				0.001
Alive	43 (57.3)	15 (37.5)	28 (80.0)
Dead	22 (29.3)	17 (42.5)	5 (14.3)
No information	10 (13.3)	8 (20.0)	2 (5.7)
Living patients	43 (100)	15 (100)	28 (100)
Cured	15 (34.9)	3 (20.0)	12 (42.8)
Minimal residual disease	9 (20.9)	1 (6.7)	8 (28.6)	0.017
Metastatic disease	19 (44.2)	11 (73.3)	8 (28.6)
Dead patients	22 (100)	17 (100)	5 (100)	0.579
Etiology of death
MEN2B-related	21 (95.5)	16 (94.1)	5 (100)
Unrelated to MEN2B	1 (4.5)	1 (5.9)
Pheochromocytoma
Patients, n (%)	26 (35)	17 (43)	9 (26)
Age at diagnosis, y	26.9 ± 6.3	26.7 ± 6.1	27.2 ± 7.0	0.859
Interval between MTC and pheochromocytoma, y	4.6 ± 6.2	6.3 ± 6.9	1.6 ± 3.5	0.035
Localization
Bilateral	21	14	7
Unilateral	4	2	2	0.525

Data presented as mean ± standard deviation, unless noted otherwise.

Among the 75 patients, the mean age at thyroidectomy was 16.4 ± 11.2 years (range, 0.1 to 58). The mean follow-up period was 9.6 ± 9.0 years (range, 0.1 to 51). MTC reached 50% penetrance at age 16 years and 100% at age 50 years (Fig. 1). Only 21% of patients had a diagnosis of localized disease (stage I and II), and 79% had tumors that extended beyond thyroid and/or metastatic disease (stage III and IV). The mean age of patients with different tumor stages at diagnosis was 3.2 ± 4.3 years for stage I; 22.7 ± 24.6 years for stage II; 19.9 ± 10.4 years for stage III; and 16.4 ± 7.4 years for stage IV.

Figure 1.

Penetrance of MTC (n = 75) and pheochromocytoma (n = 26) in patients with MEN2B (total group, n = 75).

Among the 75 patients with MEN2B, 26 (34.6%) had pheochromocytoma (Table 1). Of these 26 patients, 7 cases of pheochromocytoma had been diagnosed together with MTC, and 19 cases of pheochromocytoma had been diagnosed 4.6 ± 6.2 years after the MTC diagnosis. The mean age at the pheochromocytoma diagnosis was 26.9 ± 6.3 years. Most pheochromocytoma cases were bilateral (n = 21); only 4 were unilateral. Pheochromocytoma penetrance was 50% at the age of 31 years. At the diagnosis of pheochromocytoma, the youngest patient was 16 years old and the oldest was 41 years old (Fig. 1). No cases of extra-adrenal or malignant pheochromocytoma were found in the present study.

Clinical outcomes

Only 15 patients (mean age at surgery, 7.9 ± 7.8 years) were cured, with undetectable Ctn levels during the follow-up period (9.8 ± 5.7 years), including three familial cases, two diagnosed by RET screening after birth (Supplemental Table 1). In one patient, a Ctn value of 8.4 pg/mL was observed 3 weeks after the operation (Table 2). When we compared patients with MEN2B diagnosed before and after 2000, the proportion of patients with stage I and II increased significantly from 11% to 32% (P < 0.027), and the proportion of cured patients increased from 20% to 42% (P < 0.017; Table 1).

Table 2.

Patients With MEN2B (n = 15) Cured of MTC Based on Biochemical Evidence

Age at Diagnosis, y	Sex	Tumor Stage at Diagnosis	Ctn (pg/mL)		Follow-Up Period, y	Age at Study End, y
			Preoperatively	Last Value
0.2	Female	I	51	<1	6.0	6.2
0.3	Female	I	34	<2	7.8	8.1
0.5a	Female	I	27	<2	3.8	5.4
0.6a	Male	I	105	<2	1.4	2.0
0.9	Female	I	50	<1	6.0	6.9
1.5	Male	I	45	<2	3.3	4.8
1.6	Male	I	37	<2	3.8	5.4
3.7	Male	I	—	<2	11.2	14.9
3.7b	Male	I	91	<2	14.3	18
8.0a,b	Female	I	58	<2	25.5	33.5
12.5b	Female	III	—	<0.8	22.2	34.5
12.7	Male	IVc	376	<2	11.4	24.1
14.3	Male	I	95	<2	11.5	25.8
27.0	Male	III	429	8.4	0.1	27.1
31.5	Male	III	252	<2	5.8	37.3

^a

Familial form of MEN2B.

^b

Diagnosed before 2000.

^c

Tumor stage T4aN0M0.

We identified 21 cancer-related deaths. One patient died in a car accident. Death occurred at a mean of 8.5 ± 5.9 years after the primary operation at a mean age of 25.5 ± 10.0 years. Most patients who died had had stage IV at diagnosis (Supplemental Table 2). At the end of the study, 43 patients remained alive. No current information was available for 10 patients.

Survival

The cancer-related survival rates at 5, 10, and 20 years were 85%, 74%, and 58%, respectively (Fig. 2). At 5, 10, and 20 years, the survival rates were 100%, 100%, and 100% for patients with stages I and II, 95%, 81%, and 62% for patients with stage III, and 68%, 55%, and 0% for patients with stage IV, respectively (Fig. 3). A multivariate analysis that included age at diagnosis, sex, tumor stage at diagnosis, and diagnosis before or after 2000 showed that the only statistically significant prognostic factor was the stage at diagnosis. However, we observed a higher survival trend for patients diagnosed in the new millennium (P = 0.0587; Table 3).

Figure 2.

Cancer-specific survival in patients with MEN2B (total group, n = 75).

Figure 3.

Survival of patients with MEN2B, grouped by tumor stage (total group, n = 75).

Table 3.

Evaluation of Clinicopathological Variables as Risk Factors for Overall Survival

Variable	Univariate Analysis		Multivariate Analysis
	HR (95% CI)	P Value	HR (95% CI)	P Value
Age at MTC diagnosis, y	1.02 (0.97–1.08)	0.4771	0.99 (0.93–1.06)	0.7812
Male sex	0.90 (0.38–2.16)	0.8183	0.95 (0.39–2.32)	0.9161
Stage IV at thyroidectomy	5.90 (1.94–17.96)	0.0018	7.75 (2.42–24.87)	0.0006
Diagnosis in or before new millennium	1.75 (0.61–5.01)	0.2951	2.80 (0.96–8.10)	0.0587

Abbreviations: CI, confidence interval; HR, hazard ratio.

Discussion

In our large, long-term observational study of 75 patients with MEN2B, we have demonstrated that the outcomes and, in part, survival improved in the new millennium. The improvements were probably due to the earlier diagnosis and treatment in early childhood. An increased awareness of the phenotype seems to have had a beneficial effect on treating patients with MEN2B.

Demographic data

The classic MEN2B mutation, RET M918T, was confirmed in 96.8% of patients with the MEN2B phenotype. In addition, one patient had the rare A883F de novo mutation, with MTC and pheochromocytoma but mild expression of the phenotype (12). Another patient had a tandem mutation, E768D/L790T, that was not previously described. These data were consistent with the published data, which indicated that among patients with MEN2B, <5% had RET germline mutations in exon 15 (codon A883F) and double RET germline mutations occurred rarely (19). Most patients with MEN2B have de novoRET mutations, and, thus, they do not have a family history. Accordingly, in our study only seven patients from four families had inherited MEN2B from a parent (6.6% of all patients with MEN2B). Of these, three families had the M918T mutation, and one family had the tandem mutation E768D/L790T (20). The ratio of classic to rare RET mutations and the ratio of de novo to familial forms did not change during the observation time.

The second endocrine component of MEN2B, pheochromocytoma, emerged during the third decade of life in 34.6% of our patients. Pheochromocytoma rarely occurred before puberty; the youngest patient in our study was 16 years old (21). Compared with MEN2A, in MEN2B, pheochromocytoma developed in a greater proportion of patients and at an earlier age (22).

Clinical outcomes

Widespread failure to achieve early clinical recognition of MEN2B exists. In part, this failure has resulted from the lack of a family history component, the rarity of the disease, and the age-dependent development of the typical clinical phenotype during childhood. During the first year of life, <20% of carriers expressed the typical MEN2B phenotype (7). Because MTC develops in early infancy, it is critical to make the diagnosis as soon as possible, within the first year of life. This early diagnosis was only possible in a few of our patients. All stage I patients could be cured. Stages I and II were diagnosed in 21.1% of all patients; however, this proportion increased substantially after 2000 (10.4% before vs 32.4% after 2000). Moreover, we noted a trend toward higher survival after 2000 (P = 0.058; Tables 1 and 3 ). All patients <1 year of age were cured by surgery, and the diagnosis for all these patients was early in stage I, with preoperative Ctn levels of 27 to 105 pg/mL. Some patients aged >1.5 years and ≤31.5 years could also be cured. Of these patients, some had advanced tumor stages and high preoperative Ctn values (Table 2). Thus, apparently, the spectrum of MTC aggressiveness is broad. In our cohort, 21 patients died of MTC, with a large variability in MTC aggressiveness and age of onset. Of these patients, the age of the youngest at diagnosis was 4.4 years with stage IV disease. That patient died at 6 years of age, after 1.6 years of follow-up. The diagnosis in another patient in this group was at age 17.1 years. That patient also had stage IV disease and died at 32.1 years of age, after 15 years of follow-up (Supplemental Table 2). Long-term cures after thyroidectomy have been reported for patients with both A883F mutations (12) and the M918T mutation, with later onset and less-aggressive courses (23–25). In some cases, the clues that led to an early diagnosis were a family history (two patients) and severe constipation (four patients) within the first year of life, all with a diagnosis after 2000. However, in most de novo cases, the clinical diagnosis was too late for early thyroidectomy. This difficulty in making an early diagnosis, in particular, in de novo cases, could be resolved in the future, when whole genomic sequencing in neonates will be able to detect the 6000 known monogenetic disorders, including MEN2B, at an early stage (e.g., before MTC develops). In general, in our series, the patients who achieved cures were younger and had lower preoperative Ctn levels and, hence, had a lower tumor stage compared with patients who died of the disease.

Survival

We observed 5-, 10-, and 20-year cancer-specific survival rates of 85%, 74%, and 58%, respectively. The only prognostic factor identified on multivariate analysis was the stage of the disease at diagnosis. Similar results were reported in earlier studies. Overall, the 5- and 10-year survival rates were 82.5% and 85%, respectively, in the German MTC/MEN Study Group (32 patients with MEN2B) (26) and 66% and 75%, respectively, in a French Group study (18 patients with MEN2B) (24). In other long-term follow-up studies of patients with MEN2A or sporadic MTC, comparable survival rates were reported (26–31). In most studies, the stage of disease at diagnosis was the most important prognostic factor. After adjusting for the tumor stage in a multivariate analysis, the difference between sporadic and familial MTC disappeared (27, 28).

When we compared the survival rates of patients who had undergone surgery before and after 2000, we found a trend toward better survival in the new millennium (Table 3; P = 0.058). This trend was supported by more patients undergoing surgery at stages I and II after 2000. Thus, the after-2000 group achieved a higher cure rate than the before-2000 group. The surprisingly good long-term overall and stage-specific survival rates for patients with MEN2B found in our study suggest that MTC in MEN2B might not be intrinsically more aggressive than MTC in MEN2A or sporadic MTC. Rather, it is induced by a mutation that causes early onset of the disease. Similar observations were reported when comparing the survival data between carriers of ATA-defined moderate RET mutations and carriers of high-risk RET mutations (32).

Using the genotype–phenotype correlations found in carriers of different RET mutations, a risk stratification system was developed and has been described in the 2015 ATA guidelines for MTC management (1). A RET M918T mutation was associated with the greatest risk of MTC and is associated with metastasis development and the youngest age at onset. However, it is well recognized that, despite the establishment of this risk level stratification, variability can occur in the expression of MTC behavior and phenotype, between RET mutations within the same ATA risk level, and even within groups with the same mutation (33). The oldest patient with a cure in the present study was 31.5 years old at diagnosis. That patient had had stage III disease and a follow-up period of 5.8 years. The variability we observed in the age of onset and the aggressiveness of MTC in MEN2B might, in part, be explained by the inclusion of the milder A883F and tandem mutations and other molecular events in the RET 918 group. Further investigation of the intracellular signaling pathways and modulators associated with RET mutations might reveal the cause of this broad variability (34, 35).

Study limitations

The retrospective nature of the present study resulted in limitations that reflect the heterogeneity in patient management during the past five decades. For example, molecular analyses were not performed before 1994; thus, not all patients could be classified by identifying RET mutations. Ctn assays became increasingly more sensitive over time; thus, the comparability of the different assays was limited. The number of patients diagnosed with MEN2B annually increased over time (from 1.18 cases annually before 2000 to 2.06 annually after 2000). With reports that the incidence was stable over time (4, 5), we assumed that the awareness of the MEN2 phenotype probably increased over time. Moreover, the diagnosis could have been performed at earlier ages after 2000, which ensured a better outcome. The surgical techniques have also changed over time. Another limitation was the 10 patients lost to follow-up. However, despite these shortcomings, the present investigation has summarized the 50-year experience of two referral centers in Germany with a large number of patients. We analyzed ≤50 years of follow-up data for patients with the rare MEN2B disease.

Conclusions

The results of the present study have shown that MTC in MEN2B has variable aggressiveness. We observed patients with a very early onset and a diagnosis at an advanced tumor stage. This group had a high proportion of metastatic disease and, therefore, a high rate of death. However, we also observed patients with a more moderate course of disease with a later onset. This group experienced greater survival rates. In comparing our patients with MEN2B to the reports of patients with MEN2A or sporadic MTC, the disease course and survival at the different tumor stages seemed comparable. Given the considerable progress made in the new millennium in terms of the earlier diagnoses with molecular and biochemical screening, greater awareness of the phenotype, and increasing use of comprehensive operative techniques, we found that better long-term survival has been achieved.

Abbreviations:

 
• ATA

  American Thyroid Association

 
• Ctn

  calcitonin

 
• MEN2B

  multiple endocrine neoplasia type 2B

 
• MTC

  medullary thyroid cancer.

Acknowledgments

We are deeply grateful for the information and support provided by the patients, their relatives, and the following research colleagues: C. Wüster (Mainz), J. Bojunga (Frankfurt), W.G. Sippel (Kiel), K. Salzgeber (Ulm), T. Schilling (Stuttgart), M. Mengel (Wuppertal), T.H. Schürmeyer (Trier), R. Santen, and M. Engelbach (Frankfurt).

Disclosure Summary: The authors have nothing to disclose.