Stage II: Summary Report Secondary Findings in Adults Non-diagnostic, excludes newborn screening & prenatal testing/screening Permalink Stage I Survey Update History Stage 2 Status (Adult):Complete (Actionability curation complete.)
GENE/GENE PANEL:
RET
Condition:
Multiple Endocrine Neoplasia IIA, Familial Medullary Thyroid Cancer
Topic
Narrative Description of Evidence
Ref
1. What is the nature of the threat to health for an individual carrying a deleterious allele?
Prevalence of the Genetic Disorder
Altogether multiple endocrine neoplasia type 2 (MEN2) subtypes (MEN2A, MEN2B, and familial medullary thyroid cancer or FMTC) affect 1/30,000 to 1/35,000 individuals. Within MEN2, MEN2A accounts for roughly 70-80% of cases, and FMTC accounts for roughly 10-20% of cases. Overall, MEN2A has an estimated prevalence of 1/40,000, while the prevalence of FMTC is unknown.
Clinical Features
(Signs / symptoms)
(Signs / symptoms)
MEN2A is associated with an increased risk for medullary thyroid carcinoma (MTC), pheochromocytoma (PHEO), and primary hyperparathyroidism (PHPT). Some patients with MEN2A also develop cutaneous lichen amyloidosis (CLA) and disturbances in gut transit that resemble those seen in Hirschprung disease. FMTC is considered to be a clinical subtype of MEN2A with the presentation of MTC in the absence of PHEO and PHPT due to decreased penetrance. Criteria for FMTC versus MEN2A are not standardized, but include the diagnosis of MTC only in multiple family members either across generations or within a generation. It can be clinically very difficult to determine that a family has FMTC rather than MEN2A since the former diagnosis depends upon the absecnce of PHEO and PHPT. Thus limited family history and young patient age make distinguishing between MEN2A and FMTC difficult.
Natural History
(Important subgroups & survival / recovery)
(Important subgroups & survival / recovery)
MTC in individuals with MEN2 typically presents at a younger age than sporadic MTC and is more often associated with C-cell hyperplasia as well as multifocality or bilaterality. In FMTC, MTC typically occurs in middle age. Onset of MEN2A is typically prior to age 35, usually between ages 5 and 25. MTC is generally the first manifestation in MEN2A with probands presenting with a neck mass or neck pain. All individuals with MEN2A who have not had a thyroidectomy will demonstrate biochemical evidence of MTC by age 35. PHEOs usually present after MTC or concomitantly, but are the first manifestation in 13-27% of individuals. PHEOs are diagnosed at an earlier age, have subtler symptoms, and are more likely to be bilateral than sporadic tumors, with malignant transformation occurring in about 4% of cases. PHPT is typically mild, with most individuals with PHPT having no symptoms, and may range from a single adenoma to marked hyperplasia. PHPT usually presents many years after the diagnosis of MTC, with an average age of onset of 38 years.
2. How effective are interventions for preventing harm?
Information on the effectiveness of the recommendations below was not provided unless otherwise stated.
Information on the effectiveness of the recommendations below was not provided unless otherwise stated.
Patient Management
All patients with MEN2 or FMTC should undergo prophylactic thyroidectomy. The recommended timing of surgery is based on a classification system of RET mutations and other indicators of risk for aggressive MTC. RET mutations associated with MEN2A span the categories of "high risk" (thyroidectomy recommended by age 5 or earlier based on calcitonin levels) and "moderate risk" (thyroidectomy considered after age 5 or later based on calcitonin levels). RET mutations associated with FMTC are classified as "moderate risk". The goal of early prophylactic thyroidectomy is to intervene before metastasis, which is associated with a low cure rate. In 2 follow-up studies of MEN2 patients who had undergone thyroidectomy, there were no signs of MTC in 41/46 MEN2A/FMTC patients after an average period of 7 years and in 44/50 MEN2A patients after 10 years, showing that detection and intervention of MTC can significantly alter associated morbidity.
(Tier 1)
Surveillance
In MEN2A "moderate risk" cases and FMTC cases where prophylactic thyroidectomy has been delayed, patients should undergo annual basal serum calcitonin testing and cervical neck ultrasound starting at age 5.
(Tier 1)
PHEO surveillance should include annual plasma free metanephrines and normetanephrines or 24-hour urine collection for metanephrines and normetanephrines. Based on typical age of PHEO onset, surveillance is recommended to begin at age 11 for MEN2A "high risk" cases and age 16 for MEN2A "moderate risk" and FMTC cases. Surveillance is recommended for FMTC cases because of the inherent uncertainty in definitively assigning this diagnosis.
(Tier 2)
Because of the high risk to the fetus and mother, the presence of a PHEO must be excluded in women with a RET mutation associated with MEN2 who are planning a pregnancy or are pregnant.
(Tier 2)
Surveillance for PHPT should happen at the same time as surveillance for PHEO and should include include annual albumin-corrected calcium or ionized serum calcium measurements (with or without serum intact-parathyroid hormone [PTH]) beginning at age 11 for MEN2A "high risk" cases and at age 16 years for MEN2A "moderate risk" and FMTC cases. Age to start surveillance is based on the typical age of onset for PHPT.
(Tier 2)
Family Management
Individuals with a family history of MEN2 or FMTC should undergo RET testing. For MEN2A and FMTC, this should be done by age 5.
(Tier 1)
Circumstances to Avoid
3. What is the chance that this threat will materialize?
Mode of Inheritance
Autosomal Dominant
Prevalence of Genetic Mutations
RET mutations are identified in at least 98% cases of MEN2A and in at least 95% of families with FMTC.
(Tier 3)
Given MEN2A has an estimated prevalence of 1/40,000, RET mutations that lead to MEN2A are likely to have a similar prevalence. However, the estimated prevalence of FMTC is uknown and information on the frequency of RET mutations associated with FMTC was not available.
Penetrance
OR
Relative Risk
(Include any high risk racial or ethnic subgroups)
OR
Relative Risk
(Include any high risk racial or ethnic subgroups)
Expressivity
Patients carrying the same mutation may show a heterogenic progression of disease. Even within the same family, the natural course of disease may vary.
(Tier 2)
4. What is the Nature of the Intervention?
Nature of Intervention
The recommendations included in this report include prophylactic thyroidectomy, an invasive surgery associated with potential risk, as well as regular biochemical screening which could be burdensome.
5. Would the underlying risk or condition escape detection prior to harm in the settting of recommended care?
Chance to Escape Clinical Detection
MTC in individuals with MEN2A and FMTC is typically more aggressive and presents at an earlier age than sporadic MTC and would be highly likely to escape clinical detection in the setting of recommended clinical care.
(Tier 3)
Final Consensus Scores
Outcome / Intervention Pair
Severity
Likelihood
Effectiveness
Nature of the
Intervention
Intervention
Total
Score
Score
Medullary thyroid cancer / Thyroidectomy
2
3C
3A
1
9CA
Pheochromocytoma / Biochemical screening
2
3C
3B
3
11CB
Hyperparathyroidism / Biochemical screening
1
2C
3B
3
9CB
Description of sources of evidence:
Tier 1: Evidence from a systematic review, or a meta-analysis or clinical practice guideline clearly based on a systematic review.
Tier 2: Evidence from clinical practice guidelines or broad-based expert consensus with non-systematic evidence review.
Tier 3: Evidence from another source with non-systematic review of evidence with primary literature cited.
Tier 4: Evidence from another source with non-systematic review of evidence with no citations to primary data sources.
Tier 5: Evidence from a non-systematically identified source.
Date of Search:
06.04.2015
Reference List
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4.
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2005 Aug 31
[Updated 2015 Feb 12].
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9.
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Other.
(2012)
Website: https://www.icsi.org/_asset/3rrm36/Diabetes.pdf