CurrentCapital BluecrossPolicy MP 2.384

GERMLINE GENETIC TESTING FOR HEREDITARY DIFFUSE GASTRIC CANCER (CDH1, CTNNA1)

Defines medical necessity criteria for germline CDH1 testing for hereditary diffuse gastric cancer (HDGC) and states CTNNA1 testing is investigational; includes guideline notes on testing unaffected individuals, minors, counseling, and coding information.

Policy Summary

PayerCapital Bluecross

PolicyGERMLINE GENETIC TESTING FOR HEREDITARY DIFFUSE GASTRIC CANCER (CDH1, CTNNA1)

Policy CodePolicy MP 2.384

Change TypeAdministrative; clarified (coding/references)

Effective DateJan 1, 2026

Next Review DateAug 14, 2025

Key ActionProvider must document that the individual meets one of the listed medically necessary criteria (e.g., age at diagnosis, family history details, ethnicity, cleft lip/palate history) to support coverage for CDH1 testing.

SourceLink

POLICY UPDATE CHANGES

Policy statements unchanged during consensus reviews on 09/27/2023 and 09/23/2024; coding and references reviewed and updated.

Administrative update added new diagnosis codes effective 10/1/25.

6Listed criteria that qualify for CDH1 testing

2Genes addressed (CDH1 covered; CTNNA1 investigational)

4Consensus reviews since inception

Coverage Summary

Overview: This policy (MP 2.384) addresses germline genetic testing for hereditary diffuse gastric cancer (HDGC), specifying that CDH1 testing may be medically necessary when defined clinical criteria are met and that CTNNA1 testing is investigational. Status: CURRENT. Effective date: 2026-01-01. Last review: 2024-09-23. Next review: 2025-08-14.

Quick facts

Policy numberMP 2.384

Effective date2026-01-01

Last review2024-09-23

Next review2025-08-14

Coverage stancemixed

Medical-Necessity Criteria

Medically Necessary Criteria for CDH1 Germline Testing

Germline genetic testing for CDH1 variants may be considered medically necessary for individuals meeting ANY of the following:

A diagnosis of diffuse gastric cancer (DGC) before age 50 years.
A diagnosis of DGC at any age in individuals of Maori ethnicity, or with a personal or family history of cleft/lip palate.
A diagnosis of bilateral lobular breast cancer before age 70 years.
Personal or family history of both DGC and lobular breast cancer, with one diagnosed before age 70 years.
Two first- or second-degree relatives with a diagnosis of gastric cancer at any age, with at least one being DGC.
Two first- or second-degree relatives with a diagnosis of lobular breast cancer before 50 years of age.

Targeted testing in families with known variant

Additional testing guidance:

In individuals with a known familial CDH1 variant, targeted testing for the specific variant is recommended.
In individuals with unknown familial CDH1 variant, test an affected close relative who has cancer related to HDGC whenever possible prior to testing unaffected members.

Testing minors

Position on testing minors:

Testing minors: Genetic testing for CDH1 variants has limited or no clinical utility in minors because management does not change; testing is generally not recommended except for exceptions based on family history and/or high-risk ethnicity.

Not Medically Necessary / Investigational

The following are considered investigational:

Germline genetic testing for CDH1 variants in individuals who do not meet the medically necessary criteria above.
Germline genetic testing for CTNNA1 variants to identify individuals with or at risk for HDGC.

Provider Actions & Documentation Requirements

Documentation Required

Demonstrate qualifying criteria

Provider must document that the individual meets one of the listed medically necessary criteria (e.g., age at diagnosis, family history details, ethnicity, cleft lip/palate history) to support coverage for CDH1 testing.

Age at diagnosis (e.g., DGC before age 50, bilateral lobular breast cancer before 70)
Family history details (first- or second-degree relatives with gastric or lobular breast cancer, number affected, ages at diagnosis)
Ethnicity (e.g., Maori)
Personal or family history of cleft lip/palate

Documentation Required

Test affected family member first when possible

When the familial CDH1 variant is unknown, providers should test an affected close relative first to maximize interpretability before testing unaffected family members.

Documentation Required

Targeted testing for known familial variant

When a familial CDH1 variant is known, providers should perform targeted testing for that specific variant rather than full gene sequencing.

Documentation Required

Genetic counseling recommended

Providers should arrange formal genetic counseling by qualified personnel prior to genetic testing to discuss benefits, harms, and family implications.

Coding

Covered when medically necessary (procedure codes listed)CPTCovered

81406
81432
81435
81479

Relevant diagnosis codes (ICD-10-CM)ICD-10

C16.0	Malignant neoplasm of cardia
C16.1	Malignant neoplasm of fundus of stomach
C16.2	Malignant neoplasm of body of stomach
C16.3	Malignant neoplasm of pyloric antrum
C16.4	Malignant neoplasm of pylorus
C16.5	Malignant neoplasm of lesser curvature of stomach, unspecified
C16.6	Malignant neoplasm of greater curvature of stomach, unspecified
C16.8	Malignant neoplasm of overlapping sites of stomach
C16.9	Malignant neoplasm of stomach, unspecified
C50.011	Malignant neoplasm of nipple and areola, right female breast

1–10 of 85

1/9

Background & Evidence

Background: Hereditary diffuse gastric cancer (HDGC) is an autosomal dominant syndrome that markedly increases lifetime risk of diffuse gastric cancer (DGC) and is also associated with lobular breast cancer; it is rare and often diagnosed at younger ages. Germline pathogenic variants in CDH1 (encoding E-cadherin) are established contributors to HDGC and lobular breast cancer risk and are the primary focus of clinical testing supported by this policy. CTNNA1 (encoding Catenin Alpha-1) is a suspected susceptibility gene with limited evidence; testing for CTNNA1 is considered investigational under this policy.

Evidence summary

Penetrance estimates for CDH1Gastric cancer penetrance ~42%-70% in men and 33%-56% in women

Evidence for CDH1 testingRetrospective observational studies and guideline chains of evidence support clinical utility in qualifying individuals; evidence sufficient to improve net health outcome

Evidence for CTNNA1 testingOnly case reports and limited data; insufficient evidence to demonstrate clinical validity and considered investigational

Definitions: 1st-degree relatives = parents, siblings, and children. 2nd-degree relatives = grandparents, aunts, uncles, nieces, nephews, grandchildren, and half-siblings. Familial variant = a disease-associated variant identified in a proband for use in subsequent targeted genetic testing in first-degree relatives.

Revision History

09/27/2023clarified

Policy statements unchanged during consensus reviews on 09/27/2023 and 09/23/2024; coding and references reviewed and updated.

09/23/2024clarified

Policy statements unchanged during consensus reviews on 09/27/2023 and 09/23/2024; coding and references reviewed and updated.

09/02/2025administrativeLatest

Administrative update added new diagnosis codes effective 10/1/25.

Policy Summary

PayerCapital Bluecross

PolicyGERMLINE GENETIC TESTING FOR HEREDITARY DIFFUSE GASTRIC CANCER (CDH1, CTNNA1)

Policy CodePolicy MP 2.384

Change TypeAdministrative; clarified (coding/references)

Effective DateJan 1, 2026

Next Review DateAug 14, 2025

SourceLink

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