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CDH1 Sequencing and Deletion/Duplication

Test code(s) 92568

Question 1. What is the clinical application of this test?

This test is used to identify individuals with a high risk of developing hereditary diffuse gastric cancer (HDGC) syndrome. The test detects point mutations, deletions, and duplications in the CDH1 gene.

Question 2. Who may be appropriate for CDH1 mutation testing?        

The following individuals may be appropriate for this test:

  • Individuals with a personal history of diffuse gastric cancer or lobular breast cancer
  • Individuals with a family history of diffuse gastric cancer or lobular breast cancer

Informed consent following genetic counseling is strongly recommended. The person in the family with the earliest diagnosis of stomach and/or breast cancer should be tested first whenever possible.

Question 3. Whom can I ask for help regarding a specific case?

You can ask one of our genetic counselors. Please call Quest Genomics Client Services at 866.GENE.INFO to talk with a genetic counselor.

Question 4. What is the cancer risk associated with a positive result (pathogenic or likely pathogenic variant detected)?

Both women and men have a higher risk of stomach cancer, specifically diffuse gastric cancer, than the general population. The lifetime risk of diffuse gastric cancer is up to 83% for women and up to 67% for men.2,4 Men and women might also have an increased risk of colorectal cancer as compared to the general population. Women have a 39% to 52% lifetime risk of developing breast cancer (lobular carcinoma).3,4

Question 5. When is the right time to test my patient?

The right time is different for every patient. A patient’s current medical status, personal experience with cancer, and general readiness for genetic information all influence the decision to be tested. Having an open dialogue with your patient about these topics can assist with shared decision-making.

Question 6. My patient has a positive result. What does this mean?

Patients with a positive result (pathogenic or likely pathogenic variant detected) have an increased risk for developing certain cancers relative to that of the general population.

The National Comprehensive Cancer Network (NCCN) provides up-to-date surveillance and management recommendations (NCCN.org) for patients with a positive result. These include increased surveillance and prophylactic surgery.1 The NCCN further recommends referring patients to oncology centers experienced in treating patients with a hereditary predisposition to cancer. Counselors and doctors at these centers can discuss available options with patients. Genetic counseling for family members is advised.

Question 7. My patient has a negative result. What does this mean?

A negative result means that a pathogenic or likely pathogenic variant was not detected in the CDH1 gene. Implications of this result depend on the situation:

  • Patient previously diagnosed with cancer: Your patient’s risk of recurrence or a related new cancer is based on his/her personal and family histories of cancer. In some instances, it may be appropriate to test for other hereditary forms of cancer. Please call Quest Genomics Client Services at 866.GENE.INFO to discuss possible additional studies with a genetic counselor.
  • Patient not previously diagnosed with cancer, but with a family history of cancer: Testing an affected family member is recommended for proper risk assessment. Your patient’s risk of cancer is based on his/her personal and family histories of cancer. In some instances, it may be appropriate to test for other hereditary forms of cancer. Please call Quest Genomics Client Services at 866.GENE.INFO to discuss possible additional studies with a genetic counselor.

Question 8. My patient has a variant of unknown clinical significance (VUS). What does this mean?

A VUS result means that the variant has not been previously described in the literature or that the clinical significance is unclear based upon currently available evidence. Medical management decisions should be based on personal and family history. Family studies may help to learn more about the clinical significance of this variant. If you have questions, please call Quest Genomics Client Services at 866.GENE.INFO to speak with a genetic counselor.

References

  1. Fitzgerald RC, Hardwick R, Huntsmen D, et al. Hereditary diffuse gastric cancer: updated consensus guidelines for clinical management and directions for clinical research. J Med Genet. 2010;47:436-444. Erratum appears in J Med Genet. 2011;48:216.
  2. National Comprehensive Cancer Network. NCCN clinical practice guidelines in oncology. Gastric cancer. V2.2016. Rockledge, PA: National Comprehensive Cancer Network, 2016. Available online with free registration.
  3. National Comprehensive Cancer Network. NCCN clinical practice guidelines in oncology. Genetic/familial high-risk assessment: breast and ovarian. V1.2017. Rockledge, PA: National Comprehensive Cancer Network, 2016. Available online with free registration.
  4. Pharoah PD, Guilford P, Caldas C and the International Gastric Cancer Linkage Consortium. Incidence of gastric cancer and breast cancer in CDH1 (E-cadherin) mutation carriers from hereditary diffuse gastric cancer families. Gastroenterology. 2001;121:1348-1353.
This FAQ is provided for informational purposes only and is not intended as medical advice. A physician’s test selection and interpretation, diagnosis, and patient management decisions should be based on his/her education, clinical expertise, and assessment of the patient.
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Effective 09/26/2016 to present