Genetic Counseling in Cancer Treatment

Genetic Counseling

Cancer is genetically based at the cellular level: damage accumulates in DNA, the foundation of our genetics, driving uncontrolled proliferation. Cancer being genetic does not always mean transmission to later generations through genes. Only about 30% of cancers are hereditary or familial.

A cell cannot become cancerous without mutations in its DNA. Cancer is therefore called a genetic disease. However, being genetic does not necessarily mean hereditary because most cancers arise through somatic mutations , genetic changes not passed between generations.

Also, hereditary and familial are different concepts. Familial predisposition means family cancer history without association with transmissible mutations such as BRCA mutations. Mutations initiating hereditary cancers arise in reproductive cells (germline mutations), also known as Mendelian inheritance. About 5-10% of cancers are hereditary. Although most are not inherited, identifying the 5-10% of patients and providing counseling is crucial.

Genetic counseling provides medical and psychological information about a genetic disorder in a person or family. The recipient may not be affected by the disorder.

When Is Hereditary Cancer Suspected?

• Many people in the family have the same cancer type
• Cancers arise earlier than expected
• Cancer occurs in multiple organs in one person
• Cancer occurs bilaterally, for example in both breasts, and at multiple foci
• A sex-incongruent tumor: male breast cancer
• Syndromic cases

These are general characteristics but warning signs of possible hereditary conditions.

For Which Cancers Is Genetic Counseling Most Commonly Available?

1- Breast and ovarian cancers (for example, investigating BRCA 1 and 2 mutations)

BRCA1 and BRCA2 testing should be requested for people with:

• Diagnosis before age 45,
• Cancer in both breasts,
• Breast or ovarian cancer in the same patient and/or family,
• Multiple cancer foci in the breast,
• BRCA1-2 mutations in a family member,
• Male breast cancer,
• “Triple-negative” breast cancer before age 60.

2- Large bowel (colon and rectal) cancers (for example, investigating Lynch syndrome)

Lynch syndrome results from defects in MMR (mismatch repair) genes repairing DNA damage and substantially increases certain cancers, particularly colorectal cancer. It is also called hereditary nonpolyposis colorectal cancer (HNPCC).

Microsatellite instability for Lynch syndrome should be investigated in people with:

• Colorectal cancer before age 50,
• Lynch-associated tumors in 3 relatives (at least one first-degree, 1st degree),
• Colorectal cancer at any age with multiple bowel cancer foci or a Lynch-associated tumor in the same individual (uterine, ovarian, urinary tract, stomach, pancreatic, skin and breast cancers),

For adult-onset hereditary cancers due to Lynch syndrome or BRCA1-2 mutations, testing before age 18 is not recommended.

A woman with a BRCA1 mutation should be informed about active surveillance, preventive mastectomy or oophorectomy. A positive hereditary cancer test also concerns other family members; those at risk should be told testing may follow genetic counseling.

A negative result indicates cancer risk close to the general population, not zero. This must be emphasized during counseling.

Hereditary cancer counseling is a staged service involving molecular and clinical genetics, cancer surgery, oncology and gynecology. Ideally it is provided where these disciplines work harmoniously.

We previously discussed insufficient genetic counseling for BRCA testing. To access that article, drozdogan.com/brca-testleri-icin-genetik-uzmanlarindan-yeterince-ikinci-gorus-alinmiyor