Hereditary Cancer Risk and Genetic Testing

1. Inherited Genetic Changes Account for Approximately 5–10% of Cancers

Most cancers develop through genetic changes acquired during life rather than inherited from a parent.

However, approximately 5–10% are associated with inherited harmful genetic variants that increase susceptibility to particular cancers.

The degree of risk varies between genes and individuals. Some variants carry a high lifetime cancer risk, while others have a more moderate effect.

Importantly, carrying a pathogenic variant does not mean that cancer will inevitably develop.

2. Family History Is an Important Part of Risk Assessment

Certain family patterns may indicate hereditary cancer susceptibility.

These include cancer diagnosed at a young age, several relatives with related cancers, multiple primary cancers in one person, or rare cancers such as male breast cancer.

Both maternal and paternal family histories are relevant.

However, hereditary risk may also exist without an obvious family history, particularly in small families or when information about relatives is incomplete.

3. Several Genes Are Linked to Specific Hereditary Cancer Syndromes

BRCA1 and BRCA2 are associated with increased risks of breast, ovarian, prostate, and pancreatic cancers.

PALB2, ATM, and CHEK2 are also linked to inherited cancer susceptibility, particularly breast cancer, although the level of risk differs between genes.

Lynch syndrome involves inherited changes in DNA repair genes and increases the risk of colorectal, endometrial, and several other cancers.

APC variants can cause familial adenomatous polyposis, which carries a high risk of colorectal cancer without appropriate preventive management.

The clinical significance depends on the specific genetic variant and its associated cancer risk.

4. Genetic Testing Should Be Based on Clinical Risk

Testing is particularly relevant when personal or family history suggests an inherited cancer predisposition.

Certain cancer diagnoses may also justify genetic testing even without a strong family history.

Testing may examine one known familial variant or several genes through a multigene panel.

When possible, testing an affected family member first often provides the most informative results for other relatives.

Broader testing can identify additional risk factors, but it also increases the likelihood of uncertain findings.

5. Genetic Test Results Require Careful Interpretation

A positive result identifies a pathogenic or likely pathogenic variant associated with increased cancer risk.

A true negative result means that a person has not inherited a known pathogenic variant present in their family.

An uninformative negative result does not necessarily exclude hereditary cancer susceptibility.

A variant of uncertain significance is a genetic change whose effect on cancer risk is not yet established. It should not independently determine major preventive interventions.

All results must be interpreted alongside personal and family history.

6. Genetic Findings Can Change Cancer Prevention Strategies

Identifying an inherited pathogenic variant may allow physicians to recommend earlier or more frequent cancer screening.

Depending on the associated risk, preventive management may include specialized imaging, endoscopic surveillance, or selected risk-reducing treatments.

Genetic findings may also support targeted testing of relatives who could carry the same variant.

The aim is to identify individuals who may benefit from a different prevention strategy before cancer develops.

7. Genetic Counseling Supports Appropriate Testing and Follow-Up

Genetic counseling helps patients understand the benefits, limitations, and possible outcomes of testing.

It is particularly important when selecting multigene panels or interpreting positive and uncertain findings.

Clinical genetic testing should also be distinguished from genetic analysis of tumor tissue, which is primarily used to characterize cancer and guide treatment.

Direct-to-consumer genetic tests may examine only selected variants and cannot reliably exclude hereditary cancer risk.