3.1.1 Genetic testing (family risk)

In some cases certain pathological subtypes of cancer or tumour tests (immunohistochemistry or tumour genetic tests) may suggest an underlying inherited cancer predisposition.

Anyone diagnosed with cancer should have a detailed personal and family cancer history taken. Consult relevant guidelines to determine if referral to a familial cancer service is appropriate.

A familial cancer service assessment can determine if genetic testing is appropriate. Genetic testing is likely to be offered when there is at least a 10 per cent chance of finding a causative ‘gene error’ (pathogenic gene variant; previously called a mutation). Usually testing begins with a variant search in a person who has had cancer (a diagnostic genetic test). If a pathogenic gene variant is identified, variant-specific testing is available to relatives to see if they have or have not inherited the familial gene variant (predictive genetic testing).

Medicare funds some genetic tests via a Medicare Benefits Schedule (MBS) item number but most are not. Depending on the personal and family history, the relevant state health system may fund public sector genetic testing.

Pre-test counselling and informed consent is required before any genetic testing. In some states the treating team can offer ‘mainstream’ diagnostic genetic testing, after which referral is made to a familial cancer service if a pathogenic gene variant is identified. The familial cancer service can provide risk management advice, facilitate family risk notification and arrange predictive genetic testing for the family. The familial cancer service will be relevant to each state and jurisdiction.

Relevant to melanoma, a small percentage (1–2 per cent) of melanomas are due to heritable variations in the CDKN2A and CDK4 genes. Patients that may be appropriate for referral are those with:

  • more than one first-degree relative with melanoma (these patients should be referred to a dermatologist for clinical risk assessment)
  • three or more relatives with melanoma and/or pancreatic cancer (these patients should be referred to a familial cancer service and undergo a genetic risk assessment) (RACGP 2019).

Visit the Centre for Genetics Education website for basic information about cancer in a family.

For detailed information and referral guidelines for melanoma risk assessment and consideration of genetic testing, refer to the Royal Australian College of General Practitioners 2019 publication, Genomics in general practice.