Five to 10 per cent of all cancers are due to a genetic predisposition. The features that suggest a genetic predisposition may include:

• early age at onset
• multiple primary cancers
• family history of similar or related cancers.

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.

Refer to section section 1.3.1 ‘Genetic family history screening’ for more information.

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

For detailed information and referral guidelines for prostate cancer risk assessment and consideration of genetic testing, refer to Royal Australian College of General Practitioners 2019 ‘Genomics in general practice’.