Genetic Test Results

Genetic testing for hereditary breast and ovarian cancer in Australia is usually accessed through or in conjunction with a Family Cancer Clinic. There are different types of genetic testing, you can read more about these types here.

The first thing to know about interpreting a gene test result is it is complicated and should be done by an appropriately trained medical or genetics specialist. Factors such as, whether there is a family history of cancer, whether a hereditary gene mutation is already known to be present in a family and whether the person having a test has been affected by cancer or not, are important when interpreting the meaning of a gene test result.

Below we have listed the common terms used by Family Cancer Clinics when explaining what the results of a gene test mean when performed for hereditary breast and ovarian cancer genes such as BRCA1 and BRCA2.

Mutation detection results

Mutation detection gene testing is gene testing usually done in someone affected by breast or ovarian cancer. It is a test to search for a mutation in a known breast or ovarian cancer gene to explain the family history of cancer. The most common genes tested are BRCA1 and BRCA2.

Inconclusive test result (no gene mutation found)
This is the most common type of result and means there has been no mutation (or fault) identified in the gene that explains a personal/family history of breast or ovarian cancer.

This is the most common type of result because in Australia the threshold to offer BRCA1 and BRCA2 genetic testing is set low. This means that for many families there it is more likely even before testing is offered there is another explanation for the family history of cancer.

The most likely explanation for this result is there are many genes that contribute a small amount of risk. Whilst scientific research has identified some of these genes, researchers are still trying to understand these genes well enough for Family Cancer Clinics to then be able to offer gene testing.

Less likely explanations include; a mutation is present in the BRCA gene but was missed, this is unlikely especially if testing was performed with technology in the last 5 years. Or, there is another single high risk gene involved; this is less likely as these genes are rare.

This result also means there is no genetic testing to offer other family members. This is because it is first necessary to identify a gene mutation involved in causing a family history of cancer. If it has not been identified there is no gene test to offer others.

As knowledge about genetic causes for breast cancer will improve it is worthwhile families who have received this result to check in with a Family Cancer Clinic in the future.

A gene mutation (fault) is identified
This means an explanation for the family history has been identified. It can mean a person who has had this test result may be at high risk for other specific cancer types. This result also means other relatives including children, siblings and more distant relatives may have also inherited the gene mutation. In the case of a BRCA mutation this is a 1 in 2 (50%) chance.

Other family members can have a predictive gene test. To find out more about what predictive gene testing means click here.

Variant of uncertain significance
This means that a variation in the code of the gene has been identified but there is not enough scientific information to determine if this is harmless or if it causes a problem with the gene that would cause an increased cancer risk. In the future more scientific evidence may come to light to help reclassify the meaning of such variants and your Family Cancer Clinic will be able to guide you about whether you can contact them for an update.

In many situations it is likely there is another explanation for the family history of cancer which will be similar to those described for people receiving an inconclusive result (see above).

This result usually means predictive genetic testing cannot be offered to other relatives.

Predictive Testing

This is different to mutation detection testing in that a gene mutation has already been identified in a family and this type of testing is to test a person to see if they do or do not have that specific gene mutation. The possible results are;

Positive result
This means a person has inherited the family specific gene mutation is at higher lifetime risks for specific cancer types when compared to the general population. It also means their children (or future children) have a chance of having inherited the same gene mutation. In the case of a BRCA gene mutation this is a 1 in 2 or (50%) chance of having the same gene mutation.

Negative result
This means a person has not inherited the family specific gene mutation and is most likely at similar risk of cancer to the general population. This result means their children cannot inherit the family specific gene mutation.

Resources

More resources to help you understand your gene test results.
Centre for Genetics Education
Ask Our Genetic Counsellor

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