Genetic testing to inform the management of a person with a cancer or tumour may also be referred to as "treatment-focused genetic testing", "mainstream genetic testing" or "oncogenetic testing". The development of genetic testing protocols that are primarily to inform therapy (i.e. treatment-focused genetic testing) is outside the remit of the eviQ cancer genetics RC and should be managed by eviQ RCs with cancer treatment expertise (e.g medical oncology RC, haematology RC). Support from the eviQ cancer genetics RCs can be sought for the development of treatment-focused genetic testing protocols. eviQ cancer genetics protocols are guides only.
State- and territory-based genetic testing information
Non-genetic health professionals planning to order genetic testing should liaise regularly with their local or state/territory clinical genetics service or familial cancer centre for specific advice and information.
Ordering the appropriate test
It is ideal that a co-ordinated approach is undertaken to maximise the clinical utility of genetic testing from both a treatment focussed and familial cancer perspective (e.g. if only two genes are relevant from a treatment perspective but a larger gene panel is relevant from a familial cancer perspective, it is preferable that the larger gene panel be ordered upfront).
The ordering clinician is responsible for ensuring that the test they order is the appropriate test for the patient. Copy number variants (CNV’s, where all or part of a gene is deleted or duplicated) contribute to a clinically significant proportion of the pathogenic variants associated with familial risk of cancer. Not all available cancer panels offer CNV analysis. Furthermore, there are certain genes for which comprehensive testing requires specialised technology beyond what is offered by a standard cancer gene panel (e.g. long range PCR for the mismatch repair gene PMS2). Advice should be sought from the local clinical genetics service or familial cancer centre if there is uncertainty regarding this issue.
Online e-learning for health professionals is available from the Clinical Oncology Society of Australia (COSA) Familial Cancer Special Interest Group. These modules provide education about ordering BRCA1 and BRCA2 gene testing in patients with breast or ovarian cancer, but the principles can be applied to testing for other cancer predisposition genes.
It is recommended that all patients who undergo genetic testing provide their informed consent, ideally in writing, in a manner that meets state/territory/hospital medicolegal requirements. Patients should be informed that:
- the results of genetic testing may assist in deciding their current or future health management
- the results of genetic testing can have implications for their biological relatives
- there may be costs associated with genetic tests that are not covered by Medicare (and how much the patient will be expected to pay)
- genetic testing is voluntary and that they can decline or defer testing, and
- potential outcomes of testing might include:
- no reportable variants
- a variant of uncertain significance (class 3 variant, sometimes called an "unclassified variant")
- a pathogenic variant or likely pathogenic (class 5 or class 4) variant identified
- an incidental finding of a variant in a gene (or genes) unrelated to the reason for testing.
An example National Clinical Consent form for genomic testing has been developed by Australian Genomics. NSW Health clinicians should continue to use consent forms specific to that state.
Patients should be referred to their local clinical genetics service or familial cancer centre regardless of the outcome of treatment-focused testing where:
- they require additional specialised genetic counselling prior to or after testing
- a pathogenic variant or likely pathogenic variant is identified
- a variant of uncertain significance is identified, especially in the context of a strong family history of cancer (where family segregation testing may help to reclassify the variant), or
- they have a significant personal or family history of cancer that has not been explained by the result.
Additional information relevant to tumour genetic testing
The following resources have been developed to assist clinicians ordering tumour genetic testing to guide treatment decisions for their patient:
ID 4251 Germline testing in individuals for whom BRCA1 and BRCA2 tumour testing may inform systemic therapy options
ID 4056 Considerations for germline testing for variants identified in solid tumours