Genetics are key to screening for cancers, oncologist says
Cancer Genetic testing is already helping oncologists screen for cancers and even prevent some from developing. But, how does it work? Professor David Gallagher explains some of the mystery and limitations of the evolving genetic testing landscape.
Cancer is occasionally hereditary, and a number of responsible genes have been identified. One is BRCA2, notably in an Irish family being cared for in St. James’s Hospital.
Breast, ovarian, colorectal and prostate cancers often originate where an individual has inherited ‘faulty’ genes that can’t perform their protective function against abnormal mutations.
In cancer treatment or prevention, there are two core types of genetic testing available to clinicians, each with their own specific purpose:
- Germline genetic testing, which is performed on normal cells, generally obtained from blood or saliva;
- and tumour genetic testing, using biopsies of tumour tissue.
Germline genetic testing
Germline genetics covers our core genetic make-up, with tests predominantly focusing on those with a family history of cancer. This DNA is determined at our conception and doesn’t change until our death.
Tumour genetics, on the other hand, measures alterations to core DNA. It’s the study of how that germline DNA mutates and becomes abnormal in a cancer cell. This is a more investigational field of genetics, using biopsies of tumour tissues and is an area of active research.
Both the study of germline and tumour DNA can aid clinicians in determining which course of action to take in either preventing or treating cancers.
Professor David Gallagher is a Consultant Medical Oncologist and Geneticist at Hermitage Medical Clinic in Dublin, an oncology department providing a wide range of cancer treatments.
He says the tests help him build up a genetic picture of his patients.
“Principally, germline genetics help us identify those that are genetically predisposed to cancer. Once you’ve identified someone as carrying a gene that makes that more likely, you can either screen for cancer or take action to prevent cancer developing.”
Screening for certain cancers, such as ovarian cancer, isn’t always possible. This can mean crude, preventative measures – such as organ removal – as the only option.
Tumour genetic testing
Tumour genetic testing, an area of constant change and evolution, is primarily focused on looking for mutations in certain genes that may allow clinicians to use certain, targeted treatments on an individual patient.
However, Gallagher says this changing area of testing carries its own challenges. Tests don’t yet consistently indicate whether results will predict a response to a treatment that targets a specific gene.
Yet, oncologists often end up prescribing that treatment in the hope that it will.
“We have a lot of targeted treatments available, but we don’t yet always know which specific mutations or alterations those targeted treatments should be used for,” he explains.
“If we can figure that out, then there’s the potentially huge prize of us having more targeted, individualised treatments.”
“As part of its strategic intent in the development of research and innovation, the Hermitage Medical Clinic has signed a collaboration agreement on Genomic Cancer Testing with Sanford Health, one of the largest rural health systems in North America."
"Through this collaboration we are now able to bring patients, in Ireland, a world-class Genomic Cancer Testing service,”
- Eamonn Fitzgerald, Chief Executive, Hermitage Medical Clinic