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As science develops, GHA looks to gene testing for more cancers

Dr Terri McVeigh, the GHA's Visiting Consultant Cancer Geneticist from the Royal Marsden. Photo by Johnny Bugeja.

When patients are diagnosed with breast cancer, genetics can hold the key not just to treatment but also for loved ones who can seek out preventative treatment early. As the science develops, this could be offered to more cancer patients.

Dr Terri McVeigh is the GHA's Visiting Consultant Cancer Geneticist from the Royal Marsden, who analyses the data and advises families during this difficult time.

She holds clinics regularly and was recently in Gibraltar raising awareness of breast cancer and the vital role genetics can play.

Her role is to aid research, analyse data and inform patients and families of treatments and preventative care.

Dr McVeigh meets over 120 GHA patients annually, advising on difficult decisions during a tumultuous time in their lives.

And the message is that when it comes to cancer, the more testing, the better.

More gene testing means better care, screening, treatment and access to preventative surgery.

This is why the GHA offers a broader panel of tests, meaning Gibraltarians have access to more testing than in the UK.

"The clinic is growing and growing, once you identify a genetic risk factor in a family, every family member will need testing thereafter," Dr McVeigh said.

She added that with every new diagnosis, family members may need to be tested but also that, when the clinic opened, she needed to analyse historic cases and families.

Although the prevalence of cancer locally, she said, is similar to the UK, local families who at first glance seem unrelated can share common ancestry and the same alterations in their genes.

The more she tests, the more options are available for patients.

Dr McVeigh began visiting Gibraltar in 2018, and every six months holds four clinics locally, as well as virtual clinics every Wednesday.

"We're hoping to expand, we've been testing a lot in patients who have had breast cancer, but we need to offer the same services to people with other types of cancer as well," she said.

She said genetic testing can be done with most cancers, although with other cancers diagnoses are more likely due to environmental factors rather than genetic.

"Cervical cancer tends to be environmental, but bowel cancer certainly has a big genetic component, cancer of the womb has a big genetic component as well, pancreatic cancer [too]," she said.

She hopes to start testing as broadly as possible, particular with patients diagnosed at younger ages who are more likely to have a genetic basis for their cancer.

With ovarian cancer, for example, one in five patients are very likely to have an underlying genetic risk factor.

"Regardless of family history, we would offer testing to those individuals," she said.

"With breast cancer, we are a bit stricter, but that's something that's probably going to change in the future. I suspect we'll get to a stage when we'll be offering it to everybody as testing becomes cheaper and more easily accessible."

Currently, testing is restricted to people who have a strong family history and are diagnosed under 40.

Dr McVeigh began her career as a breast surgeon and then studied a PhD on breast cancer genetics.

"My interest in breast cancer predated starting medicine because my mum was diagnosed in her 30s," she said.

"She's alive and well and great, thankfully, but it’s kind of always been in our family. My sister did a PhD in breast cancer genetics as well, so it’s very much a family affair."

Dr McVeigh and her sister have teamed up on research studies in the past.


A person has around 20,000 genes but, Dr McVeigh said, currently scientists only know what 7,000 of these genes do.

There are 250 genes that are relevant for cancer risk.

Genes BRCA1 and BRCA2 can cause breast and ovarian cancer.

Everyone has them, but what scientists and doctors are looking for is alterations in these genes.

An alteration in these genes can confer a moderate risk of breast cancer.

In the GHA, testing is offered for 14 genes which are associated with a moderate or high risk of causing breast cancer.

BRCA1 and BRCA2 are the most common, with one in 380 people carrying the alteration in BRCA1, and one in 277 people in BRCA 2.

"If you have Ashkenazi Jewish [heritage], there’s a one in 40 chance you carry an alteration in one of those genes," Dr McVeigh said.

"If you are diagnosed with breast cancer before the age of 40, there is a one in 10 chance that you carry an alteration in one of those genes."

Around one in 700 people have an alteration in PALB2 gene, which is associated with a high risk of breast cancer.

"The difficulty with those genes is you can't tell by looking at somebody if they carry an alteration, the only way you can tell is by doing a genetic test," she said.

There is also the PTEN gene alteration that is more visible, which patients have larger than average head sizes, and this alteration can cause cancerous and non-cancerous growths.

Dr McVeigh said that, typically, a GHA patient will be tested for more than one gene alteration and every child of someone with an alteration has a 50/50 chance of inheriting the same gene alteration.

This is equal for both men and women, with men who inherit the BRCA1 or 2 alterations more likely to develop prostate and male breast cancer.

Gene testing is essentially a blood test, where DNA is extracted from blood cells.

Gibraltar's samples are sent to a lab in London and then another in America where the testing takes place.

"What we are looking for is, if you think of genes as being words, we're just checking for spelling mistakes," she said.

"The whole gene is laid out and we're looking for subtle changes in the 'letters'."

The process takes around eight weeks due to its complex nature.

"If you think about doing spell checks on a word document, that's easy because we're used to looking at words and we know what spelling mistakes are," she said.

"But genetic diversity is such that the average healthy person has about five million 'spelling mistakes' in their genome."

Dr McVeigh explained that deciphering which genes are potentially harmful is a complex process.


If Dr McVeigh finds that a patient carries a cancer-causing alteration in their genes, she will advise them on preventative care or different cancer treatments.

For preventative care, Dr McVeigh said she recommends more frequent screening, and in some circumstances, she may advise for a mastectomy or ovarian surgery.

"Gibraltarian patients tend to be much more proactive about their health so a lot of people will opt to have risk-reducing surgery more often than people in England," she said.

She described how, for someone with the BRCA1 gene alteration, the risk of developing cancer is between 60 to 90%.

If the patient undergoes a double mastectomy this risk drops to less than 5%.

Any patient deciding to have a mastectomy needs to travel to the UK as this surgery is not available in St Bernard’s Hospital.

The risk-reducing ovarian surgery is available in Gibraltar.

For cancer treatment there are 'PARP inhibitors', a drug that works against BRCA-related cancers.

She said gene testing can have "significant implications" with how cancer is treated as BRCA-related cancers respond differently to treatment.

She added that, for patients who don't want to pass on gene alterations, there are techniques to prevent this, but this is more so for those who are very high risk.

Through pre-implantation genetic testing, parents who undergo IVF can prevent these alterations from being passed on.

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