For those of us with a strong family history of breast cancer, new blood cancer tests pose an interesting conundrum.
Should we pay up and go to a private service to get one of these “liquid biopsies”, which are still a long way from being freely available on the NHS? Or should we stick with existing screening methods, such as the annual mammograms I already have?
There is no doubt that we have entered a new era in cancer detection, but, while it is obviously brilliant if it saves lives, it is still in the early stages and has not yet been rigorously tested in large-scale trials.
A “liquid biopsy” is a blood test that detects signs of cancerous tumors.
A “liquid biopsy” is a blood test that detects signs of cancerous tumors. Some can identify more than 50 different types of cancer.
The tests could be an alternative to annual mammograms for those with a family history of breast cancer.
One of these is the Galleri test, which is currently being trialled on the NHS. It looks for changes in bits of genetic code (cell-free DNA, cfDNA) that leak from tumours into the bloodstream.
It can help identify more than 50 different types of cancer (based on the results reported so far, the test is currently not as good at detecting stage 1 cancer, where the cancer is small and has not spread to other parts of the body; it is more reliable with later-stage tumors).
There is also TruCheck, a test launched privately in the UK in late 2022: it detects microscopic circulating tumour cells (CTCs), rather than genetic material that has leaked from tumours.
A 2021 study found that CTCs can help diagnose solid organ cancers: CTCs were found in 92.6 percent of samples from 6,025 people with symptoms who were later diagnosed with cancer (some of the researchers had been employed by Datar Cancer Genetics, the company behind TruCheck).
According to a study published in the journal Cancer Cytopathology, the TruCheck test has been shown to have a sensitivity of 88 per cent for detecting solid tumours, including breast cancer. “These tests are an exciting step forward in terms of cancer detection,” says Dr John Pettit, an NHS GP who also works at Goodbody Clinic, one of TruCheck’s UK providers.
“They cannot yet replace traditional screening tests, but they could be a complement. Mammograms are harder to read in younger women because their breast tissue is denser. Some types of cancer can also be difficult to detect with a mammogram.”
These include, for example, lobular tumors, which grow not in a round mass but rather like a spider web or mesh. The ability of screening mammograms to detect cancer in women who have no symptoms such as a noticeable lump ranges from 30 percent in women with especially dense breast tissue to 90 percent, according to studies.
“Unlike mammography, TruCheck appears to be proving to be a highly accurate, noninvasive blood test that involves no radiation exposure and is far less uncomfortable for the patient,” says Dr. Pettit.
However, it is important to note that the amount of radiation from each mammogram is low, similar to what we might be exposed to on a long-haul flight.
And Dr Liz O’Riordan, a retired breast surgeon and author of The Complete Guide To Breast Cancer, urges caution, saying: “The aim of screening is to detect cancer at an early stage, where there is evidence that if treated earlier, it will save lives.”
There’s a lot of evidence to support screening tests like mammography and Pap smears, she says, “but, in contrast, this blood test hasn’t been thoroughly tested, meaning we don’t yet understand all of its implications and whether it will help reduce cancer deaths.”
The most comprehensive version of TruCheck screens for 70 different types of cancer and is priced at around £1,199.
There is a cheaper option (£449) that only looks for circulating tumour cells in the breast (the test cannot detect cancers of the blood or lymphatic system, as only solid organ cancers produce CTCs).
One of the tests, Galleri, is currently being trialled on the NHS. Another, TruCheck, is due to be launched privately in the UK in 2022.
In addition to the lack of long-term research, another consideration is the anxiety involved in getting tested, as I know after being offered the opportunity to try the TruCheck blood test myself.
My two older sisters developed breast cancer (one at 38 and the other at 42) and my grandfather had prostate cancer (another risk factor). I am 45 years old and have been getting annual mammograms since I turned 40.
After a pre-test counseling call with Dr. Pettit, which included explaining how the test worked, a nurse came to my home to draw my blood; then a very anxious wait began.
Results are usually available within two to three weeks. They are sent by email, whether negative or positive, and the doctor makes a follow-up call if they are positive.
You can purchase the test without a doctor’s recommendation, although you must be over 40 years old and not have had any previous cancer diagnosis.
But Dr. Pettit says, “This is an evolving science and these tests should only be offered under appropriate medical supervision, by a physician with experience in the test and the research behind it.”
She added: ‘Positive results should only be interpreted by an oncologist as they can have various implications that must be managed appropriately, in order to adequately address any anxiety the patient may feel.
Mammograms may be difficult to read in younger women because their breast tissue is denser.
Liquid biopsies can offer “short-term reassurance or a chance of early detection”, according to NHS GP Dr John Pettit
‘Most GPs are still in the dark about the progress of these tests, but if someone with a positive result opts for NHS care, Goodbody provides all this information to their GP and asks them to be referred to the local NHS ‘two-week wait’ cancer service for advice and further testing.’
But as Dr O’Riordan, who has been treated for breast cancer, says: “If you don’t have urgent warning symptoms, you may not get seen on the NHS after two weeks of waiting.”
‘How many tests, procedures and anxiety about scans will people who test positive and possibly find nothing have to go through?’
The risk of false positives (a result indicating a certain condition exists when it does not) is a major concern for many in terms of this new technology.
Dr Pettit admits that false positives may be a cause for concern: “We don’t know yet, but it’s possible that some living cancer cells may never become a clinical problem.
“However, TruCheck’s false positive rate currently appears to be better than that of mammography, the PSA blood test for prostate cancer and the stool test for bowel cancer,” he says.
After two weeks of waiting, the email with the results arrived mid-morning. I was very nervous (opening it gave me a migraine), but I was deeply relieved when I read the results and discovered that no CTCs had been detected.
However, as Dr O’Riordan points out, it doesn’t prove anything. “Both false positives and false negatives are a problem,” she says. “This test can detect cells that don’t mean anything or miss cells, so people may be falsely reassured that they don’t have cancer and stop getting tested and monitored.
“We don’t know what it means to have CTCs in your blood long-term, which is another reason to take this with caution.”
He added: “These blood tests have future potential, after the trials have been repeated and it has been shown that this detection method has an effect on the results.
“What worries me at the moment is that this is taking advantage of the rich. It is recommended to repeat the test every year, which would be very expensive.”
Dr Pettit says: “The test will be cheaper and more widely available, but for now it may offer short-term reassurance or an opportunity for early detection for people with a strong family history of breast cancer or a known, defined genetic risk.”
I feel reassured by the results, but after speaking to Dr O’Riordan, I’m not sure I’d be getting screened privately again. Screening is certainly a future mainstay of cancer detection, but I’ll continue to get my annual mammograms on the NHS for now.