By Kelli Gallacher, University of Bristol
It may only be early in 2018, but we have already been treated to some exciting science news. Last week, a study published in Science described a blood test that is able to detect proteins and genes that are characteristic of eight common forms of cancer; ovarian, lung, breast, liver, stomach, pancreatic, colon and oesophageal. This could have a huge impact in how we diagnose cancer – but how far have we come and how soon can we see the test in practice?
A brief overview of cancer screening
The benefits of diagnosing a disease early have been appreciated for over a century. In 1861, British physician Horace Dobell proposed the use of laboratory tests to discover the ‘earliest evasive periods of defect in the physiological state’. As laboratory techniques and technology have developed throughout the 20th and 21st centuries, we have been able to see improvements in diagnosis and treatment.
In the United Kingdom, the NHS already has well established screening programs that can pick up signs of some of the most common cancers; breast, bowel and cervical. These have proved extremely beneficial to patients, as it is known that catching these cancers early can improve chances of survival.
It is now believed that 1 in 2 people will develop cancer at some point in their life. So, at first glance, it may seem confusing why screening is not offered for more types of cancer. However, Public Health England (and other regulatory bodies) state a number of criteria for screening, which include; the occurrence of the disease and the possibility of a simple (and safe) testing procedure.
Consequently, the idea of a simple and universal cancer test is considered a ‘Holy Grail’, which many research groups have dedicated their time in pursuit of.
What is the CancerSEEK test?
The team at Johns Hopkins University in the US reported a blood test that detects proteins and genes which are characteristic of certain cancers. As tumours grow, they sometimes release some of this material into the bloodstream.
The researchers looked at blood samples for changes (mutations) in 16 different genes that are known to be affected in cancer, and 8 proteins that are often released by cells.
Initial tests involved patients already known to have cancer. Out of the 1,005 patients, 70% of their cancers were detected. However, the origin of their cancer could not always be pinpointed.
How could this improve cancer diagnosis?
Five of the eight cancers detected with this test currently have no dedicated screening programme, so the overall number of early diagnoses could increase, which in turn could improve survival rates.
The blood test is cheap to carry out (approximately £360 per patient) and is less invasive than some procedures, such as a cervical smear or a colonoscopy.
It is suggested that the test could be carried out by doctors during routine check-ups, which could increase the amount of people being exposed to screening – uptake of some current procedures is poor as patients are sometimes put off by the process or unaware of its importance (for example, in the UK, only 50-58% of people eligible for bowel screening take up an invitation).
How excited should we be about this news?
Whilst the results are exciting, it is still early days. You may have read some stories in the press that seem to gloss over some of the very important questions that need to be answered before the test can be taken into a ‘real world’ setting.
Currently, the study has only used blood samples from patients who have already been diagnosed with cancer. If a patient has a more advanced cancer, the amount of tumour-specific proteins and genes in their blood may be higher and easier to detect.
The success of the test also appears to vary depending on the type of cancer – 98% of known ovarian cancers were detected, but only 33% of breast cancers. There are worries that a patient may be told they have cancer when they don’t (known as a ‘false positive’). An incorrect diagnosis could cause unnecessary anxiety for a patient and lead to potentially harmful treatments.
The next stage of the study will involve blood samples from patients without cancer, which is an important step in assessing the effectiveness of the test. If the results can be replicated in these patients, we can then start to think about taking the test into the general population.
There is still a lot of work to be done, and we may not see the test in practice for many years, but it cannot be denied that the CancerSEEK test has huge potential.
I am an MRes Medical Sciences graduate, currently working in the Cancer Epigenetics Lab at the University of Bristol. I am interested in how inhibition of PRMT5 could be beneficial in the treatment of neuroblastoma, a childhood cancer. Outside of the lab, I dabble in science outreach and communication and often annoy my friends by talking about how amazing the human body is. You can find me talking about science on Twitter – @grlwithapipette