Blood test for early cancers
A new blood test may have the potential to detect a tumour before it arrives, according to a recent article in the Eureka scientific supplement from The Times. As part of a special edition exploring the future of cancer treatment, the magazine outlined the principles behind the EarlyCDT-Lung test, which looks for an immune system response to the development of lung tumours.
While several factors contribute to cancer being a killer, the speed and accuracy of diagnosis are seen to be major factors in determining an individual’s chances of survival. As such, the article speculates about the options earlier detection might provide in the future and whether similar blood tests could be used to screen for other cancers. The test has been developed by the company Oncimmune, which is affiliated with the University of Nottingham.
Does earlier diagnosis of lung cancer mean longer survival?
The rate of survival for people with lung cancer is low, with Cancer Research UK estimating that less than 10% of adults with lung cancer survive five years beyond their diagnosis. People who are diagnosed at the earlier stages of lung cancer have longer life expectancies than those with more advanced lung cancer. For example, 58-78% of people with the earliest stage (stage 1A) of the most common type of lung cancer (called non-small cell lung cancer, NSCLC) are expected to live for five years or longer. In contrast, only 2-13% of people diagnosed with the most advanced stage of NSCLC (stage 4), where the cancer has spread, are expected to survive for five years or longer.
Cancer Research UK says that the reason that overall lung cancer survival rates are low is because most cases (over two-thirds) are diagnosed at a later stage in the disease, when treatments are no longer able to cure the condition. The charity reports that if more lung cancers were diagnosed earlier, survival rates would be significantly improved.
What are the symptoms of lung cancer?
The symptoms of lung cancer are:
- persistent coughing
- changes in a long-term cough
- being short of breath
- coughing up phlegm (sputum) with signs of blood in it
- aches or pains when breathing or coughing
- loss of appetite
- tiredness (fatigue)
- weight loss
Often, symptoms do not occur until the cancer is relatively advanced, and has spread through much of the lungs or to other parts of the body.
How does the test work?
The test works by detecting antibodies that the body’s immune system has produced in response to proteins produced by cancer cells. The theory is that testing for these antibodies can detect lung cancers before they become symptomatic or large enough to be detected by conventional scans.
How well does the test work?
One recent study, published in the peer-reviewed journal Annals of Oncology, assessed the performance of the test in 655 people with lung cancer (cases) and 655 people without cancer (controls) who had been matched in terms of age, sex and smoking history. This study found that the test correctly detected 34-37% of lung cancers, and correctly identified 90-91% of people who did not have cancer. This means that the test did not pick up 63-66% of lung cancers in this sample, and that around 9-10% of people who did not have lung cancer tested positive.
The Times reports that further research on the test is to be presented at the American Society of Clinical Oncology meeting in Chicago this month.
Does the test work for other kinds of cancer?
The story in The Times reports that the tests “can pick out breast cancer markers up to four years earlier than a mammogram might indicate a suspect nodule”. They also say that similar blood tests for ovarian, upper stomach, colon and liver cancers are planned. For each of these cancers the tests will have to be assessed to find out how well they work: primarily, how many cancers they detect, how many they miss and how many false positives they produce.
If the test is shown to perform well as a means of cancer detection, then researchers will have to go on to show that using the test can result in improved clinical outcomes for patients before screening programmes could be considered.
Will blood testing for lung cancer be introduced soon?
The Times reports that the EarlyCDT-Lung test will be available in the UK by 2011. The newspaper says that the test is initially being made available in private healthcare groups, and will cost about £209.
Before the test could be used in the NHS, the evidence regarding the balance of benefits and harms of the test would need to be considered, and it would be important to see whether the screening test improves outcomes when used in real life clinical practice. The best way to establish this would be through randomised controlled trials comparing screening against usual practice.
Speaking to The Times, Professor Sir Mike Richards, the National Cancer Director of the Department of Health seemed enthusiastic but rightly cautious about the potential benefits of the test: “Has it yet been proven to the extent that we would want to extend it to a screening programme? Not yet. But now that the test is shortly to become available [privately] we have to think about doing a wider programme to show that it can save the lives as we hope it might”.
It is also worth remembering that other ideas for lung cancer screening, such as frequent screening with chest X-rays, have seemed good at the time, but have later been shown to be potentially harmful. A systematic review showed that deaths from lung cancer were actually increased by 11% in the group frequently screened using X-rays. This suggests that a cautious, well-researched approach to the introduction of such new screening technologies is needed. The potential harms of screening tests include the risk of false positives, which can lead to a person undergoing unnecessary investigations and psychological distress.
Such advances in diagnostic techniques are important in helping to improve our ability to detect cancer early. However, as for all medical interventions, the potential benefits will need to be weighed up against the potential harms, and the test only offered in circumstances where the balance suggests an overall benefit.
What can I do to avoid lung cancer?
The main risk factor for lung cancer is smoking, so the best way to avoid lung cancer is to stop smoking.
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