A revolutionary new blood test could significantly advance our capacity for detecting cancer in its early stages. CancerSEEK, developed in John Hopkins University, could improve detection methods and consequently reduce mortality rates.
Cancer is often a treatable condition. However, in many cases, it does not display symptoms for many years. As a result, a number of cancer cases are not detected until the later stages of the disease when it is not easy to treat, if it can be treated at all.
A large amount of cancer research is dedicated to treatments that do not seek to cure the condition but to prolong the lives of those with terminal cancer. These treatments are often only marginally beneficial, sometimes prolonging the life of the individual only a few weeks. At most the effect of these medications is commonly gauged in months, rather than years.
Newer treatments can enter a six figure price range whilst only showing slight increases in survival time compared to older, cheaper medicines. An editorial in the British Medical Journal (BMJ) criticises this practise as ethically questionable. Many individuals with terminal cancer will pay whatever it takes for those few extra weeks.
The number of deaths due to cancer is declining. In the United States figures indicate a 25 percent fall between 1991 and 2014. This reduction in mortality rate was primarily attributed to advancements in early detection methods. In many cases tumours may be removed entirely by surgery if detected early enough. If the cancer has not spread the chance of remission is relatively low, and can be reduced further through therapies such as radiotherapy, chemotherapy and immunotherapy.
CancerSEEK, a revolutionary blood test
CancerSEEK is, conceptually, a standard blood test capable of detecting sixteen genes and eight proteins associated with tumour cells. Cancerous cells secrete traces of these proteins into the bloodstream, allowing for detection and therefore diagnosis. If a person tests positive for one of these genes or proteins, follow up tests can then establish if the person has cancer.
The CancerSEEK test has been trialled in the detection of eight different cancer types. Early results suggest it can detect cancers originating in the ovary, liver, stomach, pancreas, oesophagus, colon, lung and breast. This is a broad range of cancers with which to begin trials, covering many of the most common forms of cancer.
Initial trials were performed on 1,005 patients with non-metastatic, clinically detected and confirmed cancers. Results were promising, showing an average detection rate of seventy percent for the eight cancer types. The detection sensitivity ranged from 69 percent to 98 percent for the five cancer types (ovary, liver, stomach, pancreas, and esophagus) for which there are no screening tests available for average-risk individuals.
The absent 30 percent of subjects who were not detected could likely be explained by the presence of other cancer causing genes. While the blood test currently encapsulates sixteen genes, there are numerous others that can cause cancer that will not be detected by the blood test. However, for an initial trial, a seventy percent detection rate is fairly successful.
Success rates varied considerably, however, between cancer types. Only 33% of breast cancer cases were detected but the test had an accuracy rate of 98% when detecting ovarian cancer. Some experts have stated that the test must first be improved in order to be successful as a broad spectrum cancer detection method. This would likely involve the inclusion of more genes commonly linked to tumour growth.
Currently the test is undergoing trials in a general population group of 10,000 individuals in order to assess its capacity to detect undiagnosed cancers. The test will also allow the establishment of the rate at which the test generates false positive results. Some inflammatory conditions can cause elevated levels of the same proteins picked up by the blood tests. This could lead to cancer free individuals to be diagnosed.
The test will also need to increase its level of sensitivity to the genes and proteins detected. Early stage tumours release less of the detected proteins than later stage tumours. Without an adequate level of sensitivity this could allow early stage tumours to slip under the radar.
The importance of early detection
In the UK around one in four cancers are diagnosed through emergency admission to hospital. At the point that symptoms are apparent the cancer is usually in its later stages. Survival rates of late stage cancer are significantly lower. This is due to the initial tumour fragmenting and spreading throughout the body, referred to as metastasis.
Metastatic cancer is described as being the stage of cancer in which the initial tumour is no longer a solid mass. Cancerous cells from the initial tumour site break away, travelling through either the bloodstream or the lymph vessels to other locations in the body. In the bloodstream, these tumour cells have access to the entire body. Some may settle in other areas or organs of the body, forming new tumours.
This presents further complications to treatment. Surgery may be an option to remove the initial tumour, but the location of new tumours is highly variable. The location of potential new tumours is dependent on the location of the original tumour, though can be present almost anywhere in the body. Due to the process by which they move from the bloodstream, avoid immune detection and begin replicating again, the tumour cells may not be identical to those in the original tumour, further complicating treatment.
In metastatic cancer chemotherapy is the standard treatment. The survival rate for those with metastatic cancer is often very low, though varies depending on the initial cancer type. In metastatic breast cancer for example, the five year survival rate for stage four (metastatic) breast cancer is as low as 22 percent. By comparison, stage three (pre-metastatic) breast cancer has a survival rate of 72 percent. During the initial stages of cancer, stage two survival rate is 90 percent. This is a clear indicator of the importance of early stage detection.
On the other end of the spectrum for survival, stage 4 testicular cancer can show a survival rate as high as 80 percent. Breast cancer typically has a higher mortality rate upon reaching the metastatic phase due to the close proximity of a number of lymph nodes. This gives cancerous cells access to the lymph system, and so a greater capacity to spread throughout the body.
Implementation, and its implications
The impact this new test could have on cancer mortality rates is dependent upon improvements to its early stage detection, then its implementation.
The vision of one of the test’s creators, Dr Cristian Tomasetti, is “a blood test we could use once a year”. The blood test could potentially be used as a yearly test for those above an age limit, so as to restrict its use to those more at risk of developing cancer.
This is not an extreme vision. Being a simple blood test the detection method is non-intrusive, and is not time consuming for doctors to perform. This would provide a simple means to assess a large portion of the population.
The creators are also intent on developing the test to be as economical as possible. Current projections from the creators place the cost of the test at around $500 USD per patient.
Currently, only at-risk groups of people receive regular cancer check ups. This includes those with a family history of cancer, or underlying genetic conditions predisposing an individual to cancer.
Should the CancerSEEK test prove effective, it could provide a cost efficient means to assess far larger groups of people. This would, in theory, greatly improve diagnosis rates at far earlier stages. This could see the mortality rate of cancer fall further, as significantly more people would be treated during the early stages of the disease.