This release describes a preliminary study of a new proposed blood test for lung cancer that’s going to be presented at an upcoming scientific meeting. The release frames the test as a potentially useful screening tool for detecting cancer in people who seem otherwise healthy. However, that’s not the population that the researchers studied and reported on — the study results came from individuals known to have (or not have) cancer. The test’s ability to correctly identify cancer in a seemingly healthy population whose cancer status is unknown is an entirely different matter — and one that must be assessed in subsequent studies to determine how useful the test may or may not be for screening.
Other concerns include the lack of cost information and no mention of the harms from possible false positives or negatives. While the release seems more targeted to potential investors than the general public we still encourage releases to include relevant information on benefits, potential harms and clear descriptions of the evidence.
Lung cancer can be a vicious disease and many advanced cancer patients are given a poor prognosis. Part of the challenge of improving outcomes is earlier detection, so a potential blood test that could screen for the disease would be advantageous. But this work is very preliminary and its difficult to assess its potential value. Readers, particularly lung cancer patients and their families, may derive false hopes from the way the test is pitched in the release.
There’s no discussion of cost. While we understand that this news release is touting a product in the early stage of development, it would still be beneficial to give readers some idea of the projected cost.
The release touts this as a new screening tool to detect lung cancer, and the release provides numbers on both the specificity and sensitivity of the test, indicators of how good the test is at detecting disease and at ignoring disease-free individuals.
While that’s a good start, there are also big problems here. The release claims that the test will assist with the early detection of lung cancer in people who are seemingly healthy. And yet the data referenced in the release came from patients already known to have lung cancer and either current or former smokers who didn’t have lung cancer — not a general population of at-risk people whose lung cancer status is unknown. This is a crucial distinction. Testing in a much broader group is needed to determine how effective the test would actually be when used to screen healthy people in practice.
There’s no discussion on the potential harms of the screening test. False positives can result in invasive and potentially dangerous procedures and false negatives can give a false sense of security, which can prevent or delay other interventions such as smoking cessation.
The potential for false positives and negatives are very high for this blood test, according to the results presented in the release:
In particular, in the non-small-cell lung carcinoma group (n=162), the most prevalent type of lung cancer affecting about 85% of lung cancer patients, Lung EpiCheck was able to identify correctly approximately 70% of patients. With a correct identification of 59% of stage I patients, 77% of stage II, 76% of stage III and 83% of stage IV patients.
Of note, low dose CT scanning for lung cancer has reported false-positive rate that is lower than the rate reported for this blood test — and yet according to recent real-world experience, it still returns some 2,749 false positives for every lung cancer death averted.
In the study, the test used blood from either known lung cancer patients or current or former smokers known not to have lung cancer. The researchers didn’t prospectively look at individuals whose lung cancer status wasn’t known — which is a much tougher and more realistic assessment of how the test would perform in practice. Moreover, the release notes the research will be presented during an upcoming scientific conference. It has not yet gone through peer review and been published in a scientific journal. The authors’ conclusions state that this test “could” improve diagnosis in the future. That’s conjecture at this point.
Finally, the usefulness of a screening test depends upon the prevalence of disease in the population being tested. If the population had a 1-in-10 chance of getting lung cancer, the likelihood of a positive result being cancer is only about 10%. But in this study of current lung cancer patients and current and former smokers, the prevalence of lung cancer is higher at 28% (1-in-7), making the likelihood that a positive test means cancer is about 82%. (See our primer — Understanding medical tests: sensitivity, specificity, and positive predictive value — for more details on these calculations.)
In the real world, the number of people who develop lung cancer is lower than in these examples, which is why screening even with a test much more accurate than this one would likely return a prohibitive number of false-positive results — something we addressed in this recent analysis of a different experimental blood test for lung cancer.
The release doesn’t engage in disease-mongering. Lung cancer is widely understood to be a potentially devastating disease. The release provides some context on the prevalence of lung cancer worldwide.
There is some concern that people at very low risk might be encouraged to ask for the test based on the positive report on this preliminary test.
It’s clear from the release that the research was supported by the company that makes the proposed lung cancer screening tool. Neither the release or abstract provide information on whether or not there are financial conflicts of interest between the investigators and the company that makes the test.
The release notes alternatives to the blood test include the standard CT scan.
Currently, early stage lung cancer can be detected either accidentally, when testing for other conditions, or by using low-dose CT scans, which are costly, carry associated risks such as high radiation, and are employed only for a very high-risk population.
We’ll give this a marginal satisfactory for giving readers a hint that the test is not yet available when it says the company is “looking forward to begin extensive clinical trials in the US, Europe and China next year, in order to get the test to the market as soon as possible at an affordable price.” That tells us that the test is likely years away from being commercialized — if ever.
The release claims the test is a novel detection method but there are many other screening tests — often called “liquid biopsies” for lung cancer at various stages of development.
The release uses exaggeration to describe the results. One example:
Such promising results combined with the simplicity of the test, could allow us to detect lung cancer at the early stages and hence improve 5-year survival from about 15% to about 50-70%. This will offer significant added value in the fight against lung cancer.
That’s pure conjecture.