Tuesday November 5 2013
The severity of prostate cancer is hard to diagnose
"Prostate cancer test 'could prevent needless treatment'," reports The Daily Telegraph.
The news is based on a conference presentation of research looking at whether a new Prolaris test could tell slow-growing tumours from aggressive tumours among different groups of men diagnosed with prostate cancer.
The Prolaris test is said to work by identifying a distinct "genetic signature" of 31 genes related to how aggressive the cancer is.
The media reports that one of the researchers, Professor Jack Cuzick, said: “Overtreatment of prostate cancer is a serious issue so it's essential that we have an accurate way of spotting those cancers that pose an immediate risk.”
Complications arising from prostate cancer treatment can include erectile dysfunction and urinary incontinence.
According to the press release about the research, the test provides an accurate way of distinguishing slow-growing tumours from aggressive ones, so might be a useful way to predict which men need more urgent treatment.
As this research is yet to be published and peer-reviewed, limited information is available about the study methods and results, so caution should be used when interpreting these findings.
Where did the story come from?
The study was carried out by researchers from Queen Mary University of London and Universities of California and Texas among other institutions and laboratories in the US. According to the press release, the research was funded by Cancer Research UK, Queen Mary University of London, Orchid Appeal, US National Institutes of Health and the Koch Foundation.
The conference abstract and press release are published on the National Cancer Research Institute (NCRI) 2013 Cancer Conference website. The conference is sponsored by Roche. It is unclear from the abstract and press release if the research will be submitted for publication in a peer-review journal. But due to the potential benefits of this test, if proved accurate, it would be surprising if a submission did not take place in the future.
What kind of research was this?
As the study is yet to be published, limited information is available about the study methods. According to the conference abstract, multiple retrospective studiers were carried out that tested the accuracy of a diagnostic test (called the Prolaris test) in detecting different severities of prostate cancer. Other than the description that the studies were retrospective, it is unclear what type of study design was used in these multiple studies.
Randomised controlled trials comparing the diagnostic tool in question (in this case the Prolaris test) with the current "gold standard" diagnostic method (biopsy) are the best type of study design to answer diagnostic research questions.
What did the research involve?
As previously mentioned, little information about the study methodology is provided in the conference abstract and press release, so full details of how the research was conducted cannot be described here.
According to the press release, a new diagnostic test called the Prolaris test has been developed by a group of researchers. This test measures the levels of activity of genes that drive cell division, which is then said to give a measure of how active these cells are by generating a Cell Cycle Progression (CPP) score. The score is then used to determine if the disease is considered to be slow-growing or aggressive. The press release says "high levels of gene expression are suggestive of an aggressive tumour".
The conference abstract reports that the Prolaris test was used to see if it could detect disease among five groups of men:
- Two groups (of 366 and 413 men) who were "managed conservatively" (which means they did not have surgical intervention). It is unclear if these men received any other treatment, or if they were only monitored.
- Two groups (of 366 and 413 men) who underwent surgical removal of part of the prostate (radical prostatectomy).
- One group of 141 men who had received radiation therapy.
How and when the Prolaris test was performed is not described and how the results were analysed by the researchers is also not described. The methodology provided in the conference abstract and press release does not describe what the researchers' main outcome of interest was.
What were the basic results?
According to the press release the "CPP score" (used by the researchers to determine the severity of prostate cancer) is an accurate way of distinguishing slow-growing tumours from aggressive ones. They say this is a challenge that existing tests have been unable to overcome.
The press release adds that the test might be a useful way to predict which men need more urgent treatment.
How did the researchers interpret the results?
Professor Jack Cuzick, study author and Cancer Research UK scientist, is quoted in the press release as saying: "We’ve shown this test is accurate at telling apart these two different tumour types at many different stages of treatment. But we still need to work out how best to use this test to help patients.
"We want to try and shorten the time it takes to get the results and establish how frequently the test needs to be done in order to be most effective at spotting any changes."
Findings reported here are based on those presented in the conference abstract and press release. As the study is yet to be published in a peer-review journal, limited conclusions can be drawn about how well this test works and whether it should be used in routine practice.
Scientific research is often presented first at conferences. It gives researchers a chance to speak about their results and discuss them with their peers. However, the results they present are often preliminary, and haven't been through all the quality assurance processes needed for publication in a scientific journal.
Conference presentations are summarised in very brief “abstracts”, meaning very limited details are available on the study’s methods and results. This makes it difficult to judge the strengths and limitations of the study.
Some of the research presented at conferences never makes it to full publication. This could be for a number of reasons, such as initially promising findings not being able to be confirmed in further tests or analysis, or the research not being accepted by peer reviewers or journal editors. This doesn’t mean that research presented at conferences isn’t reliable, it just means that it’s best to reserve final judgement until the research has been published in a peer-reviewed journal.
Despite these limitations, the study does appear to have some strengths, in that the test was performed across multiple groups of men and in a relatively large sample.
Hopefully more detailed information on the test will be forthcoming and published in a peer-reviewed medical journal. Until that happens it is unlikely that current methods of diagnosing prostate cancer will change.
Analysis by Bazian. Edited by NHS Choices. Follow Behind the Headlines on twitter.