Prostate news article, March 2007
| A NEW SENSITIVE
AND ACCURATE DIAGNOSTIC TEST FOR PROSTATE CANCER
Dr Christiane Fenske, Tom Swallow, Christodoulos Pipinikas This is a report by Dr Fenske of work she and Mr Pipinikas have done in the Medical Genetics department at St George’s University of London (Medical School), in conjunction with Mr Swallow in the Urology Department at St George's Hospital, London. We do not usually duplicate research reports about projects we have helped to fund in this News section but the outstanding results make this an exception. |
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The story....
Here at St George's in Medical Genetics we have been carrying out research
into a test that may be used as an alternative to serum PSA - a test
that is much more accurate and much more sensitive. At the moment,
raised serum PSA levels indicate the need for biopsies - the only
way to diagnose prostate cancer accurately. However, raised serum
PSA levels may be due to other factors, and not to cancer. Therefore,
many biopsies are carried out that may not really be necessary, if
there were a more accurate test - and I am told they can be painful!
Our ultimate aim is to provide a non-invasive test with greatly increased accuracy and thereby to minimize the need for unnecessary biopsies. Also, by making it non-invasive, this would encourage men to go for the test - preferably early on.
The potential....
We have developed a test for prostate cancer diagnosis (quantitative
RT-PCR) whereby a small amount of patient's blood (10 ml) may be
analysed. This incredibly sensitive technique is able to detect a
single prostate cancer cell in the blood sample, against background
of 10 million blood cells. This is done using 'markers' - an example
being a gene - that are switched on or off, turned up or down in
a way characteristic of cancer cells, and different from normal cells.
The degree to which these markers are switched on/off/up/down depends
on the type of prostate cancer and the stage that the disease has
reached. So by measuring these levels, not only are we are able to
diagnose accurately whether a patient has cancer or not, but also
whether the disease will develop quickly or more slowly, and at which
stage of development the disease has reached. This enables tailor
made therapy - helping clinicians to decide which treatment may be
the most suitable for each patient and ensuring its effectiveness.
Patent!....
Following 2 years intensive work with an excellent team and encouraged
by Prostate UK, the research has resulted in a patent which will
enter the national phase in May 2007.
Patients!....
The close relationship between The St Georges' Trust and the Medical
School has provided an excellent base for our work. Together with
the Urology Department in the Hospital (Dr Tom Swallow and Dr Chris
Anderson) we have collected and analysed blood samples from over
600 patients, who have attended the out-patients' clinic.
Processing!....
We have analysed these samples in quadruplet, using over 25 markers.
This has generated enormous amounts of data, which has needed to
be processed. As most people are aware, statistics can be used to
show whatever you want them to show! So we have analysed our results
using a variety of statistical approaches, making sure that what
we see is correct and not because we happen to have used a clever
magic formula. This way we have absolute conviction in the accuracy
of our research.
Potential puzzles?....
We are also conducting very advanced, difficult experiments literally
to count the prostate cancer cells in blood - to find out whether
the differences in marker levels are due to the genetic on/off switch,
or whether they are due to differences in numbers of cells. In addition,
we need to make sure that the differences in marker levels that we
see are due to the cancer, and not due to the inflammation that often
accompanies the disease.
Product!....
We have identified several markers that may be used to diagnose cancer
vs non-cancer accurately. When we carry out calculations, combining
the results, their diagnostic strength is increased even more - to
a point where we can achieve 95% accuracy in correct diagnosis of
prostate cancer vs non-cancer!
Potential developmental stages!....
Markers have their own characteristics, being turned up or down, on
or off at different stages of the disease. Therefore specific markers
will be accurate in early diagnosis, and others will identify when
a cancer changes and becomes metastatic. Combining the marker results
increases their strength and accuracy of diagnosis even further.
Interestingly, just for fun, we added in serum PSA results for the
patients we analysed - there was no difference, highlighting the
fact that the serum PSA test has its limitations.
Prognosis!....
The potential format of the test would be a first screen for cancer
vs non-cancer. To validate the test and to improve the 95% accuracy
of diagnosis, we need to increase patient numbers. Should the diagnosis
be one of cancer, our test will determine how quickly the disease
will develop and therefore, whether to start therapy immediately
or wait. Should the cancer be a slower growing type, the disease
may be monitored on a regular basis, allowing the clinician to know
well in advance when to start therapy. The test will also help to
decide on the best form of therapy. Once receiving therapy, each
patient may be monitored to judge its effectiveness. This may also
include monitoring developments after surgery (radical prostatectomy).
The test is at a point now where will be developed further, with the
aim of getting it into the routine diagnostic environment as quickly
as possible. We will also continue carrying out research into other
markers that show huge promise e.g. for identifying prostate cancer
risk several years before disease onset, markers that indicate successful
surgery.
The ultimate aim is to minimise the need for biopsies and radical prostatectomies,
reducing discomfort and any side effects that these procedures carry,
and hopefully encouraging men to go for testing as early as possible.
I would like to thank Prostate UK for their support in this research - through their generous funding, but also through their encouragement and the motivation they have given to the group.
By Dr Christiane Fenske
February 2007
For another related item in, see the entry for January 2007