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The second bit of good news regards screening and diagnosis of prostate cancer. Cancer Research UK scientists in Cambridge have moved a step closer to developing a simple urine test to show which men are at higher risk of developing prostate cancer.

The story got a lot of media coverage but much of it confused screening with diagnosis, and failed to give enough detail on how effective the test was.

What the researchers have shown is that 30-40% of men of European origin, carry a genetic variant that places them at increased risk of developing prostate cancer. This variant can be picked up in a urine test, which could be done in early adulthood. The lead researcher Dr Hayley Whitaker told me that carrying the variation increases a man's likelihood of getting prostate cancer by 13%.

Of course just having the variant doesn't mean you will get prostate cancer, just as not having the variant doesn't mean you won't get it. So the screening test is of limited value.

Now for diagnosis. The CRUK researchers looked at levels of a protein found in urine called MSMB. They showed that men with prostate cancer are likely to have low levels of MSMB. In a small study they were able to diagnose prostate cancer from urine samples with about 50% accuracy.

That may not sound very precise, but it's twice as accurate as the current method, a blood test which measures levels of PSA protein. That test is accurate in just one in four cases, meaning many men undergo unnecessary biopsies.

The urine test would cut the number of wrong diagnoses, but it would not get rid of them altogether. A trial of 1,200 men is due to finish by Christmas and further studies will be carried out. Perhaps combining the tests, looking for both PSA and MSMB levels, will increase the accuracy.

Talk of a universal screening programme for prostate cancer is premature. Both the screening and the diagnostic tests are flawed, but they are nonetheless steps in the right direction for a condition that gets limited attention and funding compared to breast cancer.

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Let me give you two scenarios. First the wildly optimistic: that thirty years from now we will look back on today as one of the most significant in the history of modern medicine; the day everything began to change. The second is pessimistic: that in the near future we will see that embryonic stem cells did not live up to the hype, dashing the hopes of patients.

The truth is no-one can be sure which of the above will come true, or something more prosaic but still useful in terms of tackling disease.

So much has been written about embryonic stem cells that it seems hard to fathom that the first officially approved human trial is only now underway. To supporters they represent the best hope for repairing organs and curing disease.

The dream is that - many years from now - you will be able to use stem cells to repair a damaged heart, cure diabetes and restore function to patients with spinal cord injury.

We know that adult stem cells work, for example bone marrow transplantation. There have been using adult stem cells.

But until now, human embryonic stem cells had never been injected into a patient - at least not in a licensed trial.

Now, , a biotech firm in California has announced that it has begun a safety trial where embryonic stem cells will be injected into half a dozed patients who recently suffered spinal cord injuries. The first patient, whose details have not been released, has already had the treatment. The amount of cells injected will have been tiny because this "first in man" trial is simply there to test safety. Only if no harm is done will increasingly bigger doses be given, and only then will scientists know whether it can help restore some function.

In animal trials, paralysed rats did regain movement. But, as many trials have shown in the past, that does not assure success in humans.

Not even the most enthusiastic supporters of this research are suggesting that paralysed patients will be walking again as a result of this study. But even a minor improvement in function would be of huge benefit.

from University College London said this is an exciting moment: "It's important because these are embryonic stem cells - the most potent we have available for therapy. They can make all the 200 cell types in the body and they can make them in quantity. If this therapy is successful, and that might take five to ten years, then we will be able to manufacture it in the scale we need."

The trial will spark controversy in the United States. Critics argue that it is wrong to use cells derived from human embryos because they would have been destroyed in the process, when they are still smaller than a pinhead. In one of his first actions as President, Barack Obama lifted many restrictions on federal funding of embryonic stem cell research when he came to office last year. There is currently a legal dispute over federal funding which is going through the US Court of Appeal.

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So I hope that embarrassment, or even trepidation, will not prevent anyone from taking part in the new national screening test for bowel cancer just announced. This involves an instrument called a .

It is a long thin tube which has a tiny camera, lights and even tools on it. Inserted in the bottom, it allows medical staff to have a look at the lower part of the bowel. They can remove any pre-cancerous growths. About 75% of bowel cancers are detectable this way.

The government announcement follows the earlier this year. 40,000 people aged 55-64 had the test and were followed up for 11 years. The incidence of bowel cancer was cut by 33% and the death rate by 43% compared to a control group who were not screened.

The screening programme will take five years to be rolled out across England, but by the end of that time all adults aged 55-64 are likely to be offered the one-off test.

There were a few nervous looks in the newsroom when my report on what the test involves went out on TV. So I'm here to reassure you from personal experience. I had a "flexi-sig" more than a decade ago. It did not hurt, but ok, it was a bit embarrassing. I seem to remember at least one medical student being present, but hey, they have to learn somehow. So if you are offered the test, talk it through with your doctor. But don't let embarrassment prevent you from having a procedure which could save your life.

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