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Testing patients

by Henry Scowcroft | Analysis

10 July 2007

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Dividing chromosomesSome of you may have seen reports in the news this week about a ‘genetic test’ that can apparently predict whether you’re going to get cancer or not.

Although this sounds impressive, it’s worth taking a closer look at the science behind the story because, as is often the case with cancer news, the headline is a lot more impressive than the reality.

The research the newspapers were reporting on involved a new way of examining a person’s DNA for potentially cancer-causing mutations and variations. The technique is much quicker and cheaper than current methods.

According to news reports, this test will allow doctors to examine a person’s genes and work out their cancer risk. Or – given that our genes determine so much about our lives – whether a particular patient’s cancer is likely to come back, or be resistant to certain treatments.

According to the Daily Express, this means that “millions of cancer sufferers could be saved“.

So – what’s the story?

Currently, genetic tests tend to involve ‘reading’ the whole length of a gene, and then comparing this information to a ‘standard’ version of the gene to look for any differences.

(If, at this point, you’re getting confused with all this talk of ‘reading genes’ and ‘mutations’, have a quick read of the appropriate bit of our ‘Learn About Cancer’ tutorial…)

The new method is more cunning. Scientists have learned a lot from several decades of looking at the mutations that frequently cause cancer. One of the things they’ve found is that these faults tend to occur in just one or two places along the whole length of a gene.

So this new “high-throughput” method exploits this fact, and just examines these small regions of a gene that are often found to be damaged in cancer cells.

This is much quicker – like reading the exact page in a book that contains the information you want, rather than having to read the whole book to find it. Actually, its more like avoiding having to read a whole library, in terms of the amount of information we’re talking about here.

According to the paper, published in Nature Genetics, the researchers analysed 1000 human cancer samples, and looked for mutations in a whopping 238 different genes in each one (although this is still a tiny fraction of the estimated 25,000 genes in each and every human cell).

They found that just under a third of the 1000 samples had mutations in one or more of these 238 genes – which is pretty much in agreement with the results of decades of painstaking research.

As a bonus, they found that several mutations tended to occur together, and even discovered a few new mutations.

So the technique seems to be pretty accurate, and has already given scientists plenty of food for further thought.

But is this useful for cancer patients? Can us ordinary people get our hands on this test?

“Not yet”, is the (sadly inevitable) answer.

The reported ”test” is currently more of a “technique” that allows cancer scientists to press on with their research faster and more efficiently than before.

As is often the case with these things, it’s going to be a long time, and take a lot of work, before it can be used to make predictions about peoples’ health and disease.

This is because, despite all our recent advances, we are still a long way from being able to look at the DNA in a given cell and announce, with any degree of certainty, “this cell will develop into a cancer.”

And we’re even further away from being able to put a time limit on this and say “this cell will develop into a cancer in about X years.”

So, much as this is an extremely promising result for cancer scientists, allowing them to ratchet up the pace of progress a notch or two, it’s not yet a ‘test’ that will give any meaningful information to you or I.

And it certainly didn’t, in our opinion, justify headlines exclaiming ‘THE £25 TEST TO SAVE YOUR LIFE

Here’s the original Nature Genetics paper if anyone’s interested:

High-throughput oncogene mutation profiling in human cancer.