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Thursday, 19 April, 2001, 15:17 GMT 16:17 UK
Gene testing: who benefits?
genetic testing
Genetic testing is to be extended
Geneticists say they are likely to have identified many of the genetic mutations linked to cancers and other illnesses within the next decade.

This raises a troubling prospect for scientists and ethicists - who should be tested, and for which conditions?

And there are fears that pressure to use the technology to help insurers penalise those at higher risk of illness would be irresistable.

A spokesman for Breakthrough Breast Cancer said: "Our concern has always been that the added risk of exclusion from insurance and its potential consequences of being able to obtain a mortgage, own property or assist themselves and their families when help is most needed, acts as a strong deterrent to women who would most benefit from testing.

"With this in mind, the support from the Government for a potential moratorium by on the use of genetic testing by the insurance industry is a very positive step."

Less certainty

At the moment, insurers can ask whether for the results of a test for Huntingdon's disease, a progressive, disabling and inevitably fatal disorder.

However, a positive genetic test for Huntingdon's predicts with 100% certainty that the disease will emerge.

We have to weigh up the advantages as well as the disadvantages of giving the test

Dr Lesley Walker, Cancer Research Campaign
This is not a mark which could be equalled by tests for any of the so-called "cancer genes", even the BRCA 2 tests which will be available on the NHS from now on.

And despite the government's pledge to increase the availability of the test, there are probably only a few thousand women who would be eligible.

Two key genes in breast cancer have been spotted - BRCA 1 and 2. Mutations in these have a dramatic effect on the chances of a woman developing the disease.

In normal circumstances, a woman has a one in 10 chance of getting breast cancer before the age of 80.

Inheriting a mutated copy of either BRCA 1 or 2 from a parent means she has a greater than 50-50, and perhaps as great as 87% chance of this before the age of 70.

Screening for the presence of these mutated genes would give doctors a clear pointer to the likelihood of cancer.

Positive action could be taken for a positive result - ranging from increased screening to spot cancer early, right up to prophylactic breast removal to remove the chance of its development.

Advantages and disadvantages

Dr Lesley Walker, from the Cancer Research Campaign, said: "The test could be useful because it helps a small number of women make a very difficult decision.

"We have to weigh up the advantages as well as the disadvantages of giving the test."

The campaign, which developed the BRCA II test, recommends it only in cases where a very strong family link exists - perhaps in cases where more than two relatives have developed the disease, or where a very young close relative has fallen ill.

However, it is not like a test for the disease itself - not all women who are positive for BRCA 1 or 2 will go on to develop the disease.

Dr Eric Sidebottom, a member of the Primary Care Genetics Group, says that it would be foolish to offer BRCA testing to any woman who does not already have a strong family history of the disease.

He said: "There are over 100 different mutations of the BRCA genes, and we do not yet entirely understand the significance of different mutations - which ones are the most dangerous.

"The 'customers' think that tests like these will give them all the answers, when quite clearly they won't."

In fact, it is likely that only a small proportion of hereditary cancers have a link to the BRCA gene, so a negative result could never rule out even hereditary breast cancer.

Other genes have already been found which seem to play a role in the development of various common cancers.

For example, scientists believe they have found a group of genes which play a key role in the development of some bowel, uterine and ovarian cancers.

At the moment, however, the association between gene and disease is weaker in each case than between breast and BRCA genes.

The government's 30m injection is unlikely to lead in the short term to a glut of different genetic tests being offered to the average patient.

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