Genetic testing may be able to predict which patients can tolerate higher, more effective, doses of radiotherapy treatment for cancer, scientists say.
By Caroline Ryan
BBC News Online health staff in Copenhagen
Doses currently have to be kept to a level which will be tolerated by all patients because some can suffer damage to healthy tissue, such as scarring under the skin.
It is known that many people could be given the higher doses - but doctors currently have no way of identifying them.
However, Danish researchers told the European Cancer Conference in Copenhagen they have identified genetic differences which show who is most likely to suffer side effects.
In a separate study, Swiss researchers have devised a blood test which can
show which patients are likely to suffer serious side effects towards the
end of their radiotherapy.
The Danish researchers looked at genes known to be involved in the body's
response to radiation.
They looked at nucleotides - building blocks - which make up the DNA of each gene and found specific sites called single nucleotide polymorphisms (SNPs) where variations could affect how the body reacted to radiotherapy.
They found that 'faults' in the SNPs of four genes were linked to scarring
under the skin and telangiectasia, an increase of small blood vessels under
the skin - both side effects linked to radiotherapy.
The team, from Aarhus University Hospital, studied 41 women who received
chemotherapy between 1978 and 1982.
Women who had a "favourable" variation in any of the genes were found to be
less sensitive to the effects of radiotherapy, and were able to tolerate a
15 to 20% higher dose of radiotherapy than those who had an "unfavourable"
Dr Nicolaj Andreassen, who led the research, said that although the findings
needed to be repeated in other studies, looking at these SNPs could indicate
how someone would respond to radiotherapy.
He said: "People who have reduced sensitivity could be offered a somewhat
higher dose which may improve their chances of a cure considerably.
"Those with higher sensitivity could be offered a treatment strategy which
did not involve radiotherapy."
Dr Andreassen added: "Even though our results should be treated as
preliminary, we consider them very interesting and important.
"They shed new light on the genetic basis that seems to underlie differences
in normal tissue radio sensitivity and provide backing for the concept of
gene-based predictive tests for patients."
In separate research, Swiss researchers from the Centre Hospitalier
Universitaire Vaudois in Lausanne studied 400 cancer patients who were
given radiotherapy between 1998 and 2000.
They found a test which looks at the effect of the treatment on T-cells,
white blood cells which are part of the body's immune system, could indicate
correctly those patients who would not suffer serious side effects after
several sessions of radiotherapy.