Gene testing can help women with advanced breast cancer to get access to clinical trials offering better chances of treatment, said French doctors on Friday.
The study, the biggest of its kind, improves the chances of getting drugs that, like a sniper's rifle, aim at a specific type of tumour, they said.
Researchers led by Fabrice Andre, a professor at the Gustave Roussy Institute in Paris, unravelled the DNA of cancer cells found in more than 407 women whose breast cancer had spread dangerously to other tissues.
The goal was to pinpoint genes linked with specific types of tumour, and see if these could be matched to new, experimental drugs that were already in the test pipeline.
Previous work has looked at only part of the genetic code of cancer cells -- this one, though, was a trawl across the genome, aimed at identifying as many suspect genes as possible.
The probe found that nearly half of the patients -- 46 percent -- did have tumours whose genetic profile offered a potential target for drugs.
Of these, 43 were then enrolled in clinical trials for new drugs corresponding to this profile.
Thirteen of them responded to treatment.
"Until now, genetic testing has only analysed a limited number of genes to select which targeted drugs are suitable for individual patients and many treatment opportunities may be missed," explained Andre.
"For the first time, we have shown that scanning the whole genome can identify both frequent and rare genomic alterations and can be done in clinical practice with large numbers of women."
The study is reported in a specialist journal, The Lancet Oncology.
Despite the success of the gene trawl, the choice of drugs remains meagre for many of the rarer types of breast cancer.
Thirty-nine percent of the women had a rare type of genetic profile in their cancer, for which in most cases no treatments -- either licensed or in trials -- existed.