The first clinical trial in which the entire DNA 'genome' of breast cancer patients' tumours was scanned to help select the best treatment has been carried out in France.

The study shows that it could soon be possible to replace commonly used single-gene tests with more comprehensive whole-genome scans. The researchers say that such scans could be more likely to pick up both common and more unusual genetic faults that could be targeted by treatments.

Several drugs have been developed to target specific genetic alterations that cause cancer. For some tumours such as breast cancer, doctors already use genetic tests to work out which treatment a patient will respond to best. But in most cases only a limited number of genes are examined.

A study at the Institute Gustave Roussy in Villejuif, scanned the entire genome of breast cancer patients to find genetic faults that could be targeted by existing treatments.

In the trial, doctors took biopsies from secondary tumours in patients - those that had spread from the breast to other parts of the body.

They then analysed the genetic code of the tumour samples using a technique called array CGH, which scans the genome for gains, losses or changes in the genetic material, and gives information about genes likely to be driving the disease.

They used this information to choose treatments for the patients that were targeted at the specific cancers they had.

Biopsies were taken from 402 patients. Of these, the researchers were able to map the full genome in 248 samples. The process resulted in 172 patients being given drugs that were designed to target a specific genetic change.

The research showed that 20 per cent of the patients were found to have extremely uncommon genetic changes. The tumours shrank in 18 out of 48 patients whose treatment was selected based on the results of a genome scan.

Dr Fabrice Andre who led the research, said: "This study suggests that the time has come to bring personalised medicine to the cancer field."

Kate Law, Cancer Research UK's director of clinical research, said: "Routine whole-genome sequencing of tumours is on the horizon for cancer patients, but we're not there yet."

She said that the research shows that whole-genome tumour testing can be used to help select the most appropriate treatment for breast cancer patients, but that there are several hurdles to overcome before such tests become routine.

"The fact that genetic results weren't generated for all patients highlights the need to improve technical aspects of the tests. And before such genome tests are available in the clinic, we absolutely need further good-quality clinical trials to show they help to improve treatment for cancer patients," she added.

She also said that Cancer Research UK's Stratified Medicine Programme is working towards "standardised, high quality, cost-effective and timely genetic testing of tumours within the NHS".

The work was presented at the ESMO 2012 Congress of the European Society for Medical Oncology in Vienna.

Source: CRUK