Scientists have developed a gene test which predicts how well chemotherapy will work in cancer patients.

Starting with 829 genes in breast cancer cells, the team whittled down the possibilities to six genes which had an impact on whether a drug worked.

They then showed that these genes could be used to predict the effectiveness of a drug called paclitaxel in patients.

It is hoped the approach, reported in The Lancet Oncology, can be replicated for other cancers and treatments.

The international project, including researchers from Cancer Research UK's London Research Institute, opens the way for breast cancer treatment to be targeted to those who will benefit the most.

To find which genes, if missing or faulty, could prevent the drug from working, they deleted them one by one from cancer cells in the laboratory.

They eventually highlighted the six genes which if absent or not working prevent paclitaxel from properly killing breast cancer cells.

Spare treatment

More than 45,500 women are diagnosed with breast cancer in the UK each year - and it is estimated that around 15% of these women will be prescribed paclitaxel.

The researchers estimate they could potentially spare half of the patients currently receiving this drug from treatment which would not be effective.

Study leader, Dr Charles Swanton, head of translational cancer therapeutics at the Institute, said one of the great challenges in cancer medicine is determining which patients will benefit from particular cancer drugs, which are in themselves toxic and carry severe side effects.

"Our research shows it is now possible to rapidly pinpoint genes which prevent cancer cells from being destroyed by anti-cancer drugs and use these same genes to predict which patients will benefit from specific types of treatment."

Further studies will now be done to see if the technique can be developed into a simple diagnostic test to be given to patients to help inform doctors about whether or not to prescribe paclitaxel.

He said the challenge will be to apply these methods to other drugs in cancer medicine.

"These could include treatments that are currently deemed too expensive to fund on the NHS - however, in the future, treating only the patients that will benefit from certain treatments will save the NHS money in the long term."

Dr Lesley Walker, Cancer Research UK's director of cancer information, said: "New techniques such as these can enable drugs to be tailored to individual patients, and this could potentially improve cancer survival in the long term.