Researchers looked for a specific genetic make-up in cancer cells
Breast cancer patients could be spared unnecessary and lengthy treatment, according to new findings by researchers.
Two genes that can identify which cells will respond to a common chemotherapy drug and which will not have been revealed by Aberdeen University staff.
It is hoped the findings will help develop more tailored treatments.
More than 44,000 people are diagnosed with breast cancer each year in the UK and 80% of all cases occur in over-50s.
The research team said they looked for a specific genetic make-up in breast cancer cells that did not respond to the chemotherapy drug docetaxel.
The course is one of the most effective methods of battling the cancer, but does not work for some patients.
The findings involved the study of breast cancer cells grown in the laboratory.
They will now investigate whether the genes they identified behave the same way in patients.
Aberdeen University's Dr Andy Schofield, one of the researchers, said many women are suffering side effects for no benefit at all.
He said: "For the first time we have found two genes that identify which breast cancer cells respond to chemotherapy and which do not respond.
"We hope that in the future this will mean that before we treat patients with breast cancer with docetaxel, we can predict whether the drug will work or not, using a very simple test."
Rachel Rawson, of Breast Cancer Care, said: "We are still a long way from fully understanding the complex role that genetics plays in the treatment of breast cancer, and how this interacts with or is mediated by other factors.
"Breast Cancer Care welcomes any research that furthers our knowledge in this area.
"However this is initial research that has only been tested in a laboratory setting. Further studies are needed to fully determine how these findings can be translated into the clinical setting and offer practical benefits for people with breast cancer."
Most British women are unaware that breast cancer risk increases with age, a recent poll suggested.
A survey of 1,000 people by charity Breast Cancer Care found nearly six out of 10 women did not know getting older was a strong risk factor.
Experts said many young women can worry unnecessarily while older women do not realise they are at risk.