A leading doctor is calling on hospitals to offer breast cancer patients a new gene test to indicate if they need chemotherapy.
While the majority of sufferers are prescribed chemotherapy, research shows only around four in 100 patients with early-stage invasive breast cancer actually benefit from the treatment.
Dr Mokbel, who recommends the test to some of his private patients, said: "If the test produces a low score below 18 we say no chemotherapy.
"As a result we protect the patient from the averse effects of chemotherapy on their health, quality of life, as well as the cost."
Doctors remove a small amount of tissue during breast cancer surgery which is then sent for testing in a laboratory where scientists analyse genes.
Patients then receive a score between 0 and 100 indicating the likelihood the patient will benefit from chemotherapy and whether the cancer will return in the next ten years.
Dr Mokbel said: "For those with higher scores above 25, we would say chemotherapy would be beneficial.
"For scores between 18 and 25 we would make a decision about whether they should have chemotherapy or not.
"The basic costs of chemotherapy are £20,000 and the test costs around £2,400."
Camilla Alexander, 47, a barrister who was saved from chemotherapy after having the test, said: "After I had my lumpectomy Dr Mokbel said I could have this gene test to see whether I needed to have chemotheraphy."
Mrs Alexander, who was diagnosed with cancer last August, was prescribed a three-week course of daily radiotherapy after receiving a low score from the gene test. She will have check-ups every two months for the next couple of years.
The medicines watchdog, NICE, recommended the test for early-stage breast cancer suffers in September last year.
However it is still not available to NHS patients in England.
A St George's Hospital spokesperson said: "The Oncotype DX test is not currently routinely commissioned in England however a national commissioning policy is being developed by the chemotherapy clinical reference group. It is anticipated that this will be available in May 2014.
"Under the guidance of the London Cancer Alliance, St George’s Healthcare NHS Trust will then respond to the national commissioning policy in line with best practice."