The research looked at previous studies. Some women with breast cancer may be able to avoid chemotherapy by taking an extra drug, research suggests.

LHRH agonists like the drug Zoladex switch off the ovary and stop the production of a female hormone which can encourage some tumours to grow.

Four London centres found that even when used alone, the chemical worked as well as conventional chemotherapy in some cases, the Lancet journal said.

Breast cancer charities say that younger women might benefit the most.

Many types of breast cancer are sensitive to hormones produced naturally by a woman, including the sex hormone oestrogen, and can grow faster if a woman is producing them. This could be another option for some younger women. Dr Sarah Cant

Breakthrough Breast Cancer The treatment works by preventing another hormone, luteinising hormone, from doing its job – stimulating the release of more oestrogen.

The London researchers, from the Cancer Research UK Centre for Epidemiology, the Wolfson Institute for Preventive Medicine, and Queen Mary’s School of Medicine and Dentistry, combined the results of 16 other research projects into LHRH agonists and breast cancer.

When all the different results are added together, the overall findings offer a more reliable indicator as to how well the treatment works.

Cancer return

They found that pre-menopausal women given LHRH agonists did as well as those given standard chemotherapy. When the two treatments were given together, the women did even better – with cancer 13% less likely to come back. As expected, LHRH agonists were effective only where a tumour was proven to be sensitive to oestrogen.

The study authors said that the results proved that this was an additional, effective class of drugs in the fight against breast cancer.

Dr Sarah Cant, from Breakthrough Breast Cancer, said that additional research was now needed to see how the drug worked with the most up-to-date types of cancer chemotherapy.

She said: “Women tell us that they like to have treatment choice and this could be another option for some younger women with hormone positive breast cancer. We encourage anyone wanting to find out more to speak to their doctor.”

Maria Leadbeater, Clinical Nurse Specialist at Breast Cancer Care, said that the drugs would be particularly useful to younger patients who faced losing their fertility with conventional chemotherapy.