A drug cocktail has been found to cut the risk of breast cancer death by nearly a third.
Breast cancer treatments are evolving rapidly
Nearly 90% of patients at high risk of recurring disease survived at least five more years after the treatment.
It is a combination of standard drugs, adriamycin and cyclophosphamide, and the newer drug docetaxel (Taxotere).
The Breast Cancer International Research Group study found the new combination had more side effects but only during the period of treatment.
The study, which was published in the New England Journal of Medicine, focused on 1,491 women with breast cancer which had spread to the lymph system in the armpit.
Some 87% who took the new drug cocktail survived for more than five years, compared to 81% who were given standard therapy.
Overall, the new cocktail resulted in a 30% reduction in breast cancer deaths, and a 28% reduction in disease recurrence when compared to the standard drug treatment of fluorouracil, Adriamycin and cyclophosphamide.
The new combination had more side effects, such as infections and fever, than standard treatment, but quality of life was affected only during treatment and not afterwards.
Researcher Professor Rob Coleman, of the Weston Park Hospital, Sheffield, said: "These are important results for women with breast cancer that has spread to the glands in the axilla (armpit).
"This type of chemotherapy represents a significant advance in our treatment options and, if routinely available in the UK, would prevent the deaths of hundreds of women with breast cancer each year."
Dr Paul Ellis, consultant medical oncologist at St Thomas's and Guy's Hospital, London, said: "This is an important development that will affect many women with early breast cancer.
"Those represented in the study form about 40% of the women I see."
Dr Ellis said the new combination was also likely to benefit all women with early breast cancer - although the clinical trials to confirm that were still ongoing.
"We are talking about treatments that mean that nearly nine out of 10 women with early breast cancer will survive longer than five years, and that means they are likely to be cured."
He called on the NHS drug watchdog, the National Institute for Health and Clinical Excellence (Nice) to speed up its current review of breast cancer treatments - due to report next year.
Antonia Bunnin, of the charity Breakthrough Breast Cancer, described the results as "important".
She too called on Nice to make its review of breast cancer drugs a top priority.
"Powerful drugs such as Taxotere are known to have side-effects and women with breast cancer tell us that this is an important consideration when undergoing chemotherapy.
"It is vital women have all the information necessary to make informed decisions about their treatment."
Hazel Nunn, science information officer at Cancer Research UK, said: "The results of this study will add to our understanding of the role that these drugs may play in improving the survival of women diagnosed with early breast cancer."