Modern treatments have significantly boosted the 15-year survival rate for breast cancer, researchers say.
Chemotherapy has proved effective
Scientists found drug and hormonal therapies effectively cure many women - rather than simply delaying the recurrence of disease.
In some cases, appropriate use of treatments in combination can halve the 15-year risk of death, they said.
The Early Breast Cancer Trialists' Collaborative Group looked at 145,000 cases, The Lancet reports.
Breast cancer death rates have been falling rapidly in the UK and other countries since the 1990s.
Surgery, alone or in combination with radiotherapy, can be used to remove all apparent traces of breast cancer if the disease is picked up at an early stage.
However, undetected cancer cell deposits may sometimes remain, and can trigger a recurrence of disease.
Drug and hormonal therapy - such as tamoxifen - are often used to try to prevent this recurrence by destroying these hidden deposits.
There has been some debate about whether women should be subjected to these extra treatments, as they are often associated with unpleasant side effects.
But there is evidence that they help to boost survival rates at five years, and the latest study examined data on 145,000 breast cancer patients to determine their impact in the longer term.
The researchers found that appropriate use of the treatments in combination can approximately halve the risk of death from breast cancer for a middle-aged woman with hormone-sensitive disease from one in five to one in 10 over a 15 year period.
Alone, each treatment also has a significant impact. For instance, use of chemotherapy based on the anthracycline class of drugs can cut the 15-year risk of death for a middle aged woman with breast cancer by a third.
Professor Sarah Darby, of the University of Oxford, who worked on the study said newer treatments for breast cancer were now gaining favour.
She said: "The eventual long-term benefits from older treatments such as these are one of the main reasons why breast cancer mortality rates are now falling rapidly in countries such as the UK or USA."
Professor John Toy, of the charity Cancer Research UK, said: "This is the largest follow-up study ever done in women with early breast cancer.
"It shows that we are making great progress in treating breast cancer increasingly effectively. This is really very encouraging for this group of patients.
"Women whose breast cancer is diagnosed at an early stage and who are suitable for tamoxifen and chemotherapy are surviving longer and the study shows they continue to gain a substantial survival advantage."
Antonia Bunnin, of Breakthrough Breast Cancer, said: "It's extremely reassuring to see evidence that established treatments are helping more and more women with early breast cancer live longer
"But if this trend is to continue and women are to benefit in the future, it's vital that there is greater investment in research.
Liz Carroll, of Breast Cancer Care said the research underlined the importance of using anthracyclines-based chemotherapy rather than less effective alternatives.
In 1996-1997 the overall chance of surviving for five years after a diagnosis of breast cancer was 77% in England and Wales - although the precise odds vary depending on the form of the disease and age at diagnosis.
The odds of surviving for at least ten years have risen from around 40% in the early 1970s to more than 70% by 2001.