Substantial 15-year survival gains from standard breast cancer treatments

05/11/05

EMBARGO: 00:01H (London time) Friday May 13, 2005. In North America the embargo lifts at 6:30pm ET Thursday May 12, 2005.

The types of chemotherapy and hormonal therapy that have long been used to help prevent breast cancer recurrence have much greater effects on 15-year than on 5-year survival, according to a study published in this week's issue of THE LANCET. This extra effect is one of the main reasons why breast cancer death rates have been falling rapidly ever since the early 1990s in the UK, the US and some other countries, state the authors.

In early breast cancer, surgery (or surgery and radiotherapy) can appear to remove all traces of the disease, but undetected deposits of cancer cells may remain that could, over the next 5, 10 or 15 years, develop into a life-threatening recurrence. Chemotherapy and/or hormonal therapy are often given as additional treatments in early breast cancer to help prevent recurrence, and can improve 5-year survival.

The Early Breast Cancer Trialists' Collaborative Group coordinated the world's largest collaborative analysis of cancer trials, bringing together data from 145,000 women with early breast cancer in 194 randomised trials. The study includes information on various treatments that were being tested in the 1980s, and have since been widely used, such as 6 months of anthracycline-based chemotherapy (in which an anthracycline is combined with two older drugs, fluorouracil and cyclophosphamide) and 5 years of tamoxifen.

The investigators found that where both chemotherapy and hormonal therapy are appropriate they can approximately halve the 15-year risk of death from breast cancer. For example, if a 50-year-old women had a one in 5 risk of dying from her hormone-sensitive breast cancer, then this risk could be halved, to about one in 10. For middle-aged women with breast cancer, 6 months of anthracycline-based chemotherapy reduces the breast cancer death rate over the next 10 or 15 years by about one third. For women of any age with hormone-sensitive early breast cancer, the commonest form of the disease, 5 years of tamoxifen also reduces the breast cancer death rate over the next 10 or 15 years by about one third. For middle-aged women with hormone-sensitive disease, a combination of both of these treatments halves the breast cancer death rate. The authors note that while chemotherapy and tamoxifen can have unpleasant short-term side-effects, any long-term side effects are much smaller than the long-term survival benefits.

The analysis is restricted to trials that began by 1995, so none of the available studies involved taxanes, trastuzumab, or modern aromatase inhibitors.

Professor Sarah Darby (Clinical Trial Service Unit, University of Oxford, UK), who helped co-ordinate the collaboration, comments: "For middle-aged women with hormone-sensitive breast cancer, six months of anthracycline-based chemotherapy and five years of tamoxifen halves the long-term risk of death from the disease. Such treatments have been used widely for several years and were endorsed by a US consensus panel in 2001. Although newer treatments are now gaining favour, 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."

She adds: "This is the largest analysis of randomised evidence ever done in any type of cancer. Because so many women in previous decades agreed to join these randomised trials, millions of women in future decades will benefit." (Quote by e-mail; does not appear in published paper)

In an accompanying comment Karen Gelmon (British Columbia Cancer Agency, Vancouver, Canada) and colleagues state: "The most impressive finding is the divergence of the survival curves for breast cancer over time…The survival curves suggest that adjuvant systemic therapies do cure a proportion of women with early-stage breast cancer, rather than simply delaying recurrence; a finding that is reassuring to both oncologists and patients after 30 years of debate on the principle of [whether to use] adjuvant therapy in early breast cancer."

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