EBCTCG: Early Breast Cancer Trialists' Collaborative Group
Established in 1983
Includes researchers from every randomised trial worldwide
In high-income countries, most breast cancers are diagnosed early (stages I, II or IIIA) when all detected cancer cells are in the breast or nearby lymph nodes can be removed surgically. Although most women diagnosed with early breast cancer now survive, in some women undetected deposits of cancer cells remain after surgery in, or near, the breast, or in other parts of the body. These cells can start to proliferate, sometimes many years later, resulting in a recurrence of the original breast cancer. To try to kill or suppress any cancer cells remaining after surgery ‘adjuvant’ treatments such as radiotherapy, different types of chemotherapy and hormonal therapy may be given in addition to surgery.
Radiotherapy and chemotherapy are ‘cytotoxic’ treatments that act directly on cancer cells but can also damage healthy cells. Early clinical trials established that the benefits outweigh the harms for most patients so the focus of many recent trials has switched to identifying more effective and/or less toxic radio- and chemotherapy regimens.
There are other potential ways to treat or prevent breast cancer in addition to cytotoxic treatments, in particular using hormonal therapy. Most breast cancers express the oestrogen receptor (ER) and are driven by the female hormone oestrogen. These ‘ER-positive’ cancers can be treated effectively by greatly reducing natural oestrogen levels, e.g by removing a woman’s ovaries or stopping them from producing oestrogen with an aromatase inhibitor (AI), which blocks the pathway through which oestrogen is produced, or by blocking the oestrogen receptor, e.g, with selective oestrogen receptor modulators such as tamoxifen.
A substantial minority of breast cancers can be treated effectively by blocking other receptors (eg, with trastuzumab, which blocks the Her2-neu receptor). As we learn more about the complex biology of breast cancer, other such ’biological’ therapies that attack the breast cancer stimulation pathway are being developed and tested in clinical trials.
Since the 1950s hundreds of randomised trials of various aspects of early breast cancer treatment have assessed the long-term benefits and side-effects of different treatment options. Hundreds of thousands of women have been involved in these trials and many trials are still being undertaken. To understand this huge body of evidence, since 1985, the EBCTCG has been bringing together all the evidence on the major questions for central analysis with the emphasis on evidence from large-scale randomisation and long-term follow-up.
The EBCTCG involves almost all trialists worldwide who have done relevant randomised trials of the treatment of women with breast cancer. Trialists are periodically invited to send data on each woman who participated in their study to the EBCTCG Secretariat in the Clinical Trial Service Unit (CTSU), based in the Nuffield Department of Population Health at the University of Oxford.
Several hundred research groups have shared individual patient data on more than 600,000 women in 500 randomised trials for the EBCTCG meta-analyses that have produced definitive estimates of the effects of various treatments on time to recurrence, breast cancer death, second cancers and death from other causes. These treatments include various types of surgery, radiotherapy, chemotherapy, endocrine therapy, biological therapies, and other agents such as bisphosphonates. Reviews on the trials of mammographic screening are also being undertaken.
As well as providing definitive estimates of the overall, average effects of the treatments, the large EBCTCG datasets allow the most reliable exploration of any differences in the effects of the treatments in particular subgroups of women, or between treatments within the same class for example, different types of chemotherapy, or different types of endocrine therapy. The prognostic importance of baseline characteristics can also be investigated, for example, the impact of various tumour characteristics and body-mass index on risk of recurrence.
The EBCTCG reports are published in major medical journals and by 2018 had been cited more than 24,000 times. The group’s findings are widely used in consensus statements, clinical guidelines, decision aids, and treatment decisions around the world. They have influenced the care of millions of women over the last four decades, making a major contribution to the large falls in worldwide breast cancer mortality seen over this period. The EBCTCG results help define the treatment questions to be tested in future trials and, by developing and demonstrating appropriate methods for individual studies and systematic reviews, the EBCTCG also influences research strategies in areas of health care other than breast cancer.
The EBCTCG is funded by the long-term support of the CTSU by Cancer Research UK and the UK Medical Research Council and receives no funding from any commercial organisations.