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range of treatments

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 and can be removed surgically. Most women diagnosed with early breast cancer now survive, but in some women undetected cancer cells remain after surgery. These cells can start to proliferate, sometimes many years later, resulting in a recurrence of the original breast cancer. ‘Adjuvant’ treatments such as radiotherapy, chemotherapy and hormonal therapy may be used after surgery to try to kill or suppress these cancer cells.

Radiotherapy and chemotherapy are ‘cytotoxic’ treatments that act on cancer cells but can also damage healthy cells. Early clinical trials established that the benefits outweigh the harms for most women and recent trials have aimed to identify more effective and/or less toxic radiotherapy and chemotherapy treatments.

Hormonal therapy is used to treat or prevent breast cancer in addition to cytotoxic treatments. Most breast cancers express the oestrogen receptor (ER) and are driven by the female hormone oestrogen. These ‘ER-positive’ cancers can be treated by greatly reducing natural oestrogen levels, 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, with a selective oestrogen receptor modulator 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 biological therapies that attack the breast cancer stimulation pathway are being developed and tested in clinical trials.

global collaboration

Since the 1950s hundreds of randomised trials involving hundreds of thousands of women have assessed the long-term benefits and side-effects of different treatment options for early breast cancer, and many trials are still being undertaken. Since 1985, the EBCTCG has been bringing together and analysing the evidence on the major questions with 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 breast cancer. Trialists are periodically invited to send data on each woman who participated in their study to the EBCTCG Secretariat.

Several hundred research groups have shared individual patient data on more than 600,000 women in 500 randomised trials. The EBCTCG meta-analyses 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 under way.

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 e.g different types of chemotherapy, or different types of endocrine therapy. The prognostic importance of baseline characteristics, such as the impact of various tumour characteristics and body-mass index on risk of recurrence, can also be investigated. 

Our team

Current and Planned Projects

The international Steering Committee of the EBCTCG meets annually to discuss current and emerging results from EBCTCG meta-analyses and to prioritise future meta-analyses. Emerging results include:

  • comparing different types and methods of administration of chemotherapy
  • comparison of 10 vs 5 years of endocrine therapy (tamoxifen or AI)
  • ovarian suppression in the presence and absence of chemotherapy
  • trials of trastuzumab and other biological agents (eg bevacizumab)
  • assessing the benefits and risks of different radiotherapy techniques
  • establishing appropriate primary and adjuvant therapy for older women
  • reviews of tumour characteristics (e.g, rate of proliferation, immune response, gene expression) and of body-mass index to risk of breast cancer recurrence. 

Influential research

Our reports are published in major medical journals and by March 2024 had been cited more than 35,000 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 making a major contribution to the large falls in worldwide breast cancer mortality seen over the last four decades. 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, influences research strategies in other areas of health care.


The EBCTCG is funded by the long-term support of the CTSU, by Cancer Research UK and the UK Medical Research Council We receive no funding from any commercial organisations.


History of EBCTCG results prior to 2005 (pdf)

Original methods for EBCTCG meta-analyses

EBCTCG variables and data format (pdf)

EBCTCG Data Policy (pdf)

EBCTCG Publications Policy (pdf)

CTSU Clinical Trial Follow Up Service Privacy Notice (pdf)

PRISMA IPD Statement (pdf)

EBCTCG Steering Committee (pdf) 

EBCTCG List of Collaborators (pdf)

EBCTCG Update slides (PowerPoint)

Related research themes