ATLAS: International ATLAS (Adjuvant Tamoxifen Longer Against Shorter) Breast Cancer Treatment Trial

The last follow-up on ATLAS participants has now been completed. Analyses of the data are on-going and a paper on the results will follow.  Publication details will be posted on this website when available. For further papers on breast cancer, see the Early Breast Cancer Trialists’ Collaborative Group (EBCTCG) website.

The ATLAS trial started in 1995, completed randomisation in 2005 and finished trial treatment in 2010. 15,244 women were recruited from 36 countries. Long term annual follow up was continued until 2017/2018.

In 2013 the main results thus far available were published (Lancet 2013; 381: 805-16), focusing on women with oestrogen receptor positive (ER+) breast cancer who had already had about 5 years of tamoxifen. Whilst this group of women are of particular interest, we have continued to  follow-up all patients in the trial to allow mature analyses to about 20 years after the original diagnosis. In the 2013 Lancet report of the early ATLAS results, most of the follow-up information related to the periods 5-9 and 10-14 years after diagnosis, with little information about longer-term outcomes. The figures below are taken from the 2013 Lancet publication.

The aim of ATLAS is to assess the effects of 10 years of tamoxifen treatment on 20-year outcome. Further follow-up has consolidated the results in years 10-14 after diagnosis, and future analyses will assess the further effects during years 15-19 after diagnosis. It could be that the added benefit of an extra 5 years of tamoxifen persists and becomes somewhat greater by year 20 than by year 15. Alongside the analysis of ATLAS, the EBCTCG is planning a meta-analysis of the trials of 10 vs 5 years of tamoxifen. We anticipate this analysis will be published in 2019 and will include mature results from ECOG, the Scottish trial, NSABP B-14, updated data from ATLAS and new data from aTTom (the UK counterpart of ATLAS).