DATA Suggests Extended AI Use No Benefit For HR-Positive, Early Postmenopausal Breast Cancer

Using endocrine therapy for more than 5 years does not boost disease-free survival in postmenopausal hormone receptor-positive, early breast cancer patients

medwireNews: The DATA study has failed to find a disease-free survival (DFS) benefit in postmenopausal women with hormone receptor (HR)-positive early breast cancer who use anastrozole for 6 years after their initial course of adjuvant tamoxifen compared with patients given a 3-year course of the aromatase inhibitor (AI).

After completing 2–3 years of adjuvant tamoxifen, the study participants were all free from disease recurrence when randomly assigned to receive anastrozole 1 mg/day for 6 years or 3 years, say Vivianne Tjan-Heijnen, from Maastricht University Medical Centre in the Netherlands, and co-investigators.

Three-year DFS, starting from 3 years after randomisation, was achieved by a comparable 90.7% of the 827 patients given the extended AI course and 88.9% of the 833 given 3 years of anastrozole, with 5-year rates also similar at 83.1% versus 79.4%.

Nor was there a significant difference in 5-year overall survival between the 6-year and 3-year groups (90.8 vs 90.4%) and although the cumulative 5-year incidence of secondary breast cancer was 1.5% versus 3.3%, the hazard ratio of 0.5 did not reach statistical significance.

The researchers explain in The Lancet Oncology that, as expected, rates of adverse events were comparable between the treatment arms for the first 3 years. But over 6 years, the patients given the extended anastrozole course had a higher rate of any-grade arthralgia or myalgia than those using the AI for only 3 years (58 vs 53%), as well as a higher rate of any-grade osteopenia or osteoporosis (21 vs 16%).

However, the grade 3–4 rates of these side effects did not significantly differ between the treatment arms and there were no differences in the rates of cardiovascular adverse events.

Acknowledging findings from the NRG Oncology/NSABP B-42 trial and the IDEAL trial, the researchers summarise: “The main conclusion from all three recent trials is that if [AIS] have already been incorporated as part of the initial adjuvant therapy regimen then there is little benefit to continuing them for beyond 5 years for most patients.”

And they emphasize: “Any benefit also comes at a price, as shown by the continuous decline in treatment compliance over time. Hence, careful assessment of potential benefits and risks is required before recommending extended [AI] therapy.”

Nevertheless, Vivianne Tjan-Heijnen et al also reported post-hoc analyses suggesting that several subgroups of women may have benefited from the extended AI regimen, with 5-year DFS significantly higher with the 6-year course for women who had received chemotherapy (HR=0.68) or who were positive for both oestrogen and progresterone receptors (HR=0.70).

The author of an accompanying comment acknowledges the plausibility of these factors, and the large size of the study overall, but recommends caution when interpreting findings for “perilously small” numbers of events in such subgroups.

Kathleen Pritchard, from Sunnybrook Health Sciences Centre in Toronto, Ontario, Canada, praises the DATA trial for contributing “considerably” to the understanding of the optimal duration of endocrine therapy.

"It is to be hoped that when the results of additional studies of similar design to DATA such as LATER (ACTRN12607000137493), N-SAS-BC-05 (UMIN000000818), and MINDACT (NCT00433589) become available, comparisons between studies and appropriate meta-analyses might help to more accurately identify any robust predictive factors that will help us to personalise these therapies", she writes.


Tjan-Heijnen VCG, van Hellemond IEG, Peer PGM, et al. Extended adjuvant aromatase inhibition after sequential endocrine therapy (DATA): a randomised, phase 3 trial. Lancet Oncol; Advance online publication 11 October 2017. DOI:

Pritchard KI. Extended adjuvant therapy: the role of subset analyses. Lancet Oncol; Advance online publication 11 October 2017. DOI:

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