Extended adjuvant AI not advised for HPBC after 5+ yrs of sequential endocrine therapy

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Published: 11 Sep 2022
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Dr Vivianne Tjan-Heijnen - Maastricht University Medical Center, Maastricht, Netherlands

Dr Vivianne C Tjan-Heijnen presents the final results of the phase 3 DATA trial, exploring extended adjuvant aromatase inhibition after sequential endocrine therapy. The DATA study evaluated the use of different durations of anastrozole in patients with hormone receptor-positive breast cancer who were disease-free after 2-3 years of tamoxifen. 

The primary endpoint was adapted disease-free survival (aDFS), defined as DFS from 3 years after randomisation onwards. Adapted overall survival (aOS) was evaluated as a secondary endpoint.

The final results of the study concluded that it is not recommended extending aromatase inhibition beyond 5 years of sequential therapy in all postmenopausal women with hormone receptor-positive breast cancer. It may however be considered in patients with node-positive, ER- and PR-positive tumours.

Back in 2006 when we started this study we knew that the risk of recurrent disease was increased for many decades and we also knew that aromatase inhibitors could prevent some of these recurrences after tamoxifen. It was not tested whether patients who have been treated with aromatase inhibitors in the first five years would still benefit from extending aromatase inhibitors so that’s the reason why we started with the data study.

We randomised patients for three years versus six years of anastrozole after an initial 2-3 years of tamoxifen and we included only patients who were postmenopausal and who were disease free after 2-3 years of tamoxifen. Then as a primary endpoint we checked for the disease free survival, according to CR definition, and we decided to calculate beyond three years of randomisation as the first three years of treatment was the same for both treatment arms.

The primary endpoint was actually not statistically significant but a strong trend from improved outcome. We found that patients who were treated with extended aromatase inhibitor treatment had an improved 3.1% of disease free survival. When we looked more closely we found that patients with both hormone receptors being positive, so oestrogen and progesterone receptors, that these patients had a larger benefit which was actually 6% and that was a significant factor. When we looked more into detail to the patients who had a more poor prognosis, then the benefit increased towards 13.6% so that’s a clinical worth benefit.

It may help future patients, so all patients who have lymph node positive disease and very endocrine sensitive disease should be treated with sequential tamoxifen and aromatase inhibitor where the inhibitor treatments should in total last for five years, so a total for the endocrine treatment of eight years of treatment.

Of course the benefit should always be weighed against the side effects. So for individual patient decision making it is important to consider cardiovascular disease, bone disease and that sort of thing. So that is weighed in the decision making process.