Two-year adjuvant AI extension may be enough in postmenopausal breast cancer
medwireNews: Among postmenopausal women with hormone receptor-positive breast cancer receiving standard adjuvant aromatase inhibitor (AI) therapy, extending treatment by 2 years is associated with similar outcomes to a 5-year extension, but with fewer side effects, an Austrian trial suggests.
He told the conference delegates that they recruited 3469 women with stage I–III disease who were recurrence-free after 5 years of adjuvant treatment with tamoxifen, an AI, or tamoxifen followed by an AI. The participants were randomly assigned to receive either a further 2 or 5 years of anastrozole 1 mg/day and followed up for a median of 106.2 months.
The primary endpoint of disease-free survival did not differ significantly between groups, with 10-year rates of 71.1% and 70.3% in the 2- and 5-year groups, respectively.
Overall survival was also comparable for the 2- and 5-year arms, with a respective 85.3% and 84.9% of patients alive at 10 years, and the time to secondary carcinoma and time to contralateral breast cancer were similar as well, Gnant reported.
But the 2-year regimen appeared to have a better toxicity profile, in that bone fractures occurred less frequently in the 2-year extended anastrozole group, at 4.7% compared with 6.3% in the 5-year group, although the difference did not reach significance.
Around 80% of women in each group were adherent to the treatment at the 2-year mark, but the adherence rate in the 5-year arm declined steadily after that, dropping to around 65% by 5 years.
Gnant summarized that there seems to be “no benefit of continuing/escalating endocrine treatment beyond 7 years,” and in fact, “[e]xtension of anastrozole treatment [for] 5 additional years leads to increased side effects including fractures, and should be avoided.”
He noted, however, that “[i]n the future, translational research may identify molecular characteristics that indicate benefit of prolonged extended therapy.”