Prolonged adjuvant anastrozole confers no DFS benefit in pos
A longer duration of extended hormone therapy provided no benefit for postmenopausal women with hormone receptor-positive breast cancer who had received 5 years of adjuvant endocrine therapy, according to randomized phase 3 study results.

For postmenopausal women with hormone-receptor–positive breast cancer, the most effective duration for adjuvant therapy with an aromatase inhibitor remains unclear.

In this prospective, phase 3 trial, we randomly assigned postmenopausal women with hormone-receptor–positive breast cancer who had received 5 years of adjuvant endocrine therapy to receive the aromatase inhibitor anastrozole for an additional 2 years (2-year group, receiving a total of 7 years) or an additional 5 years (5-year group, receiving a total of 10 years). The primary end point was disease-free survival. The primary analysis included all the patients who were still participating in the trial and who had no recurrence 2 years after randomization (i.e., when treatment in the 2-year group had ended). Secondary end points were overall survival, contralateral breast cancer, second primary cancer, and clinical bone fracture.

Results:
-- Among the 3484 women who were enrolled in the trial, 3208 remained in the trial without disease progression after the first 2 years of extended anastrozole treatment following randomization.

-- Among these women, disease progression or death occurred in 335 women in each treatment group in the primary-analysis set at 8 years.

-- No between-group differences occurred in most secondary end points, and subgroup analyses did not indicate differences in any particular subgroup.

-- The risk of clinical bone fracture was higher in the 5-year group than in the 2-year group.

Conclusively, in postmenopausal women with hormone-receptor–positive breast cancer who had received 5 years of adjuvant endocrine therapy, extending hormone therapy by 5 years provided no benefit over a 2-year extension but was associated with a greater risk of bone fracture.

Source: https://www.nejm.org/doi/full/10.1056/NEJMoa2104162
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