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29-07-2021 | Breast cancer | News

Extending adjuvant AI therapy by 2 years sufficient in postmenopausal breast cancer

Author: Shreeya Nanda


medwireNews: The phase 3 SALSA trial has demonstrated no benefit of extending aromatase inhibitor (AI) therapy by 5 years versus 2 years in postmenopausal women with hormone receptor-positive breast cancer who have already received 5 years of adjuvant endocrine therapy.

In addition, the longer duration of extended AI therapy “was associated with a greater risk of bone fracture,” report Michael Gnant, from the Medical University of Vienna in Austria, and co-investigators in The New England Journal of Medicine.

Writing in an accompanying editorial, Pamela Goodwin (University of Toronto, Ontario, Canada) notes that “[t]hese findings are consistent with those of two earlier trials” and “provide strong evidence against the routine use of more than 2 years of extended aromatase-inhibitor therapy in women who are at low or average risk, similar to those who were included in this trial.”

In the SALSA (ABCSG-16) study conducted at 75 centers in Austria, 3484 postmenopausal women with stage I–III disease who had received 5 years of adjuvant treatment with tamoxifen, AIs, or both sequentially were randomly assigned to receive anastrozole 1 mg/day for an additional 2 or 5 years.

Of the 3208 participants who remained in the trial without recurrence at 2 years and thus formed the primary analysis population, the majority had T1 (72.8%) and N0 (66.9%) breast cancers that had not required adjuvant chemotherapy (71.2%).

At 8 years after the completion of treatment in the 2-year group (ie, 10 years from randomization), the primary endpoint of disease-free survival in the primary analysis population was comparable in the 2- and 5-year groups, at rates of 73.6% and 73.9%, respectively (nonsignificant hazard ratio [HR]=0.99).

“A similar result was obtained after adjustment for potential confounding factors,” say Gnant and colleagues.

The overall survival rate at 8 years was likewise comparable between women who received an additional 2 or 5 years of anastrozole, at 87.5% versus 87.3% (nonsignificant HR=1.02).

And there were also no significant between-group differences with regard to the risk for contralateral breast cancer or second primary cancer.

However, the incidence of clinical bone fractures at 5 years after randomization was lower in the 2-year than 5-year treatment arm, at 4.7% versus 6.3% (HR=1.35), with the difference observed “despite the equivalent use of bone-targeted medications in the two groups,” point out the study authors.

They add that the “[s]ide effects of anastrozole were in line with the known toxicity profile of the drug.” Serious adverse events occurred in 26.5% of patients in the 2-year group and 40.2% of those in the 5-year group; the respective rates of events considered related to anastrozole were 2.3% and 4.0%.

The editorialist says in conclusion that “[d]ecisions regarding extended aromatase-inhibitor therapy will continue to be individualized with a combined assessment of recurrence risk, treatment tolerance, and patient preference.”

She continues: “The data provided by Gnant et al. in patients with hormone-receptor–positive breast cancer who are at low or average risk underscore the importance of avoiding iatrogenic complications when making these decisions.”

medwireNews is an independent medical news service provided by Springer Healthcare Ltd. © 2021 Springer Healthcare Ltd, part of the Springer Nature Group

N Engl J Med 2021; 385: 395–405
N Engl J Med 2021; 385: 462–463