Taking adjuvant endocrine therapy for 7 to 8 years is likely sufficient for maximal disease-free survival (DFS) benefits among most postmenopausal women with hormone receptor (HR)-positive breast cancer, according to researchers.
In a meta-analysis, researchers found that 10 years of adjuvant endocrine therapy did not provide additional benefits for most patients, but patients with node-positive disease had improved DFS with 10 years of treatment.
The meta-analysis, published in the European Journal of Cancer, included 12 studies of postmenopausal patients who underwent surgery for HR-positive, HER2-negative early breast cancer. The patients had received at least 5 years of adjuvant therapy with any approved endocrine agent, such as tamoxifen followed by an aromatase inhibitor or an aromatase inhibitor alone.
The DFS was significantly longer when endocrine therapy was extended by 2 to 3 years beyond the initial 5 years of treatment (hazard ratio [HR], 0.77; 95% CI, 0.69-0.87).
Overall, an additional 5 years of endocrine therapy beyond the initial 5 years did not significantly improve DFS, compared with an additional 2 to 3 years (HR, 0.97; 95% CI, 0.88-1.08) or 3 to 4 years (HR, 0.87; 95% CI, 0.72-1.06).
For patients with node-positive disease, however, an additional 5 years of endocrine therapy significantly prolonged DFS compared with an extension of 2 to 3 years (HR, 0.86; 95% CI, 0.75-0.99) or no extension of endocrine therapy (HR, 0.75; 95% CI, 0.67-0.84).
An additional 5 years of endocrine therapy was also associated with longer DFS among patients treated with tamoxifen during their initial 5 years of adjuvant therapy. A formal analysis was not conducted, but the researchers said a longer duration of tamoxifen treatment was associated with a greater benefit of additional years of treatment with aromatase inhibitors.
Extended treatment with endocrine therapy did not affect overall survival (OS). OS was comparable with an additional 2-3 years of therapy or an additional 5 years of therapy (HR, 0.92; 95% CI, 0.8-1.6).
Based on these results, the researchers concluded that an extended duration of endocrine therapy — 7 to 8 years in total — could be considered an appropriate treatment regimen for the DFS benefit. However, 10 years of treatment should be considered a potential standard of care for patients with positive lymph nodes.
Petrelli F, Cavallone M, Dottorini L. 10 years or less of extended adjuvant endocrine therapy for postmenopausal breast cancer patients: A systematic review and network meta-analysis. Eur J Cancer. Published online September 6, 2023. doi:10.1016/j.ejca.2023.113322