Extended duration of adjuvant aromatase inhibitor in breast cancer: a meta-analysis of randomized controlled trials

Background: The risk of hormone positive breast cancer extends beyond 5 years. Extended duration of tamoxifen to 10 years has been shown to improve overall survival (OS) and disease-free survival (DFS). In post-menopausal women aromatase inhibitor (AI) is the gold standard for adjuvant endocrine therapy. Several randomized controlled trials (RCTs) showed benefit with extending the duration of AIs in postmenopausal women. However, the duration and the overall benefit is still controversial. Methods: Eligible 8 RCTs comprising of 17,190 participants were included in this meta-analysis. Results: Extending the duration of AI did not show any statistically significant advantage in OS with OR of 1.033 (95% CI: 0.925-1.154, P=0.56), DFS OR of 1.049 (95% CI: 0.930-1.185, P=0.435), recurrence-free survival (RFS) OR of 1.063 (95% CI: 0.952-1.187, P=0.276), and contralateral breast cancer (CBC) OR of 1.094 (95% CI: 0.920-1.301, P=0.311). Higher rates of side-effects of arthralgia, myalgia, hot flushes and bone toxicity was seen among the extended AI group. Conclusions: Based on this meta-analysis and current literature review, extended use of AI after 5 years of endocrine therapy should be used in selected women with high risk tumour factors. Molecular markers and genomic profiling may assist in identifying the high-risk patients. It is important to consider quality of life and patient satisfaction when considering extending the duration of AI.