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

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 post-menopausal women. However, the duration and the overall benefit is still controversial. Eligible 8 RCTs comprising of 17,190 participants were included in this meta-analysis. 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. 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.