Clinical Medicine Reviews in Oncology

Background: For patients with hormone receptor positive metastatic breast cancer (MBC), both steroidal and non-steroidal aromatase inhibitors (AIs) have demonstrated efficacy as initial and subsequent lines of treatment in trials comparing them with other hormonal agents like tamoxifen and megestrol acetate. Patients with MBC and predominant visceral involvement have a shortened survival compared to those with non-visceral disease. These patients are usually treated with chemotherapy, with under-utilization of endocrine strategies due to fear of rapid progression. In this review, we present the available data for both classes of AIs in patients with visceral predominant MBC and examine efficacy and safety differences between them.

Methods: An exhaustive Medline search to retrieve published articles based on pre-defined inclusion criteria was conducted. Data from 13 published studies of randomized comparisons of the two classes of AIs with other hormonal therapies or each other form the basis of the efficacy analyses in this report.

Conclusion: Based on our review of the available data, we argue that their manageable toxicity profile with demonstrable clinical benefit supports the use of both classes of AIs, with no significant efficacy differences between the agents, in appropriately selected patients with visceral predominant MBC. Due to the lack of randomized trial data comparing the two classes of AIs in this setting with the exception of one study, the comparisons in this review are mostly indirect and need confirmation in future prospective trials. This is likely to come from comparative trials in the adjuvant setting like the FACE and the MA-27 trials.