ONCOLOGY Vol 17 No 5

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Long-Term Toxicities of Selective Estrogen-Receptor Modulators and Antiaromatase Agents

May 1st 2003

Published literature indicates that the selective estrogen-receptormodulators (SERMs) tamoxifen and raloxifene (Evista) have favorableeffects on bone density, lipid profiles, and the incidence of secondbreast cancers, and unfavorable effects on the incidence of venousthrombosis and hot flushes. Tamoxifen increases the risk of endometrialcancer, but raloxifene does not. The effects of SERMs on sexualfunction and cognition are unclear. Because the selective antiaromataseagents are relatively new, the long-term effects of these agentson normal tissues are less well established. It appears that the nonsteroidalagents (anastrozole [Arimidex], letrozole [Femara]) and steroidal(exemestane [Aromasin]) antiaromatase agents may have differenteffects on normal tissues. Preliminary data demonstrate that anastrozoleincreases the risk of arthralgias and produces a decrease in bonedensity. In contrast, exemestane appears to favorably affect bonedensity and lipid profile, similar to tamoxifen and raloxifene. Theincidence of contralateral breast cancer is decreased in women onadjuvant anastrozole, but data for the other antiaromatase agents arenot yet available. Hot flushes have been reported with the use ofselective aromatase inhibitors, but their incidence seems to be comparableto what is reported with SERMs. Antiaromatase agents do notappear to cause venous thrombosis. More information about the effectsof the antiaromatase agents on normal tissue will become available asdata from ongoing adjuvant and chemoprevention trials are reported.Clinically, we should be conscious of the differences between antiaromataseagents and SERMs and their impact on women’s health.