This comprehensive, authoritative, Q&A guide answers all the critical questions women have about using tamoxifen to treat or prevent breast cancer, including who should consider using this drug, the long-term risks associated with tamoxifen, possible side effects, and more. Tamoxifen, the most widely used anti-cancer drug in the world, has been on the market in the U.S. since 1978 and just recently FDA-approved for breast cancer prevention.