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Tamoxifen Benefit in Lower-Risk Breast Cancer Varies by Intrinsic Subtype

Key clinical point: Benefit of tamoxifen is longer lasting in luminal A vs. luminal B postmenopausal node-negative breast cancer.

Major finding: A significant DRFI benefit of tamoxifen over no endocrine therapy was seen out to 15 years postdiagnosis for luminal A tumors (hazard ratio, 0.57) but out to only 5 years postdiagnosis for luminal B tumors (HR, 0.38).

Study details: Secondary analysis among 462 postmenopausal patients with node-negative, ER-positive breast cancer from a randomized controlled trial comparing at least 2 years of adjuvant tamoxifen therapy with no endocrine therapy (STO-3 trial).

Disclosures: Dr. Lindström disclosed no conflicts of interest. The study was supported by the Swedish Research Council, FORTE, The Gösta Milton Donation Fund, the California Breast Cancer Research Program, The Iris, Stig och Gerry Castenbäcks Stiftelse för Cancerforskning, and Konung Gustaf V:s Jubileumsfond from Radiumhemmets Forskningsfonder.

Citation:

Yu NY et al. JAMA Oncol. 2019 Aug 8. doi: 10.1001/jamaoncol.2019.1856.