Clin Cancer Res: Small doses of tymoxifen can effectively reduce the risk of breast cancer in breast radiation-treated cancer survivors

Low doses of tymoxifen reduce the risk of breast cancer, but have not yet been tested in cancer survivors who have received chest radiation -- a population with the same risk of breast cancer as individuals with BRCA mutations.
study hypothesizing that small doses of tymoxifen are safe and effective in reducing the risk of radiation-related breast cancer.
study was conducted in 15 locations in the United States in a randomized, double-blind, placebo-controlled phase IIb trial (FDA IND107367).
recruited individuals aged 25 and over who had accumulated chest radiation of 12Gy and above by the age of 40.
subjects were randomly grouped and received small doses of tanthoxifen (5 mg/day) or placebo for a period of 2 years.
end points are baseline, 1 and 2 years of breast denational clinding.
insulin growth factor-1 (IGF-1) played a role in breast cancer occurrence, with baseline, 1 and 2 years of circulating IGF-1 and IGF-BP3 levels as secondary endpoints.
72 subjects were recruited between 2010 and 2016: 34 in the small dose of moxifen, 38 in the placebo group, with a medium age of 43.8 years (35-49 years), all of which were assessed.
subjects received a medium chest radiation dose of 30.3Gy.
compared to the placebo group, the levels of breast dense shadow (p-0.02) and IGF-1 (p-lt;0.0001) in subjects taking small doses of tampoxifen decreased significantly, while IGFBP-3 levels increased significantly (p-0.02).
toxic biomarkers (serum bone-specific alkaline phosphatase, lipids and anticoagulant enzyme III, urine N-end peptide crosslinking) were not different between the treatment groups.
no 3-4 adverse reactions associated with small doses of tymoxifen.
, the trial showed that small doses of tymoxifen were effective in reducing breast cancer risk biomarkers, or as a strategy to reduce breast cancer risk in such populations.