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Table 1 Summary of the main published trials on low dose tamoxifen

From: Oral low dose and topical tamoxifen for breast cancer prevention: modern approaches for an old drug

Study Treatment Number of patients Population Primary endpoint Comment
Breuer et al. 1998 [80] TAM 20 mg/day (91%)
TAM 10 mg/day (9%)
1,385 matched with 5,196 controls Women 65 years and older Bone fracture Although standard treatment of 20 mg TAM daily offers no apparent protection against bone fracture in older nursing home residents, a daily 10 mg dose seems to be protective
Decensi et al. 1998 [11] Placebo
TAM 20 mg/day
TAM 10 mg/day
TAM 10 mg alternate days
127 Healthy women Hysterectomized 35 to 70 years Total cholesterol (primary) Surrogate markers of cardiovascular disease, IGF-I Up to a 75% reduction in the conventional dose of TAM (that is, 20 mg/day) does not affect the activity of the drug on a large number of biomarkers, most of which are surrogate markers of cardiovascular disease
de Lima et al. 2003 [25] Placebo
TAM 5 mg/day
TAM 10 mg/day
TAM 20 mg/day
56 Premenopausal women with a diagnosis of fibroadenoma of the breast ER alpha PgR Ki-67 apoptotic bodies and mitotic index Excisional biopsy was performed on the 50th day of therapy. Normal breast tissue samples were collected during surgery. Differences in the expression of ERa, PgR, Ki-67, apoptotic bodies and mitotic index between the different groups after treatment can be seen on the normal breast tissue
Decensi et al. 2003 [26]
Decensi et al. 2010 (f-up) [30]
TAM 1 mg/day
TAM 5 mg/day
TAM 20 mg/day
120 ER+, BC patients 4 weeks before surgery Ki-67 modulation Ki-67 expression decreased to a similar degree among the three TAM dose groups. Ki-67 expression after short-term TAM is a good predictor of recurrence-free survival and overall survival
Decensi et al. 2007 [44] TAM 1 mg/day
TAM 5 mg/day
TAM 10 mg/week
210 Current or de novo HRT users IGF-I IGF-I declined in all TAM arms (P = 0.005), with a greater change on 5 mg/day. Tamoxifen did not increase endometrial Ki-67 expression
Decensi et al. 2009 [35] TAM 5 mg/day
FEN 200 mg/day
235 Premenopausal women
pT1mic/pT1a BC;
OR Intraepithelial neoplasia;
OR Gail risk at five years ≥1.3%
Plasma IGF-I Mammographic density; uterine effects; breast neoplastic events after 5.5 years Despite favorable effects on plasma IGF-I levels and mammographic density, the combination of low-dose TAM plus FEN did not reduce breast neoplastic events
Bonanni et al. 2009 [41] ANA 1 mg/day
TAM 10 mg/week
75 Postmenopausal women with previous breast intraepithelial neoplasia Plasma drug concentrations Biomarker modulation The addition of weekly TAM administration did not impair anastrozole bioavailability and modulated favorably its safety profile
Guerrieri Gonzaga et al. 2010 [49] TAM 20 mg/week
TAM 5 mg/day
680 Women with previous DIN Second primary breast cancer (in situ or invasive) High ER and especially high PgR expression is a significant adverse prognostic indicator of DIN, and low-dose TAM appears to be an active treatment. Women with low-expression ER or PgR DIN do not seem to benefit from TAM
  1. ANA, anastrozole; BC, breast cancer; DIN, ductal intraepithelial neoplasia; ER, estrogen receptor; ER+, estrogen-receptor positive; FEN, fenretinide; HRT, hormone replacement therapy; IGF, insulin-like grow factor; PgR, progesterone receptor; TAM, tamoxifen.