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Tam5.2
Tamoxifen (Nolvadex) Research
Mostly mechanism / observationalLimited safety
8 peer-reviewed studies
What the evidence says
Mostly mechanism / observational
Most Tamoxifen (Nolvadex) studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from medium-quality meta-analyses and randomised trials published 1998–2019 with a typical study size of 176 participants.
Based on 8 studies · 3 meta-analyses · 3 RCTs · 13,709 total participants
Confidence
High
By outcome
Gynecomastia & testosterone
Mostly mechanism / observational6 studies
Breast cancer (treatment & prevention)
Mostly mechanism / observational3 studies
Safety profile
Mostly mechanism / observational3 studies
Male fertility
Too few graded studies2 studies
Older research base
Newest study from 2019 · Latest meta-analysis: 2019
199820082019
1Meta-Analysis2011
In oestrogen receptor (ER)-positive disease, allocation to about 5 years of tamoxifen substantially reduced recurrence rates throughout the first 10 years... Breast cancer mortality was reduced by about a third throughout the first 15 years... 5 years of adjuvant tamoxifen safely reduces 15-year risks of breast cancer recurrence and death.
Early Breast Cancer Trialists' Collaborative Group (EBCTCG); Davies C, Godwin J, Gray R, Clarke M, Cutter D, et al. · Lancet (2011)
About 5 years of tamoxifen roughly halved recurrence over the first decade (RR 0.53 years 0-4, 0.68 years 5-9) and cut breast-cancer mortality by ~one-third sustained across 15 years
The benefit was confined to ER-positive disease (little or no effect in ER-negative); the note of honesty is small absolute increases in thromboembolic and uterine-cancer mortality in women over 55
Tamoxifen reduced the risk of invasive breast cancer by 49%... The rate of endometrial cancer was increased in the tamoxifen group (risk ratio = 2.53)... The rates of stroke, pulmonary embolism, and deep-vein thrombosis were elevated in the tamoxifen group.
Fisher B, Costantino JP, Wickerham DL, Redmond CK, Kavanah M, Cronin WM, et al. · J Natl Cancer Inst (1998)
NSABP P-1: randomized, placebo-controlled prevention trial of 20 mg/day tamoxifen for 5 years in 13,388 women at increased breast-cancer risk
Cut invasive breast-cancer incidence by 49% and noninvasive by 50%, with the reduction confined to ER-positive tumors (69% lower)
Carries its own mandatory counter-evidence: endometrial cancer rose ~2.5-fold and stroke, pulmonary embolism, and deep-vein thrombosis were all elevated (predominantly in women over 50)
Bicalutamide-induced BEs can be prevented to a significant degree by prophylaxis with TAM 10 mg/day or effectively treated with TAM therapy 20 mg/day... The difference in BEs between the 2 arms was statistically significant (P < .0001).
Serretta V, Altieri V, Morgia G, Nicolosi F, De Grande G, Mazza R, et al. · Clin Genitourin Cancer (2012)
Randomized multicenter trial in 176 men on bicalutamide monotherapy for prostate cancer: reactive tamoxifen 20 mg/day (arm A) vs prophylactic tamoxifen 10 mg/day started with bicalutamide (arm B)
Breast events (gynecomastia, breast pain) reached 78.3% prevalence in the reactive arm vs 35% with prophylaxis — prophylaxis was significantly more effective (P<.0001)
No difference between arms in PSA response, plasma testosterone, or tumor progression; tamoxifen was generally well tolerated
Oestrogen antagonists use was associated with a statistically significant increased pregnancy rate compared with controls (pooled OR 2.42; 95% CI 1.47-3.94)... Significant elevation of serum follicle stimulating hormone... and testosterone... was associated with its use.
Chua ME, Escusa KG, Luna S, Tapia LC, Dofitas B, Morales M. · Andrology (2013)
Meta-analysis of 11 good-quality RCTs of estrogen antagonists (clomiphene or tamoxifen) as empiric therapy for idiopathic male infertility (oligo/asthenozoospermia)
Roughly doubled spontaneous pregnancy rate (pooled OR 2.42) and raised sperm concentration and motility versus controls
Significantly elevated serum FSH and testosterone — the surrogate readouts behind tamoxifen's hypothalamic-feedback mechanism in men — with no significant excess of adverse events in these trials
Tamoxifen, but not anastrozole, significantly reduced the incidence of gynecomastia/breast pain when used prophylactically and therapeutically. Serum testosterone levels increased with tamoxifen relative to placebo.
Saltzstein D, Sieber P, Morris T, Gallo J. · Prostate Cancer Prostatic Dis (2005)
Randomized, double-blind, placebo-controlled multicenter trial in 107 men on bicalutamide 150 mg/day, comparing tamoxifen 20 mg/day vs anastrozole 1 mg/day for prophylaxis and treatment of gynecomastia/breast pain
Tamoxifen (but NOT the aromatase inhibitor anastrozole) significantly reduced gynecomastia/breast pain both prophylactically and therapeutically
Serum testosterone rose with tamoxifen relative to placebo — a direct readout of its estrogen-feedback/HPG mechanism in men
Gynecomastia and/or mastodynia is a common medical problem in patients receiving antiandrogen treatment for prostate cancer; up to 70% of these patients result to be affected... Five studies reported pharmacological intervention with tamoxifen and/or anastrozole.
Fagerlund A, Cormio L, Palangi L, Lewin R, Santanelli di Pompeo F, Elander A, et al. · PLoS One (2015)
Systematic review (PRISMA, GRADE) of treatment options for bicalutamide-induced gynecomastia; 11 studies met inclusion, most randomized with varying risk of bias
Synthesizes the pharmacologic (tamoxifen/anastrozole) and radiotherapy evidence, positioning tamoxifen as the leading drug option for prophylaxis and treatment
Confirms gynecomastia/mastodynia affects up to 70% of antiandrogen-treated men and meaningfully harms quality of life
SERM administration increased significantly sperm concentration, total sperm count, and serum luteinizing hormone, follicle-stimulating hormone, and total testosterone levels compared with baseline values... and increased the pregnancy rate compared to the control group.
Cannarella R, Condorelli RA, Mongioì LM, Barbagallo F, Calogero AE, La Vignera S. · Expert Opin Pharmacother (2019)
Systematic review and meta-analysis of 16 controlled and uncontrolled trials of SERMs (including tamoxifen) in normogonadotropic men with idiopathic oligozoospermia
SERMs raised sperm concentration, total sperm count, LH, FSH and total testosterone versus baseline, and increased pregnancy rate versus controls
Honest about limits: no significant effect on progressive/total motility and the authors note the paucity of data prevents a definitive conclusion
Mean reduction in breast nodule diameter was 2.1 cm (95% CI 1.7, 2.7, P <.0001) after treatment with tamoxifen and 2.5 cm (95% CI 1.7, 3.3, P <.0001) with raloxifene... a greater proportion had a significant decrease (>50%) with raloxifene (86%) than tamoxifen (41%).
Lawrence SE, Faught KA, Vethamuthu J, Lawson ML. · J Pediatr (2004)
Retrospective chart review of 38 adolescents with persistent pubertal gynecomastia treated with raloxifene or tamoxifen (a 3-9 month course) versus reassurance
Raloxifene reduced breast-nodule diameter by a mean 2.5 cm (P<.0001), with some improvement in 91% and a major (>50%) response in 86% — a higher major-response rate than tamoxifen
Honest limit: small, retrospective, no controls beyond reassurance; the authors explicitly call for prospective confirmation, and there are no controlled trials in adult male gynecomastia