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Tam5.2

Tamoxifen (Nolvadex) Research

Mostly mechanism / observational

937 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 high-quality meta-analyses and randomised trials published 1976–2026 with a typical study size of 38 participants.

Based on 936 studies · 93 meta-analyses · 821 RCTs · 38 total participants

Confidence

High confidence

By outcome

Breast cancer (treatment & prevention)
Mostly mechanism / observational700 studies
Gynecomastia & testosteroneBy blocking estrogen feedback, raises gonadotropins and endogenous testosterone and improves sperm parameters (off-label male use) · Weeks to a few months
Mostly mechanism / observational23 studies
Safety profile
Mostly mechanism / observational22 studies
Male fertilityRaises FSH/LH and improves sperm parameters — the rationale for male-infertility regimens · Weeks to a few months
Mostly mechanism / observational12 studies

Slowing down

Only 53 studies in the last 5 years · Latest meta-analysis: 2026

197620012026

1Meta-Analysis2014

Ye QL, Zhai ZM · Mol Biol Rep (2014)

Tamoxifen (Nolvadex) Research

Mostly mechanism / observational

Toremifene and tamoxifen have similar efficacy in the treatment of patients with breast cancer: a meta-analysis of randomized trials.

[Tamoxifen in the treatment of patients with breast cancer: results of the latest meta-analysis of prospective randomized clinical trials].

Tamoxifen and risk of contralateral breast cancer among women with inherited mutations in BRCA1 and BRCA2: a meta-analysis.

Risk of Gastric and Colorectal Cancer After Tamoxifen Use for Breast Cancer: A Systematic Review and Meta-Analysis.

The effects of adjuvant endocrine therapy on long-term outcomes from ductal carcinoma in situ: a systematic review and meta-analysis.

Metabolism and transport of tamoxifen in relation to its effectiveness: new perspectives on an ongoing controversy.

Postoperative tamoxifen for ductal carcinoma in situ.

Two-gene expression ratio as predictor for breast cancer treated with tamoxifen: evidence from meta-analysis.

Effects of tamoxifen on the cervix and uterus in women with breast cancer: experience with Iranian patients and a literature review.

Aromatase inhibitors versus tamoxifen in early breast cancer: patient-level meta-analysis of the randomised trials.

Extended adjuvant tamoxifen for early breast cancer: a meta-analysis.

Use of tamoxifen in advanced-stage hepatocellular carcinoma. A systematic review.

A Simulation Study to Compare the Treatment Effect of Tamoxifen by CYP2D6 Genotypes and Third-Generation Aromatase Inhibitors.

Cytochrome P450 2D6 and outcomes of adjuvant tamoxifen therapy: results of a meta-analysis.

Tamoxifen for early breast cancer: an overview of the randomised trials. Early Breast Cancer Trialists' Collaborative Group.

Clinical benefit and risk of death with endocrine therapy in ovarian cancer: A comprehensive review and meta-analysis.

Surgery versus primary endocrine therapy for operable primary breast cancer in elderly women (70 years plus).

Meta-analysis of the cumulative risk of endometrial malignancy and systematic review of endometrial surveillance in extended tamoxifen therapy.

The effect of tamoxifen as an adjuvant therapy for breast cancer on apolipoproteins and lipoprotein(a) concentrations in women: A meta-analysis of randomized controlled trials.

Surgery, with or without tamoxifen, vs tamoxifen alone for older women with operable breast cancer: cochrane review.