Question explored with the scientific record
Conversation so far
- 1 Est-ce que le tamoxifène protège les hommes du retour du cancer du sein et si oui de combien de pourcentage
- 2 Quels sont les effets secondaires et risques graves du tamoxifène chez l’homme?
Answered on this page ↓
Quels sont les effets secondaires et risques graves du tamoxifène chez l’homme?
The short version: tamoxifen carries real risks in men, but most of the safety data comes from women. The male-specific evidence is too thin to quantify the risks for men.
The evidence you have about tamoxifen's side effects and serious risks comes almost entirely from studies of women. That is a problem. The two biggest proven harms of tamoxifen in women are endometrial cancer and venous thromboembolism (blood clots). In the NSABP P-1 prevention trial, tamoxifen raised the risk of endometrial cancer about 2.5 times (RR 2.53, CI 1.35 to 4.97) and doubled the risk of blood clots (RR 1.9) [5, 12]. A larger overview across prevention trials found the same pattern: endometrial cancer RR 2.4, VTE RR 1.9 [4]. But men do not have a uterus. The endometrial cancer risk does not apply to them at all.
That leaves blood clots as the main proven serious risk that crosses sexes. The evidence also suggests tamoxifen can cause cataracts and bone fractures, both seen in the NSABP P-1 trial [5]. In women, tamoxifen users had higher rates of cataract surgery and hip fractures [5]. Whether men face the same risk is plausible but not well measured.
The smaller, more common side effects matter too: hot flashes, fatigue, sexual dysfunction, and mood changes. These are reported across trials but the data is almost entirely from women. In one study of men with breast cancer, the recurrence rate on tamoxifen was 13.2% and the 5-year disease-free survival was 86.2%, but that study did not report side effect rates in detail [1].
The evidence has a structural gap. The trials that established tamoxifen's safety profile in women never enrolled enough men to generate separate safety numbers. The only serious risk that logically carries over to men is venous thromboembolism. The endometrial cancer risk is sex-specific and irrelevant. The other common side effects probably occur in men but at unknown rates.
| Serious risk | Rate in women on tamoxifen | Relevance to men |
|---|---|---|
| Endometrial cancer | ~2.3 per 1,000 women (RR 2.53) [5, 12] | Not applicable (no uterus) |
| Venous thromboembolism | ~1.9 times the placebo rate (statistically significant) [4, 5] | Applies, exact rate unknown |
| Cataract surgery | Higher in tamoxifen users [5] | Likely applies, unquantified |
| Bone fractures | Higher rate, RR not specified [5] | Likely applies, unquantified |
My call: the only proven serious risk of tamoxifen that crosses to men is blood clots, but no male-specific study has measured the rate. The other major proven risk in women, endometrial cancer, does not apply. The common side effects like hot flashes and fatigue probably occur in men but the rates are not known from evidence. Confidence: low for the exact risk magnitude in men; moderate for the principle that venous thromboembolism is the main danger to watch for.
Sources used 4
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Tamoxifen-Induced Venothromboembolic Events: Exploring Validation of Putative Genetic Association
This pilot study evaluates the feasibility of a matched case-control design to validate the association of estrogen receptor SNPs with venothromboembolic events in breast cancer patients treated with tamoxifen, revealing significant enrollment rates and a potential association o…
DOI: 10.3121/cmr.2012.1101 -
Endocrine Therapy Trials of Aromatase Inhibitors for Breast Cancer in the Adjuvant and Prevention Settings
Three major randomized trials show aromatase inhibitors (anastrozole, exemestane, letrozole) improve disease-free survival and reduce contralateral breast cancers in postmenopausal women with early breast cancer in adjuvant settings and in prevention settings, with distinct toxi…
DOI: 10.1158/1078-0432.900s.11.2 -
Breast Cancer Prevention with Selective Estrogen Receptor Modulators
A perspective synthesizing major randomized trials of tamoxifen and raloxifene for breast cancer risk reduction, detailing their efficacy (notably ER-positive cancer reductions), associated risks (endometrial/cardiovascular events, fractures), and upcoming studies that will shap…
DOI: 10.1111/j.1749-6632.2001.tb04006.x -
A review of selective estrogen receptor modulators in the treatment of breast and endometrial cancer
This review discusses the efficacy of selective estrogen receptor modulators (SERMs) like tamoxifen, raloxifene, and arzoxifene in the prevention and treatment of breast and endometrial cancer, highlighting their mechanisms and clinical trial results.
DOI: 10.1016/s0093-7754(02)70136-x