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Does tamoxifen cause cancer in humans?
1Lombardi Cancer Center, Washington, DC 20007, USA.
Summary
Tamoxifen therapy may slightly increase endometrial cancer risk in women. While it is hepatocarcinogenic in rats, human data shows no conclusive link to liver cancer due to metabolic differences.
Area of Science:
- Oncology
- Pharmacology
- Toxicology
Background:
- Tamoxifen exhibits estrogen-like effects, raising concerns about its carcinogenic potential.
- Concerns exist regarding tamoxifen's role in promoting endometrial cancers in women undergoing long-term therapy.
Purpose of the Study:
- To comprehensively review preclinical and clinical data on tamoxifen's carcinogenic potential.
- To evaluate the association between tamoxifen use and cancer development, particularly in the endometrium and liver.
Main Methods:
- A systematic MEDLINE search was performed focusing on tamoxifen carcinogenicity.
- Existing literature on tamoxifen's effects was critically reviewed and analyzed.
Main Results:
- Tamoxifen therapy is associated with a small, but statistically significant, increased risk of endometrial cancer in some studies.
- Laboratory studies indicate tamoxifen is hepatocarcinogenic in rats, linked to DNA adduct formation, but not in other species.
- Human data does not conclusively link tamoxifen to increased hepatocellular cancer rates, suggesting interspecies metabolic differences.
Conclusions:
- Tamoxifen may act as a tumor promoter in the human endometrium, though its impact is considered small.
- Routine gynecologic examinations are recommended for women on chronic tamoxifen therapy, with endometrial sampling reserved for cases of uterine bleeding.
- Differences in tamoxifen metabolism likely explain the contrasting carcinogenic potential observed between rats and humans, particularly regarding liver cancer.