Tamoxifen and the endometrium

Question 1

What is tamoxifen?
Explain its effect on different tissues.

Answer 1

SERM.

Antagonist effect on ER in breast tissues.
Agonist effect on ER in endometrium, external genitalia, bone, cardiovascular system (increased risk VTE).

Question 2

What are the possible effects of tamoxifen on the uterus?

Answer 2

• Benign cystic hyperplasia (most common)
• Increased polyp formation
• Growth in benign fibroids
• Progression of endometriosis
• Hyperplasia with or without atypia
• Increased risk of endometrial cancer in postmenopausal women (RR 4.01)
• Small increased risk uterine sarcoma

Question 3

What is the risk of endometrial cancer in women using tamoxifen?

Answer 3

• Premenopausal women - no increased risk
• Post-menopausal women RR 4.01, but absolute risk still low - 1.6% cumulative risk after 5 years use (incidence 2-3/1000 per year)

Question 4

What is the management for asymptomatic women with USS findings of thickened endometrium?

Answer 4

• In the absence of symptoms many women do not require further investigation
• If any risk factors then needs formal sampling:
  
  • Symptomatic
  • Use >2 years
  • FHx endometrial cancer
  • High BMI
  • T2DM
  • HTN

Question 5

What is the evidence for mirena IUS for endometrial protection?

Answer 5

• Not recommended
• Cochrane review found no reduction in endometrial cancer by using mirena IUS
• Unclear the effect the mirena may have on breast cancer recurrence

Question 6

What additional advice should be given to a pre-menopausal woman on tamoxifen?

Answer 6

• Tamoxifen is a teratogen
• Non-hormonal contraception should be used