Does hormone replacement therapy increase breast cancer risk?

Breast cancer risk with hormone replacement therapy is small but real - needs to be understood in overall risk-benefit context. Main evidence: (1) Estrogen + progesterone (for women with intact uterus) - raises breast cancer risk by ~1 additional case per 1000 woman-years after 5 years use (Women's Health Initiative 2002, and follow-up studies). Risk returns to baseline several years after stopping hormone replacement therapy. (2) Estrogen alone (for women without uterus) - doesn't raise breast cancer risk, with Women's Health Initiative showing slight possible reduction. (3) Modifying factors - risk lower with: transdermal hormone replacement therapy compared with oral therapy, starting hormone replacement therapy within first 5-10 years of menopause, low dose, duration <5 years. Important context: background breast cancer risk for women 50-69 is ~30 cases per 1000 women over 5 years. hormone replacement therapy adds ~5 cases - about 17% increase. Compare: daily alcohol (2+ drinks) adds ~5 cases; postmenopausal obesity adds ~25 cases. For Malaysian women: (a) No family history of breast cancer - hormone replacement therapy benefits for severe symptoms typically outweigh small risk. (b) Strong family history (mother/sister with breast cancer under 50) - discuss genetic testing (BRCA1/2) before starting hormone replacement therapy. (c) Personal history of breast cancer - hormone replacement therapy typically not recommended; alternatives include local vaginal estrogen (safe) or non-hormonal medications. Malaysian obstetrics and gynaecology specialists perform individualised risk-benefit assessment before writing prescription.