Hormone Replacement Therapy and Risk of Breast Cancer With a Favorable Histology
Results of the Iowa Women's Health Study
Susan M. Gapstur, PhD; Monica Morrow, MD; Thomas A. Sellers, PhD
JAMA. 1999;281:2091-2097.
Context Long-term, postmenopausal use of hormone replacementtherapy (HRT) appears to increase breast cancer risk. Whetherthe effect of HRT use on risk of breast cancer varies amonghistological types of invasive carcinoma is unknown.
Results Duration of ever HRT use was associated with riskof invasive carcinoma with a favorable histology, with an RRof 1.81 (95% confidence interval [CI], 1.07-3.07) for thosewho used HRT 5 or fewer years vs an RR of 2.65 (95% CI, 1.34-5.23)for those who used HRT for more than 5 years (P for trend=.005)after adjustment for age and other breast cancer risk factors.There was no association between ever HRT use and the incidenceof DCIS or invasive ductal or lobular carcinoma. Among currenthormone users, after adjusting for age and other breast cancerrisk factors, the RRs (95% CIs) of invasive carcinoma with afavorable histology were 4.42 (2.00-9.76) and 2.63 (1.18-5.89)for 5 or fewer years of use and for more than 5 years of use,respectively. Risk of invasive ductal or lobular carcinoma wasassociated with current use (5 years) of HRT with an RR of 1.38(95% CI, 1.03-1.85).
Conclusions Exposure to HRT was associated most stronglywith an increased risk of invasive breast cancer with a favorableprognosis. These data add important clinical information forassessing the risks and benefits of HRT use.
Author Affiliations: Departments of Preventive Medicine (Dr Gapstur) and Surgery (Dr Morrow), and Lynn Sage Comprehensive Breast Center (Dr Morrow), Northwestern University Medical School, Chicago, Ill; and Department of Health Sciences Research, Mayo Clinic/Foundation, Rochester, Minn (Dr Sellers).
