Oestrogen replacement therapy and breast cancer risk: a case-control study.
The relationship between oestrogen replacement therapy and breast cancer risk was examined based on data obtained from a population-based case-control study of breast cancer on Long Island, New York, USA. Cases were defined as female residents of two Long Island counties, aged 20-79, who were diagnosed with breast cancer between 1 January 1984 and 31 December 1986. Age- and county-matched controls were selected from driver's licence files. Among all postmenopausal women, there was no significant association between ever-use of hormones to treat menopausal symptoms and breast cancer risk. There was also no significant positive association in any subgroup defined by type of menopause (natural, hysterectomy with at least one ovary intact, bilateral oophorectomy) or age at menopause. Additionally, there was no increasing trend in risk with duration of use either overall or in any subgroup, nor was there an effect at any interval since last use. A significant elevation in risk was observed in women with 10-19 years since first exposure, which was concentrated in women with a natural menopause or hysterectomy with at least one ovary remaining, and women aged > 45 at menopause. Results of logistic regression analysis revealed no important confounding by any of several established breast cancer risk factors. However, a significant interaction was observed between body mass index (BMI) and oestrogen use, with an effect of oestrogen use being seen only in the thinnest tercile. Although biologically plausible explanations for this finding exist, the effect of chance cannot be ruled out.
Weinstein
A L
AL
Bureau of Cancer Epidemiology, New York State Department of Health, Albany 12237.
Mahoney
M C
MC
Nasca
P C
PC
Hanson
R L
RL
Leske
M C
MC
Varma
A O
AO
D000328:Adult; D000367:Age Factors; D000368:Aged; D015992:Body Mass Index; D001943:Breast Neoplasms / Q000139:chemically induced / Q000453:epidemiology*; D016022:Case-Control Studies; D015914:Estrogen Replacement Therapy / Q000009:adverse effects; D005260:Female; D006801:Humans; D008875:Middle Aged; D009518:New York / Q000453:epidemiology; D012044:Regression Analysis; D012307:Risk Factors; D013997:Time Factors