Factors modifying the association between hormone-replacement therapy and breast cancer risk.
OBJECTIVE
Hormone-replacement therapy (HRT) is an established risk factor for breast cancer. HRT users are different from non-users with respect to socio-economic and other characteristics. There may be women where the HRT-related risk could be modulated by other factors.


METHODS
We conducted a population-based case-control study with 688 breast cancer cases and 724 controls to characterize HRT users and to estimate odds ratios (OR) and 95% confidence intervals (CI) for HRT use and potentially risk modifying factors.


RESULTS
In women aged 50 years and older, 58% of controls and 61% of cases ever used HRT. Among women in natural menopause, HRT use for 10 years and more years was associated with an increased breast cancer risk (OR 1.79, 95% CI, 1.12-2.87), but not among women in surgical menopause (OR 0.61, 95% CI, 0.09-4.17). In the subgroup of women with a positive family history of breast cancer, each year of HRT use increased the risk by 1.22 (95% CI, 1.02-1.47). Another subgroup comprised women with at least 10 diagnostic mammograms (OR 4.04, 95% CI, 1.10-14.81 for using HRT 10 or more years).


CONCLUSIONS
Long-term HRT use was associated with a breast cancer risk in women with natural menopause. Our findings suggest that this risk may be increased in women with a positive family history of breast cancer and in women who received frequent diagnostic mammographic screens.
Pesch
Beate
B
Berufsgenossenschaftliches Forschungsinstitut für Arbeitsmedizin (BGFA), Institut der Ruhr-Universität Bochum, Bürkle-de-la-Camp-Platz 1, 44789, Bochum, Gemany.
Ko
Yon
Y
Brauch
Hiltrud
H
Hamann
Ute
U
Harth
Volker
V
Rabstein
Sylvia
S
Pierl
Christiane
C
Fischer
Hans-Peter
HP
Baisch
Christian
C
Justenhoven
Christina
C
Ranft
Ulrich
U
Brüning
Thomas
T
D000368:Aged; D001943:Breast Neoplasms / Q000139:chemically induced* / Q000453:epidemiology*; D016022:Case-Control Studies; D015914:Estrogen Replacement Therapy / Q000009:adverse effects*; D005260:Female; D005858:Germany / Q000453:epidemiology; D006801:Humans; D008875:Middle Aged; D012307:Risk Factors