Estrogen therapy and risk of breast cancer in postmenopausal women: a case-control study and results of a multivariate analysis.
OBJECTIVE
Several randomized trials and observational studies show that the use of hormone therapy (HT) increases the risk of breast cancer (BC). The aim of this study was to assess the effects of exposure to both HT and oral contraceptives (OCs) on BC risk in postmenopausal women, all residing in the same metropolitan area.


METHODS
Data regarding a series of 238 consecutive postmenopausal women with infiltrating ductal carcinoma (cases) and 255 randomly selected age-matched healthy women (controls) were reviewed. Odds ratios for no breast-feeding and HT and OC use were 1.82 (95% CI, 1.20-2.77), 2.49 (95% CI, 1.73-3.58), and 2.06 (95% CI 1.14-3.70), respectively.


RESULTS
Four independent variables (years between menarche and menopause, breast-feeding, OC use, and HT use) were included in the final multivariate analysis using logistic regression. The cumulative odds ratio calculated from the observed versus predicted values, obtained using the logistic regression function, was 4.55 (95% CI, 2.13-9.71), whereas the cumulative risk of common exposure to both OCs and HT was 2.77 (95% CI, 1.44-5.32). The logistic model correctly classified 67.5% (95% CI, 63.2-71.5) of cases. The receiver operating characteristic (ROC) curve of the complete logistic function showed a fair area of accuracy (0.77; 95% CI, 0.72-0.81).


CONCLUSIONS
Our results show that the risk of common exposure to both OCs and HT increases in women with other risk factors. However, several parameters traditionally considered in epidemiological studies do not have the same weight in each local community, suggesting the need to create different models to correctly select the high-risk population.
Lumachi
Franco
F
Department of Surgical and Gastroenterological Sciences, School of Medicine, University of Padua, 35128 Padova, Italy. flumachi@unipd
Frigo
Anna Chiara
AC
Basso
Umberto
U
Tombolan
Valeria
V
Ermani
Mario
M
D001943:Breast Neoplasms / Q000139:chemically induced / Q000453:epidemiology*; D018270:Carcinoma, Ductal, Breast / Q000139:chemically induced / Q000453:epidemiology*; D016022:Case-Control Studies; D016001:Confidence Intervals; D003278:Contraceptives, Oral, Hormonal / Q000009:adverse effects; D015914:Estrogen Replacement Therapy / Q000009:adverse effects / Q000706:statistics & numerical data*; D005260:Female; D006801:Humans; D007558:Italy / Q000453:epidemiology; D008875:Middle Aged; D015999:Multivariate Analysis; D016017:Odds Ratio; D017698:Postmenopause; D012307:Risk Factors; D014505:Urban Population / Q000706:statistics & numerical data; D016387:Women's Health
D003278:Contraceptives, Oral, Hormonal