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Identified risk factors for endometrial cancer are accepted as operating through estrogen exposure. In a recent analysis, the effect of risk factors such as body mass index (BMI) was not explained by circulating estrogen concentrations. In the present analysis, we correct for measurement error associated with obtaining only one blood sample per subject. Applying regression calibration ideas, we found that error correction of log estrone had little impact on estimates of the BMI effect, suggesting that hormone measurement error does not account for the residual importance of BMI. The biologic mechanism for the increased risk associated with BMI remains to be explained.

In a population-based case-control study of parous women less than 45 years of age, we evaluated the relations of various pregnancy characteristics to maternal breast cancer risk. Cases (N = 1,239) diagnosed with in situ or invasive breast cancer from 1990 to 1992 in Atlanta, GA, Seattle/Puget Sound, WA, and five counties in central New Jersey, and population controls (N = 1,166) identified by random-digit dialing, were interviewed regarding the details of their pregnancies. We used logistic regression to estimate relative risks (RR) and 95% confidence intervals (CI) and to adjust for breast cancer risk factors. Women who reported nausea or vomiting in their first pregnancy had a slightly lower risk of breast cancer (RR = 0.87; 95% CI = 0.72-1.0). We found no strong or consistent associations for maternal risk related to gestational length, pregnancy weight gain, gestational diabetes, pregnancy hypertension, or gender of the offspring, although we found some evidence for reductions in risk for toxemia (RR = 0.81; 95% CI = 0.61-1.1) and specific sex (RR for female twins vs singletons = 0.48; 95% CI = 0.20-1.3) and timing characteristics of twinning. Overall, these data provide little support for the hypothesis that pregnancy hormone levels are associated with subsequent maternal risk of breast cancer in young women.

Objective: To clarify several unresolved issues regarding the relationship of estrogens to endometrial cancer risk., Methods: We conducted a hospital-based case-control study involving 300 menopausal women newly diagnosed with epithelial endometrial cancer and 207 population controls matched to the cases for age, race, and residence., Results: Estrogen use significantly increased endometrial cancer risk (adjusted relative risk [RR] 3.0, 95% confidence interval [CI] 1.7-5.1). Although both short- and long-term use appeared to elevate the risk of early-stage tumors, an effect of estrogens on late-stage tumors was observed only for long-term use (RR 2.1, 95% CI 0.7-6.4). A small proportion of women reported having used progestogens simultaneously with estrogens, which was associated with a lower risk (RR 1.8) than use of estrogens alone (RR 3.4). Although the highest risks were for recent users of estrogens, persistent excess risks were seen even for those who had discontinued use of 5 or more years. There were no striking relationships according to the type of estrogen or regimen used, and associations with dose were inconsistent, although women who used low-dose preparations exclusively had the lowest risk. Estrogen injections or creams, used by only 5.9 and 5.1% of the subjects, respectively, were not significant risk factors after adjustment for estrogen pill use. Women who were thin or who smoked cigarettes appeared to be most adversely affected by estrogen use. Estrogen users failed to experience the protective effect normally associated with oral contraceptive use., Conclusion: The effect of estrogens on endometrial cancer risk appears to vary both by usage patterns and by patient characteristics.

A group of 205 women with endometrial carcinoma was matched for age, parity, and year of operation with a group of 205 women who had had hysterectomies for benign disease. In the former group, 32 patients had used conjugated estrogens, while in the latter group 12 had used this hormone, yielding a relative risk of 3.1 (P = 0.0008). Users of other forms of systemic estrogens showed similar elevations in relative risk. Relative risk was related to duration of use, progressing from no evidence of risk among those using the hormone for less than 5 years to an 11.5-fold greater risk for those using it for 10 years or more. Risk was also related to the strength of the medication. The relative risk for users of the 1.25-mg tablets was 12.7 as compared to a two- to fourfold greater risk among users of lesser strength tablets.