Breast cancer and hormone replacement therapy: putting the risk into perspective

Postmenopausal hormone replacement therapy: endometrial and breast effects

The history of hormone replacement therapy (HRT) dates back to the late 1800s, when animal extracts of ovaries were first used. With the development of synthetic hormones, widespread use in postmenopausal women extended throughout the industrialized world, so that by the late 1900s roughly one-third to one-half of all postmenopausal women in the United States and Europe were taking HRT. Two events changed the course of use of HRT: the association of an increased rate of endometrial carcinoma with estrogen-only HRT and the association of an increased breast cancer rate with combined estrogen and progestin HRT. This review explores the evidence of the effects of HRT on the endometrium and the breast, with emphasis on the pathologic changes.

Several anthropometric measurements and breast cancer risk: results of the E3N cohort study

OBJECTIVE

To investigate the association between various anthropometric characteristics and breast cancer.

DESIGN

Longitudinal prospective cohort study. Follow-up between 1995 and 2000.

SUBJECTS

In total, 69 116 women (age: 45-70 years; mean follow-up: 3.6 years), 275 premenopausal and 860 postmenopausal incident invasive breast cancers.

MEASUREMENTS

Self-reported height, weight, breast, thorax, waist and hip circumferences and calculated body mass index (BMI) and waist-to-hip ratio (WHR) at baseline.

RESULTS

A slight increase in risk with increasing height was found. Weight, BMI, thorax and waist circumferences and WHR were negatively related to breast cancer risk among premenopausal women. The relationships became non significant after additional adjustment for BMI. An increased risk of premenopausal breast cancer with an android body shape (WHR>0.87) might possibly be confined to obese women. Among postmenopausal women, all anthropometric measurements of corpulence were positively associated with breast cancer risk but became non significant after additional adjustment for BMI. No difference in risk of postmenopausal breast cancer according to HRT use was observed.

CONCLUSION

The study confirmed that adiposity was negatively associated to premenopausal breast cancer risk and positively associated to postmenopausal breast cancer risk. Further studies will be needed to specify clearly the association between WHR and breast cancer risk, particularly before menopause.

Progestins and progesterone in hormone replacement therapy and the risk of breast cancer

Controlled studies and most observational studies published over the last 5 years suggest that the addition of synthetic progestins to estrogen in hormone replacement therapy (HRT), particularly in continuous-combined regimen, increases the breast cancer (BC) risk compared to estrogen alone. By contrast, a recent study suggests that the addition of natural progesterone in cyclic regimens does not affect BC risk. This finding is consistent with in vivo data suggesting that progesterone does not have a detrimental effect on breast tissue. The increased BC risk found with the addition of synthetic progestins to estrogen could be due to the regimen and/or the kind of progestin used. Continuous-combined regimen inhibits the sloughing of mammary epithelium that occurs after progesterone withdrawal in a cyclic regimen. More importantly, the progestins used (medroxyprogesterone acetate and 19-Nortestosterone-derivatives) are endowed with some non-progesterone-like effects, which can potentiate the proliferative action of estrogens. Particularly relevant seem to be the metabolic and hepatocellular effects (decreased insulin sensitivity, increased levels and activity of insulin-like growth factor-I, and decreased levels of SHBG), which contrast the opposite effects induced by oral estrogen.

Endogenous sex hormones and subsequent breast cancer in premenopausal women

Because of large intra-individual variation in hormone levels, few studies have investigated the relation of serum sex hormones to breast cancer (BC) in premenopausal women. We prospectively studied this relation, adjusting for timing of blood sampling within menstrual cycle. Premenopausal women (5,963), recruited to the Hormones and Diet in the Etiology of Breast Tumors (ORDET) cohort study, provided a blood sample in the 20-24th day of their menstrual cycle. After 5.2 years of follow-up, 65 histologically confirmed BC cases were identified and matched individually to 4 randomly selected controls. Sera, stored at -80 degrees C, were assayed blindly for dehydroepiandrosterone sulfate, total and free testosterone (FT), androstenedione, androstanediol-glucoronide, progesterone, 17-OH-progesterone, sex hormone-binding globulin, follicle-stimulating hormone (FSH) and luteinizing hormone (LH). Fifty-five cases had information for multivariate analyses. Compared to controls, BC cases had shorter cycles and intervals between blood sampling and bleeding, and lower LH and FSH. FT was significantly associated with BC risk: relative risk (RR; adjusted for age, body mass index and ovarian cycle variables) of highest vs. lowest tertile was 2.85 [95% confidence interval (CI) = 1.11-7.33, p for trend = 0.030]. Progesterone was inversely associated with adjusted RR for highest vs. lowest tertile of 0.40 (95% CI = 0.15-1.08, p for trend = 0.077), significantly so in women with regular menses, where adjusted RR was 0.12 (95% CI = 0.03-0.52, p for trend = 0.005). These findings support the hypothesis that ovarian hyperandrogenism associated with luteal insufficiency increases the risk of BC in premenopausal women.

Anthropometry, breast cancer and menopausal status: Use of repeated measurements over 10 years of follow-up?results of the French E3N women's cohort study

The association between weight, BMI and breast cancer was analyzed on 94,805 women of the E3N cohort according to their menopausal status. Seven hundred eighty-six incident invasive premenopausal breast cancers and 1,522 incident invasive postmenopausal breast cancers occurred during a mean follow-up of 9.7 years. Weight and BMI were updated every 24 months and considered as time-dependent variables. Data were analyzed using multivariate Cox proportional hazards models. Trend RRs of premenopausal breast cancer were 0.97 (0.92-1.01) for a 5 kg increase in weight and 0.96 (0.91-1.01) for a 2 kg/m(2) increase in BMI, adjusted for other known risk factors. Opposite trend RRs were found after menopause: 1.05 (1.02-1.08) for weight and 1.06 (1.02-1.09) for BMI, respectively, for similar increases. Women with a BMI of over 30 kg/m(2) had a RR of premenopausal breast cancer of 0.66 (0.40-1.10) compared to those with a BMI of between 18.5 and 25 kg/m(2). Postmenopausal women with a BMI of over 30 kg/m(2) had a RR of breast cancer of 1.23 (1.00-1.59). The increase in risk of postmenopausal breast cancer with increased weight or BMI was similar whatever the HRT used, although the point estimates were higher in HRT users. We strongly recommend to use anthropometric measurements updated during follow-up to assess the effect of weight, BMI on breast cancer risk.