A comparative study of risk factors for hyperplasia and cancer of the endometrium

Epidemiology of Endometrial Carcinoma: Etiologic Importance of Hormonal and Metabolic Influences

Endometrial carcinoma is the most common gynecologic cancer in developed nations, and the annual incidence is projected to increase, secondary to the high prevalence of obesity, a strong endometrial carcinoma risk factor. Although endometrial carcinomas are etiologically, biologically, and clinically diverse, hormonal and metabolic mechanisms are particularly strongly implicated in the pathogenesis of endometrioid carcinoma, the numerically predominant subtype. The centrality of hormonal and metabolic disturbances in the pathogenesis of endometrial carcinoma, combined with its slow development from well-characterized precursors in most cases, offers a substantial opportunity to reduce endometrial carcinoma mortality through early detection, lifestyle modification, and chemoprevention. In this chapter, we review the epidemiology of endometrial carcinoma, emphasizing theories that link risk factors for these tumors to hormonal and metabolic mechanisms. Future translational research opportunities related to prevention are discussed.

Obesity-related proliferative diseases: the interaction between adipose tissue and estrogens in post-menopausal women

Epidemiological studies have shown that overweight and cancer are closely related, even though obesity alone does not apparently heighten cancer risk by the same amount. Given the low overall risk of all cancers with obesity, it is unlikely that obesity alone causes cancer, but should instead be considered as a tumor promoter. There are three main hypotheses that could explain how obesity might contribute to cancer development and growth: the inflammatory cytokines from adipose tissue hypothesis, the insulin resistance and hyperinsulinemia hypothesis, and the unopposed estrogen cancer hypothesis. The link between obesity and cancer is that adipocytes constitute a major component of the tumor microenvironment for breast and abdominally metastasizing cancers, promoting tumor growth. This review will mainly focus attention on the relationship between adipose tissue, estrogens, and cancer risk.

Sustained effect of the aromatase inhibitors anastrozole and letrozole on endometrial thickness in patients with endometrial hyperplasia and endometrial carcinoma

OBJECTIVE

To investigate whether there may be a role for aromatase inhibitors (AIs) in the treatment of endometrial hyperplasia (EH) and endometrial adenocarcinoma (EA) in postmenopausal women, a retrospective study on the effect of aromatase inhibitors (anastrozole or letrozole) was conducted for 16 patients who were not amenable to surgical treatment.

MAIN OUTCOME MEASURE

Resolution of endometrial thickening measured by transvaginal ultrasound at 3-month intervals; the response of metastases was assessed by standard oncological criteria.

RESULTS

In all, 16 patients were studied. The BMI of 13 of the 16 patients was known and ranged from 20.7 to 47.7 (mean 34.5) kg/m(2). During treatment with AIs, mean endometrial thickness in the eight patients with EH decreased progressively by 81.7% from 14.7 mm at the start of treatment to 2.7 mm following 36 months of treatment. A greater original mean endometrial thickness of 17 mm was seen in the four patients with localised EA, this fell progressively by 67.1% to 5.6 mm following 36 months of treatment. No responses were seen in four patients with metastatic disease.

CONCLUSION

Our results indicate that treatment of EH with anastrozole or letrozole can reduce endometrial thickness as seen ultrasonically, and that in some cases AI treatment can reduce endometrial thickness in patients with localised EA. We found no evidence to indicate that AI treatment prevents disease progression in patients with metastatic EA. Further investigations will be necessary to validate our findings from this small retrospective study and to compare AI inhibitor treatment with topical progestogen therapy.

Endometrial hyperplasia and the risk of progression to carcinoma

The primary presenting symptom of endometrial neoplasia is abnormal uterine bleeding, which typically prompts an endometrial biopsy to rule out carcinoma. Approximately 70% of women with abnormal uterine bleeding are diagnosed with benign findings and 15% are diagnosed with carcinoma. The remaining 15% receive a diagnosis of endometrial hyperplasia (EH), which includes a broad range of lesions, from mild, reversible proliferations to the immediate precursors of carcinoma. The widely used World Health Organization (WHO) system classifies EH according to four combinations of glandular crowding and nuclear atypia: simple (SH), complex (CH), simple atypical (SAH), or complex atypical hyperplasia (CAH), although the two forms of atypical hyperplasia (AH) are often collapsed into one category. Diagnoses of EH raise three issues. First, the low interobserver reproducibility-less than 50% in almost all studies-hinders the ability of WHO-based classification to effectively guide clinical management. Second, approximately 50% of women diagnosed with AH have concurrent carcinoma. Not surprisingly, most women with AH undergo hysterectomy as primary treatment, but non-surgical management can be effective. Third, data on progression risks for women with EH who retain their uterus are extremely limited. Emerging data indicate the long-term risk among women with SH or CH is less than 5%, but the risk among women with AH is approximately 30%. These data highlight priority areas for future research, such as increasing the diagnostic reproducibility of EH, improving the discrimination between AH and carcinoma, and identifying biomarkers to stratify risks or serve as indicators of response to clinical treatment.

Energy intake, physical activity, energy balance, and cancer: epidemiologic evidence

Energy intake, physical activity, and obesity are modifiable lifestyle factors. This chapter reviews and summarizes the epidemiologic evidence on the relation of energy intake, physical activity, and obesity to cancer. High energy intake may increase the risk of cancers of colon-rectum, prostate (especially advanced prostate cancer), and breast. However, because physical activity, body size, and metabolic efficiency are highly related to total energy intake and expenditure, it is difficult to assess the independent effect of energy intake on cancer risk. There are sufficient evidences to support a role of physical activity in preventing cancers of the colon and breast, whereas the association is stronger in men than in women for colon cancer and in postmenopausal than in premenopausal women for breast cancer. The evidence also suggests that physical activity likely reduces the risk of cancers of endometrium, lung, and prostate (to a lesser extent). On the other hand, there is little or no evidence that the risk of rectal cancer is related to physical activity, whereas the results have been inconsistent regarding the association between physical activity and the risks of cancers of pancreas, ovary and kidney. Epidemiologic studies provide sufficient evidence that obesity is a risk factor for both cancer incidence and mortality. The evidence supports strong links of obesity with the risk of cancers of the colon, rectum, breast (in postmenopausal women), endometrium, kidney (renal cell), and adenocarcinoma of the esophagus. Epidemiologic evidence also indicates that obesity is probably related to cancers of the pancreas, liver, and gallbladder, and aggressive prostate cancer, while it seems that obesity is not associated with lung cancer. The role of obesity in other cancer risks is unclear.

Risk of complex and atypical endometrial hyperplasia in relation to anthropometric measures and reproductive history

The authors sought to test the hypothesis that characteristics and exposures which influence the balance of estrogen and progesterone bear on the incidence of endometrial hyperplasia (EH), a noninvasive proliferation of the lining of the uterus. Cases included all female members of Group Health (Washington State) who were diagnosed with complex EH or EH with atypia during the period 1985-2003 and whose diagnoses were confirmed in a pathology review (n = 446). Controls were selected randomly from Group Health membership files and were matched to the cases by age and enrollment status at the reference date. An increased risk of EH was associated with increasing body mass index and nulliparity. There was a suggestion of a decreased risk of EH with atypia among current smokers. No association with diabetes or hypertension was found. The risk factors observed to be associated with EH in this study are similar to those associated with endometrial cancer. Whether these risk factors predispose women to cancer simply by increasing EH incidence or continue to augment cancer risk even after EH is present is currently unknown.

Transcriptional profiling endometrial carcinomas microdissected from DES-treated mice identifies changes in gene expression associated with estrogenic tumor promotion

Exposure to unopposed estrogen is a potent risk factor for developing human endometrial cancer. However, little is known about the transcriptional changes elicited by estrogens in endometrial carcinogenesis, in part, because of genetic and environmental heterogeneity of human tumors. We have begun to chart the expression signatures of endometrial tumors promoted with the synthetic estrogen, diethylstilbestrol (DES), in inbred mice. As expected, laser-capture-microdissected endometrial cancers from DES-treated mice displayed a large number of transcriptional changes when compared to uninvolved endometrial epithelium. Genes differentially expressed in carcinomas included cell adhesion and extracellular matrix genes (Decorin as 1 example), developmental genes (Hoxa11), and cytokine signaling genes (Socs3). The DES-promoted carcinomas appeared to fall into 2 distinct transcriptional classes, and expression of the tumor suppressor Pten was among the top discriminators between the 2 cancer groups. Pten was down regulated in the majority of the DES-promoted carcinomas, which is analogous to the frequent loss of PTEN expression in human endometrial tumors. Although preliminary, these observations suggest that the cancers that arise in the DES model bear similarities to human endometrial cancers and provide insights into transcriptional alterations that accompany estrogen-driven endometrial carcinogenesis.

Plasma and urinary sex hormones are differently related to lipids in healthy postmenopausal women

OBJECTIVE

Endogenous sex hormones can be measured in plasma and urine. We determined the extent to which these two methods provide different information on hormonal status by relating them to lipid profile in postmenopausal women.

METHODS

Thirty healthy postmenopausal women collected one 24-h urine sample and a blood sample was taken. Urinary estrone (UE), plasma estrone (PE) and serum lipids were measured. Sex hormone levels were measured with specific radioimmunoassays. Linear regression analysis was used to determine associations between estrone levels and lipids. Results are presented as beta-coefficients in mmol/l per standard deviation (SD) of endogenous estrone levels, adjusted for body mass index (BMI) and smoking (95% confidence interval). A stratified analysis for obese (BMI> or =27 kg/m(2)) versus lean women was performed.

RESULTS

Mean levels of endogenous sex hormones were (SD): PE, 90.1 pmol/l (37.3); and UE, 7757 pmol/24 h (2659). PE showed significant associations with HDL-cholesterol (0.18 mmol/l, 95% CI: 0.06; 0.30), triglycerides (-0.25 mmol/l, 95% CI: -0.49; -0.009) and very-low-density-lipoprotein (VLDL-cholesterol) (-0.11 mmol/l, 95% CI: -0.22; -0.003), but not with total and low-density-lipoprotein (LDL-cholesterol). UE was inversely associated with total (-0.41 mmol/l, 95% CI: -0.85; 0.02) and LDL-cholesterols (-0.42 mmol/l, 95% CI: -0.83; -0.005), but not with HDL-cholesterol, triglycerides and VLDL-cholesterol. All associations appeared to be stronger in lean women.

CONCLUSION

Both plasma and UE levels appear to be associated to serum lipids in healthy postmenopausal women. However, this relation appears to be different for estrone levels in plasma and urine. Depending on the research question, either blood samples or urine samples may be preferred.

Risk factors for endometrial hyperplasia: results from a case-control study

We analyzed epidemiologic characteristics of women at risk for endometrial hyperplasia (EH), using data from a case-control study. One hundred twenty nine women aged 35-73 (median 51 years) with histologically confirmed complex endometrial hyperplasia without atypies identified at the University of Milan during the period 1990-99 were examined. Controls were 258 non hysterectomized women aged 36-74 (median 52 years), admitted to a network of hospitals covering the same area where cases had been identified for conditions other than gynecological, malignant, or hormone-related. Cases with EH were more educated than controls (OR > 12 years of education vs. < 7: 2.8, 95% CI 1.7-4.8), more frequently obese (OR 2.7, 95% CI 1.5-5.0) and diabetic (OR 2.4, 95% CI 0.8-6.9). Parous women (OR 1.8) and women reporting induced abortions (OR 1.6) showed an increased risk of EH, but the associations were not statistically significant. Compared to premenopausal women, the OR of EH was 0.2 (95% 0.1-0.5) for postmenopausal ones. Compared to women reporting menopause at age 50 or less, the OR of endometrial hyperplasia was 1.5 (95% CI 0.6-3.5) and 2.2 (95%CI 0.7-6.7), respectively, in women with menopause at age 50-52 and > or = 53. Considering postmenopausal women only the OR was 3.1 (95% CI 1.1-9.3) for use of hormonal replacement therapy (HRT). We conclude that this study indicates that high education, obesity, diabetes, and HRT use increase the risk of endometrial hyperplasia.

Roles of androgens in the development, growth, and carcinogenesis of the mammary gland

Androgens influence the development and growth of the mammary gland in women. Treatment of animals and cultured cells with androgens has either inhibitory or stimulatory effects on the proliferation of mammary epithelia and cancer cells; the mechanisms for these dual functions are still not very clear and are discussed in this review. Epidemiological data suggest that, similar to increased estrogens, elevated androgens in serum may be associated with the development of breast cancer. Experiments in rodents have also shown that simultaneous treatment of androgen and estrogen synergizes for mammary gland carcinogenesis. Similar synergistic effects of both hormones have been observed for carcinogenesis of the uterine myometrium of female animals and for carcinogenesis of the prostate and deferens of males. There are also clinical and experimental indications for a possible association of elevated levels of both androgens and estrogens with the development of ovarian and endometrial cancers. A hypothesis is thus proposed that concomitant elevation in both androgens and estrogens may confer a greater risk for tumorigenesis of the mammary gland, and probably other female reproductive tissues than an elevation of each hormone alone.

Obesity as a risk factor for certain types of cancer

In conclusion, obesity has been associated with increased risk for a number of different types of cancer. The evidence has been most consistent for endometrial cancer, breast cancer in postmenopausal women, and renal cell cancer. More variable results have been reported for colorectal, prostate and pancreatic cancer. Possible mechanisms by which obesity may influence cancer risk include alteration in hormonal patterns, including sex hormones and insulin, and factors such as the distribution of body fat and changes in adiposity at different ages. The increasing prevalence of obesity in many parts of the world emphasizes the importance of learning more about the relationship between obesity and cancer and the mechanisms involved in their interaction.

Loss of heterozygosity of BRCA1, TP53 and TCRD markers analysed in sporadic endometrial cancer

Genetic alterations of tumour suppressor genes, for which loss of heterozygosity (LOH) is one mechanism of gene inactivation, are important steps in the development of endometrial cancer. To investigate the clinical relevance of LOH of BRCA1 (17q21), TP53 (17p13) and TCRD (14q11) in endometrial cancer, polymerase chain reaction (PCR)-based fluorescent DNA technology for the detection of microsatellite polymorphisms was applied. One hundred and thirteen archival endometrial cancer samples with matched normal tissues were examined. Allele loss at three loci were correlated with age, tumour size, lymph node status, metastases, stage, histological types, grade, expression of oestrogen receptor (ER) and progesterone receptor (PgR), family history of cancer, previous history of cancer or precursor lesions, and previous history of hormone replacement therapy (HRT). LOH for BRCA1 was detected in 18.1%, of TP53 in 26.9%, and of TCRD in 26.3% of informative cases. LOH of BRCA1 correlated with medium grade, positive ER status, and family history of cancer; LOH of TP53 correlated with younger age, high grade, positive PgR status, and with tumours from patients without HRT; LOH of TCRD correlated only with family history of cancer. LOH at all three loci correlated only with grade and positive family history. Allele loss of one of the three tumour suppressor loci did not correlate with disease-free survival (DFS), but LOH of BRCA1 correlated significantly with decreased overall survival (OS). The latter, together with the correlation of LOH of BRCA1 locus with steroid hormone receptor expression, might give a hint to the potential involvement of the co-localised 17 beta-hydroxysteroid dehydrogenase (HSD) gene in the development of endometrial cancer.