Pregnancy history and risk of endometrial cancer

Pregnancy Loss in Relation to the Risks of Female-Specific Cancers in a Population-Based Cohort and Mendelian Randomization Study - China, 2004-2017

What is already known about this topic?

Limited evidence exists regarding the relationship between pregnancy loss and female-specific cancers within the Chinese population from prospective cohort studies.

What is added by this report?

Terminations were associated with a 13% lower risk of endometrial cancer, whereas stillbirths were related to an 18% higher risk of cervical cancer. Rural residents with a history of pregnancy loss experienced a 19% and 38% increased risk of breast and cervical cancers, respectively, compared to their urban counterparts. Moreover, a positive graded relationship between live births and pregnancy loss on cervical cancer was observed.

What are the implications for public health practice?

This study has significant implications for identifying women at an increased risk for breast and genital cancers and contributes to the development of effective public health strategies for female cancer prevention. Future research on reproductive history, particularly in rural areas, should be given priority in efforts to improve female cancer screening and early detection.

Age-specific trend and birth cohort effect on different histologic types of uterine corpus cancers

To evaluate the uterine corpus cancer incidence rates, age-specific trends, and birth cohort patterns by different histologic types. We conducted a retrospective cohort study of uterine cancer patients (n = 28,769) of all ages from the National Cancer Registry of Taiwan between 1998 and 2017. We estimated the incidence trends, average annual percent changes (AAPCs), and cancer-specific survival (CSS) rate for the two main subtypes (endometrioid and nonendometrioid) of uterine cancer in Taiwan. During the study period, uterine corpus cancer incidence rates increased over time from 5.3 to 15.21 per 100,000 women. Incidence trends for endometrioid carcinoma increased in all age groups (positive AAPCs > 5% for each age group), and the rise was steeper among women aged 50 years and younger. For nonendometrioid carcinomas, incidence rates increased among women over 50 years. The CSS rate improved among women with stage I (hazard ratio [HR] 0.63, 95% confidence interval [CI] 0.49-0.81) and stage III (HR 0.72, 95% CI 0.58-0.90) endometrioid carcinomas after 2013 compared with those during 2009-2012. However, the CSS rate remained unchanged for nonendometrioid carcinomas. Age, diagnostic period, stage and histologic types were significant factors associated with the 5-year CSS rate. We found that the incidences of both endometrioid and nonendometrioid carcinomas continued to increase among contemporary birth cohorts. Etiologic research is needed to explain the causes of these trends.

Pregnancy outcomes and risk of endometrial cancer: A pooled analysis of individual participant data in the Epidemiology of Endometrial Cancer Consortium

A full-term pregnancy is associated with reduced endometrial cancer risk; however, whether the effect of additional pregnancies is independent of age at last pregnancy is unknown. The associations between other pregnancy-related factors and endometrial cancer risk are less clear. We pooled individual participant data from 11 cohort and 19 case-control studies participating in the Epidemiology of Endometrial Cancer Consortium (E2C2) including 16 986 women with endometrial cancer and 39 538 control women. We used one- and two-stage meta-analytic approaches to estimate pooled odds ratios (ORs) for the association between exposures and endometrial cancer risk. Ever having a full-term pregnancy was associated with a 41% reduction in risk of endometrial cancer compared to never having a full-term pregnancy (OR = 0.59, 95% confidence interval [CI] 0.56-0.63). The risk reduction appeared the greatest for the first full-term pregnancy (OR = 0.78, 95% CI 0.72-0.84), with a further ~15% reduction per pregnancy up to eight pregnancies (OR = 0.20, 95% CI 0.14-0.28) that was independent of age at last full-term pregnancy. Incomplete pregnancy was also associated with decreased endometrial cancer risk (7%-9% reduction per pregnancy). Twin births appeared to have the same effect as singleton pregnancies. Our pooled analysis shows that, while the magnitude of the risk reduction is greater for a full-term pregnancy than an incomplete pregnancy, each additional pregnancy is associated with further reduction in endometrial cancer risk, independent of age at last full-term pregnancy. These results suggest that the very high progesterone level in the last trimester of pregnancy is not the sole explanation for the protective effect of pregnancy.

Prenatal Biochemical Screening and a Woman’s Long-Term Risk of Cancer: A Population-Based Cohort Study

Background

Some hormones measured in pregnancy are linked to certain hormone-sensitive cancers. We investigated whether routine serum screening in pregnancy is associated with a woman’s subsequent risk of hormone-sensitive cancer.

Methods

This population-based cohort study included women aged 12–55 years who underwent prenatal screening between 11 weeks + 0 days of gestation to 20 weeks + 6 days of gestation in Ontario, Canada, 1993–2011, where universal health care is available. The hazard ratio of newly diagnosed breast, ovarian, endometrial, and thyroid cancer—arising at 21 weeks + 0 days of gestation or thereafter—was estimated in association with an abnormally low (≤5th) or high (>95th) percentile multiple of the median (MoM) for alpha-fetoprotein (AFP), total human chorionic gonadotropin (hCG), unconjugated estriol, pregnancy-associated plasma protein A, and dimeric inhibin A.

Results

Among 677 247 pregnant women followed for a median of 11.0 years (interquartile range = 7.5–16.1), 7231 (1.07%) developed breast cancer, 515 (0.08%) ovarian cancer, 508 (0.08%) endometrial cancer, and 4105 (0.61%) thyroid cancer. In multivariable adjusted models, abnormally high hCG greater than the 95th percentile MoM was associated with a doubling in the risk of endometrial cancer (adjusted hazard ratio [aHR] = 1.98, 95% confidence interval [CI] = 1.33 to 2.95), and abnormally low AFP at the fifth percentile or less MoM conferred a moderately greater risk of thyroid cancer (aHR = 1.21, 95% CI = 1.07 to 1.38). Abnormally low pregnancy-associated plasma protein A at the fifth percentile or less MoM was not statistically significantly associated with breast cancer after multivariable adjustment (aHR = 1.19, 95% CI = 0.98 to 1.36).

Conclusions

Women with abnormally high levels of serum hCG or low AFP in early pregnancy may be at a greater future risk of certain types of hormone-sensitive cancers.

Pregnancy duration and endometrial cancer risk: nationwide cohort study

OBJECTIVE

To explore the association between pregnancy duration and risk of endometrial cancer.

DESIGN

Nationwide register based cohort study.

SETTING

Denmark.

PARTICIPANTS

All Danish women born from 1935 to 2002.

MAIN OUTCOME MEASURES

Relative risk (incidence rate ratio) of endometrial cancer by pregnancy number, type, and duration, estimated using log-linear Poisson regression.

RESULTS

Among 2 311 332 Danish women with 3 947 650 pregnancies, 6743 women developed endometrial cancer during 57 347 622 person years of follow-up. After adjustment for age, period, and socioeconomic factors, a first pregnancy was associated with a noticeably reduced risk of endometrial cancer, whether it ended in induced abortion (adjusted relative risk 0.53 (95% confidence interval 0.45 to 0.64) or childbirth (0.66, 0.61 to 0.72). Each subsequent pregnancy was associated with an additional reduction in risk, whether it ended in induced abortion (0.81, 0.77 to 0.86) or childbirth (0.86, 0.84 to 0.89). Duration of pregnancy, age at pregnancy, spontaneous abortions, obesity, maternal birth cohort, fecundity, and socioeconomic factors did not modify the results.

CONCLUSIONS

The risk of endometrial cancer is reduced regardless of whether a pregnancy ends shortly after conception or at 40 weeks of gestation. This reduction in risk could be explained by a biological process occurring within the first weeks of pregnancy, as pregnancies ending in induced abortions were associated with similar reductions in risk as pregnancies ending in childbirth.

Associations of pregnancy-related factors and birth characteristics with risk of endometrial cancer: A Nordic population-based case-control study

Many pregnancy-related factors are associated with reduced endometrial cancer risk. However, it remains unclear whether pregnancy-related complications (e.g., hypertensive conditions) are associated with risk and whether these associations vary by endometrial cancer subtype. Thus, we evaluated the risk of endometrial cancer, overall and by subtype, in relation to pregnancy-related factors, pregnancy complications and birth characteristics. Utilizing population-based register data from four Nordic countries, we conducted a nested case-control analysis of endometrial cancer risk. We included 10,924 endometrial cancer cases and up to 10 matched controls per case. Odds ratios (ORs) with 95% confidence intervals (CIs) were derived from unconditional logistic regression models. We further evaluated associations by individual histology (i.e., endometrioid, serous, etc.) or, for rare exposures (e.g., pregnancy complications), by dualistic type (Type I [n = 10,343] and Type II [n = 581]). Preexisting and pregnancy-related hypertensive conditions were associated with increased endometrial cancer risk (OR [95% CI]: preexisting hypertension 1.88 [1.39-2.55]; gestational hypertension 1.47 [1.33-1.63]; preeclampsia 1.43 [1.30-1.58]), with consistent associations across dualistic type. Increasing number of pregnancies (≥4 vs. 1 birth: 0.64 [0.59-0.69]) and shorter time since last birth (<10 vs. ≥30 years: 0.34 [0.29-0.40]) were associated with reduced endometrial cancer risk, with consistent associations across most subtypes. Our findings support the role for both hormonal exposures and cell clearance as well as immunologic/inflammatory etiologies for endometrial cancer. This research supports studying endometrial hyperplasia, a precursor condition of endometrial cancer, in the context of pregnancy-related exposures, as this may provide insight into the mechanisms by which pregnancy affects subsequent cancer risk.

Long-term effect of pregnancy-related factors on the development of endometrial neoplasia: A nationwide retrospective cohort study

Objective

By identifying pregnancy-related risk factors for endometrial neoplasia, women’s risk of developing this disease after childbirth can be predicted and high-risk women can be screened for early detection.

Methods

Study data from women who gave birth in Korea in 2007 were collected from the Korea National Health Insurance (KNHI) claims database between 2007 and 2015. The adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) for the development of endometrial neoplasia were estimated by multivariate Cox proportional hazards models.

Results

Data from 386,614 women were collected for this study. By 2015, 3,370 women from the initial cohort had been diagnosed with endometrial neoplasia secondary to delivery. Multivariate Cox proportional hazards regression revealed that preeclampsia (HR 1.55, 95% CI 1.29, 1.86), advanced maternal age (≥ 35; HR 1.52, 95% CI 1.39, 1.66), multifetal pregnancy (HR 1.81, 95% CI 1.46, 2.23), multiparity (HR 1.16, 95% CI 1.08, 1.24), cesarean section (HR 1.15, 95% CI 1.07, 1.23) and delivery of a large-for-gestational-age infant (HR 1.19, 95% CI 1.02, 1.39) were independent risk factors for future endometrial neoplasia. The risk for endometrial neoplasia increased as the number of risk factors increased (risk factors ≥3: HR 2.11, 95% CI 1.86–2.40).

Conclusion

This study showed that six pregnancy-related factors—advanced maternal age, multiparity, multifetal pregnancy, cesarean section, delivery of a large-for-gestational-age infant, and preeclampsia—are positively correlated with future development of endometrial neoplasia, including endometrial hyperplasia or cancer. Close observation and surveillance are warranted to enable early diagnosis of endometrial diseases, including endometrial cancer after pregnancy in high-risk women. However, due to unavailability of clinical information, many clinical/epidemiological factors can become confounders. Further research is needed on factors associated with the risk of endometrial neoplasia.

Lifetime number of years of menstruation as a risk index for postmenopausal endometrial cancer in the Norwegian Women and Cancer Study

INTRODUCTION

Lifetime number of years of menstruation (LNYM) reflects a woman's cumulative exposure to endogenous estrogen and can be used as a measure of the combined effect of reproductive factors related to endometrial cancer (EC) risk.

MATERIAL AND METHODS

We aimed to study the association between LNYM and EC risk among postmenopausal women and calculate the population attributable fraction of EC for different LNYM categories. Our study sample consisted of 117 589 women from the Norwegian Women and Cancer (NOWAC) Study. All women were aged 30-70 years at enrollment and completed a baseline questionnaire between 1991 and 2006. Women were followed up for EC to December 2014 through linkages to national registries. We used Cox proportional hazards models to estimate hazard ratios with 95% confidence intervals (95% CIs), adjusted for potential confounders.

RESULTS

In all, 720 women developed EC. We found a statistically significant, positive dose-response relationship between LNYM and EC, with a 9.1% higher risk for each additional year of LNYM (P for trend < .001). Using the LNYM category ≥40 as a reference, the hazard ratios for LNYM <25, 25-29, 30-34, 35-39 were 0.17 (95% CI 0.22-0.27), 0.25 (95% CI 0.17-0.36), 0.43 (95% CI 0.32-0.58), and 0.68 (95% CI 0.51-0.92), respectively. The association between LNYM and EC was independent of incomplete pregnancies, menopausal hormone therapy, diabetes, and body mass index. When considering the population attributable fraction, 67% of EC was estimated to be attributable to LNYM ≥25 years.

CONCLUSIONS

Our study supports that increasing LNYM is an important and independent predictor of EC risk.

The role of pregnancy, perinatal factors and hormones in maternal cancer risk: a review of the evidence

An understanding of the origin of cancer is critical for cancer prevention and treatment. Complex biological mechanisms promote carcinogenesis, and there is increasing evidence that pregnancy-related exposures influence foetal growth cell division and organ functioning and may have a long-lasting impact on health and disease susceptibility in the mothers and offspring. Nulliparity is an established risk factor for breast, ovarian, endometrial and possibly pancreatic cancer, whilst the risk of kidney cancer is elevated in parous compared with nulliparous women. For breast, endometrial and ovarian cancer, each pregnancy provides an additional risk reduction. The associations of parity with thyroid and colorectal cancers are uncertain. The timing of reproductive events is also recognized to be important. Older age at first birth is associated with an increased risk of breast cancer, and older age at last birth is associated with a reduced risk of endometrial cancer. The risks of breast and endometrial cancers increase with younger age at menarche and older age at menopause. The mechanisms, and hormone profiles, that underlie alterations in maternal cancer risk are not fully understood and may differ by malignancy. Linking health registries and pooling of data in the Nordic countries have provided opportunities to conduct epidemiologic research of pregnancy exposures and subsequent cancer. We review the maternal risk of several malignancies, including those with a well-known hormonal aetiology and those with less established relationships. The tendency for women to have fewer pregnancies and at later ages, together with the age-dependent increase in the incidence of most malignancies, is expected to affect the incidence of pregnancy-associated cancer.

A prospective analysis of diet quality and endometrial cancer among 84,415 postmenopausal women in the Women's Health Initiative

PURPOSE

Endometrial cancer is the most commonly diagnosed gynecologic cancer, but no convincing dietary risk factors for this cancer have been identified. Among postmenopausal women, we examined how four key a priori diet quality indices--the Healthy Eating Index-2010, Alternative Healthy Eating Index-2010, alternate Mediterranean Diet, and Dietary Approaches to Stop Hypertension are related to the risk of endometrial cancer in the Women's Health Initiative Clinical Trials and Observational Study.

METHODS

Our prospective cohort study included 84,415 postmenopausal women with a uterus who completed a food frequency questionnaire at enrollment. Cox proportional hazards models were used to estimate multivariate hazard ratios (HRs) and 95% confidence intervals (CIs) for endometrial cancer associated with increasing quintiles of diet quality index scores.

RESULTS

During 13.3 years of follow-up, 1392 endometrial cancer cases occurred. After adjustment for known risk factors, having better diet quality (Q5 vs. Q1) was not associated with the risk of endometrial cancer, as evidenced using Healthy Eating Index-2010 (HR: 1.11, 95% CI: 0.93-1.33), Alternative Healthy Eating Index-2010 (HR: 0.98, 95% CI: 0.82-1.17), alternate Mediterranean Diet (HR: 0.98, 95% CI: 0.82-1.17), or Dietary Approaches to Stop Hypertension (HR: 1.00, 95% CI: 0.84-1.19).

CONCLUSIONS

Diet quality was not associated with endometrial cancer risk in this large cohort of postmenopausal women.

Female Hormonal Factors and the Risk of Endometrial Cancer in Lynch Syndrome

IMPORTANCE

Apart from hysterectomy, there is no consensus recommendation for reducing endometrial cancer risk for women with a mismatch repair gene mutation (Lynch syndrome).

OBJECTIVE

To investigate the association between hormonal factors and endometrial cancer risk in Lynch syndrome.

DESIGN, SETTING, AND PARTICIPANTS

A retrospective cohort study included 1128 women with a mismatch repair gene mutation identified from the Colon Cancer Family Registry. Data were analyzed with a weighted cohort approach. Participants were recruited between 1997 and 2012 from centers across the United States, Australia, Canada, and New Zealand.

EXPOSURES

Age at menarche, first and last live birth, and menopause; number of live births; hormonal contraceptive use; and postmenopausal hormone use.

MAIN OUTCOMES AND MEASURES

Self-reported diagnosis of endometrial cancer.

RESULTS

Endometrial cancer was diagnosed in 133 women (incidence rate per 100 person-years, 0.29; 95% CI, 0.24 to 0.34). Endometrial cancer was diagnosed in 11% (n = 70) of women with age at menarche greater than or equal to 13 years compared with 12.6% (n = 57) of women with age at menarche less than 13 years (incidence rate per 100 person-years, 0.27 vs 0.31; rate difference, -0.04 [95% CI, -0.15 to 0.05]; hazard ratio per year, 0.85 [95% CI, 0.73 to 0.99]; P = .04). Endometrial cancer was diagnosed in 10.8% (n = 88) of parous women compared with 14.4% (n = 40) of nulliparous women (incidence rate per 100 person-years, 0.25 vs 0.43; rate difference, -0.18 [95% CI, -0.32 to -0.04]; hazard ratio, 0.21 [95% CI, 0.10 to 0.42]; P < .001). Endometrial cancer was diagnosed in 8.7% (n = 70) of women who used hormonal contraceptives greater than or equal to 1 year compared with 19.2% (n = 57) of women who used contraceptives less than 1 year (incidence rate per 100 person-years, 0.22 vs 0.45; rate difference, -0.23 [95% CI, -0.36 to -0.11]; hazard ratio, 0.39 [95% CI, 0.23 to 0.64]; P < .001). There was no statistically significant association between endometrial cancer and age at first and last live birth, age at menopause, and postmenopausal hormone use.

CONCLUSIONS AND RELEVANCE

For women with a mismatch repair gene mutation, some endogenous and exogenous hormonal factors were associated with a lower risk of endometrial cancer. These directions and strengths of associations were similar to those for the general population. If replicated, these findings suggest that women with a mismatch repair gene mutation may be counseled like the general population in regard to hormonal influences on endometrial cancer risk.

Association Between a Woman's Age at First Birth and High Blood Pressure

The aim of this article is to determine whether the age of a woman at first birth is associated with treatment for high blood pressure (HBP) later in life.Baseline data for 62,914 women were sourced from the "45 and Up Study," an observational cohort study of healthy aging in Australia. These women had given first birth between the ages of 18 and 45 years. Odds ratios and 95% confidence intervals for the association between age that a woman gave first birth and treatment for HBP were estimated using logistic regression. Data were stratified by current age (<60 and ≥60 years) and adjusted for demographic and lifestyle factors.There was a significant association between age at first birth and present day HBP. Older age at first birth was associated with a lower likelihood of HBP in women aged 25 to <35 years and 35 to 45 years at first birth (in women currently <60 years) and 35 to 45 years at first birth (in women currently ≥60 years of age), compared with women aged 18 to <25 years at first birth, adjusting for demographic and lifestyle factors.Women who were older when they gave first birth had lower odds of treatment for HBP compared with women who were younger when they gave birth to their first child. The contribution of a woman's pregnancy history, including her age at first birth, should be discussed with a patient when assessing her risk of HBP.

Risk factors for endometrial cancer in black and white women: a pooled analysis from the Epidemiology of Endometrial Cancer Consortium (E2C2)

PURPOSE

Endometrial cancer (EC) is the most common gynecologic cancer in the USA. Over the last decade, the incidence rate has been increasing, with a larger increase among blacks. The aim of this study was to compare risk factors for EC in black and white women.

METHODS

Data from seven cohort and four case-control studies were pooled. Unconditional logistic regression was used to estimate adjusted odds ratios (OR) and 95 % confidence intervals for each risk factor in blacks and whites separately.

RESULTS

Data were pooled for 2,011 black women (516 cases and 1,495 controls) and 19,297 white women (5,693 cases and 13,604 controls). BMI ≥ 30 was associated with an approximate threefold increase in risk of EC in both black and white women (ORblack 2.93, 95 % CI 2.11, 4.07 and ORwhite 2.99, 95 % CI 2.74, 3.26). Diabetes was associated with a 30-40 % increase in risk among both groups. Increasing parity was associated with decreasing risk of EC in blacks and whites (p value = 0.02 and <0.001, respectively). Current and former smoking was associated with decreased risk of EC among all women. Both black and white women who used oral contraceptives for 10 +years were also at reduced risk of EC (OR 0.49, 95 % CI 0.27, 0.88 and OR 0.69, 95 % CI 0.58, 0.83, respectively). Previous history of hypertension was not associated with EC risk in either group.

CONCLUSIONS

The major known risk factors for EC exert similar effects on black and white women. Differences in the incidence rates between the two populations may be due to differences in the prevalence of risk factors.

Etiologic heterogeneity in endometrial cancer: evidence from a Gynecologic Oncology Group trial

OBJECTIVE

Although the epidemiology of typical endometrial carcinomas (grades 1-2 endometrioid or Type I) is well established, less is known regarding higher grade endometrioid or non-endometrioid carcinomas (Type II). Within a large Gynecologic Oncology Group trial (GOG-210), which included central pathology review, we investigated the etiologic heterogeneity of endometrial cancers by comparing risk factors for different histologic categories.

METHODS

Based on epidemiologic questionnaire data, risk factor associations, expressed as odds ratios (OR) with 95% confidence intervals (CI), were estimated comparing grade 3 endometrioid and Type II cancers (including histologic subtypes) to grades 1-2 endometrioid cancers.

RESULTS

Compared with 2244 grades 1-2 endometrioid cancers, women with Type II cancers (321 serous, 141 carcinosarcomas, 77 clear cell, 42 mixed epithelial with serous or clear cell components) were older; more often non-white, multiparous, current smokers; and less often obese. Risk factors for grade 3 endometrioid carcinomas (n=354) were generally similar to those identified for Type II cancers, although patients with grade 3 endometrioid tumors more often had histories of breast cancer without tamoxifen exposure while those with Type II tumors were more frequently treated with tamoxifen. Patients with serous cancers and carcinosarcomas more frequently had breast cancer histories with tamoxifen treatment compared to patients with other tumors.

CONCLUSIONS

Risk factors for aggressive endometrial cancers, including grade 3 endometrioid and non-endometrioid tumors, appear to differ from lower grade endometrioid carcinomas. Our findings support etiologic differences between Type I and II endometrial cancers as well as additional heterogeneity within Type II cancers.

Age at last birth in relation to risk of endometrial cancer: pooled analysis in the epidemiology of endometrial cancer consortium

Childbearing at an older age has been associated with a lower risk of endometrial cancer, but whether the association is independent of the number of births or other factors remains unclear. Individual-level data from 4 cohort and 13 case-control studies in the Epidemiology of Endometrial Cancer Consortium were pooled. A total of 8,671 cases of endometrial cancer and 16,562 controls were included in the analysis. After adjustment for known risk factors, endometrial cancer risk declined with increasing age at last birth (P(trend) < 0.0001). The pooled odds ratio per 5-year increase in age at last birth was 0.87 (95% confidence interval: 0.85, 0.90). Women who last gave birth at 40 years of age or older had a 44% decreased risk compared with women who had their last birth under the age of 25 years (95% confidence interval: 47, 66). The protective association was similar across the different age-at-diagnosis groups and for the 2 major tumor histologic subtypes (type I and type II). No effect modification was observed by body mass index, parity, or exogenous hormone use. In this large pooled analysis, late age at last birth was independently associated with a reduced risk of endometrial cancer, and the reduced risk persisted for many years.