The association of reproductive and menstrual characteristics and colon and rectal cancer risk in Wisconsin women

Reproductive history and risk of colorectal adenocarcinoma

BACKGROUND

Sex hormones may be associated with colorectal adenocarcinoma, although the association of pregnancy history and risk of colorectal cancer is not consistent.

METHODS

We conducted a population-based nested case-control study of persons born between 1932 and 2008 who are in the Swedish Multi-Generation Register. In total, 12,915 women and 15,519 men with colorectal adenocarcinoma were identified during follow-up in the Swedish Cancer Register; 10 age- and sex-matched controls were selected for each case. Number of children and age at first and last birth were analyzed in relation to the risk of colorectal adenocarcinoma, using conditional logistic regression, to estimate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Compared with women without children, women with 1 or 2 children had an OR of 1.02 (95% CI = 0.93-1.13) of developing adenocarcinoma in the proximal colon; those with 3 or 4 children, 1.18 (1.06-1.32); and those with ≥5 children, 1.30 (1.05-1.61) (test for trend P < 0.01). The corresponding associations in men were 0.92 (0.84-1.00), 1.02 (0.92-1.13), and 0.97 (0.78-1.20), respectively (test for trend P = 0.13).

CONCLUSIONS

Higher parity in women was associated with the risk of adenocarcinoma of the proximal colon, although not the distal colon or rectum. A similar risk with family size was not seen for fathers. Still, the influence of lifestyle factors cannot be ruled out.

Age at menarche and risk of colorectal cancer: a meta-analysis

Background

Various observational studies have focused on the relationship between menarcheal age and the risk of colorectal cancer (CRC). However, the association is still controversial because of inconsistent results. Therefore, we performed a meta-analysis to assess this issue from epidemiological studies.

Methods

After a literature search in MEDLINE, EMBASE, and Web of Science for studies of menarcheal age and CRC risk published through the end of January 2013, we pooled the relative risks (RRs) from included studies using a fixed- or random-effects model and performed heterogeneity and publication bias analyses. All statistical tests were two-sided.

Results

Eleven case-control and 11 cohort studies were eligible for inclusion in our analysis. The random-effects pooled RR for oldest versus youngest menarcheal age was 0.95 [95% confidence intervals (CIs) = 0.85–1.06], with significant heterogeneity (Q = 61.03, P<0.001, I² = 65.6%). When separately analyzed, case-control (RR = 0.95, 95% CI = 0.75–1.21) and cohort studies (RR = 0.97, 95% CI = 0.90–1.04) yielded similar results. Moreover, similar results were also observed among the subgroup analyses by study quality, population, exposure assessment, anatomic cancer site, subsite of colon cancer, and several potential important confounders and risk factors. There was no evidence of publication bias and significant heterogeneity between subgroups detected by meta-regression analyses.

Conclusions

Findings from this meta-analysis demonstrated that menarcheal age was not associated with the risk of CRC in humans. Further studies are warranted to stratify results by the subsite of colon cancer and menopause status in the future.

The relationship between gravidity and parity and colorectal cancer risk

OBJECTIVES

The influence of hormonal changes caused by pregnancy has been well studied in relation to colorectal cancer risk, but the association remains undefined. The purpose of this investigation was to examine in a case-control study the relationship between differences in gravidity and parity and colorectal cancer risk and if the association varied by microsatellite instability (MSI), a feature more common in women.

METHODS

The study population included incident colorectal cancer patients (n = 1014), aged 50-74 years, diagnosed in 1998-2002 in Washington state and controls (n = 1064) randomly selected from population lists. All study subjects completed telephone interviews to ascertain prior pregnancies, live births, and other covariates. Case tissue samples were obtained for MSI analyses. Multivariable logistic regression models estimated odds ratios (OR) and 95% confidence intervals (CI), adjusting for age, family history of colorectal cancer, body mass index (BMI), education, endoscopy screening, oral contraceptive use, hormone therapy use, smoking, and alcohol consumption.

RESULTS

There was an approximate 30%-50% reduction in risk of colon cancer associated with gravidity, which was attenuated in the analysis with parity. Increasing gravidity and parity were associated with a suggestion of a decreasing trend in risk for rectal cancer (p for trend = 0.07). Compared with women who had equal numbers of pregnancies and live births, women who were nulligravid and nulliparous had a 40%-60% increased risk of colon cancer. There was a suggestion of a reduced risk of both colon and rectal cancer associated with one more pregnancy than live birth. There was a suggestion of an increased risk of MSI-high tumors with nulligravidity and nulliparity.

CONCLUSIONS

These results confirm the importance of pregnancy events in the etiology of colon and rectal cancer.

The Effects of Twins, Parity and Age at First Birth on Cancer Risk in Swedish Women

The effect of reproductive history on the risk of cervical, colorectal and thyroid cancers and melanoma has been explored but the results to date are inconsistent. We aimed to examine in a record- linkage cohort study the risk of developing these cancers, as well as breast, ovarian and endometrial cancers, among mothers who had given birth to twins compared with those who had only singleton pregnancies. Women who delivered a baby in Sweden between 1961 and 1996 and who were 15 years or younger in 1961 were selected from the Swedish civil birth register and linked with the Swedish cancer registry. We used Poisson regression to assess associations between reproductive factors and cancer. Twinning was associated with reduced risks of breast, colorectal, ovarian and uterine cancers, although no relative risks were statistically significant. The delivery of twins did not increase the risk of any cancers studied. Increasing numbers of maternities were associated with significantly reduced risks of all tumors except thyroid cancer. We found positive associations between a later age at first birth and breast cancer and melanoma, while there were inverse associations with cervix, ovarian, uterine and colorectal cancers. These findings lend weight to the hypothesis that hormonal factors influence the etiology of colorectal cancer in women, but argue against any strong effect of hormones on the development of melanoma or tumors of the thyroid.

Menopausal hormone therapy and risk of colorectal cancer

We evaluated colorectal cancer risk associated with the duration and recency of specific menopausal hormone therapy formulations (i.e., unopposed estrogen versus estrogen plus progestin) and regimens (i.e., sequential versus continuous estrogen plus progestin use) among 56,733 postmenopausal women participating in the Breast Cancer Detection Demonstration Project follow-up study. Hormone therapy use and other risk factors were ascertained through telephone interviews and mailed questionnaires from 1979 to 1998. The final cancer group included 960 women who were identified from self-report, medical records, state registry data, and the National Death Index. Poisson regression was used to generate multivariable rate ratios (RR) and 95% confidence intervals (95% CI). We observed a decreased risk of colorectal cancer among ever users of unopposed estrogen therapy (RR, 0.83; 95% CI, 0.70-0.99). Among estrogen users, the largest reduced risk was observed for current users (RR, 0.75; 95% CI, 0.54-1.05) and users of >or=ten years duration (RR, 0.74; 95% CI, 0.56-0.96). We found a reduced risk among users of estrogen plus progestin therapy (RR, 0.78; 95% CI, 0.60-1.02), with sequential regimen users (progestin <15 days per cycle) having the largest risk reduction (RR, 0.64; 95% CI, 0.43-0.95). Past users of >or=5 years ago (RR, 0.55; 95% CI, 0.32-0.98) had the largest risk reduction. In this study, estrogen plus progestin use, especially sequential regimen use, was associated with the largest overall reduction of colorectal cancer risk.

Oral contraceptive use, hormone replacement therapy, reproductive history and risk of colorectal cancer in women

Evidence from epidemiologic studies suggests a possible role of exogenous and endogenous hormones in colorectal carcinogenesis in women. However, with respect to exogenous hormones, in contrast to hormone replacement therapy, few cohort studies have examined oral contraceptive use in relation to colorectal cancer risk. We used data from a large cohort study of Canadian women enrolled in a randomized controlled trial of breast cancer screening to assess the association of oral contraceptive use, hormone replacement therapy and reproductive factors with risk of colorectal cancer, overall and by subsite within the colorectum. Cancer incidence and mortality were ascertained by linkage to national databases. Among 89,835 women aged 40-59 at enrollment and followed for an average of 16.4 years, we identified 1,142 incident colorectal cancer cases. Proportional hazards models were used to estimate the associations between the exposures of interest and risk of colorectal cancer. Ever use of oral contraceptives at baseline was associated with a modest reduction in the risk of colorectal cancer (hazard ratio 0.83, 95% confidence interval 0.73-0.94), with similar effects for different subsites within the colorectum. No trend was seen in the hazard ratios with increasing duration of oral contraceptive use. No associations were seen with use of hormone replacement therapy (ever use or duration of use) or reproductive factors. Our results are suggestive of an inverse association between oral contraceptive use and colorectal carcinogenesis. However, given the lack of a dose-response relationship and the potential for confounding, studies with more complete assessment of exogenous hormone use throughout the life course are needed to clarify this association.

Oral Contraceptive Use, Reproductive Factors, and Colorectal Cancer Risk: Findings from Wisconsin

We investigated the association of oral contraceptive (OC) use and reproductive factors with colorectal cancer risk in a large population-based case-control study. Cases were women ages 20 to 74 years, living in Wisconsin, with a new diagnosis of colon (n = 1,122) or rectal (n = 366) cancer. Control participants were randomly selected from population lists of similarly aged female Wisconsin residents (n = 4,297). Risk factor information was collected through structured telephone interviews. Compared with never users, OC users had an odds ratio (OR) of 0.89 [95% confidence interval (95% CI), 0.75-1.06] for colorectal cancer. OC use associations did not differ significantly between colon and rectal cancer sites; however, when compared with never users, recent OC users (<14 years) seemed at reduced risk of rectal cancer (OR, 0.53; 95% CI, 0.28-1.00). Women with age at first birth older than the median (23 years) had 0.83 times the risk of colon cancer compared with women with age at first birth below the median (95% CI, 0.70-0.98). We observed an inverse trend between increasing parity and rectal cancer risk (P = 0.05). Compared with nulliparous women, women with five or more births had 0.66 times the risk of rectal cancer (95% CI, 0.43-1.02). Compared with postmenopausal women, premenopausal women were at reduced risk (OR, 0.67; 95% CI, 0.47-0.97) of colorectal cancer. No significant associations were observed between colorectal cancer risk and age at menarche or age at menopause. These findings suggest differential roles of reproductive factors in colon and rectal cancer etiology.

Cancer risk associated with early and late maternal age at first birth

OBJECTIVE

This paper provides a review of the literature associating maternal age at first birth and cancer. Potential mechanisms explaining associations between maternal age at first birth and cancer are also discussed.

METHOD

Systematic review of English language literature using searches on established databases (e.g., Medline, Popline) and the references of materials identified in these databases.

RESULTS

Older age (typically defined as 35 years or older) at first birth is associated with increased risk of breast and brain cancers. Conversely, younger age (typically defined as 19 years or younger) at first birth is associated with an increased risk of cervical and endometrial cancers. There is an unclear correlation between maternal age at first birth and site-specific malignancies such as ovarian, colorectal, thyroid, pancreatic, and kidney cancers. Causal mechanisms linking age at first birth and cancer were identified and reported for breast, brain, cervical, and endometrial cancers.

CONCLUSION

Older age at first birth increases the risk for breast and brain cancers but decreases the risk of cervical and endometrial cancers.

Colon cancer during pregnancy

The medical community should become mobilized to diagnose colon cancer earlier in pregnancy to improve prognosis. The primary care physician or obstetrician should refer the pregnant patient with significant gastrointestinal complaints to the gastroenterologist for evaluation. Likewise, the gastroenterologist should be prepared to perform sigmoidoscopy, preferably without endoscopic medications, for significant lower gastrointestinal symptoms such as persistent rectal bleeding. Sigmoidoscopy is particularly sensitive in identifying colon cancer in pregnant patients because their cancers are usually distal and within reach of the sigmoidoscope.

Modifiable risk factors for colon cancer

Although many mechanisms remain unclear, a large body of evidence indicates that several dietary and lifestyle factors are likely to have a major influence on the risk of colon cancer. Physical inactivity, excess body weight, and a central deposition of adiposity are consistent risk factors. Overconsumption of energy is likely to be one of the major contributors to the high rates of colon cancer in Western countries. Beyond their influence on energy balance, the independent role of specific macronutrients remain controversial. Red meat, processed meats, and perhaps refined carbohydrates contribute to risk. Recent evidence indicate that chronic hyperinsulinemia may increase risk of colon cancer. As insulin resistance and subsequent hyperinsulinemia is induced by excess energy intake and some aspects of the Western diet (e.g., saturated fats and refined carbohydrates), insulin may be a focus of factors influencing colon cancer risk. Recent evidence also points to a role of IGF-1, but our understanding of modifiable factors that influence levels of these is poor at present. Of note is that hyperinsulinemia increases free IGF-1 exposure [25]. High alcohol consumption, probably in combination with a diet low in some micronutrients such as folate and methionine, and smoking early in life are likely to increase risk of colon cancer. Recent epidemiologic studies have tended not to support a strong influence of fiber; instead, some micronutrients or phytochemicals in fiber-rich foods may be important. Folate is one such nutrient that has received attention lately and is being studied in randomized intervention trials. Agents with chemopreventive properties, such as aspirin and postmenopausal estrogens, have potential adverse effects so a careful consideration of the risk-benefit ratio is required before general recommendations can be made. Other NSAIDs with a potential for reduced toxicity, such as celecoxib, are currently being evaluated for efficacy and toxicity. The overwhelming evidence indicates that primary prevention of colon cancer is feasible. At least 70% of colon cancers may be preventable by moderate changes in diet and lifestyle [197]. Secondary prevention, through screening by sigmoidoscopy and colonoscopy, is also critically important to prevent mortality from colon cancer; however, many of the diet and lifestyle risk factors for colon cancers are the same for cardiovascular disease and for some other cancers, so focusing on the modifiable risk factors for colon cancer is likely to have many additional benefits beyond this cancer.

Estrogen and colon cancer: current issues

Carcinoma of the colon is common and its incidence varies according to the geographical location and dietary habits. The aims of this paper are, first, to review the current epidemiological data on the incidence and mortality of colon cancer in postmenopausal women using hormone replacement therapy (HRT); second, to review the published data on the prevalence of estrogen receptors in healthy and malignant colonic tissue; and third, to examine the available evidence of gene silencing as applicable to this and other neoplastic conditions. Estrogen use confers overall protection, with a reduction in the incidence of colon adenoma and carcinoma of about 30%. Estrogen use reduces the colon cancer-related mortality. The risk of colon cancer is decreased among current and recent users of postmenopausal HRT but the molecular mechanisms involved remain unclear. Estrogen acts either on a single major transformation step in the oncogenetic process, or is involved in multiple events that avert the course of this transformation. Aberrant methylation of the CpG islands in the promoter regions of the estrogen receptor gene, as well as of other genes, is equivalent to the silencing of that gene, with the consequence of inactivation, or reduced expression, of a number of genes downstream, including tumor suppressor genes. This epigenetic mechanism, when reversed, suppresses the growth of cancer cells in vitro and in vivo. The ubiquitous distribution of the estrogen receptor genes and their isoforms, in a tissue-specific manner, opens new avenues for the understanding of cellular behavior in health and disease.

Hormone replacement therapy and the risk of colorectal cancer: a meta-analysis

OBJECTIVE

To review systematically the association between hormone replacement therapy (HRT) and the risk of developing or dying from colorectal cancer.

DATA SOURCES

We searched the English-language literature using MEDLINE, Current Contents, CancerLit, and bibliographies of selected studies.

METHODS OF STUDY SELECTION

We included studies that specifically addressed the association of HRT with colorectal cancer, had adequate controls, and had retrievable risk estimates. We excluded letters, reviews, and multiple publications of the same data.

TABULATION, INTEGRATION, AND RESULTS

Studies were evaluated independently by two of the authors. The exposures of interest were ever, recent, or former use of HRT, and the main outcome measures were colon and rectal cancer incidence and mortality. To reduce the risk of a "healthy estrogen user" bias, we defined recent HRT use as either at time of assessment or within the previous year. The most adjusted risk estimates were extracted. We used a random-effects model to calculate summary relative risks (RRs) and confidence intervals (CIs). Recent use of HRT was associated with a 33% reduction in the risk of colon cancer (RR = 0.67; 95% CI 0.59, 0.77). Protection was limited to recent users; the risk of colon cancer with ever use of HRT was 0.92 (95% CI 0.79, 1.08). Duration of use was not significant. Three studies addressed the risk of fatal colon cancer; the summary RR for death from colon cancer in HRT users was 0.72 (95% CI 0.64, 0.81) compared with nonusers. Rectal cancer incidence was not associated with HRT.

CONCLUSION

The risk of colon cancer may be decreased among recent postmenopausal HRT users. Although data are limited, the risk of fatal colon cancer also may be lower in HRT users.

Age at menopause, body mass index, and the risk of colorectal cancer mortality in the Dutch Diagnostisch Onderzoek Mammacarcinoom (DOM) cohort

We investigated whether age at menopause is associated with subsequent mortality from colorectal cancer along with the possible modification of this association by body mass index. Our data are from the Diagnostisch Onderzoek Mammacarcinoom cohort of 10,671 postmenopausal women in the Netherlands, enrolled between 1974 and 1977, with a median follow-up of 18 years. During this follow-up, 95 women died of colorectal cancer. Women 49 years of age or older at menopause showed a lower risk of colorectal cancer mortality compared with women younger than 49 at menopause. This protective effect, however, was found only among nonoverweight women (< or =24 kg/m2), for whom the hazard ratio was 0.46 (95% confidence interval = 0.21-1.03). In larger women, the hazard ratio was 1.17 (95% confidence interval = 0.68-2.00).

Estrogen replacement therapy and colon cancer: a clinical review

Colorectal cancer is the third leading cause of cancer death in women. Studies on the potential protective effect of postmenopausal hormone replacement on the incidence of colon cancer have been contradictory. To attempt to clarify the potential protective effect of hormone replacement therapy (HRT), an English-language key word (KW) search of MEDLINE, up to August 1999, was performed for KW colon cancer or colorectal adenoma or colon adenoma or adenomatous polyp and KW estrogen replacement or hormone replacement. Additional references were obtained from reading of the reference lists. Thirty-five studies, including 3 meta-analyses, were found. Of these, 23 suggested any degree of protective effect of HRT, 11 reported neutral results, and 1 reported negative impact of hormone replacement. The single prospective randomized controlled trial included small numbers of inpatients taking high-dose estrogen. However, studies did not uniformly specify hormone type, dose, duration, and potential differential effects on right and left colon. Estrogen and progesterone effects were not often considered separately. Many studies had inadequate control of confounders, for example, family history of colon cancer or indication for endoscopy. Therefore, although the majority of studies, especially more rigorously designed recent studies, support the conclusion that postmenopausal estrogen replacement therapy (ERT) has a protective effect against colon adenomas and colon cancer, methodological limitations preclude practical application of study results at present. Prospective studies are needed to confirm the existence and degree of protective effect, as well as to specify the mechanism of protection.

Estrogen replacement therapy and colorectal cancer risk in elderly women

PURPOSE

Colorectal cancer is the fourth most common incident cancer in the United States and causes more cancer deaths than any site except lung. Twenty-two epidemiologic studies have examined the relationship of estrogen replacement therapy and colon and rectal cancers with inconsistent results. However, recent studies suggest a reduced risk among current users. The purpose of the present study was to analyze the Leisure World Cohort for possible association of estrogen replacement therapy with colorectal cancer risk.

METHODS

A cohort of 7,701 female members who were initially free of cancer and self-reported their use of estrogen replacement therapy were followed up from June 1981 through December 1995 for development of colorectal cancer.

RESULTS

We observed 249 incident colorectal cancer cases and 89 colorectal cancer deaths. Women who had used estrogen replacement therapy had an age-adjusted colorectal cancer incidence rate of 2.67 per 1,000 person-years compared with 3.30 per 1,000 person-years among lifetime nonusers (relative risk = 0.81; 95 percent confidence interval, 0.63 to 1.04). Among recent users the incidence was one-third lower than among lifetime nonusers (relative risk = 0.66; 95 percent confidence interval, 0.44 to 0.98). Risk did not differ by duration of estrogen replacement therapy, usual dose of conjugated estrogen, or route of estrogen administration. The effects of current estrogen replacement therapy on colon cancer incidence (relative risk = 0.70; 95 percent confidence interval, 0.45 to 1.09), right-sided colon cancer incidence (relative risk = 0.75, 95 percent confidence interval, 0.38 to 1.48), left-sided colon cancer incidence (relative risk = 0.76; 95 percent confidence interval, 0.41 to 1.41), rectal cancer incidence (relative risk = 0.52; 95 percent confidence interval, 0.21 to 1.31), and colorectal cancer mortality (relative risk = 0.82; 95 percent confidence interval, 0.44 to 1.54) were similar.

CONCLUSION

A reduced risk of colorectal cancer may be an additional benefit of recent estrogen replacement therapy use, which should be considered by postmenopausal women when deciding whether to use hormones.

Postmenopausal hormone therapy and the risk of colorectal cancer: a review and meta-analysis

PURPOSE

Colorectal cancer is the fourth most common cancer and the second leading cause of cancer death in the United States. Accumulating evidence indicates that postmenopausal hormone therapy may reduce the risk of colorectal cancer in women.

METHODS

Through MEDLINE computer searches (January 1966 to September 1998) and a review of references, we identified English-language articles with quantitative data on the relation of postmenopausal hormone therapy to colorectal cancer. We reviewed the studies and made summary estimates of relative risks (RR) by weighting the results of each study in proportion to its precision, using a general variance-based, fixed-effects model.

RESULTS

In our meta-analysis of 18 epidemiologic studies of postmenopausal hormone therapy and colorectal cancer, we found a 20% reduction [RR = 0.80, 95% confidence interval (CI), 0.74 to 0.86] in risk of colon cancer and a 19% decrease (RR = 0.81, 95% CI, 0.72 to 0.92) in the risk of rectal cancer for postmenopausal women who had ever taken hormone therapy compared with women who never used hormones. Much of the apparent reduction in colorectal cancer was limited to current hormone users (RR = 0.66, 95% CI, 0.59 to 0.74).

CONCLUSION

Observational studies suggest a reduced risk of colorectal cancer among women taking postmenopausal hormones. There is biologic evidence to support this association.

Immune recognition of endometrial tumor antigens induced by multiparity

OBJECTIVE

The risk of developing endometrial cancer is reduced with increasing parity. The purpose of this study was to investigate the possibility that maternal immunization against fetal antigens might be elicited during pregnancy and, if so, to characterize antigens reactive with this immune response.

METHODS

Sera were obtained from nulliparous (n = 9) and multiparous women (n = 14). Cellular proteins were isolated from normal endometrium and cultured cells from early (HEC-1A) and late (KLE and RL95-2) stage endometrial cancers. These were separated by SDS-PAGE and those proteins reactive with each individual's serum were assessed by Western immunoblot. Reactive proteins were isolated from KLE tumor cells by immunoaffinity columns. Three commonly recognized proteins were identified, separated, and processed for internal microsequencing.

RESULTS

Sera from multiparous women, used as primary antibodies, recognized multiple bands on endometrial tumors, ranging from 10 to 120 kDa. Several antigens were commonly recognized by the sera of multiparous women. The three commonly recognized proteins, normally expressed by fetal tissues, were identified as cystatin A (10 kDa), epidermal fatty acid binding protein (18 kDa), and keratin 10 (54 kDa). Nulliparous women failed to recognize these antigens.

CONCLUSION

These findings suggest that certain antigens expressed by the fetus and/or the placenta immunize women during pregnancy. This immune response may protect these women from developing endometrial cancer and explain epidemiologic findings. Future studies will explore the utility of these reexpressed fetal antigens as possible targets for active immunotherapy.

The influence of reproductive and hormonal factors on the risk of colon and rectal cancer in women

A case-control study was conducted between 1992 and 1996 in six Italian areas. It included 537 women with colon cancer, 291 women with rectal cancer and 2081 control women in hospital for acute conditions, unrelated to hormonal or gynaecological diseases. A higher age at menopause was associated with increased colon cancer risk (odds ratio (OR) for > or = 53 years compared with < 50 years = 1.39, 95% confidence interval (CI) 1.04-1.87). Among parous women, a significant trend of decreasing colon cancer risk with increasing number of births was seen for colon (OR for > or = 4 births compared with 1 birth = 0.62, 95% CI 0.42-0.90), but not for rectal cancer. Nulliparous women, however, were at lower risk than women with a single birth, and age at first birth was directly associated with risk. While oral contraceptive use showed no significant influence, ever users of hormone replacement therapy had a reduced risk of rectal cancer (OR = 0.56, 95% CI 0.31-1.01). Thus, the association of colorectal cancer with reproductive and menstrual factors is neither strong nor consistent.