Hormone replacement therapy, reproductive history, and colon cancer: a multicenter, case-control study in the United States

Colorectal cancer: molecules and populations

The epidemiology and molecular biology of colorectal cancer are reviewed with a view to understanding their interrelationship. Risk factors for colorectal neoplasia include a positive family history, meat consumption, smoking, and alcohol consumption. Important inverse associations exist with vegetables, nonsteroidal anti-inflammatory drugs (NSAIDs), hormone replacement therapy, and physical activity. There are several molecular pathways to colorectal cancer, especially the APC (adenomatous polyposis coli)-beta-catenin-Tcf (T-cell factor; a transcriptional activator) pathway and the pathway involving abnormalities of DNA mismatch repair. These are important, both in inherited syndromes (familial adenomatous polyposis [FAP] and hereditary nonpolyposis colorectal cancer [HNPCC], respectively) and in sporadic cancers. Other less well defined pathways exist. Expression of key genes in any of these pathways may be lost by inherited or acquired mutation or by hypermethylation. The roles of several of the environmental exposures in the molecular pathways either are established (e.g., inhibition of cyclooxygenase-2 by NSAIDs) or are suggested (e.g., meat and tobacco smoke as sources of specific blood-borne carcinogens; vegetables as a source of folate, antioxidants, and inducers of detoxifying enzymes). The roles of other factors (e.g., physical activity) remain obscure even when the epidemiology is quite consistent. There is also evidence that some metabolic pathways, e.g., those involving folate and heterocyclic amines, may be modified by polymorphisms in relevant genes, e.g., MTHFR (methylenetetrahydrofolate reductase) and NAT1 (N-acetyltransferase 1) and NAT2. There is at least some evidence that the general host metabolic state can provide a milieu that enhances or reduces the likelihood of cancer progression. Understanding the roles of environmental exposures and host susceptibilities in molecular pathways has implications for screening, treatment, surveillance, and prevention.

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.

Selective estrogen receptor modulators: a controversial approach for managing postmenopausal health

Hormone replacement therapy (HRT) is considered the standard of care for managing the acute (e.g., hot flashes, vaginal dryness) and long-term (e.g., increased risk of cardiovascular disease, osteoporosis) sequelae of menopause. A group of synthetic nonsteroidal compounds, which act on the estrogen receptor, have been promoted for use as an alternative to hormonal therapy for postmenopausal women. Originally called antiestrogens because of their ability to antagonize the action of estrogen, these compounds possess both agonist and antagonist properties of estrogen action. They are now referred to as selective estrogen receptor modulators (SERMs). This article reviews the mechanism of action and the efficacy and safety data for SERMs currently used for clinical purposes. These data may indicate why the use of SERMs is a controversial alternative to HRT.

Reproductive factors related to the risk of colorectal cancer by subsite: a case-control analysis

The authors hypothesized that reproductive factors of colorectal cancer, which are probably mediated by endogenous hormones, would differ according to colonic subsite. Information on reproductive factors was obtained from 372 female colorectal cancer cases (113 proximal colon, 126 distal colon, 133 rectum) and 31,061 cancer-free controls at the Aichi Cancer Center Hospital, Japan, between 1988 and 1995. Multiple logistic analysis showed that late age at interview, family history of colorectal cancer among first-degree relatives, menstrual regularity, late age at menopause, late age at first pregnancy and late age at first full-term pregnancy were significantly associated with the risk of colorectal cancer. None of the risk factors were significantly dissociated between colon and rectal cancer. In polytomous logistic regression analysis, particularly noteworthy was the fact that the odds ratios for age at menarche (P-value for heterogeneity of odds ratios = 0.010), age at first pregnancy (P = 0.016) and age at first full-term pregnancy (P = 0.028) were significantly higher for distal than for proximal colon cancer. This study supports the hypotheses that there might be an association between reproductive factors and risk of colon cancer, and that the carcinogenesis of colon cancer, by subsite, might show aetiologic distinctions.

Persistence with estrogen therapy in a postmenopausal Medicaid population

We evaluated rates of persistence with estrogen replacement therapy in postmenopausal Georgia Medicaid recipients adjusted for age and race. Data files for 1992-1994 were examined to estimate 3-year conditional survival probabilities using the Kaplan-Meier model, and 3800 subjects were identified. Over 54% of women remained compliant over 29 months, and 17% continued therapy for the entire 35 months of observation. Kaplan-Meier predictors indicated that white women have a 70% chance of being compliant for 3 years, whereas black women have a 60% chance. Monthly discontinuation rates ranged from 1-1.5% after the second month of therapy. Younger, white women were the most likely to maintain and comply with therapy.

Tamoxifen and risk of large bowel cancer in women with breast cancer

BACKGROUND

The increasingly consistent association between estrogen replacement therapy and colorectal cancer suggests that the anti-estrogen tamoxifen may also be associated with large bowel cancer incidence.

METHODS

Women with new diagnoses of breast cancer were identified from the Surveillance Epidemiology and End Results (SEER) Program, a set of geographically defined, population based cancer registries representing approximately ten percent of the U.S. population. Of 85,411 women with local or regional breast cancer diagnosed from 1983-90, 14,984 women were reported to have received hormonal therapy and 70,427 were not known to have received hormonal therapy. Subsequent cancer diagnoses were identified in this cohort beginning 6 months after initial breast cancer diagnosis until death, or December 31, 1994. Multivariate Cox proportional hazards models were used to estimate the risk of developing colorectal cancer and other second cancers according to hormonal therapy use.

RESULTS

Over the follow-up period 793 colorectal, 2,648 contralateral breast, 506 endometrial, 250 ovarian, 98 gastric, and 1,765 other cancers were identified in the study cohort. While overall there was no association between hormonal therapy use and colorectal cancer (relative risk (RR) 1.09, 95% confidence interval (CI) 0.88-1.35), in the period five or more years after diagnosis, risk was increased significantly by about 50% (95% CI 1.00-2.15). As expected, based upon clinical trials data, cancers of the contralateral breast were significantly decreased, and cancers of the uterine endometrium were significantly increased. No other meaningful associations were observed. When women were excluded for whom hormonal therapy might represent therapy other than tamoxifen (premenopausal women and those who received chemotherapy), this did not meaningfully alter these estimates.

CONCLUSIONS

The results of this large population based cohort study suggest that tamoxifen therapy may modestly increase risk of large bowel cancer in women, but only after 5 years following initiation of breast cancer therapy.

Is there an association between hormone replacement therapy and breast cancer?

The fear of breast cancer has been suggested as a potential reason why only a relatively small percentage of postmenopausal women who would benefit from hormone replacement therapy (HRT) are current users. The equivocal results from a large number of epidemiologic studies make it difficult to evaluate whether an association does indeed exist between the use of HRT and the incidence of breast cancer. The inability to provide conclusive evidence for or against this relationship may be attributed to methodologic problems in these studies, including small sample sizes, lack of information on specific hormonal preparations (e.g., dose and type), failure to control for the type of menopause, and surveillance bias. In an attempt to generalize results from different studies in a systematic manner, several meta-analyses have been conducted of the effects of estrogen replacement therapy (ERT) or HRT on the risk of breast cancer. This article summarizes the data from these meta-analyses and incorporates data from studies published after these meta-analyses that have addressed this question. Data from ongoing studies that use a randomized, controlled, longitudinal design on large numbers of women are necessary before a possible association between the use of HRT and breast cancer can be ascertained.

Oral contraceptives and colorectal tumors. A review of epidemiologic studies

Over the last two decades, the mortality rates of colorectal cancer in many developed countries have declined in women but not in men. One of the explanations of this difference between the genders may be the favorable influence of the spread of exogenous female hormone use (i.e., oral contraceptives [OC] and hormone replacement therapy) Reduced risk in ever-users of OC was found in three of four cohort studies available on this topic, and was significant in the one based on colorectal cancer mortality. The fourth one showed no difference. Of 11 case-control studies (or groups of studies), none showed significantly elevated risk. Five reported lowered colorectal cancer risk among ever-users, with a significant inverse association in the largest investigation available. Recent OC use, more than long duration use, seemed to be related to some risk reduction. One cohort study and three case-control investigations suggested that OC use was not related to the risk of colorectal adenomatous polyps. Thus, at present, it seems that OC use does not increase and may even have a favorable effect on either incidence or mortality of colorectal cancer.

Epidemiology of sociodemographic characteristics, lifestyle, medical history, and colon cancer: a case-control study among French Canadians in Montreal

Colon cancer is the second most common cancer in both men and women in North America and other developed countries. In a population-based case-control study of colon cancer among French Canadians in greater Montreal, a total of 402 cases and 668 controls were interviewed. The cancer cases were identified through the admission offices of five major Francophone teaching hospitals in Montreal from 1989 to 1993. The controls, matched by age, sex, place of residence, and language, were selected by a modified random digit dialing method. The results show that subjects who had ever been married had a lower risk for colon cancer (odds ratio [OR]: 0.58; 95% confidence interval [95% CI]: 0.48-0.84) than did individuals who had never been married. A significant association (OR: 1.90; p for trend = 0.003) was found between the height of subjects and the risk of colon cancer. The OR for individuals with a family history of colorectal cancer was 2.78 with a p value of 0.01. A direct and significant association (OR: 2.01) was found among constipation, use of laxatives (OR: 1.41), and the risk of colon cancer. Among women, a suggestive inverse association was detected between the number of full-term pregnancies and the risk of colon cancer in female subjects (the OR for five or more pregnancies was 0.58 with a p for trend of 0.08). There was also a suggestive linear trend (increased age-decreased risk) between age at menarche and the risk of colon cancer. No association was apparent between other sociodemographic characteristics and the risk of colon cancer. In conclusion, married individuals had lower risk for colon cancer, perhaps due to food habits or other characteristics of being single. Higher height and weight history 10 years before the diagnosis of cancer are risk factors for breast cancer, while both current weight and body mass index seem to be protective. Positive family history of colon cancer increased the risk of colon cancer significantly.

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.