A record-based evaluation of induced abortion and breast cancer risk (United States)

OBJECTIVE

Previous studies of induced abortion and breast cancer may have been limited by differential reporting of abortion history. We conducted a population-based case-control study to evaluate abortion (both induced and spontaneous) and breast cancer risk.

METHODS

All study subjects were aged 20-69 years and members of Group Health Cooperative of Puget Sound (GHC). Incident invasive breast cancer cases (n = 138) were identified from the linkage between the GHC enrollment file and the Seattle-Puget Sound SEER Cancer Registry. Controls (n = 252) were randomly selected from GHC enrollment files and matched to cases on age and enrollment period. All subjects had to have been enrolled at GHC for the 2 years preceding diagnosis (cases) or reference (controls) date. The unified medical record of each case was abstracted for pregnancy history, including prior induced and spontaneous abortions, menopause status, height and weight, screening practices, and other risk factors.

RESULTS

Compared to all women who had never had an induced abortion, the multivariate adjusted relative risk of breast cancer in women with an induced abortion was 0.9 (95% confidence interval 0.5-1.6). This risk was similar in parous women, and nulliparous women. There was no association between spontaneous abortion and breast cancer risk.

CONCLUSIONS

These results do not support a relation between induced abortion and breast cancer incidence.

Breast feeding practices in relation to endometrial cancer risk, USA

OBJECTIVE

Breast feeding is associated with reduced estrogen, a profile that should be associated with decreased endometrial cancer incidence. We analyzed data from a population-based case-control study of Wisconsin women to evaluate the relation between lactation and endometrial cancer risk.

METHODS

Cases (n = 586) were identified from a statewide tumor registry; controls (n = 1653) were selected randomly from driver's license lists and Medicare beneficiary files. Breast feeding practices and other factors were ascertained by telephone interview.

RESULTS

Compared with parous women who did not breast feed, the multivariate relative risk for women who breast fed for at least 2 weeks was 0.90 [95% confidence interval (CI) 0.72-1.13]; increasing duration was not strongly associated with risk of disease (p for trend 0.4). More recent breast feeding was associated with significantly reduced risks. The relative risk for lactation within the recent three decades was 0.58 (95% CI 0.36-0.96) and for first breast feeding at age 30 or greater was 0.50 (95% CI 0.28-0.90). There was a suggestion that risk was increased in women who used lactation suppressant hormones--usually estrogens--more recently (p = 0.1) or at a later age (p = 0.1).

CONCLUSIONS

This study suggests that, like breast cancer, endometrial cancer is modestly inversely associated with lactation.

Risk factors for carcinoma in situ of the breast

As more women obtain screening mammograms regularly and at younger ages, the diagnosis of breast carcinoma in situ becomes more frequent. To examine whether risk factors for carcinoma in situ correspond with risk factors for invasive breast cancer, we analyzed data from a population-based case-control study conducted in 1988-1990. We identified newly diagnosed cases of carcinoma in situ (n = 301) and invasive breast cancer (n = 3789) in women 18-74 years of age from Wisconsin's statewide tumor registry. Cases and population controls (n = 3999) completed structured telephone interviews. Overall, associations with risk of carcinoma in situ in relation to many reproductive life-style risk factors were similar to those associated with risk of invasive disease. Women who reported a family history of breast cancer had a 2-fold elevated risk of carcinoma in situ (odds ratio, 2.67; 95% confidence interval, 2.00-3.57). Personal history of benign biopsied breast disease also increased risk of carcinoma in situ (odds ratio, 2.19; 95% confidence interval, 1.62-2.95). Subgroup analysis suggested that high vitamin A intake and high alcohol intake may be associated with risk of ductal but not lobular carcinoma in situ. These data support the presence of common risk factors between in situ and invasive breast cancer.

Weight change and risk of postmenopausal breast cancer (United States)

OBJECTIVE

Although many studies have shown that higher weight increases the risk of postmenopausal breast cancer, some aspects of this association are unclear. In order to examine the risk associated with different patterns of weight change, we analyzed data from a large case-control study of postmenopausal breast cancer.

METHODS

Participants included women aged 50 79 years (n = 5031) who are newly diagnosed with invasive breast cancer in Massachusetts, New Hampshire, and Wisconsin. Similarly-aged population controls (n = 5255) were selected at random from driver's license files and Medicare beneficiary lists. Height, weight, and information on other breast cancer risk factors were ascertained by structured telephone interviews from 1992 to 1995, and logistic regression was used to estimate multivariable-adjusted odds ratios (OR) and 95% confidence intervals (CI).

RESULTS

Women in the top quintile groups for height at age 20, recent weight, and recent body mass index had significantly increased risks of breast cancer. Among women who reached their highest adult weight at younger ages (<45 years), increasing weight loss since that age was associated with a reduced risk of postmenopausal breast cancer (OR 0.90, CI 0.84 0.98, per 5 kg). However, weight loss among women whose highest weight occurred after age 45 was not associated with risk (OR 1.00, CI 0.95 1.05, per 5 kg). Weight gain since the lowest adult weight increased risk by 8% for each 5 kg of gain (OR 1.08, CI 1.06-1. 11). Temporary weight cycling (weight loss followed by weight gain) was not associated with increased risk.

CONCLUSIONS

Weight gain clearly increased risk of postmenopausal breast cancer. These data lend further support to efforts aimed at helping women avoid weight gain as they age.

Early-life physical activity and postmenopausal breast cancer: effect of body size and weight change

It is not yet known whether early-life physical activity reduces the risk of developing breast cancer. Subgroup analyses according to menopausal status and body mass may help clarify this association. Data from a population-based case-control study of female residents of Wisconsin, Massachusetts, Maine, and New Hampshire were used to examine associations between body mass and breast cancer risk. Cases (n = 4614) were identified by each state's tumor registry; controls (n = 5817) were randomly selected from population lists. Frequency of participation in strenuous physical activity when 14-22 years of age, weight at age 18 and 5 years before interview, height, and other factors were ascertained through structured telephone interviews. Adjusted odds ratios (ORs) and 95% confidence intervals (CIs) were computed using logistic regression. Reductions in postmenopausal breast cancer risk associated with strenuous physical activity were greatest for women in the fourth quartile of body mass index at age 18; the OR for women with the highest activity frequency on average (> or =once/day) was 0.45 (95% CI = 0.26-0.79). Associations with frequency of activity also varied by weight change. Compared to women with no activity and little adult weight gain, frequent physical activity was associated with reduced postmenopausal breast cancer risk in women who had lost weight since age 18 (OR = 0.19, 95% CI = 0.05-0.70) or had gained little or modest amounts of weight (weight gain: first tertile, OR = 0.36, 95% CI = 0.05-0.85; second tertile, OR = 0.31, 95% CI = 0.14-0.66). Weighted MET score analyses yielded similar but less inverse results. These findings suggest that the reduced risk of postmenopausal breast cancer associated with frequent, early-life physical activity may be greatest in women who, over the adult years, either lost weight or gained only modest amounts.

Age at any full-term pregnancy and breast cancer risk

The authors analyzed data from two multistate, population-based case-control studies to investigate the association between age at any full-term pregnancy (FP) and breast cancer risk. Study subjects included breast cancer cases aged 20-79 years identified from four statewide cancer registries and randomly selected controls interviewed from 1988 to 1996. Complete information on a comprehensive set of risk factors for breast cancer was available for 9,891 cases and 12,271 controls. The large number of subjects enabled simultaneous adjustment of the covariates and efficient application of various modeling approaches. Overall, each 5-year increase in age at first FP was associated with an odds ratio of 1.07 (95% confidence interval (CI): 1.01, 1.13) for breast cancer. The corresponding estimates were odds ratio = 1.02 (95% CI: 1.00, 1.05) for age at second through ninth FPs. For age at last FP, the effect estimate (odds ratio = 1.01, 95% CI: 0.97, 1.06) was indistinguishable from that for other FPs after the first. In this analysis, a modest and transient increase in breast cancer risk after childbirth was also observed. The relatively greater effect of age at first FP is consistent with the existence of a long-term effect of early first FP on the differentiation of mammary cells, causing them to become less susceptible to carcinogenesis.

Left-handedness in relation to breast cancer risk in postmenopausal women

Breast cancer risk may be influenced by intrauterine exposure to steroid hormones. We evaluated left-handedness, a marker of intrauterine hormone exposure, in relation to breast cancer risk in our population-based, case-control study. Case women 50-79 years of age with a first diagnosis of invasive breast cancer were ascertained through statewide cancer registries in Wisconsin, Massachusetts, and New Hampshire. Control women were identified in each state through lists of licensed drivers (for ages 50-64) and Medicare beneficiaries (for ages 65-79), and selected at random to correspond with the age distribution of case women. Exposure information, including handedness, was obtained through a telephone interview. Our results indicated a modest association between left-handedness and breast cancer risk (OR = 1.42; 95% CI = 1.10-1.83). The effect of left-handedness was modified by age; we observed the greatest risk ratio in the oldest age group. Left-handedness was not associated with breast tumor laterality. Our results are consistent with the hypothesis that intrauterine hormone exposures play a role in the development of breast cancer.

Interactions of familial and hormonal risk factors for large bowel cancer in women

BACKGROUND

Family history of colorectal cancer has been consistently associated with an increased personal risk of this disease. Since evidence suggests that hormones are related to colon cancer risk in women, the effect of family history on large bowel incidence may be modified according to endogenous and exogenous hormone levels.

METHODS

We analysed data from a population-based case-control study of female colorectal cancer to evaluate family history and cancer risk. Cases (n = 702) were female residents of Wisconsin with a new diagnosis of colorectal cancer, identified through a statewide tumour registry. Controls (n = 2274) were randomly selected from lists of licensed drivers and from rosters of Medicare beneficiaries. All relative risks (RR) were adjusted for age, body mass index, smoking and alcohol history, education, and use of hormone replacement therapy.

RESULTS

Compared with women who reported no history of cancer in a first degree relative, women with a family history had an RR of 2.07 (95% confidence interval [CI]: 1.60-2.68). Regardless of which parent was affected, risks were increased about twofold, while sibling history was associated with about a 50% increase in risk. Risk was greater if more than one family member was affected (RR 3.65, 95% CI: 1.81-7.37). The association between family history and risk was stronger for colon cancer than for rectal cancer. There were no indications that exogenous hormonal factors, notably hormone replacement use, modified these risks. There was a suggestion that high parity attenuated the risks associated with family history (P = 0.07).

CONCLUSIONS

These results confirm that family history of colorectal cancer is associated with a doubling of risk for large bowel cancer in women; some histories were associated with greater risk. This relation was not substantially different among subgroups of women with varying exogenous and endogenous hormone exposures.

Lactation in relation to postmenopausal breast cancer

A modest inverse association between lactation and breast cancer risk has most consistently been observed in premenopausal women, and certain breastfeeding patterns, such as prolonged duration and early age at first lactation, may be important determinants of risk. However, these associations have not generally been observed in relation to postmenopausal breast cancer. As part of a multicenter population-based case-control study, the authors examined postmenopausal breast cancer risk according to breastfeeding characteristics. Breast cancer patients aged 50-79 years were identified from statewide tumor registries in Massachusetts, New Hampshire, and Wisconsin from July 1992 through July 1995. Similarly aged control women were randomly selected from population lists. Information regarding lactation history and breast cancer risk factors was obtained through telephone interviews. This analysis included only data on parous postmenopausal women (3,633 cases and 3,790 controls). After adjustment for age, parity, age at first birth, and other breast cancer risk factors, breastfeeding for at least 2 weeks was associated with a slightly reduced risk of breast cancer in comparison with women who had never lactated (relative risk = 0.87, 95% confidence interval 0.78-0.96). There was only a modest suggestion that increasing cumulative duration of lactation was inversely associated with breast cancer risk; the relative risk for women who had breastfed for > or =24 months was 0.73 (95% confidence interval 0.56-0.94) (p-trend for duration = 0.10). Age at first lactation was not consistently associated with risk. Modest inverse associations appeared to persist even up to 50 years since first lactation. Use of hormones to suppress lactation was not associated with postmenopausal breast cancer, nor was inability to breastfeed related to risk. These results suggest that lactation may have a slight and perhaps long-lasting protective effect on postmenopausal breast cancer risk.

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.

The relation of breast size to breast cancer risk in postmenopausal women (United States)

OBJECTIVE

Breast size has been hypothesized to predict a woman's risk of breast cancer although studies in the main have not supported an association. In a large, population-based case-control study we examined whether breast size might emerge as a significant risk factor among very lean women in whom breast size might be a truer reflection of the volume of gland mass at risk for malignant change.

METHODS

The data derive from a population-based case-control study of women aged 50 to 79 years conducted in several New England states and Wisconsin. Incident cases of invasive breast cancer (n = 2015) were identified through state tumor registries and controls (n = 2556) were selected at random within age strata from population lists. Telephone interviews were conducted to obtain information on known and suspected risk factors which included bra dimensions (cup and back size) prior to a first birth, or at the age of 20 for nulliparous women.

RESULTS

We observed a significant positive association for cup size which was limited to women who were the most lean as young adults based on chest circumference. Among those reporting a chest size under 34 inches multivariate-adjusted relative risks were 1.34 (95% CI: 1.04 to 1.74) for cup size B, and 1.76 (95% CI: 1.04 to 3.01) for cup size C and larger, compared to a cup size smaller than B, and the trend for increasing cup size was statistically significant (P = 0.005). There was no relation with breast size among women reporting an average or larger back circumference (34 inches or larger).

CONCLUSION

Breast size before a pregnancy is a positive predictor of postmenopausal breast cancer, but this association is limited to those who were especially lean as young women.

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.

The association of calcium and vitamin D, and colon and rectal cancer in Wisconsin women

BACKGROUND

Calcium and vitamin D have been hypothesized to reduce colorectal cancer risk. Epidemiological evidence, however, is mixed.

METHODS

To explore those relationships, data were collected as part of a population-based, case-control study of colorectal cancer in Wisconsin women (678 controls, 348 colon and 164 rectal cancer cases). A semi-quantitative food frequency questionnaire was used to ascertain food and dietary supplement intake 2 years prior to interview. Logistic regression models were used to calculate odds ratios (OR).

RESULTS

Higher levels of calcium intake were associated with reduced colon and rectal cancer risk. The following adjusted OR and 95% confidence intervals (CI) were observed, comparing the fifth quintile (based on control intake) with the first: colon cancer: OR = 0.6, 95% CI: 0.4-1.0, P-trend: 0.03; rectal cancer: OR = 0.6, 95% CI: 0.3-1.1, P-trend: 0.07. Similar relationships were observed for vitamin D intake, although OR were closer to the null value and did not always behave in a step-wise fashion (fifth quintile versus the first--colon cancer: OR = 0.7, 95% CI: 0.4-1.1, P-trend: 0.05; rectal cancer: OR = 0.8, 95% CI: 0.5-1.5, P-trend: 0.42).

CONCLUSION

These data support a protective association of calcium on colon and rectal cancer risk.

Menstrual factors in relation to breast cancer risk

We evaluated menstrual factors in relation to breast cancer risk in a large, population-based, case-control study. Case women were ascertained through state-wide registries covering Wisconsin, Western Massachusetts, Maine, and New Hampshire; control women were randomly selected from driver's license and Medicare lists in each state. Information regarding menstrual characteristics was obtained through a telephone interview. The study population comprised 6888 breast cancer cases and 9529 control women. Because exogenous hormones influence menstrual cycle patterns, we repeated our analyses in a subgroup of women who had never used oral contraceptives or hormone replacement therapy. Our results indicate decreased breast cancer risk with menarcheal age of 15 years or more, relative to menarche at age 13; the relation was stronger among premenopausal [odds ratio (OR), 0.72; 95% confidence interval (CI), 0.57-0.91] as opposed to postmenopausal women (OR, 0.90; 95% CI, 0.80-1.03). Risk was slightly reduced among premenopausal women whose menstrual cycles did not become regular until at least 5 years after onset of menses, relative to those whose cycles became regular within 1 year (OR, 0.80; 95% CI, 0.63-1.02). There was no clear relation between breast cancer risk and irregular menstrual cycles, episodes of amenorrhea, or menstrual cycle length. Early menopause, whether natural or surgical, was associated with decreased breast cancer risk; surgical menopause before age 40 conferred the strongest protective effect (OR, 0.57; 95% CI, 0.47-0.71). We found no evidence of increased risk with late natural menopause (OR, 0.92; 95% CI, 0.80-1.06). Results in the subgroup of women who never used exogenous hormones were similar to those for the entire group.

Diabetes, body size, and risk of endometrial cancer

Data from a population-based case-control study of Wisconsin women were used to evaluate the relation of diabetes to the risk of endometrial cancer on the basis of body mass index (BMI). Cases (n=723) were identified from a statewide tumor registry; controls (n=2,291) were selected randomly from population lists. Diabetes status, weight, height, and other factors were ascertained by telephone interview. Subjects were categorized as not overweight (BMI, <29.1), overweight (BMI, 29.1-31.9), or obese (BMI, >31.9) according to the BMI distribution of middle-aged white women in the Second National Health and Nutrition Examination Survey. Joint associations between diabetes status, BMI, and endometrial cancer were evaluated using unconditional logistic regression models that controlled for age, parity, use of hormone replacement therapy, education, and smoking. Compared with persons without diabetes, those with diabetes had an adjusted odds ratio of 1.86 (95% confidence interval (CI) 1.37-2.52) for endometrial cancer. This association was modified by BMI (p interaction=0.04). Compared with nonoverweight nondiabetic subjects, nonoverweight and overweight women who reported diabetes had nonsignificant elevated risks of endometrial cancer (nonoverweight, odds ratio (OR)=1.10, CI 0.66-1.86; overweight, OR=1.58, CI 0.81-3.05). In contrast, elevated risk estimates were observed for obese diabetic women (OR=2.95, CI 1.60-5.46). These data contradict earlier reports and suggest that diabetes confers no additional risk of endometrial cancer in women who are neither overweight nor obese.

Risk of recurrence after ductal carcinoma in situ of the breast

A cohort study was conducted to estimate the risk of breast cancer recurrence among women diagnosed with ductal carcinoma in situ (DCIS) and to identify tumor or patient characteristics that influence that risk. A population-based cancer registry was used to identify a cohort of 709 female residents of western Washington who were diagnosed with DCIS between January 1980 and June 1992 and were treated with breast-conserving surgery. Information about breast cancer recurrences, treatment, and several patient characteristics and exposures was obtained from postal questionnaires. Recurrences were confirmed using information from the cancer registry or hospital pathology reports. Approximately 15% of women experienced a recurrence within the first 5 years after diagnosis [95% confidence interval (CI), 12-18%]; 31% had a recurrence within 10 years (95% CI, 24-38%). There was a suggestion that risk was slightly elevated for women with larger tumors (> or =1.5 cm) and tumors of comedo subtype. Relative risks (RRs) were elevated for women who were premenopausal at diagnosis of DCIS (RR = 2.3; 95% CI, 1.1-5.0). Women in the upper decile of body mass index were at twice the risk of a recurrence as those women in the lower four deciles (RR = 2.3; 95% CI, 1.1-4.8). There was also a suggestion that women who used menopausal hormones for at least 2 years after their diagnosis of DCIS were at increased risk of recurrence compared to nonusers of menopausal hormones (RR = 1.8; 95% CI, 0.7-5.0). Our results suggest that the risk of recurrence may be related to some tumor characteristics as well as the hormonal milieu of the patient at or after her diagnosis of DCIS. However, larger studies are needed to more clearly document predictors of disease recurrence after DCIS.

Usual consumption of plant foods containing phytoestrogens and sex hormone levels in postmenopausal women in Wisconsin

Consumption of phytoestrogens may reduce hormone-dependent cancer risk through alterations in the actions or metabolism of steroid hormones. Studies in humans of phytoestrogen-hormone interactions have been limited and inconsistent. Relations between the consumption of phytoestrogen-containing foods and serum sex hormones and sex hormone-binding globulin were studied in a population-based sample of postmenopausal women who participated in the Nutritional Factors in Eye Disease Study of the Beaver Dam Eye Study. Information on phytoestrogen-containing foods (broccoli, carrots, cauliflower, chili, dark bread, peas, and dried beans) was collected by interviewer-administered food-frequency questionnaires. Estrone, sex hormone-binding globulin, dehydroepiandrosterone sulfate, and total and free testosterone were measured. Analyses included 246 postmenopausal women not taking hormone replacements. Partial correlations between hormones and intake of phytoestrogen-containing foods were computed, with adjustment for age, body mass index, years since menopause, and total energy intake. Number of standard servings per week of whole-grain products from the dark bread group was inversely associated with total testosterone (r = -0.20, p = 0.002). Although not statistically significant, other hormones displayed similar inverse associations with dark bread consistent with a common metabolic pathway. Although the magnitude of association was small, the data are consistent with the possibility that consumption of some phytoestrogen-containing foods may affect levels of testosterone in postmenopausal women.

Exposure to breast milk in infancy and adult breast cancer risk

BACKGROUND

There is considerable interest in the possibility of an infectious etiology for human breast cancer. Although studies have shown that certain strains of mice transmit mammary tumor virus via breast milk, few epidemiologic studies have addressed this topic in humans.

METHODS

We evaluated the relationship between having been breast-fed as an infant and breast cancer risk among 8299 women who participated in a population-based, case-control study of breast cancer in women aged 50 years or more. Case women were identified through cancer registries in three states (Massachusetts, New Hampshire, and Wisconsin); control women were identified through statewide driver's license lists (age <65 years) or Medicare lists (ages 65-79 years). Information on epidemiologic risk factors was obtained through telephone interview. We used multiple logistic regression to assess having been breast-fed and maternal history of breast cancer in relation to breast cancer occurrence both in premenopausal women (205 case women; 220 control women) and in postmenopausal women (3803 case women; 4071 control women).

RESULTS

We found no evidence that having been breast-fed increased breast cancer risk in either premenopausal women (odds ratio [OR] = 0.65; 95% confidence interval [CI] = 0.41-1.04) or postmenopausal women (OR = 0.95; 95% CI = 0.85-1.07). In addition, breast cancer risk was not increased by having been breast-fed by a mother who later developed breast cancer.

CONCLUSION

Our results do not support the hypothesis that a transmissible agent in breast milk increases breast cancer risk. Because premenopausal women were not well represented in our study population, our findings with regard to this group may not be generalizable and should be viewed with caution.

Risk factors for breast cancer in women with a breast cancer family history

Family history (FH) is an important indicator of a woman's future risk of developing breast cancer. Using data collected in a large population-based case-control study (6705 cases and 9341 controls), we examined the associations of breast cancer with known risk factors in women reporting a first-degree FH (mother or sister), with an emphasis on lifestyle determinants that may be altered to reduce risk. First-degree FH was reported by 18.4% (n = 1234) of cases and 11.3% (n = 1058) of controls; the overall relative risk (RR) for breast cancer associated with a positive history was 1.70 [95% confidence interval (CI), 1.55-1.87] and 2.34 (95% CI, 1.80-3.02) for breast cancer at age 45 years or younger. Among women with a FH, statistically significant inverse associations were observed for increasing parity (RR per birth = 0.90; P < 0.0001), intake of carotene-rich foods (RR for >2000 IU/day = 0.73; P = 0.02), and strenuous activity as a young adult (RR per episode/week = 0.93; P = 0.02). Recent alcohol consumption increased risk (RR per 13 g/week = 1.21; P = 0.02), as did weight gain during adult life in postmenopausal women (RR per 5 kg = 1.08; P = 0.001). Breast-feeding for any duration was associated with a lower RR in parous, premenopausal women (RR = 0.59; P = 0.04). Associations for most risk factors with breast cancer were similar among women with and without a FH of breast cancer; however, a stronger inverse association was observed for parity in women with a positive history (P for interaction = 0.04). Based on these data, women with a FH may reduce their excess risk of breast cancer through adjustments in lifestyle and reproductive choices. The risk associated with FH of breast cancer seems to be largely independent of other known risk factors.

Intake of carrots, spinach, and supplements containing vitamin A in relation to risk of breast cancer

Intake of fruits, vegetables, vitamin A, and related compounds are associated with a decreased risk of breast cancer in some studies, but additional data are needed. To estimate intake of beta-carotene and vitamin A, the authors included nine questions on food and supplement use in a population-based case-control study of breast cancer risk conducted in Maine, Massachusetts, New Hampshire, and Wisconsin in 1988-1991. Multivariate-adjusted models were fit to data for 3543 cases and 9406 controls. Eating carrots or spinach more than twice weekly, compared with no intake, was associated with an odds ratio of 0.56 (95% confidence interval 0.34-0.91). Estimated intake of preformed vitamin A from all evaluated foods and supplements showed no trend or monotonic decrease in risk across categories of intake. These data do not allow us to distinguish among several potential explanations for the protective association observed between intake of carrots and spinach and risk of breast cancer. The findings are, however, consistent with a diet rich in these foods having a modest protective effect.

Alcohol consumption in relation to endometrial cancer risk

We analyzed data from a population-based case-control study of Wisconsin women to evaluate the relationship of alcohol consumption to endometrial cancer risk. Cases (n = 739) were identified from a statewide tumor registry; controls (n = 2313) were selected randomly from driver's license lists and Medicare beneficiary files. Alcohol consumption and other factors were ascertained by telephone interview. Compared with abstainers, the multivariable relative risk for recent consumption of two or more drinks per day was 1.27 [95% confidence interval (CI) 0.78-2.07]; increasing consumption was not associated with risk of disease (P for trend, 0.82). The relative risk for early adulthood consumption of two or more drinks per day was 1.00 (95% CI, 0.58-1.73), with no suggestion of a trend (P = 0.26). Although the sample size was limited, a significant inverse association was suggested in premenopausal women consuming one drink per day or more (0.20, 95% CI 0.06-0.71). Beverage-specific consumption was not associated with risk. This study suggests that, unlike breast cancer, endometrial cancer is not positively associated with alcohol intake.

Physical activity in usual occupation and risk of breast cancer (United States)

We have used data from a large population-based case-control study in the United States to evaluate the effect of occupational physical activity on breast cancer risk. Women diagnosed with breast cancer identified from four state cancer registries, and controls randomly selected from lists of licensed drivers or Medicare beneficiaries, were interviewed by telephone for information on usual occupation and other factors. We classified usual occupation into one of four categories of physical activity. After excluding subjects for whom a strength rating could not be assigned, we had a final sample size of 4,863 cases and 6,783 controls. Using conditional logistic regression models, we calculated adjusted odds ratios (OR) and 95 percent confidence intervals (CI) for occupations having light, medium, and heavy activity compared with sedentary ones. Women with heavy-activity occupations had a lower risk of breast cancer than women with sedentary jobs (OR = 0.82, CI = 0.63-1.08), as did women with jobs with medium activity (OR = 0.86, CI = 0.77-0.97) or light activity (OR = 0.92, CI = 0.84-1.01). There was a significant decreasing trend in the ORs from sedentary to heavy work (P = 0.007). Although limited by exposure misclassification, these data are consistent with the hypothesis that physical activity reduces the risk of breast cancer.

Lactation and breast cancer risk

Breast cancer is a common disease with few practical preventive measures. The recent evidence that lactation, like other reproductive experiences, is associated with a modest reduction in breast cancer risk is therefore of great interest. Overall, the reduction in risk appears to be about 20% for ever breast feeding and is even greater for women with histories of prolonged lactation, or who initiate breast feeding at young ages. In many studies this risk reduction seems to be limited to premenopausal women. It appears unlikely that this inverse association is attributable either to higher risk among women who use lactation suppressants or who have difficulty either starting or continuing breast feeding. While a strong or consistent protective effect of lactation on breast cancer risk has not been observed in some large and well conducted studies, this likely reflects the limited breast feeding practices among modern women. If early, exclusive and extended breast feeding is necessary to achieve a breast cancer risk reduction, future studies among U.S. women may be unable to clarify this association.

Body size and risk of breast cancer

The relation between body size and breast cancer remains uncertain, particularly with regard to differences between pre- and postmenopausal women. The authors examined whether height, weight, body mass index, and weight change were associated with breast cancer risk among pre- and postmenopausal women. This population-based case-control study included women aged 20-74 years (n = 6,548) who were diagnosed with invasive breast cancer during 1988-1991 in Maine, Massachusetts, New Hampshire, and Wisconsin. Similarly aged control women (n = 9,057) were selected at random from driver's license files and Health Care Financing Administration files. Height, weight, and information on other breast cancer risk factors were ascertained by telephone interview, and logistic regression was used to estimate multivariate-adjusted odds ratios and 95% confidence intervals. Among premenopausal women, the adjusted odds ratio for the upper quintile group of height relative to the lowest was 1.36 (95% confidence interval (CI) 1.05-1.76). The heaviest premenopausal women had a lower risk (odds ratio (OR) = 0.87, 95% CI 0.70-1.10). Among postmenopausal women, the adjusted odds ratios were higher for the upper quintile categories of both height (OR = 1.27, 95% CI 1.11-1.45) and weight (OR = 1.57, 95% CI 1.37-1.79). Weight gain since ages 18 and 35 years was associated with increased postmenopausal breast cancer risk, and risk was lower in women who had lost weight. These findings suggest that programs to avoid weight gain merit study as a means to reduce risk of postmenopausal breast cancer.

Parental age in relation to risk of breast cancer

Data from a population-based case-control study were analyzed to evaluate risk of breast cancer among women according to parental age at the time of subject birth. Between 1988-91, breast cancer cases (n = 1,253) were obtained from the statewide tumor registry in Wisconsin. Concurrently, population controls (n = 1,121) were randomly selected from driver's license lists (if under age 65) and Medicare beneficiary files (if 65-74 years). Information regarding parents' ages and breast cancer risk factors was obtained by telephone interview. Relative risk estimates were very slightly elevated with increasing maternal age, although no consistent trend of increasing risk was observed (P for trend = 0.38). No association between paternal age and breast cancer risk was observed (P for trend = 0.98). Older maternal or paternal age was not associated with risk among any of the subgroups examined, except for daughters who had late age at first birth. These findings are consistent with the majority of studies that have found little or no association between parental age and breast cancer risk.

Frequency of eating and risk of colorectal cancer in women

Numerous dietary constituents have been extensively studied with regard to colorectal cancer risk, but food intake patterns have been studied less frequently. The purpose of these analyses was to describe associations between frequency of eating and colorectal cancer risk in women. Female Wisconsin residents aged 30-74 years with a diagnosis of colorectal cancer within two years were identified through the statewide tumor registry. Control subjects were randomly selected from lists of licensed drivers (< 65 yrs old) and Medicare beneficiaries (65-74 yrs old). Meal and snack frequency was obtained on a subset of case (n = 189) and control (n = 322) subjects. Odds ratios and 95% confidence intervals (CIs) obtained from conditional logistic regression models were used to estimate multivariate-adjusted relative risks. Compared with women consuming three or four meals daily, women consuming one to two meals daily had an adjusted relative risk of 0.57 (95% CI = 0.34-0.94). Snacking frequency and frequency of meals + snacks were not associated with cancer risk. These results are consistent with other reports and suggest that meal frequency is associated with colorectal cancer risk.

Nonsteroidal anti-inflammatory drug use and protection against colorectal cancer in women

Several epidemiological studies have identified an association between nonsteroidal anti-inflammatory drug (NSAID) use and colorectal cancer risk in women. We examined this association in a population-based case-control study in Wisconsin women. Between 1991 and 1992, 184 women ages 40-74 years with colorectal cancer were identified through the statewide cancer registry and 293 population-based control women were randomly selected via telephone. Regular NSAID use was defined as at least twice weekly for 12 months or longer. After adjusting the data for age, controls were more likely than cases to report regular NSAID use (38 versus 27%). Following adjustment for age, prior sigmoidoscopy use, family history of large bowel cancer, and body mass index, women who regularly used NSAIDs were approximately one-third less likely to be diagnosed with colorectal cancer compared to women who did not use NSAIDs [odds ratio (OR), 0.65; 95% confidence interval (CI), 0.40-1.03]. A statistically significant effect of duration of use was identified, although the ORs did not show a consistent trend. No significant effect of frequency of NSAID use was observed. When the type of NSAID used was examined (aspirin or nonaspirin), subjects who used nonaspirin compounds had a statistically significantly lower risk of colorectal cancer (OR, 0.43; 95% CI, 0.20-0.89), compared to nonusers, whereas aspirin users had only a small, nonsignificant reduction in cancer risk (OR, 0.79; 95% CI, 0.46-1.36). These data add support to the hypothesis that regular NSAID use is associated with lower colorectal cancer risk in women and suggest that the type of NSAID used may be important.

Variation in female breast cancer risk by occupation

Data from a population-based case control study were used to estimate occupation-specific relative risks for female breast cancer, adjusted for established breast cancer risk factors. Breast cancer cases under age 75 were identified from tumor registries in four states. Controls were randomly selected from driver's license and Medicare beneficiary lists. Information on usual occupation and risk factors was obtained by telephone interview. Odds ratios from logistic regression adjusted for age, state, body mass index, benign breast disease, family history of breast cancer, menopausal status, age at menarche, parity, age of first birth, lactation history, education, and alcohol consumption were calculated for each of 26 occupational groups. Complete occupational information was obtained for 6,835 cases and 9,453 controls. Of 26 occupational groups, only "administrative support occupations" had a statistically significantly increased risk of breast cancer (OR = 1.15, 95% CI 1.06-1.24). In these data, no specific occupational group had an unusual risk of breast cancer. Increased risks reported elsewhere for nurses and teachers were not corroborated.

Recent oral contraceptive use and risk of breast cancer (United States)

We examined the association between recent oral contraceptive (OC) use and the risk of breast cancer in data from a large population-based case-control study in the United States. Cases (n = 6,751) were women less than 75 years old who had breast cancer identified from statewide tumor registries in Wisconsin, Massachusetts, Maine, and New Hampshire. Controls (n = 9,311) were selected randomly from lists of licensed drivers (if aged under 65 years) and from lists of Medicare beneficiaries (if aged 65 through 74 years). Information on OC use, reproductive experiences, and family and medical history was obtained by telephone interview. After adjustment for parity, age at first delivery, and other risk factors, women who had ever used OCs were at similar risk of breast cancer as never-users (relative risk [RR] = 1.1, 95 percent confidence interval [CI] = 1.0-1.2). Total duration of use also was not related to risk. There was a suggestion that more recent use was associated with an increased risk of breast cancer; use less than two years ago was associated with an RR of 1.3 (CI = 0.9-1.9). However, only among women aged 35 to 45 years at diagnosis was the increase in risk among recent users statistically significantly elevated (RR = 2.0, CI = 1.1-3.9). Use prior to the first pregnancy or among nulliparous women was not associated with increased risk. Among recent users of OCs, the risk associated with use was greatest among non-obese women, e.g., among women with body mass index (kg/m2) less than 20.4, RR = 1.7, CI = 1.1-2.8. While these results suggest that, in general, breast cancer risk is not increased substantially among women who have used OCs, they also are consistent with a slight increased risk among subgroups of recent users.

Occupational exposure to 60-hertz magnetic fields and risk of breast cancer in women

We used data from a large population-based case-control study to test the hypothesis that women whose "usual occupation" entailed exposure to higher than background 60-Hz magnetic fields had a higher risk of breast cancer than women without such exposure. Breast cancer cases were identified from four statewide tumor registries, and controls were randomly selected from lists of licensed drivers and Medicare beneficiaries. Information on usual occupation and breast cancer risk factors was obtained by telephone interview. We calculated adjusted odds ratios from logistic regression models for women holding occupations with potential for low, medium, or high magnetic field exposure, compared with background exposure. There was a modest increase in risk for women with potential for high exposure [odds ratio (OR) = 1.43; 95% confidence interval (CI) = 0.99-2.09], and no increase for women with potential for medium (OR = 1.09; 95% CI = 0.83-1.42) or low (OR = 1.02; 95% CI = 0.91-1.15) exposure The risk among premenopausal women in the highest-exposure category was higher (OR = 1.98; 95% CI = 1.04-3.78) than for postmenopausal women (OR = 1.33; 95% CI = 0.82-2.17).

Jewish religion and risk of breast cancer

BACKGROUND

The excess risk of breast cancer among Jewish women has been attributed to the effects of difference in lifestyle and reproductive patterns, but there is now evidence that Jewish women may be more likely than other women to inherit mutations in breast-cancer genes. We investigated whether any excessive risk among Jewish women is confined to those with a family history of breast cancer.

METHODS

We assessed the effect of Jewish religion on breast cancer in a large population-based case-control study (6611 women with breast cancer and 9026 controls) in USA. Participants were given telephone interviews and asked about known and suspected risk factors for breast cancer.

FINDINGS

Overall, Jewish women had only a slightly raised relative risk of breast cancer (1.10 [95% CI 0.84-1.44]; p=0.49). However, the relative risk was much higher for Jewish women with a first-degree relative who had breast cancer (3.78 [1.74-8.16]; p<0.001). The effect of family history was greater in Jewish women than in women of other religions (p interaction = 0.05).

INTERPRETATION

These results are consistent with data suggesting that certain groups of Jewish women have a higher than expected rate of mutation in the breast-cancer gene BRCA1.

Cigarette smoking and breast cancer

A priori hypotheses suggest that cigarette smoking could either increase or decrease breast cancer incidence. To clarify these competing hypotheses, we used data from a very large population-based breast cancer case-control study to investigate the impact of smoking on breast cancer risk. Breast cancer patients less than 75 years old were identified from statewide tumor registries in Wisconsin, Massachusetts, Maine, and New Hampshire; controls were randomly selected from driver's license lists (age less than 65) or lists of Medicare beneficiaries (age 65-74). Information on reproductive history, medical history, and personal habits including cigarette smoking was obtained by telephone interview. A total of 6,888 cases and 9,529 controls were interviewed. There was virtually no relationship between current smoking and breast cancer risk (multivariate odds ratio, 1.00; 95% confidence interval, 0.92-1.09), and former smokers had a barely increased risk (odds ratio, 1.10; 95% confidence interval, 1.01-1.19). Similar results were observed among both premenopausal and postmenopausal women. There was no suggestion that heavy or long-term smoking increased or decreased risk, nor were there indications that women who began smoking at an early age were at increased risk, as has been hypothesized. The results of this large population-based study indicate that smoking does not influence the risk of breast cancer, even among heavy smokers who began smoking at an early age.

Self-reported stress and risk of breast cancer

BACKGROUND

Many women attribute the development of their breast cancer to psychosocial factors such as stress and depression. Yet investigations of the relationship between breast cancer and stressful life events have had inconsistent outcomes, due in part to studies with small sample sizes and reliance on hospital-based populations.

METHODS

As part of a population-based, case-control study of breast cancer etiology, we evaluated the association between stressful life events and the risk of breast cancer among 258 breast cancer patients and 614 randomly selected population-based controls. Information on 11 stressful life events was collected in telephone interviews with women aged 50-79 who were participating in the ongoing study.

RESULTS

Breast cancer patients and controls experienced the same number of stressful life events in the five years prior to diagnosis or an equivalent reference date (controls), averaging 2.4 and 2.6 events, respectively. After adjustment for known breast cancer risk factors, there was no association between weighted stressful life event scores and the risk of breast cancer (odds ratio [OR] = 0.90 per unit increase; 95% confidence interval [CI], 0.78-1.05). Only one life event, death of a close friend, was significantly more often reported by controls (OR = 0.72; 95% CI, 0.52-1.00). Other life events were inconsistently and nonsignificantly associated with breast cancer risk. CONCLUSIONS. The results of this retrospective study do not suggest any important associations between stressful life events and breast cancer risk.

Exogenous sex hormone use, correlates of endogenous hormone levels, and the incidence of histologic types of sarcoma of the uterus

BACKGROUND

We analyzed data from a population-based, multi-center, case-control study to determine whether the occurrence of histologic types of uterine sarcoma is related to exogenous hormone use and/or to two correlates of endogenous estrogens: excess weight and cigarette smoking.

METHODS

One hundred sixty-seven women with newly-diagnosed uterine sarcoma (56 leiomyosarcoma, 85 mixed mullerian tumors, and 26 endometrial stromal sarcomas) were interviewed by telephone regarding possible risk factors for these neoplasms, For comparison, 208 women identified at random from the general population of the study areas were interviewed as controls.

RESULTS

Use of oral contraceptives was positively associated with the risk of leiomyosarcoma (odds ratios [OR] = 1.7, 95% confidence interval [CI] = 0.7, 4.1), primarily among women who last used these medications 15 or more years prior to diagnosis. Use of noncontraceptive estrogens was directly associated with the risk of mixed mullerian tumors, but only among recent and long-term users of these medications. Women in the highest quantile of body mass index (> or = 27.5 kg/m2) one year prior to diagnosis were at increased risk of each type of uterine sarcoma (leiomyosarcoma, OR = 2.5, 95% CI = 1.1, 5.7; mixed mullerian tumors, OR = 2.9, 95% CI = 1.3, 6.7; stromal sarcoma, OR = 3.5, 95% CI = 1.1, 10.9). Women who had ever smoked cigarettes were at reduced risk of leiomyosarcoma (OR = 0.6, 95% CI = 0.3, 1.1) and stromal sarcoma (OR = 0.5, 95% CI = 0.2, 1.2), but the relationship was not more pronounced among heavy smokers; no association with smoking was observed with mixed mullerian tumors.

CONCLUSIONS

Several of these findings parallel those from studies of endometrial carcinoma and may indicate a role for unopposed estrogen in the etiology of histologic types of uterine sarcoma.

Pregnancy termination in relation to risk of breast cancer

OBJECTIVE

To evaluate the association between pregnancy terminations and risk of breast cancer.

DESIGN AND SETTING

Population-based case-control study in Wisconsin, Massachusetts, Maine, and New Hampshire.

STUDY PARTICIPANTS

Cases were women younger than 75 years with a new diagnosis of breast cancer (n = 6888), identified from statewide tumor registries. Controls younger than 65 years (n = 9529) were randomly selected from lists of licensed drivers, or for older subjects, from lists of Medicare beneficiaries. EXPOSURES AND OUTCOMES: Breast cancer risk in relation to spontaneous or induced abortions.

RESULTS

After adjustment for parity, age at first birth, and other risk factors, pregnancy termination (induced or spontaneous) was associated with a relative risk (RR) of breast cancer of 1.12 (95% confidence interval [CI], 1.04 to 1.21), compared with the risk among women who had never had a termination. Induced terminations were associated with a RR of 1.23 (95% CI, 1.00 to 1.51), which was somewhat greater than the risk associated with spontaneous terminations (RR, 1.11; 95% CI, 1.02 to 1.20). The association with induced abortions was stronger for those performed before legalization of abortion in 1973 (RR, 1.35; 95% CI, 1.01 to 1.80) than after this time (RR, 1.12; 95% CI, 0.84 to 1.49), suggesting a bias in reporting this sensitive procedure.

CONCLUSIONS

A weak positive association was observed between abortion--whether induced or spontaneous--and risk of breast cancer. The increase in risk of breast cancer was somewhat greater among women with a history of induced terminations. However, this association may be due to reporting bias and was not significantly different than the slight risk for spontaneous terminations.

Body mass and breast cancer. Relationship between method of detection and stage of disease

BACKGROUND

Obesity is associated with advanced stage breast cancer at diagnosis and a poorer prognosis. Stage of breast cancer at diagnosis is also strongly influenced by the method of cancer detection. The objective of this study was to determine the relationship between body mass index (BMI) and breast cancer disease stage, taking into account the method of cancer detection (i.e., self-detection, screening mammography, and clinical breast examination [CBE]).

METHODS

From 1988 to 1990, 2863 patients with invasive breast cancer were identified through a statewide, population-based, cancer reporting system and were interviewed as part of a larger study of breast cancer etiology. Stage of disease was classified as either localized or nonlocalized (regional and distant disease combined). The relation between BMI and disease stage was examined by using multiple logistic regression adjusting for age, education, race, year of diagnosis, and prior mammography use.

RESULTS

Thirty-eight percent (1092 of 2863) of the women had nonlocalized breast cancer. A strong dose-response relationship was observed between increased BMI and the likelihood of nonlocalized disease (P < 0.001). However, this association was present only among the 55% of women (1585 of 2863) who self-detected their tumors. The odds ratios for nonlocalized cancer increased from 1.0 for the lowest quintile of BMI to 1.3, 1.6, 1.7, and 1.8 for the second through fifth quintiles, respectively, for this group.

CONCLUSIONS

Greater body mass was associated with nonlocalized breast cancer; however, this association was restricted to women who detected their own cancer. No association was found between BMI and stage of disease among cases detected by either mammography or CBE.

Relation of sex hormones and dehydroepiandrosterone sulfate (DHEA-SO4) to cardiovascular risk factors in postmenopausal women

Sex hormones play a major role in determining the risk of cardiovascular disease. While several studies have shown that reduced sex hormone-binding globulin is associated with an atherogenic pattern of lipoproteins and increased glucose concentrations in premenopausal women, little data are available examining the association of sex hormone-binding globulin and sex hormones with cardiovascular risk factors in postmenopausal women, a group with high rates of cardiovascular disease. The investigators hypothesized that in postmenopausal women decreased sex hormone-binding globulin and increased testosterone would be associated with an atherogenic pattern of cardiovascular risk factors. The sex hormone-binding globulin, total and free testosterone, estrone, and dehydroepiandrosterone sulfate (DHEA-SO4) in 253 postmenopausal women who were not taking hormones were measured in a population-based study, the Beaver Dam Eye Study (Beaver Dam, Wisconsin, 1988-1990). Sex hormone-binding globulin was significantly inversely correlated with body mass index (r = -0.53, p 0.001), glycosylated hemoglobin (r = -0.34, p < 0.001), and diastolic blood pressure (r = -0.25, p < 0.001), and positively correlated with high density lipoprotein cholesterol (HDL cholesterol) (r = 0.31, p < 0.001), and HDL cholesterol/total cholesterol (r = 0.31, p < 0.001). Total (r = -0.20, p < 0.01) and free (r = -0.14, p < 0.05) testosterone were significantly inversely correlated with HDL cholesterol/total cholesterol ratio. Total testosterone concentrations were also significantly positively correlated with total cholesterol (r = 0.15), body mass index (r = 0.16), and systolic (r = 0.17) and diastolic (r = 0.18) blood pressures (all p < 0.01). DHEA-SO4 was not associated with any of the metabolic variables, while estrone was inversely associated only with the HDL cholesterol/total cholesterol ratio (r = 0.13, p < 0.05). The authors conclude that increased androgenization in postmenopausal women is associated with atherogenic changes in cardiovascular risk factors.

Cigarette smoking in relation to risk of large bowel cancer in women

Smoking habits were ascertained by interview from Wisconsin women aged 30-74 years with newly reported diagnoses of colon (n = 536) and rectal (n = 243) cancer and 2315 randomly selected population controls. After controlling for age, body mass index, alcohol consumption, family history of large bowel cancer, and history of screening sigmoidoscopy, significantly elevated risks were observed for women who had ever smoked, in both the colon (odds ratio, 1.28; 95% confidence interval, 1.03-1.58) and rectum (odds ratio, 1.44; 95% confidence interval, 1.08-1.92). Risk significantly increased with greater number of cigarettes smoked per day, longer duration of smoking, and earlier age at initiation for both the colon and the rectum; however, only duration of smoking was not independently associated with risk. Among former smokers, risk for both colon and rectal cancer remained elevated. These data suggest that women who smoke are at elevated risk of both colon and rectal cancer and that increased risk persists even among former smokers.

Long-term hormone replacement therapy and risk of breast cancer in postmenopausal women

Despite extensive study, concerns remain about a possible association between long-term postmenopausal hormone treatment--particularly use of combination preparations--and risk of breast cancer. The authors evaluated the use of postmenopausal hormone replacement therapy in relation to breast cancer risk in a large multicenter, population-based case-control study. Women with a new diagnosis of breast cancer were identified through statewide tumor registries in Wisconsin, Massachusetts, Maine, and New Hampshire. Controls were randomly selected from population lists in each state. For this analysis of postmenopausal women, data were available from 3,130 breast cancer cases and 3,698 controls interviewed between 1989 and 1991. Replacement hormone use was not associated with breast cancer risk in women who had ever undergone this treatment (relative risk (RR) = 1.05, 95% confidence interval (CI) 0.93-1.18). Among women who had used replacement hormones for 15 years or more, there was no clear increase in risk, although the small sample size did not preclude the possibility of a modest association (RR = 1.11, 95% CI 0.87-1.43). Risk among women using progestins in combination with estrogens was similar to that in women using estrogens alone. Risk did not vary according to type of menopause, family history of breast cancer, history of benign breast disease, or alcohol intake. These results are consistent with the majority of reports which find no overall increased risk associated with the use of replacement hormones. However, in contrast to several other studies, this study did not find long-term use to be associated with increased risk. These results also do not support a hypothesized effect of combined progestin and estrogen use on the risk of breast cancer.

Postmenopausal hormone use and risk of large-bowel cancer

BACKGROUND

The epidemiology of large-bowel cancer suggests a role for endocrine factors in its development. Although analytic studies have not consistently provided evidence for an association between reproductive history and large-bowel cancer, some relatively small studies have observed a reduced risk among women using postmenopausal hormone replacement therapy (HRT).

PURPOSE

This study was planned to evaluate more precisely the relationship between HRT and the risk of colon and rectal cancers.

METHODS

Female residents of Wisconsin aged 30-74 years with a diagnosis of colon or rectal cancer within 2 years were identified through a statewide tumor registry. Control subjects were randomly selected from lists of licensed drivers if the case subjects were less than 65 years old and from lists of Medicare beneficiaries if they were 65-74 years old. Information on post-menopausal hormone replacement use, medical history, and family history was obtained in telephone interviews. After premenopausal women were excluded, 694 case subjects and 1622 control subjects remained for analysis. The odds ratios and 95% confidence intervals (CIs) obtained from conditional logistic regression models were used to estimate relative risks (RRs). All RRs were adjusted for age, family history of large-bowel cancer, use of screening sigmoidoscopy, and recent alcohol consumption.

RESULTS

Compared with postmenopausal women who never used HRT, recent users had an RR of 0.54 (95% CI = 0.36-0.81) for colon cancer and an RR of 0.91 (95% CI = 0.54-1.55) for rectal cancer. This inverse association was observed among users of both estrogen only and combined estrogen and progestin preparations. Decreasing time since last use was inversely associated with colon cancer risk (P for trend < .001). The effect of HRT appeared to be stronger among women at lower absolute risk of colon cancer, particularly among women with lean body mass.

CONCLUSIONS

Use of HRT was associated with a statistically significant reduced risk of colon cancer. In contrast, no statistically significant relationship was observed for rectal cancer. Given the widespread use of postmenopausal hormones and the morbidity and mortality from adenocarcinoma of the bowel in women, these findings may have potentially important public health implications.

Multiple births and risk of breast cancer

Data from a large, multicenter, population-based case-control study were analyzed to investigate the relation between multiple birth pregnancies and subsequent breast-cancer risk in the gravidas. Women less than 75 years old who had breast cancer were identified from statewide tumor registries in Wisconsin, western Massachusetts, Maine and New Hampshire. Controls aged less than 65 years were selected randomly from lists of licensed drivers, and controls aged between 65 and 74 were selected randomly from lists of Medicare beneficiaries. Information on reproductive history and other factors was obtained by means of telephone interviews. After excluding nulliparous women, 5,880 case subjects and 8,217 controls remained for analysis. Multiple birth pregnancies occurred in 146 cases and 218 controls. Adjusted for the number of full-term pregnancies and other confounders, the odds ratio (OR) for any multiple birth pregnancy was 0.94 (95% confidence interval, 0.75 to 1.17). The null association between multiple birth pregnancies and breast cancer remained if the mother's first pregnancy or last pregnancy resulted in a multiple birth. In addition, no trend in risk emerged for age at first multiple birth or time since last multiple birth. While other investigators have suggested biological mechanisms to explain both protective and detrimental effects of multiple births and subsequent development of breast cancer, this study does not support either assertion.

Strenuous physical activity in young adulthood and risk of breast cancer (United States)

The epidemiologic data on the relation between strenuous physical activity and breast cancer are limited and inconsistent. Because risk of breast cancer may be influenced by ovarian function which, in turn is modulated by physical activity, the hypothesis that exercise may be associated with a reduced risk of breast cancer merits further investigation. We, therefore, conducted a large case-control study in 1988-1991, and interviewed 6,888 women (17 to 74 years of age) with breast cancer in Maine, Massachusetts, New Hampshire, and Wisconsin (United States). Interviewed controls (9,539 women, 18 to 74 years of age) were selected randomly from lists of licensed drivers (for younger women) or from a roster of Medicare enrollees (for older women). We used multivariate adjusted odds ratios (OR) and 95 percent confidence intervals (CI) from logistic regression models to estimate relative risks between self-reported physical activity when 14 to 22 years of age and breast cancer. When compared with sedentary controls, women who reported any strenuous physical during ages 14 to 22 years had a modest reduction in the risk of breast cancer (OR = 0.95, CI = 0.93-0.97). However, those who exercised vigorously at least once a day had a 50 percent reduction in risk of breast cancer (OR = 0.5, CI = 0.4-0.7). These data support the hypothesis that women who are physically active have a reduced risk of breast cancer.

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

Reproductive and menstrual characteristics were ascertained by telephone interview from Wisconsin women with newly reported diagnoses of carcinoma of the colon (n = 536) and rectum (n = 243) and 2315 population control subjects. The relationships of parity, age at first full-term pregnancy, age at menarche, regularity and length of menstrual cycles, age at menopause, and type of menopause to colon and rectal cancer were examined. In our study population, no reproductive or menstrual characteristics were significantly associated with colon cancer, although subsite analyses suggested an increased risk for transverse colon cancer in women reporting irregular menstrual cycles. Only parity was associated with rectal cancer; women who had given birth five or more times were at significantly lower risk compared to those who were nulliparous (odds ratio: 0.60; confidence interval: 0.36, 0.99). The odds ratio per birth also suggested an inverse association. These data give little support to the hypothesis that female reproductive events modify colon and rectal cancer risk.

Risk of breast cancer in relation to lifetime alcohol consumption

BACKGROUND

Although an association between alcohol consumption and risk of breast cancer has been observed in many studies, questions of major importance remain, including the nature of the dose-response relationship and the effects of drinking at various periods in life.

PURPOSE

Our goal was to address the issues listed above with a large case-control study.

METHODS

We conducted a population-based case-control study in Maine, Massachusetts (excluding the four counties that include metropolitan Boston), New Hampshire, and Wisconsin. Case patients were eligible if their diagnosis of invasive breast cancer was first reported to one of the four statewide cancer registries during the period of 1988 through 1991. During the accrual period, 11,879 potentially eligible case patients and 16,217 control subjects were identified. After excluding ineligible women from the study, telephone interviews were obtained from 6888 case patients and 9424 control subjects. Complete data for recent alcohol consumption, and thus final eligibility for study participation, were determined for 6662 case patients and 9163 control subjects. The average age at time of interview was 58.7 years. The questions on alcohol use addressed average consumption during five periods of the subjects' lives: ages 16-19, 20-29, 30-39, 40-59, and 60-74 years. Similar responses from 211 control subjects upon reinterview 6-12 months later were taken to be indicative of the reliability of the questionnaire used in this study.

RESULTS

Lifetime average alcohol consumption (measured as the average grams per day consumed from age 16 to the recent past) and recent alcohol consumption (average grams per day consumed in the previous age interval) were associated with risk of developing breast cancer. The multivariate relative risk of breast cancer, in those who drink compared with abstainers, associated with average lifetime consumption of 12-18 g/day of alcohol (about one drink) was 1.39 (95% confidence interval [CI] = 1.16-1.67), of 19-32 g/day (about two drinks) was 1.69 (95% CI = 1.36-2.10), of 33-45 g/day (about three drinks) was 2.30 (95% CI = 1.51-3.51), and of greater than or equal to 46 g/day (four or more drinks) was 1.75 (95% CI = 1.16-2.64) (P for trend < .0001). The multivariate relative risk per 13 g/day (about one drink) of alcohol consumed before 30 years of age was 1.09 (95% CI = 0.95-1.24), whereas the relative risk associated with recent consumption of 13 g/day was 1.21 (95% CI = 1.09-1.34).

CONCLUSIONS

In these data, alcohol consumption was clearly related to breast cancer risk. Risk appeared to increase even at moderate levels of consumption. For women of all ages combined, consumption before 30 years of age was not an important determinant of risk.

Association of dietary and life-style factors with sex hormones in postmenopausal women

We examined the relations between endogenous sex hormones and alcohol intake, dietary constituents, and life-style factors in a population-based sample of 253 postmenopausal women not using replacement hormones. Estrone, dihydroepiandrosterone sulfate (DHEA-S), sex hormone-binding globulin (SHBG), and free and total testosterone were measured in serum. Age and years since menopause were negatively associated with dihydroepiandrosterone sulfate and positively associated with sex hormone-binding globulin levels. Higher relative weight was strongly and negatively associated with sex hormone-binding globulin. Other factors were only very weakly associated with sex hormones. Since, except for weight, few potentially modifiable factors appear to influence these hormone profiles, it may be that behaviors earlier in life mediate hormone levels and subsequent disease risk.

Assessing breast self-examination

BACKGROUND

Women practice breast self-examination (BSE) according to their own schedule and skill. This variation in how BSE is performed has complicated the interpretation of studies of BSE efficacy and utilization.

METHODS

We compared two methods commonly used to assess BSE competency, self-report of practice and ability to detect lumps in a model, among 81 women participating in a controlled toxicity trial of tamoxifen. Subjects were postmenopausal, were under 65 years of age, and had a history of breast cancer within the past 10 years but were currently free of disease. Women were asked to describe their usual BSE practice and were assigned a score (0-10) based on the number of recommended techniques and positions mentioned. Subjects were then instructed to examine a silicone breast model embedded with lumps (HealthEdCo) and to report any abnormalities.

RESULTS

Overall proficiency was low by both measures. No significant correlation (r = 0.16, P = 0.15) was found between the two measures of proficiency. Higher correlations were observed among older women and among those practicing BSE monthly.

CONCLUSIONS

This study suggests that the two techniques are not comparably evaluating BSE proficiency. Further, both of these methods are likely to be poor measures of true BSE practice.

Determinants of breast cancer detection among Wisconsin (United States) women, 1988-90

Early detection is advocated widely as the best method to reduce the high rate of breast cancer mortality in women. The purpose of this study was to describe the detection histories of women with breast cancer and to identify factors related to the method of detection. During the period 1988-90, 3,197 women with invasive breast cancer, identified through the Wisconsin (United States) tumor registry, were interviewed. The method of cancer detection (classified as self, screening mammography, or clinical breast examination [CBE]) was analyzed using polychotomous logistic regression. Fifty-five percent (1,754/3,197) of the women found their own cancers, while 35 percent (1,122/3,197) were detected by screening mammography. Compared with self-detection, the likelihood of non-localized disease was significantly lower for tumors detected by mammography (odds ratio [OR] = 0.3, 95 percent confidence interval [CI] = 0.2-0.4) and CBE (OR = 0.6, CI = 0.4-0.7). The likelihood of cancer being detected by screening mammography increased with increasing age, education, number of prior mammograms, family history, and body mass index (weight/height2) (BMI). Women in the highest BMI quintile were 2.3 times (CI = 1.7-3.0) more likely than women in the lowest BMI quintile to have their cancers diagnosed by mammography. This association most likely results from breast tumors being more difficult to palpate in heavier women.

The association of body size and large bowel cancer risk in Wisconsin (United States) women

Body size is associated with the risk of many diseases, including diabetes, heart disease, and some cancers. To evaluate the association of body size with large bowel cancer, height and weight measurements were ascertained by telephone interview from 779 Wisconsin (United States) women with newly reported diagnoses of carcinoma of the colon and rectum. Controls (n = 2,315) interviewed for this case-control study were selected randomly from Wisconsin driver's license files and Health Care Financing Administration files. The effects of weight and height were examined using multiple logistic regression to control for potential confounding variables. In this study, weight adjusted for height increased the risk of colon cancer (odds ratio [OR] for 72.57-148.33 kg cf 36.29-58.05 kg = 1.4, 95 percent confidence interval [CI] = 1.0-1.9) but did not increase the risk of rectal cancer. Height did not influence risk for cancer of either the colon or the rectum. Left-colon subsite analysis showed especially strong associations with current weight and with percent change in weight since age 18. These data suggest that a dose-response relationship exists between body size and risk of colon cancer in women; body size did not appear to influence risk of rectal cancer.

Early adulthood physical activity and colon cancer risk among Wisconsin women

Frequency of strenuous activity during ages 14-22 was ascertained retrospectively from 536 Wisconsin women with newly reported diagnoses of colon cancer and 2315 controls randomly selected from Wisconsin driver's license and Medicare beneficiary lists. Thirty-five % of cases and 34% of controls reported strenuous activity during this period of early adulthood. After adjusting for age, family history of large bowel cancer, history of screening sigmoidoscopy, and body mass index in logistic regression models, women who reported any strenuous activity were at a similar risk of colon cancer as women who did not report activity [odds ratio (OR), 1.02; 95% confidence interval (CI), 0.82-1.27); no significant decrease in risk was seen with increase in frequency of activity (P for trend = 0.84). Results were similar for the right and left colon subsites. These data suggest that early adulthood physical activity may not confer the same protective effect that has been observed with recent physical activity.