Breastfeeding and risk of ovarian cancer in two prospective cohorts

Objective To describe the association between breastfeeding and ovarian cancer risk in two prospective cohorts. Materials & methods We pooled data from the Nurses’ Health Study and Nurses’ Health Study II. There were 391 cases of epithelial ovarian cancer diagnosed among 149,693 parous women with up to 16 years of follow-up. Data were analyzed using multivariate Cox proportional hazards models, controlling for age, parity, duration of oral contraceptive use, tubal ligation, and age at menarche. Results Ever breastfeeding was associated with a non-significant reduction in ovarian cancer risk compared with never breastfeeding (RR = 0.86, 95% CI 0.70–1.06); the median duration of breastfeeding among women who breastfed was nine months. Breastfeeding of 18 or more months was associated with a significant decrease in ovarian cancer risk compared to never breastfeeding (RR = 0.66, 95% CI 0.46–0.96). For each month of breastfeeding the relative risk decreased by 2% (RR = 0.98 per month, 95% CI 0.97–1.00). Conclusions These data support a linear inverse association between breastfeeding and risk of epithelial ovarian cancer.     

Height, body mass index, and ovarian cancer: a pooled analysis of 12 cohort studies.

BACKGROUND: Although many studies have investigated the association between anthropometry and ovarian cancer risk, results have been inconsistent. METHODS: The associations of height, body mass index (BMI), and ovarian cancer risk were examined in a pooled analysis of primary data from 12 prospective cohort studies from North America and Europe. The study population consisted of 531,583 women among whom 2,036 epithelial ovarian cancer cases were identified. To summarize associations, study-specific relative risks (RR) were estimated using the Cox proportional hazards model and then combined using a random-effects model. RESULTS: Women with height > or =1.70 m had a pooled multivariate RR of 1.38 [95% confidence interval (95% CI), 1.16-1.65] compared with those with height <1.60 m. For the same comparison, multivariate RRs were 1.79 (95% CI, 1.07-3.00) for premenopausal and 1.25 (95% CI, 1.04-1.49) for postmenopausal ovarian cancer (P(interaction) = 0.14). The multivariate RR for women with a BMI > or =30 kg/m(2) was 1.03 (95% CI, 0.86-1.22) compared with women with a BMI from 18.5 to 23 kg/m(2). For the same comparison, multivariate RRs were 1.72 (95% CI, 1.02-2.89) for premenopausal and 1.07 (95% CI, 0.87-1.33) for postmenopausal women (P(interaction) = 0.07). There was no statistically significant heterogeneity between studies with respect to height or BMI. BMI in early adulthood was not associated with ovarian cancer risk. CONCLUSION: Height was associated with an increased ovarian cancer risk, especially in premenopausal women. BMI was not associated with ovarian cancer risk in postmenopausal women but was positively associated with risk in premenopausal women.     

Reproductive factors and pancreatic cancer risk: a Norwegian cohort study

A cohort of 63,090 Norwegian women born 1886-1928 was followed more than 38 years, and relations between reproductive factors and risk of pancreatic cancer were explored; 449 cases were recorded at ages 50-89 years. Age at menopause showed a moderately positive association with risk (rate ratio (RR)=1.08 per 2 years delay in menopause; 95% confidence interval (CI)=1.00-1.17). Neither parity nor duration of breastfeeding showed significant associations with risk after adjusting only for demographic factors. With mutual adjustment, however, parity became positively associated (RR=1.13 per delivery; 95% CI=1.05-1.22) while duration of breastfeeding was inversely associated (RR=0.87 per 12 months; 95% CI=0.78-0.97). These associations lessened in magnitude with increasing age, and were essentially absent above age 80 years. Risk was raised among women reporting at least one abortion, but no trend was seen with number of abortions. Together with previous studies, the findings raise questions about the role of chance, but do not exclude hormonal factors related to breastfeeding and pregnancy from affecting pancreatic cancer risk.     

Aspirin and cancer risk: a quantitative review to 2011

BackgroundAspirin has been associated to a reduced risk of colorectal and possibly of a few other common cancers.MethodsTo provide an up-to-date quantification of this association, we conducted a meta-analysis of all observational studies on aspirin and 12 selected cancer sites published up to September 2011.ResultsRegular aspirin is associated with a statistically significant reduced risk of colorectal cancer [summary relative risk (RR) from random effects models = 0.73, 95% confidence interval (CI) 0.67–0.79], and of other digestive tract cancers (RR = 0.61, 95% CI = 0.50–0.76, for squamous cell esophageal cancer; RR = 0.64, 95% CI = 0.52–0.78, for esophageal and gastric cardia adenocarcinoma; and RR = 0.67, 95% CI = 0.54–0.83, for gastric cancer), with somewhat stronger reductions in risk in case–control than in cohort studies. Modest inverse associations were also observed for breast (RR = 0.90, 95% CI = 0.85–0.95) and prostate cancer (RR = 0.90, 95% CI = 0.85–0.96), while lung cancer was significantly reduced in case–control studies (0.73, 95% CI = 0.55–0.98) but not in cohort ones (RR = 0.98, 95% CI = 0.92–1.05). No meaningful overall associations were observed for cancers of the pancreas, endometrium, ovary, bladder, and kidney.ConclusionsObservational studies indicate a beneficial role of aspirin on colorectal and other digestive tract cancers; modest risk reductions were also observed for breast and prostate cancer. Results are, however, heterogeneous across studies and dose–risk and duration–risk relationships are still unclear.     

Breastfeeding reduces breast cancer risk: a case–control study in Tunisia

In this report, we examined the relationship between mother’s breastfeeding history and her risk of breast cancer, in a case–control study in Tunisia between 2006 and 2009. About 400 breast cancer cases and 400 controls were included. Cases and controls were interviewed using a standardized structured questionnaire to obtain information on breastfeeding and other risk factors. Mean duration of breastfeeding per child was significantly associated with a reduced risk of breast cancer for women who breastfed for >24 months per child. The OR was 0.46 (95% CI, 0.28–0.76) when compared those who breastfed for <6 months. The test for trend was significant (p = 0.01). A significantly reduced risk of breast cancer was found for those whose lifetime duration of breastfeeding was 73–108 months (OR = 0.65, 95% CI, 0.36–1.18) and for those who breastfed for ≥109 months (OR = 0.42, 95% CI, 0.20–0.84). Stratification by menopausal status showed a reduced risk of breast cancer associated with a longer duration of breastfeeding for both pre- and postmenopausal women. The risk reduction was more consistent for lifetime duration of breastfeeding, the test for trend being significant for both pre- (p = 0.03) and postmenopausal (p = 0.01) women. These results support an inverse association between breastfeeding and breast cancer risk.     

Sex hormones, hormonal interventions, and gastric cancer risk: a meta-analysis

Estrogens may influence gastric cancer risk, but published studies are inconclusive. We therefore carried out a meta-analysis addressing the associations of gastric cancer in women with menstrual and reproductive factors and with use of estrogen- and antiestrogen-related therapies. Searches of PubMed up to June, 2011 and review of citations yielded a total of 28 independent studies, including at least one exposure of interest. Random effects pooled estimates of relative risk (RR) and corresponding 95% CIs were calculated for eight exposures reported in at least five studies, including: age at menarche, age at menopause, years of fertility, parity, age at first birth, oral contraceptive use, hormone replacement therapy (HRT), and tamoxifen treatment. Longer years of fertility (RR = 0.74, 95% CI: 0.63-0.86) and HRT (RR = 0.77; 95% CI: 0.64-0.92) were each associated with decreased gastric cancer risk. Conversely, tamoxifen treatment was associated with increased risk (RR = 1.82; 95% CI: 1.39-2.38). The other five exposures were not significantly associated. Our analysis supports the hypothesis that longer exposure to estrogen effects of either ovarian or exogenous origin may decrease risk of gastric cancer. Additional studies are warranted to extend this finding and to identify the underlying mechanisms.     

Fruits and vegetables and ovarian cancer risk in a pooled analysis of 12 cohort studies.

Because fruits and vegetables are rich in bioactive compounds with potential cancer-preventive actions, increased consumption may reduce the risk of ovarian cancer. Evidence on the association between fruit and vegetable intake and ovarian cancer risk has not been consistent. We analyzed and pooled the primary data from 12 prospective studies in North America and Europe. Fruit and vegetable intake was measured at baseline in each study using a validated food-frequency questionnaire. To summarize the association between fruit and vegetable intake and ovarian cancer, study-specific relative risks (RR) were estimated using the Cox proportional hazards model, and then combined using a random-effects model. Among 560,441 women, 2,130 cases of invasive epithelial ovarian cancer occurred during a maximum follow-up of 7 to 22 years across studies. Total fruit intake was not associated with ovarian cancer risk-the pooled multivariate RR for the highest versus the lowest quartile of intake was 1.06 [95% confidence interval (95% CI), 0.92-1.21; P value, test for trend = 0.73; P value, test for between-studies heterogeneity = 0.74]. Similarly, results for total vegetable intake indicated no significant association (pooled multivariate RR, 0.90; 95% CI, 0.78-1.04, for the highest versus the lowest quartile; P value, test for trend = 0.06; P value, test for between-studies heterogeneity = 0.31). Intakes of botanically defined fruit and vegetable groups and individual fruits and vegetables were also not associated with ovarian cancer risk. Associations for total fruits and vegetables were similar for different histologic types. These results suggest that fruit and vegetable consumption in adulthood has no important association with the risk of ovarian cancer.     

Breastfeeding and breast cancer risk by age 50 among women in Germany

Background: Epidemiological evidence which suggests that prolonged breastfeeding protects against breast cancer has accumulated in recent years. Issues with regard to the timing of breastfeeding and effect modification by correlates of breastfeeding and other risk factors of breast cancer remain unresolved. Methods: A population-based case–control family study of breast cancer among women diagnosed by the age of 50, conducted in two geographic areas in Germany, was used to evaluate the effect of breastfeeding on risk of breast cancer. Results: Among parous women in this study (553 cases, 1094 age-matched population controls), having ever breastfed a child for at least 1 month did not confer protection (odds ratio of 0.9 and 95% confidence interval (CI) 0.8–1.2). However, risk of breast cancer significantly decreased with increasing duration of breastfeeding (p for trend = 0.01) and the estimated relative risk was 0.6 (95% CI 0.4–0.9) for 13–24 months of cumulative breastfeeding and 0.5 (95% CI 0.3–1.1) for 25 months or more. Risk was less related to number of children breastfed than to increasing average length of breastfeeding per child (p for trend = 0.03). Conclusions: The reduction in risk associated with duration of breastfeeding was not primarily due to breastfeeding the firstborn and more evident in women who were older ( > 25 years) when they first breastfed and among women who experienced a recent full-term pregnancy. Risks were modified somewhat by a first-degree family history of breast cancer whereby a greater reduction in risk per additional month of breastfeeding was observed among women with a family history than those without (0.9 vs. 1.0). The study results support a protective role of prolonged breastfeeding against the development of breast cancer in predominantly premenopausal women in Germany.     

Lack of Associations of the COMT Val158Met Polymorphism with Risk of Endometrial and Ovarian Cancer: a Pooled Analysis of Case-control Studies

This meta-analysis was conducted to examine whether the genotype status of Val158Met polymorphism in catechol-O-methyltransferase (COMT) is associated with endometrial and ovarian cancer risk. Eligible studies were identified by searching several databases for relevant reports published before January 1, 2014. Pooled odds ratios (ORs) were appropriately derived from fixed-effects or random-effects models. In total, 15 studies (1,293 cases and 2,647 controls for ovarian cancer and 2,174 cases and 2,699 controls for endometrial cancer)were included in the present meta-analysis. When all studies were pooled into the meta-analysis, there was no evidence for significant association between COMT Val158Met polymorphism and ovarian cancer risk (Val/Met versus Val/Val: OR=0.91, 95% CI=0.76-1.08; Met/Met versus Val/Val: OR=0.90, 95% CI=0.73-1.10; dominant model: OR=0.90, 95% CI=0.77-1.06; recessive model: OR=0.95, 95% CI=0.80-1.13). Similarly, no associations were found in all comparisons for endometrial cancer (Val/Met versus Val/Val: OR 0.97, 95% CI=0.77-1.21; Met/Met versus Val/Val: OR=1.02, 95% CI=0.73-1.42; dominant model: OR=0.98, 95% CI=0.77-1.25; recessive model: OR=1.02, 95% CI=0.87-1.20). In the subgroup analyses by source of control and ethnicity, no significant associations were found in any subgroup of population. This meta-analysis strongly suggests that COMT Val158Met polymorphism is not associated with increased endometrial and ovarian cancer risk.     

Recreational Physical Activity and Risk of Ovarian Cancer: a Meta-analysis

Our aim was to access the association between recreational physical activity (RPA) and risk of ovarian cancer (OC). The studies were retrieved from the PubMed and Embase databases up to February 20th, 2014. Risk ratios (OR) and 95% confidence intervals (CI) were used to estimate effect sizes. Random-effects or fixed-effects models were used to pool the data. The trim and fill method was applied for sensitivity analysis. Begg’s rank correlation test and Egger’s regression asymmetry test were employed to assess the publication bias. A total of 6 studies (435398 participants including 2983 OC patients) were included in this meta-analysis. The overall estimate indicated that there was weakly inverse association between RPA and OC risk (RR=0.90, 95%CI: 0.72-1.12, p=0.335). Meanwhile, for prospective cohort studies, a result consistent with the overall estimate was obtained (RR=1.12, 95% CI: 0.88-1.42, p=0.356). However, for case control studies, the pooled estimate of RR was 0.76 (95%CI: 0.64-0.90, p=0.002), indicating a clear significant association between RPA and OC risk. In addition,the sensitivity analysis indicated a significant link between RPA and risk of OC after removing Lahmann’s study (RR=0.80, 95% CI: 0.68-0.93, p=0.004). No significant publication bias was found (Begg’s test: p=1.00; Egger’s test: p=0.817). In conclusion, our meta-analysis indicated a weakly inverse relationship between RPA and the occurrence of OC.     

A Pooled Analysis of 12 Cohort Studies of Dietary Fat, Cholesterol and Egg Intake and Ovarian Cancer

Fat and cholesterol are theorized to promote ovarian carcinogenesis by increasing circulating estrogen levels. Although case–control studies have reported positive associations between total and saturated fat intake and ovarian cancer risk, two cohort studies have observed null associations. Dietary cholesterol and eggs have been positively associated with ovarian cancer risk. A pooled analysis was conducted on 12 cohort studies. Among 523,217 women, 2,132 incident epithelial ovarian cancer cases were identified. Study-specific relative risks (RR) and 95% confidence intervals (CI) were calculated by Cox proportional hazards models, and then pooled using a random effects model. Total fat intake was not associated with ovarian cancer risk (pooled multivariate RR = 1.08, 95% CI 0.86–1.34 comparing ≥45 to 30–<35% of calories). No association was observed for monounsaturated, polyunsaturated, trans-unsaturated, animal and vegetable fat, cholesterol and egg intakes with ovarian cancer risk. A weakly positive, but non-linear association, was observed for saturated fat intake (pooled multivariate RR = 1.29, 95% CI: 1.01–1.66 comparing highest versus lowest decile). Results for histologic subtypes were similar. Overall, fat, cholesterol and egg intakes were not associated with ovarian cancer risk. The positive association for saturated fat intake at very high intakes merits further investigation.     

Differences in Cancer Risks in the South and North of Viet Nam

Background: As there are few available data regarding cancers in Viet Nam, the aim of the present study was toevaluate cancer risk ratios and geographical differences in cancer incidences between the south and north populationsin the 1990s.Methods: Data for cancer incidences in Ho Chi Minh (HCM) and Hanoi were derived from published reports.The method for comparison of cancer incidence in two groups used in the present study was the Mantel-Haenszeltest.Results: In HCM, all cancers were observed to be lower in males , (RR = 0.87, 95% CI = 0.83-0.91) but higher infemales, (RR = 1.06, 95% CI = 1.01-1.12) than in Hanoi. For males, significantly higher incidences in HCM wereobserved for cancers of the oesophagus (RR = 1.66, 95% CI = 1.19-2.32), liver (RR = 1.22, 95% CI = 1.09-1.36), gallbladder (RR = 5.95, 95% CI = 2.49-14.23), and larynx (RR = 3.54, 95% CI = 2.26-5.55). In contrast, there were muchlower incidences in HCM for cancers of the nasopharynx (RR = 0.5, 95% CI = 0.41-0.61), stomach (RR = 0.76, 95%CI = 0.67-0.86), and lung (RR = 0.7, 95% CI = 0.64-0.78). For females, breast cancer incidence was much lower (RR= 0.65, 95% CI = 0.57-0.73) but that of cervical cancer was significantly higher in HCM than in Hanoi, (RR = 3.94,95% CI = 3.36-4.62), especially for the age group 55-64, (RR = 8.7, 95% CI = 5.9-13.3).Conclusion: The present findings show that cancer risk is quite different in the south and north populationswithin Viet Nam.     

Physical activity and epithelial ovarian cancer risk: a case-control study in China

A case-control study was conducted in China during 1999-2000 to investigate the effects of intensity and duration of physical activity on the risk of epithelial ovarian cancer. Cases were 254 patients with histologically confirmed epithelial ovarian cancer. The 652 controls comprised 340 hospital visitors, 261 non-neoplasm hospital outpatients and 51 women recruited from the community. Physical activity was measured by a validated questionnaire. The risks of ovarian cancer were assessed using multivariate logistic regression analysis accounting for age, demographic, lifestyle and familial factors, hormonal status, family ovarian cancer history and total energy intake. The study found that increasing total physical activity was associated with a lower ovarian cancer risk among Chinese women. The odds ratio was 0.54 (95% CI 0.34-0.87) for high vs. low levels of total weekly metabolic equivalent tasks. Ovarian cancer risk tended to decline with increasing duration of strenuous sports and frequency of activity-induced sweating among pre-menopausal women, with adjusted OR 0.13 (95% CI 0.03-0.64) and 0.45 (95% CI 0.24-0.85), respectively. Increasing duration of moderate activity in post-menopausal women also appeared to be protective against ovarian cancer, with adjusted OR 0.36 (95% CI 0.18-0.73).     

Effect of lifetime lactation on breast cancer risk: a Korean women's cohort study

The objective of our study was to examine the effect of lifetime lactation on breast cancer risk among premenopausal women. The data were from a prospective cohort study with a follow-up period of 6 years in Korea (1995-2000). The cohort was composed of 110,604 premenopausal parous Korean women, aged 20 years and older, who received health insurance from the Korea Medical Insurance Corporation and who had medical evaluations in 1992 and 1994. Multivariate Cox proportional hazard models were tested, controlling for age, age at menarche, number of children, age at first pregnancy, oral contraceptive use, smoking, exercise and obesity. At baseline, 57,440 (51.9%) reported breastfeeding and 4,584 (4.1%) reported breastfeeding more than 24 months. From 1995-2000, 360 incident cases of breast cancer (61.8/100,000 person-years) occurred. Compared to parous women who had no history of lactation, a period of lactation of 13-24 months decreased the risk of breast cancer (RR, 0.7; 95% CI, 0.5-1.1), and this risk was decreased even further for those who breastfed for more than 24 months (RR, 0.6; 95% CI, 0.3-1.0). There was a clear trend of decreasing breast cancer risk with the duration of lactation (p for trend <0.001). In conclusion, our study of a large Korean cohort provides additional empirical evidence to current theoretical conjecture that lactation decreases the risk of breast cancer among premenopausal women.     

Prospective study of talc use and ovarian cancer

BACKGROUND: Perineal talc use has been associated with an increased risk of ovarian cancer in a number of case-control studies; however, this association remains controversial because of limited supporting biologic evidence and the potential for recall bias or selection bias in case-control studies. In this study, we conducted a prospective analysis of perineal talc use and the risk of ovarian cancer. METHODS: The Nurses' Health Study is a prospective study of 121 700 female registered nurses in the United States who were aged 30-55 years at enrollment in 1976. Talc use was ascertained in 1982 by use of a self-administered questionnaire: after exclusions, 78 630 women formed the cohort for analysis. Three hundred seven epithelial ovarian cancers subsequently diagnosed in this cohort through June 1, 1996, were confirmed by medical record review and met inclusion criteria. Proportional hazards models by use of pooled logistic regression were used to derive relative risks (RRs) and 95% confidence intervals (CIs). RESULTS: In 1982, 40.4% (n = 31 789) of the cohort reported ever using talc, and 14.5% (n = 11 411) reported ever using talc daily. We observed no overall association with ever talc use and epithelial ovarian cancer (multivariate RR = 1.09; 95% CI = 0.86-1.37) and no increase in risk of ovarian cancer with increasing frequency of use. There was a modest elevation in risk for ever talc use and invasive serous ovarian cancer (multivariate RR = 1.40; 95% CI = 1.02-1.91). The risk of epithelial ovarian cancer for talc users was not greater among women who had never had a tubal ligation (multivariate RR = 0.97; 95% CI = 0.71-1.32). CONCLUSION: Our results provide little support for any substantial association between perineal talc use and ovarian cancer risk overall; however, perineal talc use may modestly increase the risk of invasive serous ovarian cancer.     

A meta-analysis of diabetes mellitus and the risk of prostate cancer.

BACKGROUND: Studies investigating the association between diabetes mellitus and prostate cancer have reported inconsistent findings. We examined this association by conducting a detailed meta-analysis of the studies published on the subject. METHODS: MEDLINE and EMBASE databases and bibliographies of retrieved articles were searched. Studies investigating the relationship between diabetes mellitus and prostate cancer were included in the meta-analysis. Potential sources of heterogeneity between studies were explored and publication bias was evaluated. Pooled relative risk (RR) was calculated using the random-effects model. Numerous relevant subgroup analyses were also done. RESULTS: We included 19 studies, published between 1971 and 2005, in the meta-analysis and found an inverse association between diabetes mellitus and prostate cancer [RR, 0.84, 95% confidence interval (CI), 0.76-0.93, P for heterogeneity 相似文献   

Family history of breast cancer as a risk factor for ovarian cancer in a prospective study

BACKGROUND: A family history of breast cancer has been associated with increased ovarian cancer risk. However, few studies have assessed risk according to characteristics that suggest an inherited cancer susceptibility disorder, such as earlier-than-usual age at cancer diagnosis, family members with double primary cancers of different types, multiple relatives with cancer, and cancer in both members of paired organs. METHODS: Ovarian cancer risk was assessed according to a detailed breast cancer family history among 49,975 participants in the Breast Cancer Detection Demonstration Project Breast Cancer Defection Demenstration Project (BCDDP) Follow-up Study (1979-1998). In all, 362 incident ovarian cancers were identified during follow-up and rate ratios (RRs) were calculated by Poisson regression. RESULTS.: Breast cancer in a first- or second-degree relative was associated with increased risk of ovarian cancer (RR = 1.4; 95% confidence interval [CI] = 1.1-1.7). Having 2 or more affected first-degree relatives was associated with increased risk (RR = 1.8; 95% CI = 1.1-2.8), especially for women diagnosed with ovarian cancer before age 60 (RR = 4.2; 95% CI = 1.9-9.2) or with a personal history of breast cancer (RR = 3.7; 95% CI 1.8-7.7). Risk was also particularly high for women with 2 or more first-degree relatives with breast cancer and at least 1 affected relative diagnosed before age 50 (RR = 2.6; 95% CI = 1.4-4.8) or with bilateral breast cancer (RR = 4.2; 95% CI = 1.7-10). CONCLUSIONS: A detailed breast cancer family history as well as an individual's age and personal history of breast cancer are useful for identifying women at elevated genetic risk of ovarian cancer.     

Postmenopausal hormone therapy and lung cancer risk in the cancer prevention study II nutrition cohort.

BACKGROUND: Studies of postmenopausal hormone therapy and lung cancer incidence have reported positive, negative, and null associations. Most of these studies, however, have had limited ability to control rigorously for cigarette smoking or to examine risk separately by smoking status. METHODS: We examined the association between postmenopausal hormone therapy and lung cancer incidence by smoking status among 72,772 women in the Cancer Prevention Study II Nutrition Cohort. Proportional hazards modeling was used to calculate rate ratios (RR). RESULTS: During follow-up from 1992 to 2003, we identified 659 cases of incident lung cancer. Current use of any postmenopausal hormone therapy was significantly associated with decreased risk of incident lung cancer [multivariate RR, 0.76; 95% confidence interval (95% CI), 0.62-0.92]. Similar risk estimates were observed for unopposed estrogen use (RR, 0.76; 95% CI, 0.60-0.94) and for estrogen plus progestin (RR, 0.76; 95% CI, 0.57-1.01). Risk associated with current use of postmenopausal hormone therapy was decreased among never smokers (RR, 0.56; 95% CI, 0.33-0.95) as well as current smokers (RR, 0.76; 95% CI, 0.55-1.05) and former smokers (RR, 0.76; 95% CI, 0.58-0.99). Former hormone use was not associated with lung cancer. No trend with duration of hormone use was detected. CONCLUSION: These results support the hypothesis that postmenopausal hormone therapy is associated with reduced risk of lung cancer, although the absence of a dose-response relationship weakens the evidence for causality.     

Lactation and breast cancer risk: a case-control study in Connecticut

In this report, we examined the relationship between lactation and breast cancer risk, in a case-control study of breast cancer, conducted in Connecticut between 1994 and 1998. Included were 608 incident breast cancer cases and 609 age frequency matched controls, aged 30-80 years old. Cases and controls were interviewed by trained study interviewers, using a standardized, structured questionnaire, to obtain information on lactation and other major risk factors. Parous women who reported ever lactation had a borderline significantly reduced risk of breast cancer (OR = 0.83, 95% CI, 0.63-1.09). An OR of 0.53 (95% CI, 0.27-1.04) was observed in those having breastfed more than 3 children compared to those who never lactated. Women having breastfed their first child for more than 13 months had an OR of 0.47 (95% CI, 0.23-0.94) compared to those who never breastfed. Lifetime duration of lactation also showed a risk reduction while none of the ORs were statistically significant. Further stratification by menopausal status showed a risk reduction related to lactation for both pre- and postmenopausal women, while the relationship is less consistent for the latter. These results support an inverse association between breastfeeding and breast cancer risk.     

Risk factors by molecular subtypes of breast cancer across a population-based study of women 56 years or younger

Differences in incidence, prognosis, and treatment response suggest gene expression patterns may discern breast cancer subtypes with unique risk factor profiles; however, previous results were based predominantly on older women. In this study, we examined similar relationships in women ≤ 56 years, classified by immunohistochemical staining for estrogen receptor, progesterone receptor, and human epidermal growth factor receptor-2 for 890 breast cancer cases and 3,432 frequency-matched population-based controls. Odds ratios (OR) and 95% confidence intervals (CI) for tumor subtypes were calculated using multivariate polytomous regression models. A total of 455 (51.1%) tumors were considered luminal A, 72 (8.1%) luminal B, 117 (13.1%) non-luminal HER-2/neu+, and 246 (27.6%) triple negative. Triple negative tumors were associated with breast feeding duration (per 6 months: OR = 0.76, 95% CI 0.64-0.90). Among premenopausal women, increasing body size was more strongly associated with luminal B (OR = 1.73, 95% CI 1.07-2.77) and triple negative tumors (OR = 1.67, 95% CI 1.22-2.28). A history of benign breast disease was associated only with increased risk of luminal A tumors (OR = 1.89, 95% CI 1.43-2.50). A family history of breast cancer was a risk factor for luminal A tumors (OR = 1.93, 95% CI 1.38-2.70) regardless of age, and triple negative tumors with higher risks for women <45 (OR = 5.02, 95% CI 2.82-8.92; P for age interaction = 0.005). We found that little-to-no breastfeeding and high BMI were associated with increased risk of triple negative breast cancer. That some risk factors differ by molecular subtypes suggests etiologic heterogeneity in breast carcinogenesis among young women.