Prospective study of smoking and the risk of breast cancer

Lifetime personal cigarette smoking and risk of young-onset breast cancer by subtype among non-Hispanic Black and White women in the Young Women's Health History Study

PURPOSE

To evaluate the association between lifetime personal cigarette smoking and young-onset breast cancer (YOBC; diagnosed <50 years of age) risk overall and by breast cancer (BC) subtype, and whether risk varies by race or socioeconomic position (SEP).

METHODS

Data are from the Young Women's Health History Study (YWHHS), a population-based case-control study of non-Hispanic Black (NHB) and White (NHW) women, ages 20-49 years (n = 1812 cases, n = 1381 controls) in the Los Angeles County and Metropolitan Detroit Surveillance, Epidemiology, and End Results (SEER) registry areas, 2010-2015. Lifetime personal cigarette smoking characteristics and YOBC risk by subtype were examined using sample-weighted, multivariable-adjusted polytomous logistic regression.

RESULTS

YOBC risk associated with ever versus never smoking differed by subtype (Pheterogeneity = 0.01) with risk significantly increased for Luminal A (adjusted odds ratio [aOR] 1.34; 95% confidence interval [CI] 1.06-1.68) and HER2-type (aOR 1.97; 95% CI 1.23-3.16), and no association with Luminal B or Triple Negative subtypes. Additionally, ≥30 years since smoking initiation (versus never) was statistically significantly associated with an increased risk of Luminal A (aOR 1.55; 95% CI 1.07-2.26) and HER2-type YOBC (aOR 2.77; 95% CI 1.32-5.79), but not other subtypes. In addition, among parous women, smoking initiated before first full-term pregnancy (versus never) was significantly associated with an increased risk of Luminal A YOBC (aOR 1.45; 95% CI 1.11-1.89). We observed little evidence for interactions by race and SEP.

CONCLUSION

Findings confirm prior reports of a positive association between cigarette smoking and Luminal A YOBC and identify a novel association between smoking and HER2-type YOBC.

The Impact of Treatment for Smoking on Breast Cancer Patients’ Survival

Simple Summary

This was a retrospective analysis of breast cancer patients who were self-identified as smokers at diagnosis and who were invited to participate in a comprehensive tobacco treatment program (TP) that provided pharmacotherapy and motivational counseling to quit smoking. Our study shows that quitting smoking is associated with improved survival among breast cancer patients who smoke across all tumor stages. In our survival analysis, tobacco abstainers were more likely than smokers to be alive with no evidence of disease (hazard ratio = 0.616 95%CI (0.402–0.945), p = 0.026). Comprehensive approach to address smoking cessation may prolong survival outcomes when started as early as the time of diagnosis.

Abstract

Background: Smoking negatively affects overall survival after successful breast cancer (BC) treatment. We hypothesized that smoking cessation would improve survival outcomes of BC patients who were smokers at the time of diagnosis. Methods: This was a retrospective analysis of self-identified smokers with BC treated at The University of Texas MD Anderson Cancer Center. Patient demographics, date of diagnosis, tumor stage, tobacco treatment program (TP) participation, and time to death were extracted from our departmental databases and institutional electronic health records. We examined associations between tobacco abstinence status and survival using survival models, with and without interactions, adjusted for personal characteristics and biomarkers of disease. Results: Among all 31,069 BC patients treated at MD Anderson between 2006 and 2017, we identified 2126 smokers (6.8%). From those 2126 self-identified smokers, 665 participated in the TP, reporting a conservative estimate of 31% abstinence (intent-to-treat) 9 months into the program. Patients without reported follow-up abstinence status (including TP and non-TP participants) were handled in the analyses as smokers. Survival analysis controlled for multiple factors, including disease characteristics and participation in the TP, indicated that abstainers were more likely to be alive with no evidence of disease compared to non-abstainers (HR, 0.593; 95% CI, 0.386–0.911; p = 0.017). Conclusion: Our results suggest that quitting smoking is associated with improved survival among BC patients who were smokers at time of diagnosis across all tumor stages. Comprehensive approaches for smoking cessation in patients diagnosed with BC may prolong survival when started as early as the time of diagnosis.

Smoking and risk of breast cancer in the Generations Study cohort

Background

Plausible biological reasons exist regarding why smoking could affect breast cancer risk, but epidemiological evidence is inconsistent.

Methods

We used serial questionnaire information from the Generations Study cohort (United Kingdom) to estimate HRs for breast cancer in relation to smoking adjusted for potentially confounding factors, including alcohol intake.

Results

Among 102,927 women recruited 2003–2013, with an average of 7.7 years of follow-up, 1815 developed invasive breast cancer. The HR (reference group was never smokers) was 1.14 (95% CI 1.03–1.25; P = 0.010) for ever smokers, 1.24 (95% CI 1.08–1.43; P = 0.002) for starting smoking at ages < 17 years, and 1.23 (1.07–1.41; P = 0.004) for starting smoking 1–4 years after menarche. Breast cancer risk was not statistically associated with interval from initiation of smoking to first birth (P-trend = 0.97). Women with a family history of breast cancer (ever smoker vs never smoker HR 1.35; 95% CI 1.12–1.62; P = 0.002) had a significantly larger HR in relation to ever smokers (P for interaction = 0.039) than women without (ever smoker vs never smoker HR 1.07; 95% CI 0.96–1.20; P = 0.22). The interaction was prominent for age at starting smoking (P = 0.003) and starting smoking relative to age at menarche (P = 0.0001).

Conclusions

Smoking was associated with a modest but significantly increased risk of breast cancer, particularly among women who started smoking at adolescent or peri-menarcheal ages. The relative risk of breast cancer associated with smoking was greater for women with a family history of the disease.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-017-0908-4) contains supplementary material, which is available to authorized users.

Impacts of smoking on endocrine treatment response in a prospective breast cancer cohort

BACKGROUND

The association between smoking and breast cancer prognosis remains unclear. The purpose of this study was to investigate whether preoperative smoking was associated with prognosis in different treatment groups.

METHODS

This population-based cohort consisted of 1065 breast cancer patients without preoperative treatment included between 2002 and 2012 in Lund, Sweden. Smoking status was examined in relation to patient and tumour characteristics, and prognosis in different treatment groups.

RESULTS

At the preoperative visit, 21.0% smoked. Median follow-up time was 5.1 years. Overall, in the 1016 patients included in the survival analyses, there was no significant association between smoking and risk of breast cancer events (adjusted hazard ratio (adjHR): 1.45; 95% confidence interval (CI): 0.95-2.20). For the 309 aromatase inhibitor (AI)-treated patients ⩾50 years with oestrogen receptor-positive (ER+) tumours, smoking was associated with risk of breast cancer events (adjHR: 2.97; 95% CI: 1.44-6.13), distant metastasis (adjHR: 4.19; 95% CI: 1.81-9.72), and death (adjHR: 3.52; 95% CI: 1.59-7.81). Smoking was not associated with breast cancer events or distant metastasis in other treatment groups.

CONCLUSIONS

Preoperative smoking was only associated with an increased risk for breast cancer events and distant metastasis in AI-treated patients. If confirmed, smoking status should be taken into consideration when selecting an endocrine therapy.

Cigarette Smoking Before and After Breast Cancer Diagnosis: Mortality From Breast Cancer and Smoking-Related Diseases

PURPOSE

Cigarette smoking increases overall mortality, but it is not established whether smoking is associated with breast cancer prognosis.

METHODS

We evaluated the association between smoking status before and after breast cancer diagnosis and mortality in the Collaborative Breast Cancer and Women's Longevity Study, a population-based prospective observational study conducted in Wisconsin, New Hampshire, and Massachusetts. Participants included 20,691 women, ages 20 to 79 years, diagnosed with incident localized or regional invasive breast cancer between 1988 and 2008; a subset of 4,562 of these women were recontacted a median of 6 years after diagnosis. Hazard ratios (HRs) with 95% CIs were calculated according to smoking status for death as a result of breast cancer; cancers of the lung, pharynx, or intrathoracic organs; other cancer; respiratory disease; and cardiovascular disease.

RESULTS

During a median of 12 years, 6,778 women died, including 2,894 who died as a result of breast cancer. Active smokers 1 year before breast cancer diagnosis were more likely than never smokers to die of breast cancer (HR, 1.25; 95% CI, 1.13 to 1.37), respiratory cancer (HR, 14.48; 95% CI, 9.89 to 21.21), other respiratory disease (HR, 6.02; 95% CI, 4.55 to 7.97), and cardiovascular disease (HR, 2.08; 95% CI, 1.80 to 2.41). The 10% of women who continued to smoke after diagnosis were more likely than never smokers to die of breast cancer (HR, 1.72; 95% CI, 1.13 to 2.60). When compared with women who continued to smoke after diagnosis, those who quit smoking after diagnosis had lower mortality from breast cancer (HR, 0.67; 95% CI, 0.38 to 1.19) and respiratory cancer (HR, 0.39; 95% CI, 0.16 to 0.95).

CONCLUSION

Smoking before or after diagnosis was associated with a higher mortality from breast cancer and several other causes.

Cigarette Smoking and Breast Cancer Risk in Hispanic and Non-Hispanic White Women: The Breast Cancer Health Disparities Study

OBJECTIVE

Few epidemiological studies have included Hispanics with the evaluation of the effects of cigarette smoking and breast cancer. We examined the relationship between cigarette smoking, ethnicity, and breast cancer risk using data from the Breast Cancer Health Disparities Study (BCHDS).

MATERIALS AND METHODS

The BCHDS is a consortium of three population-based case-control studies, including U.S. non-Hispanic whites (NHWs) (1,525 cases; 1,593 controls), U.S. Hispanics/Native Americans (1,265 cases; 1,495 controls), and Mexican women (990 cases; 1,049 controls). Multivariable logistic regression was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs).

RESULTS

Breast cancer risk was elevated among Mexican former smokers (OR 1.43, 95% CI 1.04-1.96) and among those who smoked ≥ 31 years (OR 1.95, 95% CI 1.13-3.35), compared to never smokers. In addition, Mexican former smokers with a history of alcohol consumption had increased breast cancer risk (OR 2.30, 95% CI 1.01-5.21). Among NHW premenopausal women, breast cancer risk was increased for smoking ≥ 20 cigarettes per day (OR 1.61, 95% CI 1.07-2.41).

CONCLUSION

Our findings suggest the possibility of ethnic differences with the associations between cigarette smoking and breast cancer risk.

Active cigarette smoking and risk of breast cancer

Although epidemiological evidence on the role of active cigarette smoking in breast cancer risk has been inconsistent, recent literature supports a modest association between smoking and breast cancer. This association is particularly observed in women who smoke for a long duration, or who smoke for a long time prior to their first pregnancy. Here, we provide updated results on cigarette smoking and breast cancer risk in the Canadian National Breast Screening Study (NBSS). The NBSS is a large cohort of 89,835 women, aged 40-59, who were followed for a mean of 22.1 years, resulting in the ascertainment of 6,549 incident cases of breast cancer. Cox proportional hazard models were used to estimate hazard ratios (HR) and 95% confidence intervals (CI) for the association of cigarette smoking variables with breast cancer risk. We found breast cancer to be associated with duration (40 years vs. 0: HR = 1.57; 95%CI = 1.29-1.92), intensity (40 cigarettes per day vs. 0: HR = 1.21; 95%CI = 1.04-1.40), cumulative exposure (40 pack-years vs. 0: HR = 1.19; 95%CI = 1.06-1.13) and latency (40 years since initiation vs. 0: HR = 1.19; 95%CI = 1.10-1.53) of cigarette smoking. Number of years smoked prior to first full-term pregnancy was associated with higher risk of breast cancer than comparative years smoked post-pregnancy (among parous women, 5 years pre pregnancy vs. 0: HR = 1.18; 95%CI = 1.10-1.26). These results strongly support a role for cigarette smoking in breast cancer etiology and emphasize the importance of timing of this exposure.

Active and passive cigarette smoking and breast cancer risk: results from the EPIC cohort

Recent cohort studies suggest that increased breast cancer risks were associated with longer smoking duration, higher pack-years and a dose-response relationship with increasing pack-years of smoking between menarche and first full-term pregnancy (FFTP). Studies with comprehensive quantitative life-time measures of passive smoking suggest an association between passive smoking dose and breast cancer risk. We conducted a study within the European Prospective Investigation into Cancer and Nutrition to examine the association between passive and active smoking and risk of invasive breast cancer and possible effect modification by known breast cancer risk factors. Among the 322,988 women eligible for the study, 9,822 developed breast cancer (183,608 women with passive smoking information including 6,264 cases). When compared to women who never smoked and were not being exposed to passive smoking at home or work at the time of study registration, current, former and currently exposed passive smokers were at increased risk of breast cancer (hazard ratios (HR) [95% confidence interval (CI)] 1.16 [1.05-1.28], 1.14 [1.04-1.25] and 1.10 [1.01-1.20], respectively). Analyses exploring associations in different periods of life showed the most important increase in risk with pack-years from menarche to FFTP (1.73 [1.29-2.32] for every increase of 20 pack-years) while pack-years smoked after menopause were associated with a significant decrease in breast cancer risk (HR = 0.53, 95% CI: 0.34-0.82 for every increase of 20 pack-years). Our results provide an important replication, in the largest cohort to date, that smoking (passively or actively) increases breast cancer risk and that smoking between menarche and FFTP is particularly deleterious.

Active smoking and the risk of estrogen receptor-positive and triple-negative breast cancer among women ages 20 to 44 years

BACKGROUND

Evidence regarding the correlation between smoking and breast cancer among young women is mixed, and previous studies have not assessed whether smoking is associated differentially with risks of the major breast cancer subtypes.

METHODS

This was a population-based, case-control study of 778 women with estrogen receptor (ER)-positive breast cancers and 182 women with ER-negative, progesterone receptor-negative, and human epidermal growth factor receptor 2-negative (triple-negative [TN]), invasive breast cancers ages 20 to 44 years who were diagnosed from 2004 to 2010 in the Seattle-Puget Sound metropolitan area. A control group of 938 cancer-free women also was included. Associations between various aspects of smoking history and the risks of ER-positive and TN breast cancer were assessed using polytomous logistic regression.

RESULTS

Ever-smokers had a 1.3-fold increased risk (95% confidence interval [CI], 1.1-fold to 1.7-fold increased risk) of breast cancer overall; and, when stratified by cancer subtype, they had a 1.4-fold increased risk (95% CI, 1.1-fold to 1.8-fold increased risk) of ER-positive breast cancer, but there was no elevation in their risk of TN disease (odds ratio, 1.1; 95% CI, 0.7-1.6). Current/recent smokers with a ≥10 pack-year history of smoking had a 1.6-fold increased risk (95% CI, 1.1-fold to 2.4-fold increased risk) of ER-positive breast cancer but had no increase in their risk of TN breast cancer (odds ratio, 1.0; 95% CI, 0.5-1.9).

CONCLUSIONS

The current results suggested that young women who are current/recent smokers with high pack-year histories may have an increased risk of ER-positive breast cancer but not TN breast cancer. Although this association was modest, the findings suggest that an increased risk of ER-positive breast cancer may be another health risk incurred by young women who smoke.

Cigarette smoking and postmenopausal breast cancer risk in a prospective cohort

Background:

The relationship between cigarette smoking and breast cancer risk has been inconsistent, potentially due to modification by other factors or confounding.

Methods:

We examined smoking and breast cancer risk in a prospective cohort of 186 150 female AARP (formerly American Association of Retired Persons) members, ages 50–71 years, who joined the study in 1995–96 by responding to a questionnaire. Through 2006, 7481 breast cancers were diagnosed. Multivariable-adjusted hazard ratios (HRs) were estimated, overall and stratified by breast cancer risk factors, using Cox proportional hazards regression. Multiplicative interactions were evaluated using the likelihood ratio test.

Results:

Increased breast cancer risk was associated with current (HR 1.19, 95% confidence interval (CI) 1.10–1.28) and former (HR 1.07, CI 1.01–1.13) smoking. The current smoking association was stronger among women without (HR 1.24, CI 1.15–1.35) as compared to those with a family history of breast cancer (HR 0.94, CI 0.78–1.13) (P-interaction=0.03). The current smoking association was also stronger among those with later (⩾15 years: HR 1.52, CI 1.20–1.94) as compared with earlier (⩽12 years: HR 1.14, CI 1.03–1.27; 13–14 years: HR 1.18, CI 1.05–1.32) ages at menarche (P-interaction=0.03).

Conclusions:

Risk was elevated in smokers, particularly in those without a family history or late menarche. Research into smoking's effects on the genome and breast development may clarify these relationships.

Cigarette smoking and breast cancer risk in relation to joint estrogen and progesterone receptor status: a case-control study in Japan

An association of cigarette smoking with breast cancer risk has been hypothesized. However, results from previous studies have been inconsistent. This case-control study investigated the association of cigarette smoking with breast cancer risk in terms of estrogen-receptor/progesterone-receptor (ER/PgR) status. From among female patients aged 30 years and over admitted to a single hospital in Japan between 1997 and 2011, 1,263 breast cancer cases (672 ER+/PgR+, 158 ER+/PgR-, 22 ER-/PgR+, 308 ER-/PgR- and 103 missing) and 3,160 controls were selected. History of smoking (ever, never), some smoking-related measures, and passive smoking from husbands (ever, never) were assessed using a self-administered questionnaire. Polytomous logistic regression and tests for heterogeneity across ER+/PgR + and ER-/PgR- were conducted. For any hormone receptor subtype, no significant association was observed between history of smoking (ever, never) and breast cancer risk. Analysis of smoking-related measures revealed that starting to smoke at an early age of ≤19 years was significantly associated with an increased risk of postmenopausal ER-/PgR- cancer (odds ratio = 7.01, 95% confidence interval: 2.07-23.73). Other measures of smoking such as the number of cigarettes per day, the duration of smoking, and start of smoking before the first birth were not associated with breast cancer risk for any receptor subtype. There was no association between passive smoking (ever, never) and breast cancer risk for any of the four subtypes. These results indicate that history of smoking and passive smoking from husbands may have no overall effect on breast cancer risk for any hormone receptor subtype. However, it is possible that women who start to smoke as teenagers may have a higher risk of developing postmenopausal ER-/PgR- cancer. Further studies are needed to clarify the association of smoking with breast cancer risk, especially the role of starting to smoke at an early age.

Cigarette smoking and the incidence of breast cancer

BACKGROUND

Tobacco smoke contains carcinogens, which may increase the risk of breast cancer (BC). Conversely, cigarette smoking also has antiestrogenic effects, which may reduce the risk of BC. The association between smoking and BC remains controversial.

METHODS

Prospective cohort study of 111 140 participants of the Nurses' Health Study from 1976 to 2006 for active smoking and 36 017 women from 1982 to 2006 for passive smoking.

RESULTS

During 3 005 863 person-years of follow-up, 8772 incident cases of invasive BC were reported. After adjustment for potential confounders, the hazard ratio (HR) of BC was 1.06% (95% confidence interval [CI], 1.01%-1.10%) for ever smokers relative to never smokers. Breast cancer incidence was associated with a higher quantity of current (P for trend = .02) and past (P for trend = .003) smoking, younger age at smoking initiation (P for trend = .01), longer duration of smoking (P for trend = .01), and more pack-years of smoking (P for trend = .005). Premenopausal smoking was associated with a slightly higher incidence of BC (HR, 1.11; 95% CI, 1.07-1.15 for every increase of 20 pack-years), especially smoking before first birth (1.18; 1.10-1.27 for every increase of 20 pack-years). Conversely, the direction of the association between postmenopausal smoking and BC was inverse (0.93; 0.85-1.02 for every increase of 20 pack-years). Passive smoking in childhood or adulthood was not associated with BC risk.

CONCLUSION

Active smoking, especially smoking before the first birth, may be associated with a modest increase in the risk of BC.

Smoking and alcohol consumption in relation to risk of triple-negative breast cancer in a cohort of postmenopausal women

PURPOSE

Little is known about the risk factors for triple-negative breast cancer (TNBC), which has a worse prognosis compared to hormone receptor-positive breast cancer. We examined the association of smoking and alcohol intake with TNBC and estrogen receptor-positive (ER+) breast cancer.

METHODS

Among 148,030 women enrolled in the Women's Health Initiative, 300 TNBC cases and 2,479 ER+ cases were identified over a median of 8.0 years of follow-up. Cox proportional hazards models were used to estimate hazard ratios (HR) and 95% confidence intervals (95% CI).

RESULTS

Cigarette smoking was not associated with TNBC, whereas drinkers had reduced risk compared to never drinkers. In contrast, both exposures showed slight positive associations with ER+ breast cancer: for women with ≥ 40 pack-years of smoking, the HR was 1.24, 95% CI 1.06-1.44; for women consuming ≥ 7 servings of alcohol per week, the HR was 1.26, 95% CI 1.06-1.50. Intakes of wine and hard liquor were also significantly positively associated with ER+ breast cancer.

CONCLUSIONS

These findings from a large cohort of postmenopausal women suggest that smoking and alcohol consumption are not associated with increased risk of TNBC, but may be modestly associated with increased risk of ER+ breast cancer.

Association of active and passive smoking with risk of breast cancer among postmenopausal women: a prospective cohort study

OBJECTIVE

To examine the association between smoking and risk of invasive breast cancer using quantitative measures of lifetime passive and active smoking exposure among postmenopausal women.

DESIGN

Prospective cohort study.

SETTING

40 clinical centres in the United States.

PARTICIPANTS

79,990 women aged 50-79 enrolled in the Women's Health Initiative Observational Study during 1993-8.

MAIN OUTCOME MEASURES

Self reported active and passive smoking, pathologically confirmed invasive breast cancer.

RESULTS

In total, 3520 incident cases of invasive breast cancer were identified during an average of 10.3 years of follow-up. Compared with women who had never smoked, breast cancer risk was elevated by 9% among former smokers (hazard ratio 1.09 (95% CI 1.02 to 1.17)) and by 16% among current smokers (hazard ratio 1.16 (1.00 to 1.34)). Significantly higher breast cancer risk was observed in active smokers with high intensity and duration of smoking, as well as with initiation of smoking in the teenage years. The highest breast cancer risk was found among women who had smoked for ≥ 50 years or more (hazard ratio 1.35 (1.03 to 1.77) compared with all lifetime non-smokers, hazard ratio 1.45 (1.06 to 1.98) compared with lifetime non-smokers with no exposure to passive smoking). An increased risk of breast cancer persisted for up to 20 years after smoking cessation. Among women who had never smoked, after adjustment for potential confounders, those with the most extensive exposure to passive smoking (≥ 10 years' exposure in childhood, ≥ 20 years' exposure as an adult at home, and ≥ 10 years' exposure as an adult at work) had a 32% excess risk of breast cancer compared with those who had never been exposed to passive smoking (hazard ratio 1.32 (1.04 to 1.67)). However, there was no significant association in the other groups with lower exposure and no clear dose response to cumulative passive smoking exposure.

CONCLUSIONS

Active smoking was associated with an increase in breast cancer risk among postmenopausal women. There was also a suggestion of an association between passive smoking and increased risk of breast cancer.

Circulating endothelial cells and circulating progenitor cells in breast cancer: relationship to endothelial damage/dysfunction/apoptosis, clinicopathologic factors, and the Nottingham Prognostic Index

BACKGROUND AND METHODS

Abnormal circulating endothelial cell (CEC) and circulating progenitor cell (CPC) numbers are present in cancer, but their relationship with angiogenesis, apoptosis, vascular biology, and prognosis is unclear. We prospectively studied 160 patients with breast cancer and 63 age-matched controls free of breast cancer, measuring CECs (CD45(-)/CD146(+)/CD34(+)) and CPCs (CD45(-)/CD133(+)/CD34(+)) by flow cytometry and plasma markers of endothelial damage/dysfunction (von Willebrand factor), apoptosis (Fas/Fas-L) and angiogenesis (vascular endothelial growth factor [VEGF], angiogenin) by ELISA. These were compared with clinicopathophysiologic features and the Nottingham Prognostic Index (NPI). An additional blood sample was taken 6 to 8 weeks after surgery from 15 women to test the effect of tumor removal.

RESULTS

CECs were significantly higher in the NPI poor prognostic group compared with moderate and good prognostic groups, and the cancer-free controls, whereas CPCs were lower in the poor prognosis group (both P < .05). Levels of von Willebrand factor, VEGF, angiogenin, and Fas-L (but not soluble Fas) were abnormal in breast cancer compared with controls (P < .05), with no relationship to prognosis groups. VEGF (P = .04) and angiogenin (P = .001) were markedly different after surgery. In multivariate analysis, vascular invasion (P < .05) and tumor size (P < .001) were independently associated with CECs. CPCs did not significantly associate with NPI in a linear regression model; age (P < .05) was a negative predictor, whereas Her-2 status (P < .05) positively predicted CPCs. After adjustment, no variable independently predicted CPC levels.

CONCLUSIONS

CECs and CPCs demonstrate a strong relationship with NPI groups, but only CECs positively predict higher NPI scores and correlate with tumor invasiveness and size, possibly reflecting total tumor vascular volume.

Smoking and the risk of breast cancer in BRCA1 and BRCA2 carriers: an update

Among women with a mutation in BRCA1 or BRCA2, the risk of breast cancer is high, but it may be modified by exogenous and endogenous factors. There is concern that exposure to carcinogens in cigarette smoke may increase the risk of cancer in mutation carriers. We conducted a matched case-control study of 2,538 cases of breast cancer among women with a BRCA1 (n = 1,920) or a BRCA2 (n = 618) mutation. One non-affected mutation carrier control was selected for each case, matched on mutation, country of birth, and year of birth. Odds ratios were calculated using conditional logistic regression, adjusted for oral contraceptive use and parity. Ever-smoking was not associated with an increased breast cancer risk among BRCA1 carriers (OR = 1.09; 95% CI 0.95-1.24) or among BRCA2 carriers (OR = 0.81; 95% CI 0.63-1.05). The result did not differ when cases were restricted to women who completed the questionnaire within two years of diagnosis. A modest, but significant increase in risk was seen among BRCA1 carriers with a past history of smoking (OR = 1.27; 95% CI 1.06-1.50), but not among current smokers (OR = 0.95; 0.81-1.12). There appears to be no increase in the risk of breast cancer associated with current smoking in BRCA1 or BRCA2 carriers. There is a possibility of an increased risk of breast cancer among BRCA1 carriers associated with past smoking. There may be different effects of carcinogens in BRCA mutation carriers, depending upon the timing of exposure.

Morbidity and mortality in relation to smoking among women and men of Chinese ethnicity: the Singapore Chinese Health Study

OBJECTIVES

We examined the association among cigarette smoking, smoking cessation and a broad range of cancer incidence and all cause and cause-specific mortality in a population-based cohort of adults of Chinese ethnicity in Singapore.

METHODS

Subjects were 61,320 participants of the Singapore Chinese Health Study (44.5% men, aged 45-74 years, recruitment from 1993-1998) who were free of cancer at the baseline examination. Main outcomes-of-interest included cancer incidence, all cause and cause-specific mortality as of December 31, 2005.

RESULTS

Cigarette smoking was positively associated with overall cancer incidence, including cancers at the following specific sites: head and neck region, upper gastrointestinal tract, hepatobiliary and pancreas cancer, lung, and bladder/renal pelvis cancer. Compared to never smokers, the relative risk (RR) (95% confidence interval [CI]) of cancer incidence (all cancer sites) among current smokers smoking >22 cigarettes/day was 1.9 (1.7-2.1), p-trend<0.0001. Similarly, cigarette smoking was associated with all cause and cause-specific mortality, including deaths due to cancer, ischemic heart disease, other heart diseases, and chronic obstructive pulmonary disease. Compared to never smokers, RR (95%CI) of all cause mortality among current smokers smoking >22 cigarettes/day was 1.8 (1.6-2.0), p-trend<0.0001. Also, relative to current smokers, ex-smokers experienced reduced cancer incidence and total mortality. The population attributable risk of smoking in men for cancer incidence as well as all-cause mortality was 23%, whereas in women it ranged from 4-5%.

CONCLUSIONS

Cigarette smoking is an important risk factor for cancer incidence and major causes of mortality in Chinese men and women of Singapore.

Cigarette smoke condensate-induced level of adenomatous polyposis coli blocks long-patch base excision repair in breast epithelial cells

Our previous studies have shown that treatment with cigarette smoke condensate (CSC) transforms normal breast epithelial cell line, MCF-10A. In the present study, the mechanism of CSC-induced transformation of breast epithelial cells was examined. We first determined whether benzo[a]pyrene (B[a]P)- and CSC-induced levels of APC are capable of inhibiting long-patch base excision repair (LP-BER) since our earlier studies had shown that an interaction of APC with DNA polymerase beta (pol-beta) blocks strand-displacement synthesis. With the use of a novel in vivo LP-BER assay, it was demonstrated that increased and decreased APC levels in different breast cancer cell lines were associated with a decrease or increase in LP-BER activity, respectively. The effect of APC on LP-BER in malignant and pre-malignant breast epithelial cell lines was produced by either overexpression or knockdown of APC. Furthermore, it was shown that the decreased LP-BER in B[a]P- or CSC-treated pre-malignant breast epithelial cells is associated with an increased level of APC and decreased cell growth. Our results suggest that the decreased growth allows cells to repair the damaged DNA before mitosis, and failure to repair damaged DNA has the potential to transform pre-malignant breast epithelial cells.

The relationship between various measures of cigarette smoking and risk of breast cancer among older women 65-79 years of age (United States)

Results from studies evaluating the relationship between cigarette smoking and breast cancer have been inconsistent. Though most studies have found that smoking does not alter risk, others have observed both increased and decreased risks associated with smoking. The reasons for these inconsistencies are unclear, but they may be related to differences in study populations, designs, and exposure definitions. In particular, this relationship may vary by age, and few studies have focused on older women many of whom have smoked for very long durations. We conducted a population-based case-control study (975 cases/1007 controls) of women 65-79 years of age in western Washington State. Women who were current smokers, smoked for > or =40 years, had > or =11 pack-years of lifetime smoking, or started smoking before their first full-term birth each had 30-40% elevated risks of breast cancer (p < 0.05). Recency, length, and intensity of smoking are all associated with modest increased risks of breast cancer. A further understanding of the timing of smoking, and its interaction with other factors, may enhance our knowledge of whether and by what mechanisms smoking alters breast cancer risk.

Breast Cancer Risk Among Women Who Start Smoking as Teenagers

Objective: To examine the effect of smoking on breast cancer risk in a large population-based cohort of women, many of whom started smoking as teenagers.

Methods: We followed 102,098 women, ages 30 to 50 years, completing a mailed questionnaire at recruitment to the Norwegian-Swedish Cohort Study in 1991/1992, through December 2000. We used Cox proportional hazard regression models to estimate relative risk (RR) of breast cancer associated with different measures of smoking initiation, duration, and intensity adjusting for confounding variables. We conducted analyses on the entire study population, among women who had smoked for at least 20 years, among nondrinkers, and separately for each country.

Results: Altogether, 1,240 women were diagnosed with incident, invasive breast cancer. Compared with never smokers, women who smoked for at least 20 years and who smoked 10 cigarettes or more daily had a RR of 1.34 (95% CI, 1.06-1.70). Likewise, those who initiated smoking prior to their first birth (1.27, 1.00-1.62), before menarche (1.39, 1.03-1.87), or before age 15 (1.48, 1.03-2.13) had an increased risk. In contrast, women who had smoked for at least 20 years, but started after their first birth, did not experience an increased breast cancer risk. The increased RR associated with smoking was observed among nondrinkers of alcohol, women with and without a family history of breast cancer, premenopausal and postmenopausal women, and in both countries.

Conclusion: Our results support the notion that women who start smoking as teenagers and continue to smoke for at least 20 years may increase their breast cancer risk.

Active and passive smoking and breast cancer risk in middle‐aged Japanese women

To examine the hypothesis that tobacco smoke is associated with the risk of female breast cancer, we estimated the relative risks of active and passive smoke in middle-aged Japanese women in a population-based prospective study. The cohort consisted of residents in 4 public health center areas, aged 40 to 59 years. A self-administered questionnaire survey was conducted in 1990. This analysis included 21,805 subjects, 180 of whom had developed breast cancer by December 31, 1999. When the reference was defined as never-active smokers without passive smoking, adjusted relative risks (RRs) were 1.9 (95% confidence interval [CI] = 1.0-3.6) in current active smokers, 1.2 (95% CI = 0.4-4.0) in ex-active smokers and 1.2 (95% CI = 0.8-1.6) in never-active smokers with passive smoking. The elevated risk for ever-smokers was clearly observed in premenopausal women at baseline (RR = 3.9, 95% CI = 1.5-9.9) but not in postmenopausal women (RR = 1.1, 95% CI = 0.5-2.5). In never-active smokers, the adjusted RR for passive smoking, residential or occupational/public tobacco smoke exposure was 1.1 (95% CI = 0.8-1.6). In premenopausal women, passive smoking increased the risk (RR = 2.6; 95% CI = 1.3-5.2) but not in postmenopausal women (RR = 0.7; 95% CI = 0.4-1.0). We conclude that tobacco smoking increases the risk of female breast cancer in premenopausal women.

Etiology of Hormone Receptor–Defined Breast Cancer: A Systematic Review of the Literature

Breast cancers classified by estrogen receptor (ER) and/or progesterone receptor (PR) expression have different clinical, pathologic, and molecular features. We examined existing evidence from the epidemiologic literature as to whether breast cancers stratified by hormone receptor status are also etiologically distinct diseases. Despite limited statistical power and nonstandardized receptor assays, in aggregate, the critically evaluated studies (n = 31) suggest that the etiology of hormone receptor–defined breast cancers may be heterogeneous. Reproduction-related exposures tended to be associated with increased risk of ER-positive but not ER-negative tumors. Nulliparity and delayed childbearing were more consistently associated with increased cancer risk for ER-positive than ER-negative tumors, and early menarche was more consistently associated with ER-positive/PR-positive than ER-negative/PR-negative tumors. Postmenopausal obesity was also more consistently associated with increased risk of hormone receptor–positive than hormone receptor–negative tumors, possibly reflecting increased estrogen synthesis in adipose stores and greater bioavailability. Published data are insufficient to suggest that exogenous estrogen use (oral contraceptives or hormone replacement therapy) increase risk of hormone-sensitive tumors. Risks associated with breast-feeding, alcohol consumption, cigarette smoking, family history of breast cancer, or premenopausal obesity did not differ by receptor status. Large population-based studies of determinants of hormone receptor–defined breast cancers defined using state-of-the-art quantitative immunostaining methods are needed to clarify the role of ER/PR expression in breast cancer etiology.

The effect of cigarette smoke exposure on pulmonary metastatic disease in a murine model of metastatic breast cancer

INTRODUCTION

Women who smoke have a higher rate of fatal breast cancer than nonsmoking women. An association between smoking and pulmonary metastases from breast cancer has been suggested by epidemiologic studies.

STUDY OBJECTIVES

To examine the relationship between exposure to cigarette smoke and pulmonary metastasis in a murine model of metastatic mammary cancer.

STUDY DESIGN

Prospective, randomized study.

SETTING

Animal research laboratory.

EXPERIMENTAL SUBJECTS

Female sexually mature BALB/cAnN mice.

INTERVENTIONS

Mice were randomly divided into experimental and control groups. Experimental animals were exposed to cigarette smoke in specialized exposure chambers, at concentrations chosen to approximate active cigarette smoking. Control animals were exposed to filtered air. One week after the initiation of exposures, mouse mammary tumor cells (tumor cell line 4526) were injected into the tail veins of experimental animals at one of three concentrations (50,000, 100,000, or 150,000 cells per 100 micro L). Three weeks later, the mice were killed, and pulmonary metastases were counted and measured.

RESULTS

The mean metastatic burden in the lungs was consistently greater for smoke-exposed animals at each concentration of cells injected (at 50,000 cells per 100 micro L, 9.8 vs 4.8 micro m(3), respectively [p < 0.01]; at 100,000 cells per 100 micro L, 34.5 vs 17.4 micro m(3), respectively [p < 0.10]; and at 150,000 cells per 100 micro L, 54.0 vs 31.5 micro m(3), respectively [p < 0.05]). This was largely attributable to a significant increase in the number of metastatic nodules per animal (at 50,000 cells per 100 micro L, 8.7 vs 4.8, respectively [p < 0.001]; at 100,000 cells per 100 micro L, 24.3 vs 14.0, respectively [p > 0.10]; and at 150,000 cells per 100 micro L, 42.0 vs 20.1, respectively [p < 0.02]) rather than to a change in nodule size.

CONCLUSIONS

Cigarette smoke exposure is associated with an increase in the total pulmonary metastatic burden in this murine model of metastatic mammary cell cancer. This study provides experimental support for an adverse effect of smoking on the metastatic process and suggests a possible mechanism for smokers' increased breast cancer mortality.

A Prospective Study of Smoking and Risk of Breast Cancer in Young Adult Women

Objective: To investigate the association between smoking and invasive breast cancers characterized by their estrogen receptor status in a large prospective study of mainly premenopausal women. Method: 112,844 women aged 25–42 years in 1989 were followed 10 years; questionnaire information on medical illnesses and risk factors was collected biennially and information on diet was collected in 1991 and 1995. During this period of follow-up (1,077,536 person-years), 1009 incident breast cancer cases were documented. Results: In the multivariate-adjusted models, smoking status was not significantly related to overall breast cancer risk: compared with never smokers, the relative risks (RRs) were 1.18 [95% confidence interval (CI) 1.02–1.36] for past smokers and 1.12 (95% CI 0.92–1.37) for current smokers. Increasing duration of smoking before the first pregnancy was associated with a greater risk of breast cancer, although little increase was seen in the highest category: compared with never smokers, RRs were 1.42 (95% CI 1.10–1.83) for 15–19 years of smoking and 1.10 (95% CI 0.80–1.52) for ≥20 years of smoking (P for trend = 0.01). Smoking was related most strongly to the risk of estrogen receptor-positive breast cancers. For women who had smoked for ≥20 years, the RR of estrogen receptor-positive cancer was 1.37 (95% CI 1.07–1.74) and the RR of estrogen receptor-negative cancer was 1.04 (95% CI 0.71–1.53). For smoking before age 15, the RRs were 1.49 (95% CI 1.03–2.17) for estrogen receptor-positive cancer and 1.19 (95% CI 0.69–2.08) for estrogen receptor-negative cancer. Conclusion: Our results suggest that longer duration of smoking may be related to the risk of estrogen receptor-positive breast cancer but possibly less so for estrogen receptor-negative breast cancer.

Active smoking, household passive smoking, and breast cancer: evidence from the California Teachers Study

BACKGROUND

There is great interest in whether exposure to tobacco smoke, a substance containing human carcinogens, may contribute to a woman's risk of developing breast cancer. To date, literature addressing this question has been mixed, and the question has seldom been examined in large prospective study designs.

METHODS

In a 1995 baseline survey, 116 544 members of the California Teachers Study (CTS) cohort, with no previous breast cancer diagnosis and living in the state at initial contact, reported their smoking status. From entry into the cohort through 2000, 2005 study participants were newly diagnosed with invasive breast cancer. We estimated hazard ratios (HRs) for breast cancer associated with several active smoking and household passive smoking variables using Cox proportional hazards models.

RESULTS

Irrespective of whether we included passive smokers in the reference category, the incidence of breast cancer among current smokers was higher than that among never smokers (HR = 1.32, 95% confidence interval [CI] = 1.10 to 1.57 relative to all never smokers; HR = 1.25, 95% CI = 1.02 to 1.53 relative to only those never smokers who were unexposed to household passive smoking). Among active smokers, breast cancer risks were statistically significantly increased, compared with all never smokers, among women who started smoking at a younger age, who began smoking at least 5 years before their first full-term pregnancy, or who had longer duration or greater intensity of smoking. Current smoking was associated with increased breast cancer risk relative to all nonsmokers in women without a family history of breast cancer but not among women with such a family history. Breast cancer risks among never smokers reporting household passive smoking exposure were not greater than those among never smokers reporting no such exposure.

CONCLUSION

Our study provides evidence that active smoking may play a role in breast cancer etiology and suggests that further research into the connection is warranted, especially with respect to genetic susceptibilities.

A null association between active or passive cigarette smoking and breast cancer risk

The effect of smoking on breast cancer risk has been null in large, well-conducted cohort studies. In a previous study, we stratified the population into active smokers, passive smokers, and never-active never-passive smokers and modeled early life cigarette smoke exposures as causal and later life cigarette smoke exposure as preventive. We observed a complex association between cigarette smoke and breast cancer risk. Using a similar design and population, this study did not confirm the earlier result. Neither ever-active smoking (adjusted odds ratio (OR) = 0.72, 95% confidence intervals (CI) 0.55-0.95) nor ever-passive smoking (adjusted OR = 0.85, 95% CI 0.63-1.1) were strongly associated with breast cancer risk compared with never-active never-passive smoking. No patterns of effects were observed in subgroup analyses.

Perceptions of risk factors for breast cancer and attitudes toward mammography among women who are current, ex- and non-smokers

Understanding risk perceptions for breast cancer among women smokers is important because smokers tend to underutilize breast cancer screening. Perceptions of the relative importance of a variety of factors which may increase breast cancer risk and the benefits/barriers of mammography, were examined among women who were current (n = 185), ex- (n = 632) and never (n = 623) smokers. Participants were a subset of women taking part in a project to increase mammography utilization among women aged 50 and over. Current smokers, but not ex-smokers, were significantly less likely than never smokers to agree that health risk behaviors most frequently seen in smokers (e.g., smoking cigarettes, high-fat diet, low intake of fruits and vegetables, physical inactivity, drinking alcohol) may increase risk for breast cancer. Current smokers, but not ex-smokers, perceived more barriers and fewer benefits of mammography, than never smokers.

Exposures in childhood, adolescence and early adulthood and breast cancer risk: a systematic review of the literature

A growing body of work indicates that exposures over the life course have important roles to play in the aetiology of breast cancer. This review synthesises the literature that has been published in the area of early life events and female breast cancer risk. The review finds some evidence, primarily from cohort studies on the relationship between birthweight and breast cancer, to suggest that in utero events are related to breast cancer risk in adulthood. Strong evidence to support a positive association between height and breast cancer exists. Postulated mechanisms for this relationship include the role of early diet in subsequent disease risk, and the influence of endogenous growth factors mediating the relationship. There is some evidence to suggest that leg length is the component of height which is generating the observed associations between height and breast cancer. There is no consistent pattern of association between relative weight in childhood or adolescence and risk of breast cancer. The evidence to suggest an association between physical activity in early life and breast cancer risk is convincing from case-control studies, but is not fully substantiated by the results of three cohort studies. There are inconsistent results regarding the association between smoking at a young age and breast cancer risk. There is little evidence for an association between passive smoking in early life and breast cancer risk. No clear association between early drinking and breast cancer risk exists. These results are discussed in relation to possible underlying mechanisms and health promotion strategies which could reduce breast cancer risk.

Cigarette smoking and breast cancer risk: a long latency period?

The association between cigarette smoking and breast cancer risk remains unclear. Few studies have examined cigarette smoking of very long duration as there may not have been a sufficient number of long-term smokers in studies conducted before the 1980s. Therefore, we examined the association between smoking and breast cancer risk using data from participants in a randomized controlled trial of screening for breast cancer involving 89,835 women aged 40-59 years at recruitment and with up to 40 years of smoking duration at that time. Women with breast cancer diagnosed through 31 December 1993 were identified by linkage to the Canadian Cancer Database. Cox proportional hazards models were used to estimate rate ratios (RRs) and 95% confidence intervals (CIs). During an average of 10.6 years of follow-up, we observed 2,552 incident cases of breast cancer. We found a positive association between cigarette smoking and breast cancer risk, driven mainly by women who had smoked for several decades and who, therefore, had commenced smoking many years earlier. Relative to never-smokers, women who had smoked 40 years or more and 20 cigarettes/day or more were at the highest risk (RR = 1.83, 95% CI 1.29-2.61); for women who had commenced smoking 40 years or more before assessment (a measure of smoking latency rather than duration and intensity), the RR was 1.22 (95% CI 0.99-1.59). Our findings suggest that smoking of very long duration and high intensity may be associated with increased risk of breast cancer.

Active and passive smoking in breast cancer: prospective results from the Nurses' Health Study

BACKGROUND

The role of active and passive smoking in breast cancer remains controversial.

METHODS

Using data collected in the prospective Nurses' Health Study, we examined the influence of active and passive smoking on the incidence of invasive breast cancer. The analysis was based on women responding to the 1982 questionnaire, which included questions on passive smoking exposure. Information on active smoking was collected in biennial questionnaires. A total of 78,206 women were followed prospectively from 1982 until June 1996.

RESULTS

Of these women, 3,140 reported a diagnosis of invasive breast cancer during follow-up. Compared with never active smoking, relative risks (RR) of breast cancer were 1.04 (95% CI = 0.94-1.15) for current active smoking and 1.09 (95% CI = 1.00-1.18) for past active smoking. The RR for regular passive exposure at work and at home was 0.90 (95% CI = 0.67-1.22). For active smoking, a modest increase in risk was confined to women who began smoking before the age of 17 (RR = 1.19; 95% CI = 1.03-1.37).

CONCLUSION

Results suggest that passive smoking is unrelated to breast cancer. However, results for active smoking are compatible with a small increase in risk when smoking is initiated at young ages.

Smoking (active and passive) and breast cancer: epidemiologic evidence up to June 2001

The first generation of studies evaluating the association between exposure to tobacco smoke and breast cancer merely compared active to nonactive smokers, with varying degrees of detail in the definition of active smoking. With rare exceptions, studies of this kind failed to show an effect of smoking on breast cancer risk. However, such analysis is probably insufficient. The most recent reports on the smoking-breast cancer connection have two characteristics. Some have separated women exposed to passive smoking from those nonexposed to either active or passive smoke. Other reports have focused on factors that modify the effect of smoking on breast cancer incidence, such as genetic markers or hormone receptors. A minority of reports combines these two characteristics. This review addresses the epidemiologic evidence for a link between smoking and breast cancer and discusses the implications of this evidence for future studies.

Breast carcinoma in situ: risk factors and screening patterns

BACKGROUND

Risk factors associated with invasive breast cancer are well documented, but those associated with breast carcinoma in situ are not well defined.

METHODS

We conducted a population-based, case-control study among female residents of Connecticut to identify risk factors for breast carcinoma in situ. Case patients, diagnosed with ductal carcinoma in situ (DCIS) (n = 875) or lobular carcinoma in situ (LCIS) (n = 123), were matched by 5-year age groups with control subjects (n = 999). Case patients were diagnosed between September 15, 1994, through March 14, 1998, and all subjects were between the ages of 20 and 79 years. Information on risk factors and cancer-screening history was collected by telephone interviews. Conditional logistic regression was used to determine odds ratios (ORs) for the association of these factors with the risk of DCIS and LCIS.

RESULTS

Case patients with DCIS were more likely than control subjects to report a family history of breast cancer (OR = 1.48; 95% confidence interval [CI] = 1.19 to 1.85) or previous breast biopsy (OR = 3.56; 95% CI = 2.86 to 4.43). They also had fewer full-term pregnancies (OR = 0.86; 95% CI = 0.80 to 0.93) and were older at first full-term pregnancy (OR for being 20-29 years old relative to being <20 years old = 1.68; 95% CI = 1.17 to 2.43) and at menopause (OR for being > or =55 years old relative to being <45 years old = 1.71; 95% CI = 1.05 to 2.77). DCIS case patients were more likely than control subjects to have had a mammographic examination (OR = 2.46; 95% CI = 1.78 to 3.40) or an annual clinical breast examination (OR = 1.83; 95% CI = 1.48 to 2.26). DCIS patients and control subjects did not differ with respect to oral contraceptive use, hormone replacement therapy, alcohol consumption or smoking history, or breast self-examination. Associations for LCIS were similar.

CONCLUSIONS

The risk factors associated with DCIS and LCIS are similar to those associated with invasive breast cancer. Diagnosis of DCIS is associated with increased mammography screening.

Cigarette smoking and the risk of pulmonary metastasis from breast cancer

STUDY OBJECTIVES

To determine whether there is an association between cigarette smoking and the development of pulmonary metastatic disease among women with breast cancer.

DESIGN

A case-control study.

SETTING

The University of California, Davis Medical Center.

PARTICIPANTS

Eighty-seven women patients with unilateral, invasive breast cancer and pulmonary metastatic disease were identified as cases, and each patient was matched with two control patients who did not have pulmonary metastatic disease. Case patients and control patients were matched for year of diagnosis, age at diagnosis, size of primary tumor, and nodal status.

DATA ANALYSIS

Multivariate analysis using conditional logistic regression was used to determine the odds of smoking among women with pulmonary metastatic disease compared to matched control patients without pulmonary metastatic disease, after correction for potential confounding factors.

RESULTS

Thirty-eight percent of the case patients vs 29% of the control patients were classified as ever-smokers; 24.1% of case patients were actively smoking at the time of breast cancer diagnosis vs 15.3% of the control patients. The unadjusted odds ratio for active smoking was 1.76 for women with pulmonary metastatic disease compared to women without pulmonary metastatic disease (p = 0.06). In the final multivariate model, the odds ratio for active smoking among women with pulmonary metastatic disease was 1.96 (p = 0.06).

CONCLUSIONS

There appears to be an association between cigarette smoking and the development of pulmonary metastatic disease among women with breast cancer. This may explain the previously noted higher breast cancer fatality rate among smokers. The relationship between smoking behavior and pulmonary metastasis from breast and other cancers warrants further investigation.

Smoking associated with hormone receptor negative breast cancer

Women who smoke have less favourable prognosis following breast-cancer diagnosis. Some studies suggest that this is due to a more advanced stage at diagnosis, on average. Our present aim was to assess whether smoking is associated with other prognostic markers as well, e.g., hormone receptor status, histopathology and tumour differentiation. The evaluation was based on 268 incident cases in a cohort of 10,902 women (35% smokers) followed for an average of 12.4 years. An immunohistochemical method on recuts of tumour tissue was used to assess hormone receptor status. One pathologist classified all tumours according to the WHO system, Nottingham grade and Nottingham Prognostic Index. The relative risk (RR) of oestrogen receptor-negative tumours was, for current smokers, 2.21 [95% confidence interval (CI) 1.23-3.96] and, for ex-smokers, 2.67 (95% CI 1.41-5.06) compared to never-smokers. Ex-smokers had an increased risk of progesterone receptor-negative tumours (RR = 1.61, 95% CI 1.07-2.41), but there were no other significant associations between smoking habits and oestrogen receptor-positive or progesterone receptor-positive or -negative tumours. The incidence of Nottingham grade III tumours was higher in ex-smokers than in never-smokers (RR = 2.03, 95% CI 1.17-3.54). In terms of histopathological type or Nottingham Prognostic Index, there were no significant differences between smoking groups. We conclude that smoking is associated with an increased occurrence of hormone receptor-negative tumours.

Breast cancer incidence in relation to smoking cessation

High plasma levels of oestrogens are associated with increased breast cancer risk. If smoking, as has been suggested, have both a tumour initiating mutagenic effect and a protective anti-oestrogenic effect, one would assume that smokers who give up smoking have the highest incidence of breast cancer. This was evaluated in the follow-up of a cohort of 10,902 women of whom 4,359 were premenopausal. Record-linkage with official cancer registries yielded 416 incident cases during an average follow-up of 13.6 years. The adjusted relative risk in all ex-smokers was 1.31 (1.02-1.69), as compared to never smokers, and in premenopausal ex-smokers it was 1.57 (1.07-2.30). Breast cancer incidence in premenopausal ex-smokers was inversely related to time since cessation, (p for trend = 0.01), and was highest among the women who had given-up smoking less than 12 months before screening: 2.76 (1.55-4.91). There was no significant association between current smoking and breast cancer risk. We conclude that incidence of breast cancer in premenopausal women who have given up smoking is higher than it is in smokers and never smokers. To what extent this may be related to endocrine effects associated with smoking cessation remains to be evaluated.

Smoking and hormone-related disorders

Through its antiestrogenic effect, cigarette smoking is linked to a variety of hormone-related disorders, both benign and malignant. Diseases that depend on this hormone for growth and development tend to be less common among smokers, such as endometrial cancer and uterine fibroids. Some normal, estrogen-dependent physiologic processes are affected by smoking, making osteoporosis and premature menopause more common among women who smoke. In other disorders, the link between sex hormone levels, cigarette smoking, and disease development is less clear.

The adverse health effects of tobacco and tobacco-related products

Tobacco use continues to occur in epidemic proportions and with it, significant morbidity and mortality. One third of smokers will die prematurely of a smoking-related disease. This article reviews the adverse health effects of tobacco use so that clinicians can be aware of the benefits patients will reap when they stop using this lethal substance.

The Nurses' Health Study: 20-year contribution to the understanding of health among women

The Nurses' Health Study was designed as a prospective follow-up study to examine relations between contraception and breast cancer. With follow-up questionnaires mailed every 2 years, investigators have added extensive details of lifestyle practices. The study, currently in its 20th year, has maintained high follow-up with > 90% of participants responding to each of the follow-up cycles since 1988. The relations between use of hormones, diet, exercise, and other lifestyle practices have been related to the development of a wide range of chronic illnesses among women. This review describes the methods used to follow up the study participants and summarizes the major findings that have been described over the first 20 years of the study. We highlight additional areas added to the study in recent years to address emerging issues in women's health. Special emphasis is placed on the recent findings from the study, including relations between weight gain and heart disease, diabetes, and mortality, the lack of relation between calcium and osteoporotic fractures, and the positive relation between postmenopausal use of hormones and risk of breast cancer.

Prognostic and aetiological relevance of 8-hydroxyguanosine in human breast carcinogenesis

In order to estimate the level of oxidative damage and its role in breast cancer, the promutagenic oxidative lesion, 8-hydroxy-2'-deoxyguanosine (8-OHdG), was determined in DNA isolated from 75 human breast tissue specimens and from normal and transformed human breast cell lines, utilising a newly developed solid-phase immunoslot blot assay. The amount of 8-OHdG was found to be 0.25 +/- 0.03 pmol/microgram in normal breast tissue from reduction mammoplasty, 0.98 +/- 0.174 pmol/microgram in benign tumours and 2.44 +/- 0.49 pmol/microgram DNA in malignant breast tissue with invasive ductal carcinoma. The malignant tissue had a statistically significant 9.76-fold higher level of 8-OHdG than normal tissue (P < 0.001, Mann-Whitney). A statistically significant 12.9-fold (P = 0.004) higher endogenous formation of 8-OHdG was also observed in cultured breast cancer cells compared with normal breast epithelial cells. In addition, a significantly elevated level (3.35-fold higher, P < 0.05) of 8-OHdG observed in oestrogen receptor-positive compared with oestrogen-negative malignant tissues, and in breast cancer cell lines (9.3-fold higher, P = 0.007) suggests a positive relationship between 8-OHdG formation and oestrogen responsiveness. The extent of 8-OHdG adducts did not show a discernible correlation with either the age or the smoking status of the patients. These results indicate that the accumulation of 8-OHdG in DNA has a predictive significance for breast cancer risk assessment and is conceivably a major contributor in the development of breast neoplasia.

Tobacco alkaloid derivatives as inhibitors of breast cancer aromatase

The inhibition of estrogen biosynthesis by the use of aromatase inhibitors is emerging as a valuable approach to breast cancer therapy. Because smoking has a profound effect on estrogen-related processes we examined the ability of tobacco constituents to suppress estrogen production by breast cancer aromatase. N-n-octanoylnornicotine and N-(4-hydroxyundecanoyl) anabasine suppressed aromatase activity in culture of two human breast cancer cell lines, MDA-MB-231 (IC50 of 310 and 20 microM, respectively) and SK-BR-3 (IC50 of 450 and approximately 2 microM, respectively). MDA-MB-231 cells induced by 250 nM dexamethasone or 1 mM (Bt)2cAMP were slightly more sensitive to both inhibitors. Kinetic analyses showed that inhibition by N-(4-hydroxyundecanoyl)anabasine is competitive with respect to androstenedione as substrate, with apparent Ki values of 0.2 microM against microsomal aromatase activity derived from both (Bt)2cAMP-induced MDA-MB-231 cells and human breast tumor tissue. The corresponding apparent Ki against human placental microsomal aromatase activity was 0.4 microM. These results indicate that acyl derivatives of nornicotine and anabasine block estrogen formation in breast tumor cells and tissue and could contribute to the decreased intra-tissue estrogen levels in women who smoke.

Mortality in relation to smoking history: 13 years' follow-up of 68,000 Norwegian men and women 35-49 years

A total of 44,290 men and 24,535 women aged 35-49 have been followed with respect to different causes of death during 13.3 years on average. A detailed history of smoking, together with other important risk factors, were recorded in a standardized way. Compared with the classical American and British studies, the excess mortality for the smokers was largely the same for the majority of causes. The exceptions were cerebrovascular mortality and suicides and accidents, which were more strongly related to smoking in this study. Furthermore, men who smoked only pipe, had nearly the same coronary heart disease mortality as men who smoked only cigarettes. The same applies to lung cancer mortality. Among men who had quit cigarette smoking, the coronary heart disease mortality decreased with time since quitting to almost the level of the never cigarette smokers after 5 years or more.

Epidemiology of breast cancer. Findings from the nurses' health study

BACKGROUND

The epidemiology of breast cancer was reviewed in the context of hormonal, hereditary, histologic, and dietary risk factors.

METHODS

Literature review.

RESULTS

Late age at menarche and early age at first birth decrease the risk of breast cancer as does an early age at menopause. These risk factors relate to the lifetime exposure of the breast tissue to ovarian hormones. Although an early first birth is associated with a transient increase in the risk of breast cancer, perhaps as a result of the breast's exposure to high levels of hormones before terminal differentiation, in older women, parity is associated with a decreased risk of breast cancer. Among postmenopausal women, obesity is associated with higher levels of estrogens and an increased risk of breast cancer. Within the strata of breast cancer stages at diagnosis, obesity is associated with increased mortality, again supporting the influence of endogenous estrogens on this disease's incidence, recurrence, and survival rates. Consistent with these relationships, current use of estrogen therapy among postmenopausal women is associated with an increased risk of breast cancer. A family history of breast cancer is associated with approximately a two-fold increase in the risk of breast cancer, and this risk is greater if the diagnosis was made when the woman's mother was young, although even a diagnosis in an older mother is associated with an increased risk in her daughters. The follow-up of women with a history of benign breast biopsy results shows that atypical hyperplasia is associated with a fourfold increase in risk compared with a biopsy specimen without proliferative changes. Atypia doubles the risk. These data support the concept of atypia as a precursor lesion for breast cancer and may warrant its use as a marker in further studies. Consistent data from retrospective and prospective studies show a positive association between moderate alcohol intake and the risk of breast cancer. This may reflect the increase in estrogen levels observed among women who consume alcohol. Data from prospective studies do not support a relationship between dietary fat intake and the risk of breast cancer either in premenopausal or postmenopausal women.

CONCLUSIONS

Few of these associations offer the potential for intervention to reduce the breast cancer risk.

Professional and consumer concerns about the environment, lifestyle, and cancer

Although it cannot be said that "everything causes cancer," our environment will never be carcinogen-free. As a result, there are many substances we come in contact with daily that could be potentially harmful to our health. Even with the growing knowledge of the mechanisms of carcinogenesis, it is difficult to single out the exact cancer-causing or -promoting effects of single substances. The confusion that exists about the environment, lifestyle, and cancer can be overwhelming for everyone. Garfinkel offered the following suggestions for health care providers to use in putting this issue into better perspective for consumers: (1) no single study of cancer risk factors should be used as a basis for writing or changing public health policy; (2) animal studies should be supportive of findings in epidemiological studies; (3) any environmental factor-cancer effect relationship should be demonstrated biologically; (4) regulatory agencies such as the EPA tend to be conservative in their interpretation of study results, and may suggest caution even when the risk of developing cancer is low; (5) regulatory agencies have been known to extrapolate future effects of carcinogen exposure from current incomplete or limited information about the carcinogen in question. With the knowledge that we do have, we must strive to take personal control over life-style factors that may cause cancer.