Smoking and high-risk mammographic parenchymal patterns: a case-control study

Abstract

Current smoking was strongly and inversely associated with high-risk patterns, after adjustment for concomitant risk factors. Relative to never smokers, current smokers were significantly less likely to have a high-risk pattern. Similar results were obtained when the analysis was confined to postmenopausal women. Past smoking was not related to the mammographic parenchymal patterns. The overall effect in postmenopausal women lost its significance when adjusted for other risk factors for P2/DY patterns that were found to be significant in the present study, although the results are still strongly suggestive. The present data indicate that adjustment for current smoking status is important when evaluating the relationship between mammographic parenchymal pattern and breast cancer risk. They also indicate that smoking is a prominent potential confounder when analyzing effects of other risk factors such as obesity-related variables. It appears that parenchymal patterns may act as an informative biomarker of the effect of cigarette smoking on breast cancer risk. ]. There are no published studies that assessed the relationship between smoking and mammographic parenchymal patterns. ], the association between smoking habits and mammographic parenchymal patterns are examined. The full results will be published elsewhere. Study subjects were members of the EPIC cohort in Norwich who also attended the prevalence screening round at the Norwich Breast Screening Centre between November 1989 and December 1997, and were free of breast cancer at that screening. Cases were defined as women with a P2/DY Wolfe's mammographic parenchymal pattern on the prevalence screen mammograms. A total of 203 women with P2/DY patterns were identified as cases and were individually matched by date of birth (within 1 year) and date of prevalence screening (within 3 months) with 203 women with N1/P1 patterns who served as control individuals. Two views, the mediolateral and craniocaudal mammograms, of both breasts were independently reviewed by two of the authors (ES and RW) to determine the Wolfe mammographic parenchymal pattern. ]. In the present study we examined the subjects' personal history of benign breast diseases, menstrual and reproductive factors, oral contraception and hormone replacement therapy, smoking, and anthropometric information such as body mass index and waist:hip ratio. ], and were adjusted for possible confounding factors. . Cases were leaner than controls. A larger percentage of cases were nulliparous, premenopausal, current hormone replacement therapy users, had a personal history of benign breast diseases, and had had a hysterectomy. A larger proportion of controls had more than three births and were current smokers. shows the unadjusted and adjusted OR estimates for Wolfe's high-risk mammographic parenchymal patterns and smoking in the total study population and in postmenopausal women separately. Current smoking was strongly and inversely associated with high-risk patterns, after adjustment for concomitant risk factors. Relative to never smokers, current smokers were significantly less likely to have a high-risk pattern (OR 0.37, 95% CI 0.14-0.94). Similar results were obtained when the analysis was confined to postmenopausal women. Past smoking was not related to mammographic parenchymal patterns. The overall effect in postmenopausal women lost its significance when adjusted for other risk factors for P2/DY patterns that were found to be significant in the present study, although the results were still strongly suggestive. There was no interaction between cigarette smoking and body mass index. ] found a reduced risk of breast density in association with smoking, although the magnitude of the reduction was unclear. The present findings suggest that this reduction is large. ], who reported that breast cancer risk in younger women (younger than 45 years) may be reduced among current smokers who began smoking at an early age (OR 0.59, 95% CI 0.41-0.85 for age 15 years or younger) and among long-term smokers (OR 0.70, 95% CI 0.52-0.94 for those who had smoked for 21 years or more). ], however, do not support these findings. ]. The present data indicate that adjustment for current smoking status is important when evaluating the relationship between mammographic parenchymal pattern and breast cancer risk. They also indicate smoking as a prominent potential confounder when analyzing effects of other risk factors such as obesity-related variables. It seems that parenchymal patterns may act as an informative biomarker of the effect of cigarette smoking on breast cancer risk.

Introduction:

]. There are no published studies that assessed the relationship between smoking and mammographic parenchymal patterns.

Aims:

], the association between smoking habits and mammographic parenchymal patterns are examined. The full results will be published elsewhere.

Methods:

Study subjects were members of the EPIC cohort in Norwich who also attended the prevalence screening round at the Norwich Breast Screening Centre between November 1989 and December 1997, and were free of breast cancer at that screening. Cases were defined as women with a P2/DY Wolfe's mammographic parenchymal pattern on the prevalence screen mammograms. A total of 203 women with P2/DY patterns were identified as cases and were individually matched by date of birth (within 1 year) and date of prevalence screening (within 3 months) with 203 women with N1/P1 patterns who served as control individuals.

Two views, the mediolateral and craniocaudal mammograms, of both breasts were independently reviewed by two of the authors (ES and RW) to determine the Wolfe mammographic parenchymal pattern.

]. In the present study we examined the subjects' personal history of benign breast diseases, menstrual and reproductive factors, oral contraception and hormone replacement therapy, smoking, and anthropometric information such as body mass index and waist:hip ratio.

], and were adjusted for possible confounding factors.

Results:

. Cases were leaner than controls. A larger percentage of cases were nulliparous, premenopausal, current hormone replacement therapy users, had a personal history of benign breast diseases, and had had a hysterectomy. A larger proportion of controls had more than three births and were current smokers.

shows the unadjusted and adjusted OR estimates for Wolfe's high-risk mammographic parenchymal patterns and smoking in the total study population and in postmenopausal women separately. Current smoking was strongly and inversely associated with high-risk patterns, after adjustment for concomitant risk factors. Relative to never smokers, current smokers were significantly less likely to have a high-risk pattern (OR 0.37, 95% CI 0.14-0.94). Similar results were obtained when the analysis was confined to postmenopausal women. Past smoking was not related to mammographic parenchymal patterns. The overall effect in postmenopausal women lost its significance when adjusted for other risk factors for P2/DY patterns that were found to be significant in the present study, although the results were still strongly suggestive. There was no interaction between cigarette smoking and body mass index.

Discussion:

] found a reduced risk of breast density in association with smoking, although the magnitude of the reduction was unclear. The present findings suggest that this reduction is large.

], who reported that breast cancer risk in younger women (younger than 45 years) may be reduced among current smokers who began smoking at an early age (OR 0.59, 95% CI 0.41-0.85 for age 15 years or younger) and among long-term smokers (OR 0.70, 95% CI 0.52-0.94 for those who had smoked for 21 years or more).

], however, do not support these findings.

].

The present data indicate that adjustment for current smoking status is important when evaluating the relationship between mammographic parenchymal pattern and breast cancer risk. They also indicate smoking as a prominent potential confounder when analyzing effects of other risk factors such as obesity-related variables. It seems that parenchymal patterns may act as an informative biomarker of the effect of cigarette smoking on breast cancer risk.

Introduction

].

gene mutations.

].

There are no published studies that assessed the relationship between smoking and mammographic parenchymal patterns.

], the association between smoking habits and mammographic parenchymal patterns are examined. The full results will be published elsewhere.

Statistical methods

].

Results

. The mean age of cases and controls was similar (because they were matched on date of birth). Cases were leaner than controls. A larger percentage of cases were nulliparous, similar proportions of cases and controls had between one and three births, and a larger proportion of controls had more than three births. A larger proportion of cases were pre-menopausal, current hormone replacement therapy users, had a personal history of benign breast diseases, and had had a hysterectomy, whereas a larger proportion of controls were current smokers. The cases and controls were similar with respect to age at menarche and age at menopause.

=0.73 and 0.72 in the whole study population and in postmenopausal women, respectively).

Discussion

] found a reduced risk of breast density in association with smoking, although the magnitude of the reduction was unclear. Our findings suggest that this reduction is large.

], who reported that breast cancer risk in younger women (younger than 45 years) may be reduced among current smokers who began smoking at an early age (OR 0.59, 95% CI 0.41-0.85 for age 15 years or younger) and among long-term smokers (OR 0.70, 95% CI 0.52-0.94 for those who had smoked for 21 years or longer).

] do not support these findings, however.

].

= 0.15). There was no difference in time since menopause among current smokers.

These data indicate that adjustment for current smoking status is important when evaluating the relationship between mammographic parenchymal patterns and breast cancer risk. They also indicate smoking to be a prominent potential confounder when analyzing effects of other risk factors, such as obesity-related variables. It appears that parenchymal patterns may act as an informative biomarker of the effect of cigarette smoking on breast cancer risk.

Acknowledgements

We thank Anglia and Oxford Health Authority, R & D Programme for funding this study. We are most grateful to the staff of EPIC-Norfolk for their contribution to the study. We thank Dr Graham Hurst, director of the Norwich Breast Screening Unit, and all the staff of the Norwich Breast Screening Unit for their invaluable help during data collection.

Figures and Tables

Characteristics of the study population

HRT, hormone replacement therapy.

Odds ratio estimates for high-risk mammographic patterns according to smoking status

Adjusted for menopausal status, parity, hormone replacement therapy, history of benign breast diseases, body mass index and waist:hip ratio in the whole study population; adjusted for parity, hysterectomy, body mass index, and waist:hip ratio in postmenopausal women. OR, odds ratio; CI, confidence interval.

Keywords

• mammography
• screening
• smoking
• Wolfe's parenchymal patterns