Use of Oral Contraceptives. Dietary Fat Intake. Alcohol Consumption.
Use of Oral Contraceptives
Soon after the approval of oral contraceptives, a number of epidemiologic studies reported on the risk of breast cancer associated with them. Oral contraceptives are widely used, and any effect on the risk of breast cancer will have important public health implications. Studies suggest that, overall, there has been no increase in the risk of breast cancer for women who had ever used oral contraceptives; however, women who had used oral contraceptives for long periods were at higher risk of premenopausal breast cancer. This was noted among women who had used oral contraceptives before their first full-term pregnancy. It will be important to determine whether this finding in a subgroup of women using oral contraceptives is confirmed, and more important, whether the risk remains at advancing age.
Another study reexamined the data from the Cancer and Steroid Hormone Study to determine whether oral contraceptive use had different effects on the risk of breast cancer at different ages at diagnosis. Among women 20-34 years of age at diagnosis, those who had ever used oral contraceptives had a slightly higher risk of breast cancer than did women of the same ages who had never used oral contraceptives. The slightly increased risk in young women is compatible with the findings of other investigators. There appear to be no data to suggest changes in the prescribing practice for the use of oral contraceptives.
Dietary Fat Intake
International differences in rates of breast cancer and the striking increase among populations migrating from low-to high-incidence areas has suggested that environmental factors, possibly dietary, influence the occurrence of breast cancer. A number of studies addressing this issue have produced conflicting results and recommendations. In a recent study, no evidence was found of a positive association between total dietary fat intake and the risk of breast cancer. There was no reduction in risk, even among women whose energy intake from fat was less than 20% of the total energy intake. It appears unlikely that a reduction in total fat consumption by women in middle age and older will substantially reduce their risk of breast cancer.
Alcohol Consumption
A number of epidemiologic studies have shown a possible relationship between moderate drinking and breast cancer. However, the benefit of decreasing alcohol consumption, if any, needs to be evaluated by considering all the potential effects of alcohol on a woman’s overall risk profile. In that connection, data have also been published suggesting that among women, light to moderate alcohol consumption is associated with a reduced mortality rate. The apparent survival advantage is largely confined to women at greater risk for coronary heart disease.
Other Factors
Approximately 10% of patients with breast cancer have a history of trauma to the breast. This trauma probably results in increased attention to the breast and the discovery of a tumor or other changes that initiate breast self-examination.
Virus-like particles have been identified in human breast milk. There is no evidence, however, that viruses are involved in breast cancer risk.
A number of histologic changes have been noted in benign fibrocystic breasts, and some have been associated with the later development of breast cancer. The College of American Pathologists has published a consensus statement indicating that there is no increased risk for breast cancer in patients with conditions such as macrocysts or microcysts, duct ectasia, fibroadenoma, mild hyperplasia, mastitis, or squamous metaplasia. There is a slight increase in risk in patients with sclerosing adenosis; biopsy-proven hyperplasia that is moderate or florid, solid or papillary; and those who had papillomas with a fibrovascular core. Finally, risk increases substantially–fourfold to fivefold–in women with biopsy-proven atypical hyperplasia or a ductal or lobular carcinoma in situ.
Pathology
The histologic patterns of breast cancers can be divided into two types: 1) carcinomas of lobular epithelial original and 2) carcinomas of ductal epithelial origin. Carcinomas of lobular epithelial origin are generally classified on the basis of invasion: lobular cancer in situ or lobular neoplasia and invasive lobular cancer. In situ lobular carcinoma is almost always diagnosed as an incidental finding after the biopsy of a dominant mass or an occult lesion. The most important features of this lesion when planning treatment include bilaterality, multicentricity, and the relatively low rate of development of subsequent infiltrating carcinoma. If after biopsy the margins are clear, a reasonable treatment plan includes biannual physical examination and annual mammography. The alternative is to recommend mastectomy, usually bilateral.
In situ ductal carcinoma, if untreated, will develop in the ipsilateral breast in approximately 50% of cases. Standard treatment has been total mastectomy with or without conventional axillary dissection. Because of the advent of conservative techniques for small, invasive cancers, there has been considerable debate about conservative treatment for in situ ductal carcinoma. The most recent trial has suggested that appropriate treatment consists of wide local excision or segmental mastectomy followed by radiation therapy.