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Page 320
| Reproductive Factors |
| Early menarche. Women with an early menarche (before age twelve) compared to woman whose menarche occurred after age thirteen have a fourfold increase in breast cancer risk. A longer menstrual cycle seems to give an overall reduced risk. 26 |
| Not breast-feeding. This risk factor is attributed to the fact that lactation delays ovulation, which causes a woman to have a lower estrogen exposure over her lifetime. Having a first child before the age of twenty lowers this risk by half.27,28 |
| Late menopause. The body is exposed to estrogen for a longer period of time. |
| No pregnancies. Pregnancy brings with it an increase in estriol, an anti-cancer fraction of estrogen. |
| Environmental Factors |
| Electromagnetic fields. Exposure to electromagnetic fields can decrease production of melatonin by the pineal gland. Melatonin has been shown to suppress mammary tumorigenesis in experimental animals.29 |
| Environmental toxins. Exposure to environmental toxins, such as pesticides, hydrocarbons, PCBs, and DDT, are risk factors for breast cancer. I believe environmental chemical contamination is an important etiological factor in breast cancer that has been greatly understated. Studies have shown that exposure to PCBs and DDE, the major metabolite of DDT, are associated with breast cancer risk in women. In one study, a fourfold increase in the risk of breast cancer was demonstrated when serum DDE levels increased from 2.0 ng/ml to 191 ng/ml.30,31 Environmental chemical compounds that accumulate and remain in human adipose tissue reach levels two to three hundred times higher than those observed in serum. In breast cancer cells, DDT causes proliferation by itself and also enhances proliferation in collaboration with estradiol. Other examples of estrogen-mimicking (xenoestrogenic) chemicals that tend to accumulate in the body include kepone, dieldrin, methoxychlor, alkyl phenols, and bisphenol-A.32,33 |
| Fission products. Low doses of radiation that are released from nuclear power plants result in the appearance of fission products in our food supply.34 Radiation causes genetic damage, which increases the overall risk for breast cancer. It is now known that radiation causes mutation of the important p53 suppressor gene. For this reason, I do not recommend postlumpectomy radi- |
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