Can breast cancer be prevented?
Vatten, L.J.
Tidsskrift for den Norske Laegeforening Tidsskrift for Praktisk Medicin Ny Raekke 111(14): 1745-1748
1991
ISSN/ISBN: 0029-2001 PMID: 2063386 Document Number: 327746
In 1980, there were 570,000 cases of breast cancer in the world. In Norway, there are an average of 2000 new cases per year, and incidence had increased 50% from 1955 to 1984. About 40% of those afflicted die of the disease. Environmental, age, and reproductive factors seem to be implicated in its genesis. The rate increased almost fivefold in the course of a generation among Polish people who migrated to California from low incidence areas. It doubled among Chinese and Japanese who moved to California. The rate increases sharply up to age 50, then it levels off, thus early menopause is protective. Ovarial hormones (estrogen and progesterone) play a role in the development of preclinical tumors. Younger age at first delivery offers protection, but women who give birth to their first child after age 35 face a higher risk than nulliparas. Women with early menarche, which can be delayed by a lower caloric intake and vigorous physical activity, also face a heightened risk. Before menopause, overweight women are relatively protected, but the reverse is true after age 60. The consumption of animal fat is another risk factor, although a US study that involved 90,000 nurses did not bear this out. The Japanese increased their intake of animal fat from 10-25% from 1955-1975 without a corresponding increase in the rate of breast cancer. A vegetarian diet is nonprotective. Even the moderate consumption of alcohol increases the risk by 40% for women aged 15-30. Long-term use of oral contraceptives before birth of the first child up to age 35 increases the risk. Tamoxifen has protected women with a familial history of breast cancer who face a 3-5 fold higher risk. After menopause, its estrogenic properties promote the risk. Tamoxifen has an antitumor effect that can treat tumors clinically which are not manifested; it also lowers LDL (low density lipoprotein) and increases HDL (high density lipoprotein) cholesterol.