Principal cancers among women: breast, lung and colorectal.

The major variations in the pattern and level of cancer throughout the world reflect for the most part differences in the environment. It is generally agreed that carcinogenesis may arise as a result of chemical, physical, biologic, and genetic insults to cells. In addition, specific external factors may initiate and/or support malignant transformation, such as smoking, occupational and environmental chemicals, radiation, dietary factors, and specific viruses. Furthermore, endogenous compounds, such as steroid sex hormones, may be promoters for carcinogenesis of hormone-dependent tissue. Although some cancers seem to be related to inherited traits, research generally does not support the notion of group or inherited differences in cancer statistics. The leading causes of cancer death in females in 1991 in the United states were lung cancer (52,068), breast cancer (43,583), and colorectal cancer (29,017). According to the American Cancer Society, this year 182,000 women will be diagnosed with breast cancer, 73,900 with lung cancer, and 66,000 with colorectal cancer. Even with our knowledge about the influence of life style and environmental causes of cancer, little progress has been made. In breast cancer, only 25 to 30% can be attributed to known risk factors. Lung cancer in females, on the other hand, once a rare disease, turns out to be the leading cause of cancer death among women in industrialized countries, mostly due to smoking.