Risks of Cancer

As part of the drive to improve cancer detection, 90 leading scientists met 14 months ago in Key Biscayne, Fla., under the auspices of the National Cancer Institute and the American Cancer Society, to identify individuals and groups who are most susceptible to cancer. Last week, in a 544-page volume titled Persons at High Risk of Cancer (Academic Press), they published their conclusions. They found that the occurrence of cancer seems to be influenced by a large variety of factors that fall into three broad categories:

ENVIRONMENT. A mass of evidence indicates that the incidence of certain types of cancer--lung, liver and bladder, for example--is markedly higher for workers in such "dirty" industries as chemicals, mining and asbestos processing (TIME, Oct. 20). Cancer may also be linked with more elusive agents, including the level of radiation and the amount of sunlight in a given region. Some statistics are already available to support this thesis. Melanoma, a form of skin cancer, seems more prevalent in the sunny U.S. South, for example, than in the North. Man-made chemicals and pollutants in water, air and food have already been indicted in some kinds of cancer and are suspect in many more. Even so, the researchers pointed out that the work in this area is only beginning. Said Dr. Brian MacMahon of the Harvard School of Public Health: "Environmental causes of cancer must be far more numerous than those [already] identified."

LIFESTYLE. While such personal habits as smoking and drinking alcohol have long been linked with cancer, the researchers noted an intriguing new finding: for people who both drink and smoke, the risk of cancer appears to rise proportionately higher than for those who do only one of these things. The report also implicates diet; for example, the incidence of bowel cancer seems to increase with the amount of meat and fatty foods consumed. Cancer may also be linked with dietary deficiencies; one researcher pointed out that an absence of vitamin A may contribute to the development of several kinds of cancer, including cancer of the salivary glands. Finally, the specialists noted, there may be a connection between genital cancer and lifestyle. For example, cancer of the penis occurs more commonly in regions where circumcision and bodily cleanliness are not practiced, while cervical cancer seems higher among women who are sexually promiscuous.

HEREDITY. The researchers agreed that heredity may be at least as important as any other factor in causing cancer. Indeed, as long ago as the 17th century, doctors noticed that a predisposition to cancer seems to run in certain families. Nonetheless, the researchers conceded that despite great progress in unraveling the workings of the cell's DNA--the molecule of heredity--the genetic tendency toward cancer remains one of medicine's major mysteries.

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