Current Trends Smoking and Cancer

The Department of Health and Human Service's (DHHS) 1982 report to Congress on the health consequences of smoking presents a comprehensive evaluation of the relationship between cigarette smoking and cancer. It identifies cigarette smoking as the major single cause of cancer mortality in the United States (1).

Since 1937 cancer has been the second most frequent cause of death in the United States and will account for an estimated 430,000 deaths this year. The mortality rate for cancer, unlike the declining rates for other chronic diseases, has changed little over 2 decades, and that change has been a small but measurable increase. This increase in mortality has occurred in the face of remarkable improvements in survival rates associated with some cancer sites through earlier or better diagnosis and treatment. Unfortunately, however, these advances have failed to counter the increases in mortality from smoking-related cancer.

Tobacco's contribution to cancer deaths is currently estimated to be 30%. This means that 129,000 Americans are likely to die of cancer this year because of the higher overall cancer death rates for smokers as compared with nonsmokers. Cigarette smokers have total cancer death rates that are 2 times greater than those for nonsmokers. Heavy smokers (those who smoke more than 1 pack a day) have a 3-4 times greater excess risk of cancer mortality. Lung Cancer and Smoking

Cigarette smoking is the major cause of lung cancer in the United States. Lung cancer alone accounts for fully 25% of all cancer deaths in this country; it is estimated that 85% of lung-cancer cases are due to cigarette smoking. The number of lung-cancer deaths in the United States increased from 18,313 in 1950 to 90,828 in 1977.

The American Cancer Society estimates that 111,000 persons will die of lung cancer in 1982--80,000 men and 31,000 women. The lung-cancer death rate for women is currently rising faster than that for men, reflecting the more recent adoption of smoking by large numbers of women. When 5-year age-specific lung cancer mortality rates for white females are plotted by calendar year and age, the 3-dimensional graph of lung-cancer mortality (Figure 1) shows a sharp increase in recent years. If these trends continue, the lung-cancer death rate for women will soon surpass that of breast cancer, currently the leading cause of cancer mortality in women. The 5-year survival rate for lung cancer is less than 10%. This rate has not changed appreciably in over 15 years. Lung Cancer and Involuntary Exposure to Smoking

The DHHS report states that 3 epidemiologic studies examined involuntary or passive smoking and lung cancer in nonsmokers this past year. Two studies found a statistically significant correlation between involuntary smoking and lung-cancer risk in nonsmoking wives of men who smoked. The third noted a positive, but not statistically significant, association. While the nature of this association is unresolved, it does raise the concern that involuntary smoking may pose a carcinogenic risk to the nonsmoker. Cancer of the Larynx, Oral Cavity, and Esophagus

Cigarette smoking is a major cause of cancer of the larynx, oral cavity, and esophagus. Smokers have a mortality-risk ratio for laryngeal cancer at least 5 times greater than that of nonsmokers. Heavy smokers have laryngeal-cancer mortality ratios 15-30 times those for nonsmokers. In several prospective studies, mortality ratios for these types of cancer could not be calculated because all of the deaths occurred among smokers. An estimated 40,000 individuals will develop laryngeal and oral cancer, which will result in approximately 13,000 deaths this year in the United States. These types of cancers are also strongly associated with use of cigars and pipes in addition to cigarettes. All 3 forms of tobacco carry approximately the same excess relative risk of at least 5-fold. The long-term use of snuff appears to be a factor in the development of oral cancer, particularly of the cheek and gum.

This year 8,300 deaths are expected due to cancer of the esophagus; only about 4% of patients are alive 5 years after diagnosis, and most die within 6 months. Patients with this form of cancer have one of the poorest survival rates for any form of cancer. The use of alcohol in conjunction with smoking acts synergistically to increase the risk of cancer of the larynx, oral cavity, and esophagus. Cancer of the Bladder, Pancreas, and Kidney

Cigarette smoking is a contributory factor for the development of cancer of the bladder, pancreas, and kidney. The term "contributory factor" by no means excludes the possibility of a direct role of smoking in the causation of these types of cancer. The consistent demonstration of an excess risk of cancer of these sites among smokers in comparison with nonsmokers suggests that if smoking were not to exist in these populations, a measurable proportion of these diseases would not occur. Over 50,000 Americans are expected to develop bladder and kidney cancer this year; about 20,000 will die. The 5-year survival rates are approximately 50%-60%. Numerous investigators have estimated that between 30% and 40% of cases of bladder cancer are smoking related, with slightly higher estimates for males than for females.

Approximately 24,000 people will develop cancer of the pancreas this year, and there will be an estimated 22,000 deaths from pancreatic cancer. Like cancer of the lung and esophagus, pancreatic cancer is often fatal. Patients with this form of cancer have one of the poorest 5-year survival rates for any form of cancer. While few estimates are available as to the proportion of these deaths attributable to smoking, it would appear to be about 30%. Pancreatic cancer appears to be increasing at a more rapid rate than cancer of most other sites except the lung. Stomach Cancer

Cancer of the stomach has been declining as a cause of death in the United States for many years. The age-adjusted death rate for both males and females declined by 60% from 1950 through 1977. Reasons for this decline are unknown. It is estimated that there will be 24,200 new cases of stomach cancer in the United States in 1982 and 13,800 deaths.

Numerous epidemiologic studies have noted a link between smoking and cancer of the stomach. This association is smaller than that noted between smoking and other cancer sites. The nature of this association cannot be determined at this time because of a lack of supporting clinical and animal-experimentation evidence. Uterine Cervix Cancer

There is conflicting evidence on the role of smoking in the development of cancer of the uterine cervix; further studies are necessary to determine whether an association exists. Lower-Tar Cigarettes

Smokers of filtered or lower-tar cigarettes have statistically lower death rates from lung cancer than do smokers of nonfiltered or higher-tar brands. This reduced risk was also noted for laryngeal cancer. However, cancer death rates for smokers of lower-tar cigarettes were still significantly higher than those noted for nonsmokers. Cessation of Smoking

Although cigarette smoking is a cause of many forms of cancer, encouraging facts are presented in this report. Even after many years of cigarette smoking, stopping smoking reduces one's cancer risk substantially compared with that of the continuing smoker. The more years one refrains from smoking cigarettes after stopping, the greater the reduction in excess cancer risk. Fifteen years after stopping cigarette smoking, for example, a former smoker's lung-cancer risk is reduced to nearly the level observed for nonsmokers. This same reduction in cancer risk is observed for other cancer sites associated with smoking. There is no single action an individual can take to reduce the risk of cancer more effectively than to stop smoking--particularly smoking cigarettes. Reported by the Office on Smoking and Health.

Reference

1. Office on Smoking and Health. The health consequences of smoking: cancer. A report of the Surgeon General. Rockville, Md.: Public Health Service, U.S. Department of Health and Human Services, 1982. Note: Copies of the full report can be obtained by writing

to: Office on Smoking and Health, Park Building, Room 1-58, 5600 Fishers Lane, Rockville, Md. 20857.

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