75
PRIMARY PREVENTION OF CANCER* PHILIP COLE, M.D. Associate Professor, Department of Epidemiology Harvard University School of Public Health Boston, Mass.
THE brochure announcing this conference asserts that the health of persons in developed countries has improved greatly in the last 200 years. It is also implied that this is due primarily to the development and application of preventive measures. These assertions are correct but, in part at least, they leave a false impression. A somewhat less optimistic picture emerges from Table I. During the last 70 years there has been a steady improvement, totalling 40%, in life expectancy at birth. This is primarily due to increased control over the environment, mainly through improvement in water and sewage treatment and nutrition. However, the table shows that there has been little improvement in the life expectancy of adults, especially during the last 30 years. Adults, of course, die from diseases not known to be infectious, such as cancer, for which control measures are unknown or, like antismoking campaigns, ineffective. Table II gives an idea of one burden imposed upon men in the United States as a result of cancer. The major burdens of costs and morbidity are not shown. Each year cancer kills about i8,ooo men and about the same number of women, comprising about i6% of all deaths. Nearly 2.5 million man-years of life are lost each year, about one half of which are below age 6o. If cancer were eliminated as a cause of death, the average life expectancy would increase 1.4 years for men and 2.I years for women.' However, these figures leave a somewhat erroneous impression since they are averages; only one of six people die from cancer. If cancer were eliminated as a cause of death, one person in six would live about io.8 years longer. If we could eliminate cigarette smoking, which accounts for about 85% of lung *Presented in a panel, Strategies for Prevention: Cancer and Heart Disease, as part of the 1974 Annual Health Conference of the New York Academy of Medicine, Prevention and Health Maintenance Revisited, April 25 and 26, 1974. This research was supported wholly by Faculty Research Award PRA No. 115 from the American Cancer Society, New York, N. Y.
Vol. 51, No. 1, January 1975
76
6
P.- COLE
.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
7P
COLE
TABLE I. AVERAGE YEARS OF LIFE REMAINING BY AGE AND TIME PERIOD FOR WHITE MALES IN THE UNITED STATES
Increase Age
1900
1940
1950
1960
1968
Years
%
0 40 65
48.2 27.7 11.5
62.8 30.0 12.1
66.3 31.2 12.8
67.6 31.7 13.0
67.5 31.6 12.8
19.3 3.9 1.3
40 14 11
TABLE II. YEARS LOST* FROM ALL MALIGNANT NEOPLASMS AMONG MALES IN THE UNITED STATES IN 1968 BY AGE GROUP
Age group 0-14 15-29 30-44 45-59 60-74 75+ Total
Average remaining years of life
61.6 47.4 33.8 21.2 11.7 5.9
Deaths
2,175 2,515 7,292
38,754 77,684 45,245 173,665
Total years lost
134,464 119,133 233,475 786,662 914,521 287,609 2,475,864
*Based upon average life expectancy for each age group at time of death.
cancer, there would be a 20% reduction in deaths from cancer. Nothing else that we now know could have a comparable impact on mortality. Taken together, this information suggests that we have accomplished little in the control of chronic diseases and that, as is true of vascular diseases, the control of cancer would be a rewarding accom-
plishment. Before we can eliminate cancer or any disease, all who are interested in preventive medicine should not only become more familiar with, but should actually use certain straightforward epidemiologic measures. If we have reason to believe, for example, that a particular exposure causes a certain cancer we should first ask ourselves, "Approximately what proportion of this cancer is likely to be caused by this exposure?" How can we intelligently discuss and plan programs for the prevention of cancer unless we have some idea of what we can hope to accomplish with a specific approach? To this end I shall Bull. N. Y. Acad. Med.
77
PRIMARY PREVENTION OF CANCER TABLE III. DATA DISPLAY FOR AN EPIDEMIOLOGIC STUDY
Exposed Not exposed Total
Diseased
Not diseased
Total
a c
b d
a+b
a+c
b + d
c+ d N
Relative risk = (a/a + b) / (c/c + d) Risk ratio (RR) ad/bc (rare disease)
TABLE IV. TONSILLECTOMY STATUS OF PERSONS WITH HODGKIN'S DISEASE AND THEIR SIBLING CONTROLS. CONVENTIONAL ANALYSIS*
Patients
Siblings
165 90 With tonsillectomy 307 84 Without tonsillectomy 472 174 Total p
PRIMARY PREVENTION OF CANCER* PHILIP COLE, M.D. Associate Professor, Department of Epidemiology Harvard University School of Public Health Boston, Mass.
THE brochure announcing this conference asserts that the health of persons in developed countries has improved greatly in the last 200 years. It is also implied that this is due primarily to the development and application of preventive measures. These assertions are correct but, in part at least, they leave a false impression. A somewhat less optimistic picture emerges from Table I. During the last 70 years there has been a steady improvement, totalling 40%, in life expectancy at birth. This is primarily due to increased control over the environment, mainly through improvement in water and sewage treatment and nutrition. However, the table shows that there has been little improvement in the life expectancy of adults, especially during the last 30 years. Adults, of course, die from diseases not known to be infectious, such as cancer, for which control measures are unknown or, like antismoking campaigns, ineffective. Table II gives an idea of one burden imposed upon men in the United States as a result of cancer. The major burdens of costs and morbidity are not shown. Each year cancer kills about i8,ooo men and about the same number of women, comprising about i6% of all deaths. Nearly 2.5 million man-years of life are lost each year, about one half of which are below age 6o. If cancer were eliminated as a cause of death, the average life expectancy would increase 1.4 years for men and 2.I years for women.' However, these figures leave a somewhat erroneous impression since they are averages; only one of six people die from cancer. If cancer were eliminated as a cause of death, one person in six would live about io.8 years longer. If we could eliminate cigarette smoking, which accounts for about 85% of lung *Presented in a panel, Strategies for Prevention: Cancer and Heart Disease, as part of the 1974 Annual Health Conference of the New York Academy of Medicine, Prevention and Health Maintenance Revisited, April 25 and 26, 1974. This research was supported wholly by Faculty Research Award PRA No. 115 from the American Cancer Society, New York, N. Y.
Vol. 51, No. 1, January 1975
76
6
P.- COLE
.~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
7P
COLE
TABLE I. AVERAGE YEARS OF LIFE REMAINING BY AGE AND TIME PERIOD FOR WHITE MALES IN THE UNITED STATES
Increase Age
1900
1940
1950
1960
1968
Years
%
0 40 65
48.2 27.7 11.5
62.8 30.0 12.1
66.3 31.2 12.8
67.6 31.7 13.0
67.5 31.6 12.8
19.3 3.9 1.3
40 14 11
TABLE II. YEARS LOST* FROM ALL MALIGNANT NEOPLASMS AMONG MALES IN THE UNITED STATES IN 1968 BY AGE GROUP
Age group 0-14 15-29 30-44 45-59 60-74 75+ Total
Average remaining years of life
61.6 47.4 33.8 21.2 11.7 5.9
Deaths
2,175 2,515 7,292
38,754 77,684 45,245 173,665
Total years lost
134,464 119,133 233,475 786,662 914,521 287,609 2,475,864
*Based upon average life expectancy for each age group at time of death.
cancer, there would be a 20% reduction in deaths from cancer. Nothing else that we now know could have a comparable impact on mortality. Taken together, this information suggests that we have accomplished little in the control of chronic diseases and that, as is true of vascular diseases, the control of cancer would be a rewarding accom-
plishment. Before we can eliminate cancer or any disease, all who are interested in preventive medicine should not only become more familiar with, but should actually use certain straightforward epidemiologic measures. If we have reason to believe, for example, that a particular exposure causes a certain cancer we should first ask ourselves, "Approximately what proportion of this cancer is likely to be caused by this exposure?" How can we intelligently discuss and plan programs for the prevention of cancer unless we have some idea of what we can hope to accomplish with a specific approach? To this end I shall Bull. N. Y. Acad. Med.
77
PRIMARY PREVENTION OF CANCER TABLE III. DATA DISPLAY FOR AN EPIDEMIOLOGIC STUDY
Exposed Not exposed Total
Diseased
Not diseased
Total
a c
b d
a+b
a+c
b + d
c+ d N
Relative risk = (a/a + b) / (c/c + d) Risk ratio (RR) ad/bc (rare disease)
TABLE IV. TONSILLECTOMY STATUS OF PERSONS WITH HODGKIN'S DISEASE AND THEIR SIBLING CONTROLS. CONVENTIONAL ANALYSIS*
Patients
Siblings
165 90 With tonsillectomy 307 84 Without tonsillectomy 472 174 Total p
