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Sigmoidoscopy and mortality from colorectal cancer: The Kaiser permanente multiphasic evaluation study
AMERICAN
SOCIETY OF PREVENTIVE
ONCOLOGY
ABSTRACTS
281
more-often-reported increased risk for right-sided colon cancer in women (odds ratio 1.1, 95% contidence limits 0.8, I .6). The discrepant results from several studies (l-5) need explanation. Many persons with gallstones do not undergo cholecystectomy. We propose that a propensity among either patients or care providers to pursue diagnosis and treatment of abdominal symptoms aggressively may explain the apparent association in some settings. This could be tested in studies showing the association by restricting attention to fatal cases of cancer.
REFERENCES I. Abrams, J. S., Anton, J. R., and Dreyfuss, D. C. The absence of a relationship between cholecystectomy and the subsequent occurrence of cancer of the proximal colon. Dis. Co/on Rectum 26, 141-144 (1983). 2. Adami, H.-O., Meireik, O., Gustavsson, S., Nyren, O., and Krusemo, U.-B. Colorectal cancer after cholecystectomy: Absence of risk increase within 1l- 14 years. Gastroenterology 85, 859-865 (1983). 3. Linos, D. A., Beard, C. M., O’Fallon, W. M., Dockerty, M. B., Beart, R. W., Jr., and Kurland, L. T. Cholecystectomy and carcinoma of the colon. Lancer 2, 379-381 (1981). 4. Moorehead, R. J., Kernohan, R. M., Patterson, C. C., McKelvey, S. T. D., and Parks, T. G. Does cholecystectomy predispose to colorectal cancer? A case control study. Dis. Colon Rectum
29, 36-38
(1986).
5. Vernick, L. J., and Kuller, L. H. Cholecystectomy and right-sided colon cancer: An epidemiological study. Lance? 2, 381-383 (1981).
13. Sigmoidoscopy uation Study.
and Mortulity
from
Colorectal
Cancer:
The Kaiser
Permanente
Multiphasic
Eval-
JOE V. SELBY, M.D., M.P.H., AND GARY D. FRIEDMAN, M.D., M.S., Division of Research, Kaiser Permanente Medical Care Program, 3451 Piedmont Avenue, Oakland, California 94611.
The Kaiser Permanente Multiphasic Evaluation Study (2,4) is often cited as evidence that screening sigmoidoscopy lowers mortality from colorectal cancer (1, 3). Because previous reports have not clearly established that sigmoidoscopy was the effective agent in reducing study group mortality, we reviewed the 1 IO incident cases of colorectal cancer occurring in the cohort from randomization in 1965 through 1982 for tumor location, stage, mode of discovery, and present mortality status. We also reanalyzed chart review data for each cohort member for the years 1965- 1974 to determine exposure to sigmoidoscopy among study and control group members. Study group members had both a lower incidence (P = 0. IO) and a better stage distribution (P = 0.01) than control group members for tumors within reach of the sigmoidoscope. However, chart review data showed that only 25% of study group members were ever exposed to a screening sigmoidoscopy compared with 18% of controls. This small difference does not explain the study group’s improved stage distribution or lower mortality. No difference between groups was found in the rate of removal of colorectal polyps. The Multiphasic Evaluation Study was not designed to evaluate the effectiveness of screening sigmoidoscopy, and its results should not be used for this purpose.
REFERENCES 1. Crespi, M., Weissman, G. D., Gilbertsen, V. A., Winawer, S. J., and Sherlock, P. The role of proctosigmoidoscopy in screening for colorectal neoplasia. Ca Cancer J. Phys. 34, 158- 165 (1984). 2. Dales, L. G., Friedman, G. D., and Cohen, M. F. Evaluating periodic multiphasic health checkups: A controlled trial. J. Chronic Dis. 32, 385-404 (1979). 3. Eddy, D. Guidelines for the cancer-related checkup: Recommendations and rationale. Ca Cancer J. Phys. 30, 194-240 (1980). 4. Friedman, G. D., Cohen, M. F., and Fireman, B. H. Multiphasic health checkup evaluation: A 16-year follow-up. J. Chronic Dis. 39, 453-436 (1986).
SOCIETY OF PREVENTIVE
ONCOLOGY
ABSTRACTS
281
more-often-reported increased risk for right-sided colon cancer in women (odds ratio 1.1, 95% contidence limits 0.8, I .6). The discrepant results from several studies (l-5) need explanation. Many persons with gallstones do not undergo cholecystectomy. We propose that a propensity among either patients or care providers to pursue diagnosis and treatment of abdominal symptoms aggressively may explain the apparent association in some settings. This could be tested in studies showing the association by restricting attention to fatal cases of cancer.
REFERENCES I. Abrams, J. S., Anton, J. R., and Dreyfuss, D. C. The absence of a relationship between cholecystectomy and the subsequent occurrence of cancer of the proximal colon. Dis. Co/on Rectum 26, 141-144 (1983). 2. Adami, H.-O., Meireik, O., Gustavsson, S., Nyren, O., and Krusemo, U.-B. Colorectal cancer after cholecystectomy: Absence of risk increase within 1l- 14 years. Gastroenterology 85, 859-865 (1983). 3. Linos, D. A., Beard, C. M., O’Fallon, W. M., Dockerty, M. B., Beart, R. W., Jr., and Kurland, L. T. Cholecystectomy and carcinoma of the colon. Lancer 2, 379-381 (1981). 4. Moorehead, R. J., Kernohan, R. M., Patterson, C. C., McKelvey, S. T. D., and Parks, T. G. Does cholecystectomy predispose to colorectal cancer? A case control study. Dis. Colon Rectum
29, 36-38
(1986).
5. Vernick, L. J., and Kuller, L. H. Cholecystectomy and right-sided colon cancer: An epidemiological study. Lance? 2, 381-383 (1981).
13. Sigmoidoscopy uation Study.
and Mortulity
from
Colorectal
Cancer:
The Kaiser
Permanente
Multiphasic
Eval-
JOE V. SELBY, M.D., M.P.H., AND GARY D. FRIEDMAN, M.D., M.S., Division of Research, Kaiser Permanente Medical Care Program, 3451 Piedmont Avenue, Oakland, California 94611.
The Kaiser Permanente Multiphasic Evaluation Study (2,4) is often cited as evidence that screening sigmoidoscopy lowers mortality from colorectal cancer (1, 3). Because previous reports have not clearly established that sigmoidoscopy was the effective agent in reducing study group mortality, we reviewed the 1 IO incident cases of colorectal cancer occurring in the cohort from randomization in 1965 through 1982 for tumor location, stage, mode of discovery, and present mortality status. We also reanalyzed chart review data for each cohort member for the years 1965- 1974 to determine exposure to sigmoidoscopy among study and control group members. Study group members had both a lower incidence (P = 0. IO) and a better stage distribution (P = 0.01) than control group members for tumors within reach of the sigmoidoscope. However, chart review data showed that only 25% of study group members were ever exposed to a screening sigmoidoscopy compared with 18% of controls. This small difference does not explain the study group’s improved stage distribution or lower mortality. No difference between groups was found in the rate of removal of colorectal polyps. The Multiphasic Evaluation Study was not designed to evaluate the effectiveness of screening sigmoidoscopy, and its results should not be used for this purpose.
REFERENCES 1. Crespi, M., Weissman, G. D., Gilbertsen, V. A., Winawer, S. J., and Sherlock, P. The role of proctosigmoidoscopy in screening for colorectal neoplasia. Ca Cancer J. Phys. 34, 158- 165 (1984). 2. Dales, L. G., Friedman, G. D., and Cohen, M. F. Evaluating periodic multiphasic health checkups: A controlled trial. J. Chronic Dis. 32, 385-404 (1979). 3. Eddy, D. Guidelines for the cancer-related checkup: Recommendations and rationale. Ca Cancer J. Phys. 30, 194-240 (1980). 4. Friedman, G. D., Cohen, M. F., and Fireman, B. H. Multiphasic health checkup evaluation: A 16-year follow-up. J. Chronic Dis. 39, 453-436 (1986).