The Second Fifty Years Promoting Health and Preventing Disability (1992) / Chapter Skim
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Screening for Cancer
Screening for Cancer
Pages 136-156
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From page 136... ...
, and prevalence rate refers to the number of existing cases of cancer at a particular point in time E.g., 180 per 100,000 persons on Tanuary 1, 19821. Unless otherwise designated, prevalence rates include those with previously diagnosed cancer Whether or not they are free of cancer at the time of the survey)
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From page 137... ...
This methodology limits the case-control comparisons to a fraction of the total cohortfor example, all cases who died from the cancer and five times as many age-stratified controls (the remaining controls are excluded. Levels of assurance are based on whether evidence for efficacy involves the following: (1J different research designs, which may include ecologic and case-control studies, observational cohort studies, controlled nonranclomized studies, and randomized controlled trials; j2J the magnitude of the observed protective effect (e.g., an observed reduction in risk of 50 percent versus 10 percentJ; ;3J the extent of care given to collecting data on the screening modality and on the outcome {e.g., death from the cancerJ, and the extent to which covariables such as socioeconomic status and race were considered; t4J the consistency in the results across different studies; t5J supporting data on sensitivity ant!
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From page 139... ...
population may have a prevalence rate for a given cancer that is quite different from that shown in Table 9-2.) Incidence rates for colorectal cancer are about 5 to 10 percent higher in Connecticut than in remaining portions of the SEER areas; for breast cancer, they are somewhat higher in Connecticut as compared with other SEER areas.
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From page 140... ...
2. Bone pain [particularly with lung, breast, and prostate cancers I
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From page 141... ...
Long-term trencis in incidence rates since around 1950 have a more positive slope than do corresponding Tong-term trends in mortality rates for invasive breast cancer, colorectal cancer, cancer of the uterine cervix, and melanoma skin cancer.26~7i These patterns apply to the oiliest age groups as well as to younger populations.53 7i The differential patterns in incidence and mortality trends coincide with the introduction and increasing availability of breast physical exam and mammography, pap testing, physical exam of the skin, and increasing scrutiny of the large bowel using rigid sigmoidoscopy, fecal occult blood testing, and, since the 1970s, flexible sigmoidoscopy. In these studies, however, the so-called ecologic fallacy may apply because the unit of analysis is an aggregate population.
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From page 142... ...
56, for further analysis.) eFemale inhabitants of Nijmegen, Netherlands, were invited to participate in a nested study using single-view mammography as the screening modality.
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From page 143... ...
Table 9-3 is consistent with a recent independent review.28 In fact, there may be some improvement in sensitivity or specificity of breast cancer screening with age, perhaps in part related to menopause, declining estrogen stimulation, and declining benign breast disease. Independent of this feature of the screening test, its predictive value would increase with age because positive predictive value is affected by the underlying prevalence of the cancer in the population subjected to the test, and Tables 9-1 and 9-2 demonstrate the increase in cancer incidence, mortality, and prevalence that occurs with age.
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From page 144... ...
Further supporting evidence comes from three case-control studies that have shown protective effects from pap testing by a factor of 2- to 3-fold or more. Clarke and Anderson demonstrated that the relative risk of death from cervical cancer was reduced in those who had undergone prior pap testing; the overall reduction in risk was similar to or greater in magnitude than that for invasive cancer.
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From page 145... ...
Such information is relevant to determining whether arbitrary termination of cervical cancer screening in elderly persons is wise; this problem chapter. Cancer of the Colon and Rectum is discussed later in the Data on sigmoidoscopy35 36 43 6~ 75 and fecal occult blood testings demonstrate the potential of these procedures as effective screening tests for colorectal cancer.
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From page 146... ...
data fail to show a protective effect from screening, and prospective data do not support a benefit from cytology as compared with chest x-rays among smokers.73 Regarding prostate cancer, ultrasound screening of the prostate is probably a more sensitive measure than the digital rectal exam.50 Whether use of the ultrasound procedure will leac! to actual reductions in morbidity and mortality has not been fully evaluated.50 70 Prostatic antigen assays do not appear to have sufficient specificity to allow their use in screening.9 Controlled studies to account for lead-time and length bias sampling isee the next section)
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From page 147... ...
are based on whether {11 evidence comes from studies with different designs, which may include ecologic or casecontrol studies, observational cohort studies, controlled nonrandomized studies, and randomized controlled trials; (2) the extent of care given to collecting data on the screening modality and the occurrence of outcome and whether covariables were considered; {31 the consistency across different studies; and t4)
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From page 148... ...
Although data on screening for cervical cancer in women over age 50 are sparse, the Clarke and Anderson case-control studyi6 and the ecologic studies noted earlier are consistent with a strong protective effect from cervical cancer screening through age 65. Taken together, the data on these two very different epithelial cancers support the conclusion that the predictive value of screening tests in the elderly is at least as good if not better than the positive predictive values characteristic of younger age groups.
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From page 149... ...
are an interesting possibility, but they TABLE 9-6 Percentage of Persons Reporting No Prior Screening Procedures Fecal Occult Blood Testing Age Group Pap Smear Mammography Men Women White 40-49 4.3 57.7 67.6 72.7 50-59 4.2 53.7 63.1 58.1 60-69 7.7 61.4 55.1 54.1 70+ 22.6 71.8 61.4 60.4 Black 40-49 2.7 64.0 78.6 77.3 50-59 10.7 69.9 72.7 69.9 60-69 21.9 71.7 62.2 69.2 70+ 43.4 82.4 73.6 78.0 SOURCE: National Health Interview Survey, 1987.
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From page 150... ...
Initially, at least, all elderly persons should be considered candidates for physical exam of the breast and mammography, pap testing, physical exam of the skin, fecal occult blood testing and flexible sigmoidoscopy to 35 centimeters, and oral exam. The frequency of screening and the balancing of the limited screening options for this group E.g., hemoccult versus flexible sigmoidoscopy)
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From page 151... ...
mammography. Because of uncertainties regarding colorectal screening and the need to judge individually whether elderly persons should undergo fecal occult blood testing and endoscopy, education regarding screening for large bowel cancer is not recommen~lec3.
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W Does screening by "pap" smears help prevent cervical cancer?
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From page 153... ...
J Change in American Cancer Society checkup guidelines for detection of cervical cancer.
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From page 154... ...
Screening and rescreening for colorectal cancer: A controlled trial of fecal occult blood testing in 27,700 subjects. Cancer 1988; 62:645-651.
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From page 155... ...
S., et al. Efficacy of fecal occult blood screening (abstract)
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From page 156... ...
J., Andrews, M., Flehinger, B., et al. Progress report on controlled trial of fecal occult blood testing for the detection of colorectal neoplasia.
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