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Experimental and observational findings suggest that calcium intake may protect against colorectal neoplasia. To investigate this hypothesis, we conducted a randomized, double-blind trial of colorectal adenoma recurrence. Nine hundred thirty patients with a recent history of colorectal adenomas were randomly given calcium carbonate (3 gm daily; 1200 mg elemental calcium) or placebo, with follow-up colonoscopies one and four years after the qualifying examination. The main analysis focused on new adenomas found after the first follow-up endoscopy, up to (and including) the second follow-up examination. Risk ratios of at least one recurrent adenoma and ratios of the average numbers of adenomas were calculated as measures of calcium effect. There was a lower risk of recurrent adenomas in subjects assigned calcium. Eight hundred thirty-two patients had two follow-up examinations and were included in the main analysis; the adjusted risk ratio of one or more adenomas was 0.81 (95 CI 0.67 to 0.99); the adjusted ratio of the average numbers of adenomas was 0.76 (95 CI 0.60 to 0.96). Among subjects who had at least one follow-up colonoscopy, the adjusted risk ratio of one or more recurrent adenomas was 0.85 (95 CI 0.74 to 0.98). The effect of calcium seemed independent of initial dietary fat and calcium intake. No toxicity was associated with supplementation. These findings indicate that calcium supplementation has a modest protective effect against colorectal adenomas, precursors of most colorectal cancers.

Random digit dialing is an effective method for creating a probability sample of households for telephone interviews. Epidemiologists have successfully used the technique to select controls for population-based case-control studies. However, a modified version of random digit dialing used in some institution-based studies of childhood cancer etiology involves a selection process which is biased against children from families with closely spaced births. The author discusses alternative approaches to reducing this bias in control group selection.

The survival experience of 582 women with premenopausal breast cancer was examined to determine whether prognosis was related to body size or to demographic and reproductive factors. During the follow-up period 228 patients died and 18 emigrated or were lost to follow-up. Usual body weight, reported at the time of diagnosis, was a strong predictor of survival, with a statistically significant trend towards lower survival with increasing weight. Height and obesity (Quetelet index) were not significantly related to survival, although the tallest women and the most obese women appeared to fare worst. Other characteristics of prognostic importance were disease stage and reproductive history (women who were older when their first child was born fared better). Women aged 46-50 when diagnosed also appeared more likely to survive but no clear trend with age was evident. Other characteristics of the women including social class, cigarette use and oral contraceptive use were not significantly related to survival probability.

The associations of retinol and beta-carotene plasma concentrations with eight personal variables and the use of seven classes of cardiovascular drugs were studied in over 1,750 patients with nonmelanoma skin cancer enrolled at four American study centers in a cancer prevention clinical trial. Dietary carotene and female sex were positively related to beta-carotene levels, while cigarette smoking and Quetelet index were negatively related. Use of vitamins, beta blockers, or other antihypertensive drugs were also related to beta-carotene levels, but were associated with much smaller changes in these levels. Age and use of other types of cardiovascular drugs were not associated with beta-carotene levels to a statistically significant extent. There was no statistically significant interaction of smoking and dietary carotene in predicting plasma beta-carotene levels. The multiple correlation coefficient between log plasma beta-carotene and the full model was R = 0.50. Retinol levels were positively related to male sex and use of vitamins, diuretics, beta blockers, other cardiovascular drugs, and menopausal estrogens, and negatively related to current cigarette smoking and use of nitrates. The multiple correlation coefficient between plasma retinol and the full model was R = 0.33. These findings confirm the importance of several previously reported predictors of plasma retinol and beta-carotene levels. They also identify several new predictors of these micronutrient levels.

The authors examined discrepant findings between a 1978 proportional mortality study and a 1981 cohort study of workers at the Portsmouth, New Hampshire, Naval Shipyard to determine whether the healthy worker effect, selection bias, or measurement bias could explain why only the proportional mortality study found excess cancer deaths among nuclear workers. Lower mortality from noncancer causes in nuclear workers (the healthy worker effect) partly accounted for the observed elevated cancer proportional mortality. More important, however, was measurement bias which occurred in the proportional mortality study when nuclear workers who had not died of cancer were misclassified as not being nuclear workers based on information from their next of kin, thereby creating a spurious association. Although the proportional mortality study was based on a small sample of all deaths occurring in the cohort, selection bias did not contribute materially to the discrepant results for total cancer deaths. With regard to leukemia, misclassification of occupation in the proportional mortality study and disagreement about cause of death accounted for some of the reported excess deaths.

Background: Epidemiological studies have indicated that aspirin consumption can lower the risk of large-bowel cancer. These studies are not entirely consistent, however, and their interpretation has been complicated by the possibility that cancer symptoms may have led patients to avoid aspirin or that aspirin may have influenced cancer diagnosis and treatment. Purpose: Our purpose was to determine the effect of aspirin on risk of large-bowel neoplasms in a study in which aspirin use would not be expected to affect tumor detection and tumor-related symptoms would not likely influence aspirin use. A less complicated assessment of the relationship between aspirin and large-bowel tumors should thus be possible. Methods: We studied 793 patients enrolled in a clinical trial of nutrient supplements to prevent large-bowel adenomas. Unlike invasive cancers, adenomas usually do not cause symptoms or detectable gastrointestinal bleeding; thus, adenomas are unlikely to influence aspirin use. Each patient had at least one large-bowel adenoma diagnosed and removed shortly before study entry and had been judged to be free of further tumors by colonoscopy. Use of aspirin was assessed by responses on questionnaires administered 6 and 12 months after enrollment. We performed complete colonoscopies on all patients 1 year after they entered the study and removed all polyps. Results: Patients who reported taking aspirin on both questionnaires (consistent users) had a lower risk of new adenomas at their 1-year follow-up colonoscopy (odds ratio = 0.52; 95% confidence interval = 0.31–0.89) compared with patients who did not report using aspirin on either of the questionnaires. The apparent protective effect of consistent aspirin use was present among both men and women and did not appear to be influenced by the number of prior adenomas. Conclusions: These data further support the hypothesis that aspirin has an antineoplastic effect in the large bowel. Nevertheless, the question of whether aspirin should be used to prevent large-bowel tumors would be best answered by a randomized controlled clinical trial specifically designed to address this issue. (J Natl Cancer Inst 85:912–916, 1993)