Diet and cancer of the colon and rectum: a case-control study in China

A case-control study was carried out in Harbin city to assess the role of diet in the aetiology of colorectal cancer. A total of 336 incident cases of histologically confirmed colorectal cancer (111 colon cancer and 225 rectal cancer) and an equal number of controls with other non-neoplastic diseases were interviewed in hospital wards. Data concerning the average frequency of consumption and amount consumed of single food items were obtained by a dietary history questionnaire. Odds ratios and their confidence limits were computed. Multiple regression for risk status was also used. Vegetables, particularly green vegetables, chives and celery, have a strong protective effect against colorectal cancer. Reduced consumption of meat, eggs, bean products and grain was associated with increasing risk for cancer of the rectum. Alcohol intake was found to be an important risk factor for developing colon cancer and male rectal cancer.

A hypothesis: nonsteroidal anti-inflammatory drugs reduce the incidence of large-bowel cancer

Nonsteroidal anti-inflammatory drugs (NSAIDs) inhibit prostaglandin synthesis and tumor growth in the rodent colon. We assessed NSAID use in relation to risk of human large-bowel cancer in a hospital-based, case-control study of 1326 patients with colorectal cancer and 4891 control patients. For regular NSAID use that continued into the year before interview, the multivariate relative risk estimate was 0.5 (95% confidence interval, 0.4 to 0.8); the estimate decreased as the duration of use increased, but the trend was not statistically significant. Similar results were obtained whether cancer or non-cancer controls were used, and the inverse association was apparent for both colon cancer and rectal cancer in men and women and in subjects younger and older than 60 years. Regular NSAID use that had been discontinued at least 1 year previously and non-regular use were not associated with risk. Almost all regular NSAID use was of aspirin-containing drugs. The present data suggest that the sustained use of NSAIDs reduces the incidence of human large-bowel cancer.

Is there a preference for different ways of performing faecal occult blood tests?

Low compliance with faecal occult blood screening reduces the power of clinical trials, potential benefit, and efficiency. It has been proposed that the faecal manipulation required to perform conventional guaiac based tests may be an important factor in low compliance. The aim of this study was to evaluate whether use of a new method (vehicle) of stool collection for the faecal occult blood guaiac test would be preferred to the established standard. A novel self-interpreted test, Early Detector (ED), requires the subject to apply a guaiac/peroxide spray to a stool sample collected simply by wiping the anus with a specimen pad. To determine whether this method would be preferred to the stool manipulation required by Haemoccult (HO) and to compare test validity, employees at a London company were invited to use both tests. Eight-hundred and fifty-seven subjects were shown both tests. Before use, 48% indicated a preference for the method of Early Detector; 24% chose Haemoccult (p less than 0.001), while 28% indicated no immediate preference. Seven-hundred and one performed both tests. After use, 74% preferred ED; 5% preferred HO (p less than 0.001); 21% had no preference (NP). The preference for the ED test method was consistent by sex categories, age groups and occupational class. Logistics, aesthetics, and immediacy of results were the main reasons indicated for choosing ED. Whether the preference for ED could result in higher compliance remains to be proven. Its high positivity (14%), however, would preclude its use as a sole test to determine the need for endoscopic and/or radiologic investigation in the screened patient.

Results of a work-site educational and screening program for hypertension and cancer

Cardiovascular disease and cancer account for 68% of deaths in the United States each year. Office-based screening efforts to detect early or asymptomatic disease have been modestly successful at best, as neither patients nor physicians routinely follow American Cancer Society guidelines. The work site, representing a captive group of patients, is an alternative screening site. Eight hundred eighty-eight employees at 10 work sites were screened for hypertension and six types of cancer (oral, breast, rectal, colon, prostate, and testicular). Fifty-one employees with new onset or poorly controlled hypertension were identified, along with two early cancers (rectal, breast) and four malignant precursors. Potential dollar savings to employee, employer, and society were three times the cost of the screening program. Screening at the work site represents an efficient, cost-effective approach for the early detection of hypertension and cancer.

Colorectal cancer prevention. In search of risk factors and increased effectiveness of surveillance programs

The increasing incidence of colorectal cancer has emphasized the need for tools for the detection of polyps at risk of cancer or detection of malignant tumors in a more favorable stage. So far, no general prognostic risk factors are known which enable the diagnosis of cancer on the basis of simple tests or clinical symptoms. We know, however, that the prevalence of cancer and adenomas is age-related, with the highest incidence between 65 and 80 years. This should enable us to perform endoscopic screening programs on selected age groups to detect the malignant lesions at an earlier stage or to prevent the development of malignancy by removal of large polyps. Such screening programs should be performed in a controlled manner, to verify the impact of endoscopy on the prognosis and incidence of colorectal cancer. Meanwhile, the endoscopic surveillance of polyp-bearing patients will have to be conducted in accordance with the calculated risk of malignancy. Our increasing knowledge of risk factors in adenomas has, so far, allowed us to perform endoscopic controls of these patients less frequently than 10 years ago. For the future we hope to be able to select the high-risk individuals and adenomas for treatment, which in turn will enable us to ignore the majority of adenomas, which will definitely not undergo malignant transformation.

The effect of iron on experimental colorectal carcinogenesis

The effect of parenteral and oral iron was examined in the rat 1,2 dimethylhydrazine (DMH) colorectal carcinogenesis model in a series of experiments. Parenteral supplementation of iron was found to augment tumor yield (p = 0.012) and oral iron was found to augment tumor incidence (p = 0.03, when control groups were combined). In addition, phytic acid, a significant component of dietary fiber was found to reverse the augmenting effect of oral iron on tumor yield and incidence (p = 0.09 for both). Furthermore, in a short term DMH nuclear toxicity assay, analysis of the karyorrhectic index (KI), there was no difference in the KI between oral iron and phytate dietary groups (p = 0.53 for the left colon and p = 0.2 for the right colon), implying that iron's effect on colorectal tumor induction takes place during the promotional phase of carcinogenesis and not during initiation. These experiments support the epidemiologic observation that dietary iron may augment colorectal cancer risk and that the mechanism by which dietary fiber diminishes colorectal cancer risk may be the chelation of dietary iron by the phytic acid component of dietary fiber.

Some points of interest in the management of rectal cancer

The author presents the surgeon's viewpoint in the management of rectal cancer outlining the possible contribution of early detection, precise pre-operative evaluation of the tumour extension and the necessity to provide a form of curative and radical treatment while given the best possible quality of life.

Screening for large bowel cancer

Is there a need for yet another screening process to be applied in general practice with all the consequent costs in terms of materials, doctors' time and patient anxieties? What is the evidence for and against screening for colorectal cancer?

Value of a risk questionnaire in screening for colorectal neoplasm

The value of a postal questionnaire and of Hemoccult II (Smith Klein Diagnostic Inc., Sunnyvale, California, USA) testing in screening for colorectal neoplasms was compared. In the questionnaire, the subjects were asked about previous treatment for colorectal neoplasm and rectal bleeding during the previous 6 months, specified as to type. All participants were asked to perform Hemoccult II blood testing over 3 days. Of 13,759 randomly selected subjects 9040 (66 per cent) performed the test and returned the questionnaire. Three hundred and fifty-four subjects with a positive Hemoccult II test and/or a proven previous colorectal neoplasm had a full assessment including double-contrast enema and rectosigmoidoscopy to 60 cm. Eighteen carcinomas and 61 adenomas were thus diagnosed. The population was followed for from 20 to 29 months, during which time rescreening was undertaken. An additional 34 subjects with carcinomas and 90 with adenomas were identified during this period. A significant correlation between the presence of a colorectal neoplasm and a previous history of colorectal neoplasm, a positive Hemoccult II and a previous history of bright red bleeding but not dark bleeding was found. The possibility of diagnosing a neoplasm was two, four and 19 times higher in a subject with a previous history of bleeding, a history of colorectal neoplasm, or a positive Hemoccult II respectively. Screening by faecal occult blood testing, therefore, at the moment seems to be the best and only practicable method.

Inositol hexaphosphate inhibits large intestinal cancer in F344 rats 5 months after induction by azoxymethane

A treatment regimen of 2% Na-InsP6 in drinking water was effective in significantly reducing large intestinal cancer in F344 rats even when the treatment was begun 5 months after carcinogenic induction with azoxymethane (AOM 8 mg/kg/wk X 6). Compared to untreated (AOM-only) rats, animals on InsP6 had 27% fewer tumors (P less than 0.02). The tumors were approximately two-thirds smaller in size (P less than 0.01) and percentage mitotic rate in the non-neoplastic epithelium was less than half (1.0 +/- 0.1, compared to 2.3 +/- 0.2 of AOM-only animals, significant at P less than 0.001). We postulate that InsP6 may exert its antineoplastic effect by way of regulating cellular proliferation even after effective carcinogenic stimuli and thus may be an important candidate for chemointervention.

[The role of epidemiologic research of the natural history of cancer for evaluating cancer screening programs--a prospective study of colorectal polyps on the occurrence of colorectal cancer]

In order to elucidate the natural history of colorectal polyps and to examine the effectiveness of endoscopic polypectomy in reducing the incidence of colorectal cancer, we conducted a retrospective cohort study of all patients who had undergone endoscopic examination at the Center for Adult Diseases, Osaka in 1970-82. The study subjects consist of 653 non-polyp cases and 431 colorectal polyp cases including 222 cases treated by endoscopic polypectomy. These were followed up until the end of 1985 by the method of a record linkage with the Osaka Cancer Registry's file. The colorectal polyp group and the endoscopic polypectomy group experienced 4.4 and 2.9 times, respectively, as much incidence of colorectal cancer as the non-polyp group. The magnitude of the prevented fraction by the use of endoscopic polypectomy was estimated at 31.3%. A large-scale and long-term study is necessary to elucidate the original study purpose.

Screening of colorectal tumours using an improved faecal occult blood test. Quantitative aspects

A recently developed double test for detecting faecal occult blood (a sensitive guaiac test combined with a quantitative immunological human haemoglobin test), was adapted to population screening. The study involved an unselected population of 10,343, aged 49-74 years. There was 66.5% participation. 174 colonoscopies were done, yielding seven adenocarcinomas, 44 adenomas and four hyperplastic polyps. By eliminating benign anal tract bleeding, the number of endoscopies decreased from 340 to 174. Most tumours showed an absorbance over 0.80, and it is suggested that by setting the lower limit of positivity at the 0.80 absorbance level, the number of clinical examinations could fall to about 1%, without substantially missing tumours.

A randomized trial of vitamins C and E in the prevention of recurrence of colorectal polyps

Because supplements of vitamins C and E had been associated with reduction of fecal mutagen levels, a double-blind randomized trial was designed to examine the effects of these vitamins on the rate of recurrence of colorectal polyps, presumed precursors for colorectal cancer. Two hundred patients believed to be free of polyps after removal of at least one colorectal polyp were randomized to receive a supplement of 400 mg each of ascorbic acid and alpha-tocopherol, or a placebo. Fifteen patients had to be excluded because a review of pathology indicated that their polyps were not adenomatous. A second colonoscopic examination was planned after 2 yr of supplementation. One hundred thirty-seven people (75% of eligible subjects) completed the study; polyps were observed in the second colonoscopy in 41.4% of 70 subjects on vitamin supplements and in 50.7% of 67 subjects on placebos. After adjustment for differences between groups in demographic and dietary factors before study entry, the relative risk of polyp occurrence was 0.86, with 95% confidence limits from 0.51 to 1.45, in an analysis of 129 subjects with complete information on demographic and dietary factors who had completed the trial. Of the 48 patients who had not completed the study, 7 had died, 33 had not returned to their physician for an examination, and 8 had had a follow-up colonoscopy or sigmoidoscopy. Inclusion of the three polyps found in these eight examinations led to an estimate of relative risk of 0.86 (95% confidence limits, 0.51 to 1.43). The findings of this investigation suggest that any reduction in the rate of polyp recurrence associated with vitamin supplementation is small, and a larger study would be required to ensure that an effect of this size was not a chance finding.

Postoperative follow-up for colorectal cancer: who are we kidding?

The results of treatment of colorectal cancer have improved little over the last 40 years. This reflects both the advanced age of the patients and the advanced stage of the disease at diagnosis. Currently, extensive multimodality, periodic evaluation of patients is advocated following potentially curative resections in the hope that colorectal cancer recurrence will be identified when metastases are isolated and curable. Such efforts, however, have failed to make any substantial impact on survival. At this time, the identification of colorectal cancer at an earlier than usual stage appears to be the only means by which survival can be improved. Despite this, substantially more effort and resources are devoted to the postoperative follow-up of patients with colorectal cancer than to the identification of early curable colorectal cancer. In the current economic climate and with limited medical resources, it may be more appropriate to aim primarily at identifying early curable lesions by more routine colonscopy.

Role of sigmoidoscopy in screening for colorectal cancer: a critical review

The use of sigmoidoscopy as a screening method for colorectal cancer is controversial. Evidence regarding its efficacy is reviewed critically, with special attention given to potential biases in screening studies. The vast majority of studies are uncontrolled and without follow-up information and thus shed little light on the actual benefits of sigmoidoscopy. Two uncontrolled studies with follow-up and one randomized trial suggest a colorectal cancer mortality reduction because of the use of sigmoidoscopy, but all three studies have major shortcomings. The authors conclude that the currently available data are insufficient to establish a national recommendation for screening with sigmoidoscopy. To establish such a recommendation, a properly conducted randomized trial with colorectal cancer mortality as an outcome is needed.

[Screening for cancer of the large intestine]

A reduction of the high mortality figures from colorectal cancer is possible only when early diagnosis is achieved. This is the aim of annual screening of asymptomatic persons starting at age 45. The only practicable and effective screening method at present is searching for occult blood in feces with the Hemoccult-test. This test should therefore be part of the routine laboratory programme.