The epidemiology of large-bowel cancer

A Rural-Urban Comparison of Knowledge, Risk- Factors and Preventive Practices for Colorectal Cancer among Adults in Lagos State

Objective:

To assess and compare the knowledge, risk-factors and preventive practices for colorectal cancer among adults in Lagos State.

Material and methods:

This was a cross-sectional comparative study conducted among 607 respondents selected from one rural (Ikorodu) and one urban (Surulere) LGA using a multistage sampling technique. Data were collected using a pre-tested questionnaire administered by trained research assistants between April and September 2017.Data was analyzed using Epi-info statistical software version 3.5.1. Univariate and bivariate analysis was carried out and -p values of ≤0.05 were considered statistically significant.

Results:

Respondents’ knowledge of colorectal cancer was generally low, (rural-78.2%, urban- 62.2%, p<0.001). Urban respondents were significantly more knowledgeable than their rural counterparts (rural- 21.8%, urban- 37.8%, p<0.001). The presence of CRC risk-factors were higher among urban respondents (urban-49.3%, rural-42.6%, p= 0.09), however this difference was not statistically significant. Preventive practices were generally poor in both groups, although more (18.1%) urban respondents significantly took preventive actions against CRC compared with rural (6.9%) respondents, (p<0.001).Increasing levels of education were significantly associated with higher knowledge level in both groups (p≤0.05).

Conclusion:

The level of knowledge of colorectal cancer was generally poor in both groups but significantly poorer among rural respondents. The presence of known risk- factor was higher among urban respondents while preventive practices were poor in both groups.

Cancer Risk Related to Uncommon Migration within Italy

Aims and background

Given the industrialization in Italy over this past century much migration has occurred within the country especially from southern to northern regions. Following repeated drainings of the pre-existing marsh area (Pontina plain) during the 1930s the Latina province received an unusual north-south immigration from the regions of Veneto, Friuli and Emilia Romagna. This consisted principally of manual workers, farmers and their families. Four new towns developed after a few years (Littoria, later renamed Latina, Sabaudia, Pontinia and Aprilia), and the whole province quickly reached a population of 60,000. The availability of a population-based Cancer Registry in the Latina province allowed us to assess the cancer risk in this migrant population.

Methods

Standardized Incidence Ratios (SIRs) according to cancer site and sex were computed for residents over the age of 55 years, born in northern Italy. Population data, by sex, age and region of birth were based on the 1981 census. The age-sex-site specific incidence rates for the 1983-1987 period for the entire population of the Latina province over 55 years of age were used as standard.

Results

A significant excess of cancer risk for subjects of both sexes born in northern Italy was found. In addition, a statistically significant higher risk was observed for the cancers of the lung, skin (non-melanomas) and prostate in males, and of the mouth-pharynx, lung and skin (non-melanomas) in females.

Conclusions

SIRs for all sites confirm the findings from other studies on migrants in Italy and strongly support the hypothesis that the place of birth has an important influence on the frequency of cancer. Some possible etiological factors are suggested for cancer sites with higher frequencies in northern-born subjects.

In vitro fermentation of NUTRIOSE(®) FB06, a wheat dextrin soluble fibre, in a continuous culture human colonic model system

Wheat dextrin soluble fibre may have metabolic and health benefits, potentially acting via mechanisms governed by the selective modulation of the human gut microbiota. Our aim was to examine the impact of wheat dextrin on the composition and metabolic activity of the gut microbiota. We used a validated in vitro three-stage continuous culture human colonic model (gut model) system comprised of vessels simulating anatomical regions of the human colon. To mimic human ingestion, 7 g of wheat dextrin (NUTRIOSE^® FB06) was administered to three gut models, twice daily at 10.00 and 15.00, for a total of 18 days. Samples were collected and analysed for microbial composition and organic acid concentrations by 16S rRNA-based fluorescence in situ hybridisation and gas chromatography approaches, respectively. Wheat dextrin mediated a significant increase in total bacteria in vessels simulating the transverse and distal colon, and a significant increase in key butyrate-producing bacteria Clostridium cluster XIVa and Roseburia genus in all vessels of the gut model. The production of principal short-chain fatty acids, acetate, propionate and butyrate, which have been purported to have protective, trophic and metabolic host benefits, were increased. Specifically, wheat dextrin fermentation had a significant butyrogenic effect in all vessels of the gut model and significantly increased production of acetate (vessels 2 and 3) and propionate (vessel 3), simulating the transverse and distal regions of the human colon, respectively. In conclusion, wheat dextrin NUTRIOSE^® FB06 is selectively fermented in vitro by Clostridium cluster XIVa and Roseburia genus and beneficially alters the metabolic profile of the human gut microbiota.

Lipoxygenase and Cyclooxygenase Pathways and Colorectal Cancer Prevention

Colorectal cancer is one of the commonest malignancies in both men and women. In spite of significant progress in screening and in surgical and therapeutic interventions, colorectal cancer (CRC) is still a major public health problem. Accumulating evidence suggests that targeting inflammatory pathways may provide protection against the development of CRC. Eicosanoids derived from the enzymes cyclooxygenase (COX) and lipoxygenase (LOX) may contribute to CRC carcinogenesis. Approaches for targeting COX-1 and COX-2 with traditional nonsteroidal anti-inflammatory agents or targeting COX-2 with specific inhibitors are highly successful at the preclinical and clinical levels; however, large-scale clinical applicability of these agents is limited owing to unwanted side effects. Emerging studies suggests that 5-LOX-derived leukotrienes may contribute to colon tumor development and risk of thrombotic events. Thus, developing drugs that target both 5-LOX and COX-2 may provide a safer strategy. In this review, we discuss evidence for the involvement of 5-LOX in colon tumor development and targeting 5-LOX and COX-2 with synthetic and naturally occurring agents for CRC prevention.

Farnesol attenuates 1,2-dimethylhydrazine induced oxidative stress, inflammation and apoptotic responses in the colon of Wistar rats

Colon cancer is the major health hazard related with high mortality and it is a pathological consequence of persistent oxidative stress and inflammation. Farnesol, an isoprenoid alcohol, has been shown to possess antioxidant, anti-inflammatory and chemopreventive properties. The present study was performed to evaluate the protective efficacy of farnesol against 1,2-dimethylhydrazine (DMH) induced oxidative stress, inflammatory response and apoptotic tissue damage. Farnesol was administered once daily for seven consecutive days at the doses of 50 and 100 mg/kg body weight in corn oil. On day 7, a single injection of DMH was given subcutaneously in the groin at the dose of 40 mg/kg body weight. Protective effects of farnesol were assessed by using caspase-3 activity, tissue lipid peroxidation (LPO) and antioxidant status as end point markers. Further strengthening was evident on histopathological observations used to assess the protective efficacy of farnesol. Prophylactic treatment with farnesol significantly ameliorates DMH induced oxidative damage by diminishing the tissue LPO accompanied by increase in enzymatic viz., superoxide dismutase (SOD), catalase, glutathione peroxidase (GPx), glutathione reductase (GR), glutathione-S-transferase (GST) and quinone reductase (QR) and non-enzymatic viz., reduced glutathione (GSH) antioxidant status. Farnesol supplementation significantly decreased caspase-3 activity in colonic tissue. Histological findings also revealed that pretreatment with farnesol significantly reduced the severity of submucosal edema, regional destruction of the mucosal layer and intense infiltration of the inflammatory cells in mucosal and submucosal layers of the colon. The data of the present study suggest that farnesol effectively suppress DMH induced colonic mucosal damage by ameliorating oxidative stress, inflammatory and apoptotic responses.

Synthesis and characterization of a novel iNOS/Akt inhibitor Se,Se'-1,4-phenylenebis(1,2-ethanediyl)bisisoselenourea (PBISe)--against colon cancer

Our studies demonstrate that substitution of sulfur with selenium in known iNOS inhibitor increases the compound's potency by several folds in variety of different cancers cell lines tested. Hence, this approach may be used as a strategy to increase the efficacy of the anticancer agents.

Etiologic insights from surface adjustment of colorectal carcinoma incidences: an analysis of the U.S. SEER data 2000-2004

BACKGROUND AND AIMS

The subsite-specific comparison of the incidence of carcinoma within the colorectum is complicated because the mucosal surface, and therefore the amount of epithelial cells at risk, varies among the subsites. The aim of this study was to provide the subsite-specific estimates of the colon mucosal surface and the mucosal surface-adjusted carcinoma incidence estimates of colon subsites that allow a more valid comparison of the subsite-specific incidences.

METHODS

We extracted subsite-specific incidence rates of colorectal carcinoma from the Surveillance, Epidemiology, and End Results (SEER) Program of the years 2000-2004. The rates were age-standardized to the U.S. standard population in the year 2000. We estimated the mucosal surface of each segment of the colorectum and calculated the surface-adjusted incidence rates by dividing the observed age-standardized incidence rates by the estimated surface areas.

RESULTS

After adjustment for surface area, the incidence relations among the colorectal subsites changed. Within the colon, the surface-adjusted rates tend to be highest in the cecum, followed by the vermiform appendix, ascending colon, and sigmoid colon. The rates of the transverse and descending colon are considerably lower. The surfaced-adjusted incidence of rectal carcinoma is about 12- to 23-fold higher than the rate of carcinoma of the transverse colon.

CONCLUSIONS

The distribution of the incidence of carcinomas is markedly influenced by the adjustment of surface area of the colorectum. Similar surface-adjusted rates of the vermiform appendix and ascending colon may implicate that these subsites share a similar etiology. Considerable differences of the surface-adjusted rates of the sigmoid colon and rectum may indicate different etiologies of carcinomas of these subsites.

Colorectal cancer risk, chronic illnesses, operations and medications: case control results from the Melbourne Colorectal Cancer Study. 1988

The associations between colorectal cancer risk and several chronic illnesses, operations and various medications were examined in 715 colorectal cancer cases and 727 age- and sex-matched controls in data derived from a large, comprehensive population-based study of this cancer conducted in Melbourne, Australia. There was a statistically significant deficit among cases of hypertension, heart disease, stroke, chronic chest disease and chronic arthritis and a statistically significant excess of 'haemorrhoids' among cases, and all of these differences were consistent for both colon and rectal cancers and for both males and females. Although no statistically significant differences were found for other cancers, there were twice as many breast cancers among cases (16) than among controls (8) and also there were 9 uterine cancers among cases and only 2 among controls. There was a statistically significant deficit among cases in the use of aspirin-containing medication and vitamin supplements and this was consistent for both colon and rectal cancers and for both males and females. There was a statistically significant excess of large bowel polypectomy among cases. The modelling of these significant associations simultaneously in a logistic regression equation indicated that hypertension, heart disease, chronic arthritis and aspirin use were each independent effects and consistent for both colon and rectal cancers for both males and females and also that these effects were independent of dietary risk factors previously described in the Melbourne study. The possible relevance of these findings towards an understanding of colorectal cancer risk and aetiology is discussed.

Unexplained inversion of the incidence ratio of colon and rectal cancer among men in East Germany. A time trend analysis including 147,790 cases

INTRODUCTION

The incidence rate ratio of colon to rectal cancer is usually about 2:1. It has been observed for a while that the incidence of colon cancer among men (as opposed to women) in the Former German Democratic Republic (GDR) is lower than the rate of rectal cancer. Detailed analyses of this phenomenon have not been done so far. The aim was to give insights in this observation by detailed incidence and mortality analyses and to explore the worldwide ratio of colon and rectal cancers based on population-based cancer registry data.

METHODS

We analyzed age-standardized incidence and mortality data of colorectal cancers in East Germany (1961-1989 and 1996-2002; mortality 1980-2002), West Germany, Saarland (1970-2002) and all over the world (1978-82 up to 1993-97).

RESULTS

With the incidence increase of colorectal cancers in the GDR, the ratio of colon to rectal cancer incidence became larger and surpassed the reference value (ratio = 1) during the time of the reunification. Also the mortality data revealed a similar pattern. Estimated annual percentage increases of colon subsite incidences tended to be higher within the distal colon as compared to the proximal colon

CONCLUSIONS

Our analyses of international cancer registries over a period of 20 years show that the colon-rectum cancer ratio is positively associated with the overall incidence of colorectal cancer with a stronger association among women than men. Non-causal factors such as underdetection or registration artefacts are unlikely to explain the unusual colon/rectal rate ratio among men. A gradual decrease of the job-related physical activity among men may have contributed to the findings.

Acetylated, propionylated or butyrylated starches raise large bowel short-chain fatty acids preferentially when fed to rats

Maize starch was acylated with acetic, propionic or butyric anhydride to produce the corresponding acylated starch. In the first experiment, butyrylated starch at a degree of substitution (DS) of 0.25 (i.e., 1 acyl unit per 4 glucosyl units) was fed to rats for 3 d. Cecal and distal colonic SCFA concentrations were 170 and 78% higher, respectively, in rats fed the butyrylated starch. However, the greatest increase was in butyrate with corresponding increases of 460 and 212%. Subsequently, acetylated, propionylated or butyrylated starches with DS of approximately 0.18 were prepared on a larger scale. Body weight gain did not differ between rats fed these acylated starches or a control starch for 14 d. Large bowel pH was significantly lower and digesta mass significantly higher throughout the large bowel in rats fed the acylated starches. Cecal + distal colonic starch averaged 12 mg in rats fed the control starch and 103, 134 and 135 (pooled SEM = 6) mg in rats fed acetylated, propionylated or butyrylated starch, respectively. Large bowel SCFA concentrations and pools were significantly higher in rats fed the three acylated starches and were disproportionately greater in the SCFA that had been esterified to the starch. In the cecum, acetate, propionate and butyrate pools were 280, 690 and 1060% higher, respectively, in rats fed the corresponding acylated starch than in those fed the control diet. In the distal colon, the corresponding increases were 320, 940 and 1370%. These data indicate that acylated starches are resistant starch (RS) and raise large bowel SCFA, apparently through bacterial release of the esterified fatty acid and fermentation of the residual starch.

Physical activity and colorectal cancer

Physical activity has been shown to reduce risk of colon cancer. Some studies have shown site-specific associations while others have not. The inverse association between physical activity and colon cancer is consistent although only 7 of 13 studies that have collected both colon and rectal cancer data in the same manner report reduced risk for rectal cancer; four of these studies detected statistically significant inverse associations. The frequency, duration and intensity of activity are important components of a public health message to reduce risk of colon cancer through performance of physical activity. However, difficulties in estimating the exact amount of activity needed and frequency and intensity of activity result in only crude estimates of dose needed for a protective effect. Much of the literature suggest that more intense activity is needed to reduce colon cancer risk and that somewhere between 3.5 and 4 hours of vigorous activity per week may be needed to optimise protection. Several biological mechanisms have been proposed to explain the association between physical activity and colon cancer; many of these mechanisms also support the observation that intense activities are most protective. Biological mechanisms include: physical activity increasing gut motility; enhancing the immune system; decreasing insulin and insulin-like growth factor levels; decreasing obesity; enhancing free radical scavenger systems; and influencing prostaglandin levels. The evidence taken together provides strong support for lack of physical activity being causally related to colon cancer. It has been estimated that 12-14% of colon cancer could be attributed to lack of frequent involvement in vigorous physical activity.

Short-chain fatty acids and human colonic function: roles of resistant starch and nonstarch polysaccharides

Resistant starch (RS) is starch and products of its small intestinal digestion that enter the large bowel. It occurs for various reasons including chemical structure, cooking of food, chemical modification, and food mastication. Human colonic bacteria ferment RS and nonstarch polysaccharides (NSP; major components of dietary fiber) to short-chain fatty acids (SCFA), mainly acetate, propionate, and butyrate. SCFA stimulate colonic blood flow and fluid and electrolyte uptake. Butyrate is a preferred substrate for colonocytes and appears to promote a normal phenotype in these cells. Fermentation of some RS types favors butyrate production. Measurement of colonic fermentation in humans is difficult, and indirect measures (e.g., fecal samples) or animal models have been used. Of the latter, rodents appear to be of limited value, and pigs or dogs are preferable. RS is less effective than NSP in stool bulking, but epidemiological data suggest that it is more protective against colorectal cancer, possibly via butyrate. RS is a prebiotic, but knowledge of its other interactions with the microflora is limited. The contribution of RS to fermentation and colonic physiology seems to be greater than that of NSP. However, the lack of a generally accepted analytical procedure that accommodates the major influences on RS means this is yet to be established.

Evaluation of fecal mutagenicity and colorectal cancer risk

Colorectal cancer is one of the most common internal malignancies in Western society. The cause of this disease appears to be multifactorial and involves genetic as well as environmental aspects. The human colon is continuously exposed to a complex mixture of compounds, which is either of direct dietary origin or the result of digestive, microbial and excretory processes. In order to establish the mutagenic burden of the colorectal mucosa, analysis of specific compounds in feces is usually preferred. Alternatively, the mutagenic potency of fecal extracts has been determined, but the interpretation of these more integrative measurements is hampered by methodological shortcomings. In this review, we focus on exposure of the large bowel to five different classes of fecal mutagens that have previously been related to colorectal cancer risk. These include heterocyclic aromatic amines (HCA) and polycyclic aromatic hydrocarbons (PAH), two exogenous factors that are predominantly ingested as pyrolysis products present in food and (partially) excreted in the feces. Additionally, we discuss N-nitroso-compounds, fecapentaenes and bile acids, all fecal constituents (mainly) of endogenous origin. The mutagenic and carcinogenic potency of the above mentioned compounds as well as their presence in feces, proposed mode of action and potential role in the initiation and promotion of human colorectal cancer are discussed. The combined results from in vitro and in vivo research unequivocally demonstrate that these classes of compounds comprise potent mutagens that induce many different forms of genetic damage and that particularly bile acids and fecapentaenes may also affect the carcinogenic process by epigenetic mechanisms. Large inter-individual differences in levels of exposures have been reported, including those in a range where considerable genetic damage can be expected based on evidence from animal studies. Particularly, however, exposure profiles of PAH and N-nitroso compounds (NOC) have to be more accurately established to come to a risk evaluation. Moreover, lack of human studies and inconsistency between epidemiological data make it impossible to describe colorectal cancer risk as a result of specific exposures in quantitative terms, or even to indicate the relative importance of the mutagens discussed. Particularly, the polymorphisms of genes involved in the metabolism of heterocyclic amines are important determinants of carcinogenic risk. However, the present knowledge of gene-environment interactions with regard to colorectal cancer risk is rather limited. We expect that the introduction of DNA chip technology in colorectal cancer epidemiology will offer new opportunities to identify combinations of exposures and genetic polymorphisms that relate to increased cancer risk. This knowledge will enable us to improve epidemiological study design and statistical power in future research.

Reproductive factors related to the risk of colorectal cancer by subsite: a case-control analysis

The authors hypothesized that reproductive factors of colorectal cancer, which are probably mediated by endogenous hormones, would differ according to colonic subsite. Information on reproductive factors was obtained from 372 female colorectal cancer cases (113 proximal colon, 126 distal colon, 133 rectum) and 31,061 cancer-free controls at the Aichi Cancer Center Hospital, Japan, between 1988 and 1995. Multiple logistic analysis showed that late age at interview, family history of colorectal cancer among first-degree relatives, menstrual regularity, late age at menopause, late age at first pregnancy and late age at first full-term pregnancy were significantly associated with the risk of colorectal cancer. None of the risk factors were significantly dissociated between colon and rectal cancer. In polytomous logistic regression analysis, particularly noteworthy was the fact that the odds ratios for age at menarche (P-value for heterogeneity of odds ratios = 0.010), age at first pregnancy (P = 0.016) and age at first full-term pregnancy (P = 0.028) were significantly higher for distal than for proximal colon cancer. This study supports the hypotheses that there might be an association between reproductive factors and risk of colon cancer, and that the carcinogenesis of colon cancer, by subsite, might show aetiologic distinctions.

Clinical models of chemoprevention for colon cancer

Colon cancer is a common malignancy in the westernized world and is incurable in its advanced stages. This article summarizes the currently available information on colorectal cancer chemoprevention. A brief outline of the incidence and etiologic factors is followed by a discussion of the evidence on which chemopreventive strategies for colon cancer are modeled. This includes a description of the development of surrogate endpoint biomarkers and experimental models to study colorectal cancer chemopreventives, a review of the promising colorectal cancer chemopreventives, and a discussion of the issues to be addressed in the design of future chemoprevention trials. The article concludes with an emphasis on the development and validation of biomarkers and selection of high-risk cohorts using genetic and epidemiologic tools as the main goals of future colon cancer chemoprevention trials before large-scale, risk-reduction trials are conducted.

Colorectal adenocarcinoma in a defined Jordanian population from 1990 to 1995

PURPOSE

This study aims to evaluate cancer of the large bowel as it occurred in a defined Jordanian population, with special reference to its epidemiologic aspects. Second, this study was undertaken to compare these results with those of other countries and those previously reported from Jordan.

METHODS

Records of patients diagnosed as having colorectal adenocarcinoma during a six-year period in Irbid province, Jordan, were reviewed. The material was analyzed retrospectively with respect to various epidemiologic features, and the results were compared with those of other countries and those previously published about the Jordanian population.

RESULTS

Between January 1990 and December 1995, 109 new patients with colorectal adenocarcinoma were managed, an incidence of 3.8/100,000/year. Male to female ratio was 1:1.05 for colonic cancer and 1.36:1 for rectal cancer. The maximum incidence was seen in the sixth and seventh decades. A total of 12.8 percent of the patients were younger than 40 years of age. The rectum was the most common site involved in 30.3 percent of the patients, followed by the sigmoid, right colon, and the rest of the colon. When compared with previous Jordanian figures, a shift toward the western figures was noted. The delay in diagnosis was noted from the 8.2 months of delay before diagnosis and the advanced stage of the disease at the time of diagnosis. A total of 49.5 percent of the cases were in Dukes B stage, 30.3 percent in Dukes C, and 19.3 percent in Dukes D. Only one patient was in Dukes A stage. A total of 13.8 percent of the cases were mucinous adenocarcinoma. A total of 26.5 percent of the patients presented with complications.

CONCLUSIONS

As for colorectal adenocarcinoma, we still share the epidemiologic characteristics of developing countries, but there is a shift toward those of western communities. Flexible sigmoidoscopy is encouraged for evaluation of lower gastrointestinal symptoms, and education of the public and medical staff about colorectal diseases is needed to improve the outcome.

Secretory component mRNA and protein expression in colorectal adenomas and carcinomas

Secretary component (SC) is expressed basolaterally as a transmembrane protein (pIg receptor) on secretory epithelial cells. As pIg receptor it plays a central role in humoral immunity by mediating the external translocation of dimeric IgA and pentameric IgM. A few case reports have suggested that reduced or absent SC protein expression is associated with diarrhoeal disease, but there is no convincing evidence that a primary pIg receptor deficiency can occur. In this study the relative presence of SC mRNA was determined by Northern blot analysis and related to immunohistochemically determined SC protein expression in 33 colorectal adenomas (31 patients) with increased risk of developing sporadic colorectal cancer, as well as in 19 colorectal carcinomas from 19 patients with such sporadic tumours. In the adenomas, SC mRNA levels were positively related to SC protein expression; both mRNA and SC protein were negatively related to histological grade. Similarly, SC mRNA levels tended to be related to the SC protein expression in the carcinomas. SC mRNA was detected in all adenomas, and only two of ten carcinomas (10.5%) deemed to be SC deficient by immunohistochemistry also lacked SC mRNA expression, suggesting diallelic alterations in the SC-encoding gene (locus PIGR). This possibility agreed with Southern blot analysis performed on a separate sample of 32 other colonic carcinomas in which the diallelic loss of D1S58 (which exhibits a close linkage centromerically to PIGR) was calculated to be 6.4%. Together these findings suggested that reduced SC protein expression in colorectal adenomas might be a transcriptional defect reflecting the degree of cellular dysplasia, whereas absent SC protein expression in colorectal carcinomas might also involve post-transcriptional defects and occasional diallelic gene deletions representing late events in carcinogenesis.

Nutrition and colorectal cancer

Epidemiologic evidence on the relation between nutrition and colorectal cancer is reviewed. Colon cancer varies approximately 20-fold internationally. Although there is clear evidence of genetic predisposition to colon cancer, much of this variation appears to be related to differences in dietary habits. At present, the data suggest that vegetables are associated with lower risk, and that fiber alone does not account for this association. Further, meat consumption is associated with increased risk but this, too, is not explained solely by its fat content. Several microconstituents of the diet may be associated with reduced risk--including folate and calcium--but phytochemicals of other sorts may be relevant. Mutagenic compounds, particularly heterocyclic amines, produced when protein is cooked, plausibly explain the meat association. The most consistent inverse association is with physical activity. Alcohol is associated, though inconsistently, with increased risk. Rectal cancer is less well studied but, at present, there are few data to suggest that the dietary risk factors are markedly different. Physical activity does not appear to be associated with a lower risk. Colorectal adenomatous polyps also appear to share the spectrum of risk factors seen with colon cancer, although, for adenomas, tobacco smoking is also a clear and consistent risk factor. There are a variety of links between the dietary epidemiology and physiology of colorectal neoplasia and the relevant pathologic and molecular changes. Other causal connections remain to be explicated.

Anatomic site distribution of colon cancer by race and other colon cancer risk factors

PURPOSE

Black patients with colon cancer are more likely to have poorer survival from colon cancer than are white patients. To determine whether anatomic site differences might contribute to survival differences, we compared anatomic site distributions of black and white patients.

METHODS

As part of the Black/White Cancer Survival Study, we collected medical record data for 1,045 patients from Atlanta, New Orleans, and San Francisco/Oakland, newly diagnosed in 1985 or 1986 and interviewed 745 of them.

RESULTS

In polychotomous logistic regression analysis, site was related to stage, grade, and histologic type and among women with age, parity, and possibly smoking. However, it was not related to race, except perhaps among men age 65 and older, among whom blacks were somewhat likely to have more transverse and distal, not proximal, cancer. These relations were consistent across subgroups and were independent of other factors examined.

CONCLUSION

Results suggest that site differences are unlikely to contribute to poorer survival commonly observed among black colon cancer patients in the United States.

Southwestern internal medicine conference: hereditary predisposition to colorectal cancer: new insights

Hereditary predisposition to colorectal cancer assumes two well-defined forms: familial adenomatous polyposis and hereditary nonpolyposis colon cancer. These tumors segregate as autosomal dominant conditions whose penetrance increases with age; cancer is expected to develop ultimately in as much as 50% of the offspring of affected individuals. These traits account for less than 1% and approximately 5% of all colorectal cancer, respectively. In addition, first-degree relatives of patients with common (sporadic) colorectal neoplasia are at increased risk of colorectal cancer. This relative risk averages approximately twofold but is significantly higher for relatives of younger patients (age at diagnosis, < 55 years). Familial adenomatous polyposis and a major subset of hereditary nonpolyposis colon cancer are due to loss-of-function germline mutations of genes located on chromosomes 5q and 2p, respectively. Both of these genes have been cloned recently. The gene affected in familial polyposis, APC, encodes a protein of unknown function that normally is found on the surface of maturing cells in the upper colonic crypts. The relevant gene in many hereditary nonpolyposis colon cancer kindreds is hMSH2. This gene encodes the human homologue of a bacterial protein MutS, which is part of a system known to repair base mismatches in newly replicated DNA. Loss of hMSH2 function may explain the strikingly erroneous replication of short DNA repeats (microsatellites) in colon tumors from patients with hereditary nonpolyposis colon cancer. Because this error-prone replication is found in approximately 13% of nonfamilial colon cancers, defective mismatch repair may contribute to the development of both hereditary and sporadic colon neoplasia. Molecular genetic assays to detect mutated alleles of these genes will facilitate presymptomatic identification of carriers in families with familial polyposis and hereditary nonpolyposis colon cancer. Current recommendations for surveillance of family members are presented in the light of the new genetic understanding of these diseases.

Obesity and adenomatous polyps of the sigmoid colon

The relation between obesity and adenomatous polyps of the sigmoid colon was investigated in male self-defense officials who received a retirement health examination at three hospitals of the Self-Defense Forces in Japan between January 1991 and December 1992. Body mass index (BMI) and waist-hip circumference ratio (WHR) were used as indices of obesity. A total of 228 adenoma cases and 1484 controls with normal sigmoidoscopy were identified in 2228 men: cases having small adenomas (< 5 mm in diameter) and those with large adenomas (5 mm or greater) numbered 115 and 102, respectively. Smoking, alcohol use, physical activity, rank, and hospital were controlled for by multiple logistic regression analysis. BMI and WHR were classified into four levels using the 30th, 60th, and 90th percentiles of each distribution in the control as cut-off points. There was a significant two-fold elevation in the overall adenoma risk among men at the highest BMI level (> or = 26.95) compared with those at the lowest level (< 22.48), but the risk did not linearly increase: a similar increase was also noted for large adenomas. While WHR was only weakly related to the overall adenoma risk, the risk of large adenomas progressively increased with increasing levels of WHR; odds ratio (OR) 2.9 (95% confidence interval (CI) 1.4-5.9) for the highest (> or = 0.958) versus lowest (< 0.878) levels. BMI was not materially associated with adenoma risk after additional adjustment for WHR, but a positive association between WHR and large adenomas was independent of BMI: OR 3.4 (95% CI 1.5-7.6) for the highest versus lowest levels. These findings suggest that obesity is associated with an increased risk of colon adenomas, probably with adenoma growth.

Familial aggregation of cardiovascular diseases in African-American pedigrees

Familial aggregation of cardiovascular diseases and diabetes has been consistently demonstrated. However, virtually all of the evidence on the familial patterns of these diseases has come from white population samples. This study evaluates the level of familial excess risk among first degree relatives of 232 African-American pedigrees which included 1,420 individuals recruited from the Chicago, IL, area. Excess disease risk was observed among relatives (parents and offsprings) of affected probands compared to relatives of unaffected probands for coronary heart disease (odds ratio [OR] = 5.30; 95% confidence interval [CI] = 2.51-11.23); hypertension (OR = 1.98; CI = 1.41-2.80); stroke (OR = 3.24; CI = 1.08-9.70); and diabetes (OR = 2.95; CI = 1.55-5.62). The results of this study clearly show that coronary heart disease, hypertension, stroke, and diabetes aggregate in some African-American families and not others. Unaffected relatives of persons suffering from these diseases should be encouraged to have their blood pressure, lipid, and blood glucose levels measured at frequent intervals. These recommendations are particularly urgent in African-American communities because of the disproportionately high morbidity and mortality experienced from cardiovascular diseases and diabetes.

Variation in colorectal cancer incidence in the United States by subsite of origin

BACKGROUND

Colorectal cancer incidence rates vary widely internationally, by race and gender, and have changed over time. Investigation of the patterns by subsite within the colorectum may suggest clues of possible etiologic significance for further study.

METHODS

Using population-based data on more than 120,000 cases diagnosed 1976-1987 in the United States Surveillance, Epidemiology, and End Results program, colorectal cancer incidence was evaluated by subsite of origin.

RESULTS

Little racial variation was evident for cecum and ascending colon cancers; rates were higher among blacks than whites for transverse and descending colon cancers but lower for sigmoid, rectosigmoid, and rectal cancers. Rates generally increased over time for most colon sites, especially sigmoid colon among white men, but declined slightly for rectal cancer among whites. The sex ratio increased among whites monotonically from 1.12 for cecum to 1.71 for rectal cancers. The distal colon cancer excess among men was most notable at older ages, contrasting with slightly higher rates among women at younger ages. Geographic differences were particularly notable for transverse and rectosigmoid colon cancers.

CONCLUSIONS

It may be fruitful for future studies to evaluate factors affecting colorectal carcinogenesis by subsite of origin.

Age-period-cohort modelling of large-bowel-cancer incidence by anatomic sub-site and sex in Connecticut

In order to investigate etiologic distinctions among the anatomic sub-sites of the large bowel by sex, the relationship between large-bowel-cancer incidence and age at diagnosis, time period at diagnosis, and birth cohort was analyzed by anatomic sub-site and by sex, using data from the Connecticut Tumor Registry. Included in the study were all incident large-bowel-cancer cases occurring between 1950 and 1984 among Connecticut residents aged 40 to 79. Cancers of the large bowel were classified into 5 anatomic sub-sites: ascending colon (including cecum), transverse colon (including flexures), descending colon, sigmoid colon, and rectum (including rectosigmoid junction, anal canal, and anus). The data were fitted to log-linear age-period-cohort models. For each of the sub-sites, the age-period-cohort patterns for males and females differed. Within each sex, sub-site groupings with common patterns were indicated. Among males, the age-period-cohort patterns for the colon sub-sites were fairly similar; but the pattern for the rectum differed markedly from that for the colon sub-sites. There were secondary differences among the colon sub-sites that pointed to a secondary distinction between the right and the left colons. Among females, the age-period-cohort patterns for the left colon sub-sites and the rectum were fairly similar. The pattern for the transverse colon differed moderately from that of the left colon, and differed substantially from that of the rectum and the ascending colon. The ascending colon differed markedly from each of the other sub-sites. It is possible that these differences in age-period-cohort patterns reflect etiologic distinctions among sub-site groupings and between the sexes.

Characteristics of arachidonic-acid-mediated brain protein kinase C activation: evidence for concentration-dependent heterogeneity

Arachidonic acid (AA) activates brain protein kinase C (PKC) in a specific manner, and which differs from that of diacylglycerol (DG)-mediated PKC activation in cofactor Ca2+ and phosphatidylserine (PtdSer) requirements. We presently report that characteristics of AA-mediated activation are heterogenous, and are dependent upon the concentrations of AA. Highly sensitive PKC activation (HS) occurring at concentrations of 20 microM AA can be distinguished from less sensitive PKC activation (LS) requiring concentrations of at least 160 microM AA, on the basis of the effects of phorbol ester TPA or DG, phosphatidylcholine (PtdCho) and sodium deoxycholate (DOC). TPA, like DG suppressed the HS reaction whereas it enhanced the LS reaction. PtdCho, a phospholipid which does not affect DG-mediated activation, also prevented the HS reaction without affecting the LS reaction. This latter was inhibited at 100 microM DOC, a concentration which slightly stimulated the HS reaction. The substrate specificity was also different in the two reactions: the preferential substrate for PKC in HS was histone type VII-S, while it was histone type V-S in LS. Both reactions were similarly affected by PtdSer. In 0.1 mM CaCl2, PtdSer stimulated AA-mediated activation without evoking additive responses while this phospholipid prevented this activation in 0.5 mM EGTA, suggesting that AA and PtdSer bind PKC on the same or related sites. Together these results provide evidence for the existence of different modes of AA-mediated PKC activation with unique characteristics which presumably involve two different binding sites for AA on the same molecule and/or different PKC isoforms.

Increased serum deoxycholic acid levels in men with colorectal adenomas

BACKGROUND

Epidemiological and animal studies have suggested that the secondary bile acid deoxycholic acid is cocarcinogenic in colorectal cancer, but this hypothesis was not confirmed by case-control studies investigating fecal bile acids.

METHODS

Individual serum bile acid concentrations were investigated in 25 men and 25 women with colorectal adenomas and in an equal number of age- and sex-matched controls by gas-liquid chromatography.

RESULTS

Deoxycholic acid levels were significantly higher in the sera of men with colorectal adenomas (1.70 +/- 0.59 vs. 1.16 +/- 0.39 mumol/L, P < 0.0005) and in a combined analysis of both sexes (1.47 +/- 0.78 vs. 1.08 +/- 0.39 mumol/L, P < 0.0025). Six- and 12-month follow-up measurements of deoxycholic acid concentrations in a subgroup of 22 men and 17 women showed higher serum levels in men with adenomas, indicating that measurement of deoxycholic acid concentration may be a reliable parameter to investigate its pathogenetic role in colonic neoplasia.

CONCLUSIONS

The data of this study support the hypothesis that deoxycholic acid may play a role in the pathogenesis of colorectal cancer.

Relationship of diet to small and large adenomas of the sigmoid colon

The relation of dietary factors to the risk of adenomas of the sigmoid colon was examined in men receiving a retirement health examination at the Self-Defense Forces Fukuoka Hospital between October 1986 and 1990. A total of 187 adenoma cases and 1557 controls with normal colonoscopy were identified in the series. Cases were further classified into small-adenoma (< 5 mm, n = 78) and large-adenoma (> or = 5 mm, n = 67) groups. The consumptions of selected foods and beverages were ascertained before colonoscopy by means of a self-administered questionnaire. After adjustment for smoking, alcohol use, rank and body mass index, low rice consumption and high meat intake were independently associated with an increased risk of large adenomas. The risk of small adenomas was not related to either rice consumption or meat intake. Adjusted odds ratios of large adenomas for the low, intermediate and high consumption levels of rice were estimated to be 1.0 (referent), 0.83 and 0.43, respectively (trend P = 0.08), and the corresponding figures for meat consumption were 1.0 (referent), 1.58 and 2.38, respectively (trend P = 0.02). The findings suggest that low rice consumption and high meat intake may promote the growth of colon adenomas, thereby increasing the risk of colon cancer.

The effect of dietary calcium supplementation on intestinal lipid metabolism

Population studies in man and experimental animal work support the contention that dietary supplementation with calcium may prevent the development of colorectal cancer. The mechanism of action is postulated to be bile acid chelation in the small-bowed forming non-toxic calcium soap compounds but such substances have yet to be isolated and quantified. In this 2-part study faecal concentrations of acidic lipids and neutral sterols were measured in 93 Sprague-Dawley rats whose calcium intake was modulated by enriching the chow and adding calcium lactate (24 milligrams) to the drinking water. In study-1 (dietary calcium intake doubled from 0.4-0.8%) small bowel resection was used to manipulate colonic lipid concentration for comparison with control rats who had undergone transection with immediate restoration of bowel continuity at an equivalent point. Faecal concentrations of free bile acids were 53-67% less in animals receiving added calcium [1.76 +/- 1.33 vs 0.82 +/- 0.65 mg/g (transection); 2.74 +/- 3.73 vs 1.03 +/- 1.27 mg/g (small bowel resection): P less than 0.001]. In study-2 (dietary calcium intake trebled to 1.21%) faecal bile acid concentration was reduced by 32% (1.86 +/- 0.57 vs 1.27 +/- 0.34 mg/g: NS) whereas long chain fatty acid concentrations were increased by 117% (6.77 +/- 2.39 vs 14.67 +/- 4.82 mg/g: P less than 0.001) in animals receiving added calcium. Serum calcium levels remained unchanged in these animals. Calcium soaps of the bile acids were not detected in faeces and therefore contrary to popular theory these results indicate that conditions within the intestinal lumen favour calcium chelation of long chain fatty acids rather than bile acids.

Epidemiology of large bowel cancer

Results from epidemiologic studies have provided insights into the etiology of large bowel cancer. Markedly diverse incidences of colorectal cancer exist in various parts of the world and within different regions of a given country. Studies of migrant populations have revealed a role for environmental factors, particularly dietary, in the etiology of colorectal cancers. Genetic factors and inflammatory bowel disease also place certain individuals at increased risk. Sedentary lifestyle, cholecystectomy, and ureterosigmoidostomy may also increase the risk of developing large bowel cancer.

The measurement of DNA strand breaks in rat colonic mucosa by fluorometric analysis of DNA unwinding

We describe the detection of DNA strand breaks in the rat colonic mucosa (in vivo and in vitro) by fluorometric analysis of DNA unwinding. DNA strand breaks were detected, in a dose-dependent manner, 2 h following an intracaecal dose of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG, 5-100 mg/kg). Levels of double-stranded DNA in the colonic mucosa of control animals, after 60 min unwinding time, were 62.8 +/- 3.4% (n = 6) and were significantly reduced at 5 mg/kg to 52.1 +/- 1.9% (n = 3). DNA strand breaks were also detected in isolated rat colonic mucosal cells following 15 min treatment with MNNG (0.1-1 mM) in vitro. The percentage of double-stranded DNA, after 60 min unwinding time, was significantly reduced (13.6 +/- 5.4%, n = 3) from control levels following treatment with 0.1 mM. A post-treatment incubation (30 min) of cells treated at a MNNG concentration of 0.25 mM resulted in 78.2 +/- 24.0% (n = 3) of these lesions being repaired.

Is the incidence of colorectal cancer related to reproduction? A prospective study of 63,000 women

Relationships between reproductive factors and risk of colorectal cancer were examined in a population-based prospective study in Norway. Available for analysis were 831 cases (581 colon cancer, 250 rectal cancer) diagnosed in a cohort of 63,090 women, surveyed in 1956-1959 and followed through 1980. Overall, the analyses showed no strong effects of reproductive factors. In particular, high parity was not associated with reduced risk, and late age at first or last birth was not associated with an increased overall risk. However, in age-specific analyses of colon cancer, adverse effects of late age at first birth and late age at last birth were observed in women with cancer diagnosed before the age of 60. A non-significant overall excess risk in parous compared to nulliparous women was strongest for women with a cancer diagnosis before the age of 50 years. Having had many abortions was associated with increased risk for all sub-sites. Neither age at menarche nor age at menopause were related to risk of colorectal cancer. The results suggest that reproductive factors, which are of importance in the etiology of cancer of the breast and genital organs in women, are not similarly related to risk of colorectal cancer.

[Dietary fiber. Effect on colon carcinogenesis]

The etiopathogenesis of colon carcinogenesis is supposed to be a two-step process consisting of initiation and promotion. In human nutrition the range of xenobiotics acting possibly as initiators occurs mostly in very low concentrations. Therefore, performing a one-factorial consideration they are not claimed seriously to account for initiation. On the contrary, it can be taken for granted that bile acids exert promoting effects in connection with colon carcinogenesis. All factors influencing the promoting effect of bile acids are able to do so probably due to a decrease of pH and as a result the shift of the two bile acid fractions in favour of the soluble fraction, and/or due to the intensification of shift of bile acid metabolism (7-alpha-dehydroxylase). These processes are indirectly influenced to a large extent by the lipid content of food as a result of cholegenesis induction. The "protective Effect" of dietary fibre in colon carcinogenesis (reduced number of tumour carriers, and/or number of tumors per animal) cannot been interpreted as such. Only a delayed promotion phase could been proven. It can be reached only by plant products (bran, lupin), but not by dietary fibre in general.

Physical activity, dietary habits and adenomatous polyps of the sigmoid colon: a study of self-defense officials in Japan

Physical activity and dietary habits were compared between 80 men with adenomatous polyps of the sigmoid colon and 1148 men with normal colonoscopy among male retiring self-defense officials. Physical activity as expressed in terms of time spent doing strenuous activities during leisure time was inversely related to the risk of adenomatous polyps. Controlling for rank, smoking, alcohol and body mass index (BMI), odds ratios for the categories of 0, 1-59, 60-119 and greater than or equal to 120 minutes per week were 1.0, 0.88, 0.70 and 0.44, respectively (trend p = 0.015). Among a limited range of foods and beverages, the consumption of rice, green tea and instant coffee tended to be associated with a decreased risk of adenomatous polyps. Although the associations observed with dietary habits still need to be substantiated, the findings on physical activity lend further evidence to the hypothesis that physical activity may be protective in the development of colon cancer.

Natural history of colorectal polyps and the effect of polypectomy on occurrence of subsequent cancer

To elucidate the natural history of colorectal polyps and to observe the influence of endoscopic polypectomy on the incidence of colorectal cancer, we conducted a retrospective cohort study of all patients who had undergone colonoscopic examination at the Center for Adult Diseases, Osaka, between April 1974 and December 1985. The study subjects consisted of a control group (760 non-polyp patients) and a polyp group (648 polyp patients, including 136 treated by polypectomy at the initial examination). These subjects were followed up until the end of 1987 by record linkage with the Osaka Cancer Registry's file to observe the occurrence of colorectal cancer. The O/E (observed/expected numbers derived from the general population) was 5.1 (95% confidence interval = 2.5-9.4) and 1.0 (0.1-3.6) for the polyp and control group, respectively. When subjects in the polyp group were categorized into polypectomy and non-polypectomy sub-groups, the O/E was 2.3 (0.1-12.6) and 8.0 (3.4-15.8) respectively. The relative risk of undergoing polypectomy to developing subsequent cancer was estimated at 0.3 (0.1-2.1). These results suggest an increased risk of developing cancer among polyp patients and the possibility of prophylactic effect of polypectomy against subsequent cancer. A large-scale and long-term follow-up study is required to confirm these findings.

DNA content of rectal scrapings from individuals at low and high risk for the development of colorectal cancer. A feasibility study

Scrapings of superficial rectal mucosa were collected from 31 patients with colorectal carcinoma, 66 patients with sporadic adenoma, and 53 control subjects with no personal or family history of colorectal cancer. The DNA ploidy level and proliferative patterns of each specimen were analyzed by flow cytometry (FCM). A GMS index, calculated as the ratio of G2 + M:S, was found to be significantly lower in control subjects than in any of the high-risk groups studied. Aneuploidy was more prevalent in rectal scrapings from cancer patients and adenoma patients than in those from control subjects. Aneuploid cell populations were detected in apparently normal rectal scrapings from two control subjects. Some high-risk individuals (i.e., cancer patients and patients with adenomas and a family history of cancer) exhibited higher proportions of tetraploid (designated G2/M) cells and a higher G2/M:S phase ratio than control subjects. The results accumulated thus far show that the rectal scraping procedure is safe and easy to perform. Our limited findings give hope that the DNA content analysis of cells obtained by rectal scraping may eventually prove useful in mass screening for colorectal cancer risk. However, definitive evaluation will require further refinement and elaboration of analytic technique and testing on more patients at various levels of predetermined risk.

Relation of changes in amount and type of dietary fat to fecapentaenes in premenopausal women

Correlation studies suggest that fecal mutagenicity is increased in groups eating high-fat diets, the same groups who are often found to have high colorectal cancer incidence and mortality. The fecapentaenes are the best characterized class of fecal mutagens, but the relationship of dietary fat intake to the excretion of these potent genotoxins is unknown. We studied the effect of changes in amount and type of dietary fat on fecapentaene levels in 31 premenopausal women 20-40 years of age who participated in a controlled feeding study. After a pre-diet free-living period lasting 1 menstrual cycle, women were placed on a high-fat (40% energy from fat) diet for 4 menstrual cycles and then switched to a low-fat (20% energy from fat) diet for an additional 4 menstrual cycles. One-half the subjects were maintained throughout the study at a ratio of polyunsaturated-to-saturated fatty acids (P/S ratio) of 1.0, the other half at 0.3; body weight was constant. All meals during the controlled diet periods were prepared at the Human Study Facility of the Beltsville Human Nutrition Research Center. Fecapentaene and fecapentaene precursor levels were measured in acetone extracts from 3-day pooled stool samples collected during the study. No differences in fecapentaene or precursor levels were observed between the high- and low-fat diets at either P/S ratio. Fecapentaene and precursor levels were higher while on controlled diets than during the pre-diet free-living period, and levels declined again in the post-diet free-living period. We conclude that dietary fat has no significant effect on fecapentaene or precursor levels in acetone extracts of stool in premenopausal women. The effect of other dietary or non-dietary factors on fecapentaenes remains unknown.

The role of chronic constipation, diarrhea, and laxative use in the etiology of large-bowel cancer. Data from the Melbourne Colorectal Cancer Study

Life-long bowel habits of 685 colorectal cancer cases and 723 age/sex frequency matched community controls were investigated as one part of a large, comprehensive, population-based study of colorectal cancer incidence, etiology, and survival, The Melbourne Colorectal Cancer Study. Self-reported chronic constipation was statistically significantly more common in cases than in controls (P = .05). Three or more bowel actions per day were reported by more cases than controls but the total number of respondents in this subset consisted of only ten cases and two controls. Otherwise, the frequency and consistency of bowel motions was similarly distributed among cases and controls. Constipation disappeared as a significant risk when simultaneously adjusted for previously determined dietary risk factors, indicating that it is the diet and not the constipation that is associated with the risk of large-bowel cancer. Additionally, a highly statistically significant association (P = .02) was found with the risk of colorectal cancer in those who reported constipation and also had a high fat intake, a finding consistent with current hypotheses of colorectal carcinogenesis. It is concluded that chronic constipation, diarrhea, and the frequency and consistency of bowel motions, as well as laxative use, are unlikely to be etiologic factors in the development of colorectal cancer. Self-reported chronic constipation is a marginally significant indicator of excess risk of large-bowel cancer and may be used as one of the indices in the screening of individuals for this cancer.

Effect of low-fat, high-carbohydrate, high-fiber diet on fecal bile acids and neutral sterols

The effect of a diet low in total fat and high in complex carbohydrates on the excretion of bile acids and neutral sterols and on serum lipids was studied in women, 46-47 years old, who were consuming a mixed Western diet. Participants kept an initial 3-day food record while consuming their normal diet (pre-diet period). During the dietary intervention period (experimental diet) which lasted for 26 days, all volunteers consumed a low-calorie, low-fat (less than 10% of total calories), high-fiber (37 g/day, high-carbohydrate diet. At the 1-year follow-up, the participants completed another 3-day food record, which indicates that these volunteers maintained their caloric and fat intake at levels slightly higher than the experimental diet, but lower than the pre-diet period. Individual 24-hr fecal samples for 2 days and blood samples were collected from the volunteers during each dietary period. Fecal samples were analyzed for neutral sterols and bile acids, and blood samples were analyzed to ascertain cholesterol and triglyceride levels. There were no significant differences in the excretion of neutral sterols between the dietary periods. Fecal secondary bile acids were significantly lower during the experimental and follow-up diet periods compared with the pre-test diet period. Serum cholesterol levels were significantly lower during the experimental and follow-up diet periods than during the pre-test diet period. These results suggest that switching from a high-fat, low-fiber diet to a low-fat, high-fiber diet can reduce the excretion of bile acids which are thought to be involved in the promotion of colon cancer.

Aspects of descriptive epidemiology and survival in colorectal cancer

World-wide cancer of the colon and rectum emerges as the third most frequent form of cancer in males and the fourth in females. Patients with colorectal cancer suffer from a considerable excess mortality during the first six to eight years after diagnosis, and the cure rate, which is in the order of 35-40% in the Swedish population, has remained largely unchanged over several decades. The incidence rates show a steep rise with age, marked international differences, increasing incidence in developing countries, adjustments in cancer risk within few decades in populations who move from low- to high-risk areas, and no consistent differences in relation to race. In addition, the incidence rates display a complex network of relationship to age, sex, segment of the large bowel and secular trends. These observations indicate that environmental factors play a predominant role in the development of colorectal cancer, that such factors may have specific influences in certain segments of the large bowel, and that they modulate the risk even in adult life.