Variation In Incidence Of Colorectal Cancer Research Articles

Colorectal cancer spatial pattern in the northeast region of São Paulo, Brazil

BackgroundThis study examined the spatial pattern of the colorectal cancer (CRC) in the 18 municipalities that compose the Regional Health Department of Barretos (RHD-V), which is in the northeast of the state of São Paulo, Brazil. MethodsAll incident cases and deaths from CRC between 2002 and 2016 were included. Age-standardized rates (ASR) for incidence and mortality per 100,000 person-years were used to evaluate the spatial distribution for the total and five-year periods. The lethality rates were also assessed. Excess risk maps compared the observed and expected events. Age-standardized net survival was used to evaluate CRC survival. ResultsFor CRC incidence, the ASR value for the general population over the entire period (2002–2016) was 17.7 (95% CI: 16.7, 18.6), ranging from 16.7 (95% CI: 14.9, 18.4) (2002–2006) to 20.0 (95% CI: 18.3, 21.7) (2012–2016) per 100,000. When males and females were compared, the ASR was 20.1 (95% CI: 18.6, 21.6) and 15.7 (95% CI: 14.5, 17.0) per 100,000, respectively. For CRC mortality (2002–2016), the ASR was 8.2 (95% CI: 7.6, 8.9), ranging from 9.0 (95% CI: 7.8, 10.3) (2002–2006) to 8.2 (95% CI: 7.2, 9.3) (2012–2016) per 100,000. Overall, the excess risk up to 2.0 was more frequent. In terms of survival, municipalities with large port populations had lower survival in comparison with medium port. ConclusionsThis study showed a variation in CRC incidence and mortality, with differences considering five-year periods and gender, being the incidence higher in males than females in the entire period, with mortality equivalent to half the incidence. The survival was lower in municipalities with large port populations in comparison with medium port. Knowing spatial patterns of incidence, mortality, lethality, and survival can be necessary to support policymakers to advance or implement effective cancer control programs.

Time Trends in Colorectal Cancer Incidence From 1992 to 2016 and Colorectal Cancer Mortality From 1980 to 2018 by Age Group and Geography in Canada.

Several reports have highlighted increasing colorectal cancer (CRC) incidence among younger individuals. However, little is known about variations in CRC incidence or mortality across age subgroups in different geographical locations. We aimed to examine time trends in CRC incidence and mortality in Canada by age group and geography in this population-based, retrospective cohort study. Individuals diagnosed with CRC from 1992 to 2016 or who died of CRC from 1980 to 2018 in Canada were studied. Geography was determined using an individual's postal code at diagnosis from the Canadian Cancer Registry or province or territory of death from the Canadian Vital Statistics Death Database. Geography was categorized into Atlantic, Central, Prairies, West, and Territories. Canadian Cancer Registry data were used to determine CRC incidence from 1992 to 2016. Canadian Vital Statistics Death data were used to determine CRC mortality from 1980 to 2018. Among all age groups, CRC incidence was highest in Atlantic Canada, was lowest in Western Canada, and increased with age. CRC incidence increased over time for individuals aged 20-44 years and was stable or decreased for other age groups in all regions. CRC mortality was highest in Atlantic Canada and lowest in the Prairies and Western Canada. CRC mortality decreased for individuals in all age groups and regions except among individuals aged 20-49 years in the Territories. Most of Canada has not yet seen an increase in CRC burden in the age group of 45-49 years, which is a reason to not lower the start age for CRC screening in Canada. Targeted CRC screening should be considered for individuals younger than 50 years who live in the Territories.

Geographic Variation in Colorectal Cancer Incidence Among Asian Americans: A Population-Based Analysis 2006–2016

Among Asian Americans, cancer is the leading cause of death and colorectal cancer (CRC) is the second most common cancer.1 The uptake of CRC screening influences incidence and mortality trends; however, the most recent American Cancer Society CRC statistics reveals ongoing disparities in screening based on race and ethnicity, with people of Asian descent demonstrating the lowest CRC screening rates despite being the fastest growing racial or ethnic group in the United States.2,3.

Exploring geographical differences in the incidence of colorectal cancer in the Norwegian Women and Cancer Study: a population-based prospective study.

PurposeNorway has experienced an unexplained, steep increase in colorectal cancer (CRC) incidence in the last half-century, with large differences across its counties. We aimed to determine whether geographical distribution of lifestyle-related CRC risk factors can explain these geographical differences in CRC incidence in Norwegian women.MethodsWe followed a nationally representative cohort of 96,898 women with self-reported information on lifestyle-related CRC risk factors at baseline and at follow-up 6–8 years later in the Norwegian Women and Cancer Study. We categorized Norwegian counties into four county groups according to CRC incidence and used Cox proportional hazard models to estimate hazard ratios (HRs) and 95% confidence intervals (CIs) for risk factors. We used the Karlson, Holm, and Breen (KHB) method of mediation analysis to investigate the extent to which the risk factors accounted for the observed differences in CRC incidence between counties.ResultsDuring an average of 15.5 years of follow-up, 1875 CRC cases were diagnosed. Height (HR=1.12; 95% CI 1.08, 1.17 per 5 cm increase); being a former smoker who smoked ≥10 years (HR=1.34; 95% CI 1.15, 1.57); or being a current smoker who has smoked for ≥10 years (HR=1.28; 95% CI 1.12, 1.46) relative to never smokers was associated with increased CRC risk. Duration of education >12 years (HR=0.78; 95% CI 0.69, 0.87) vs ≤12 years, and intake of vegetables and fruits >300 g (HR=0.90; 95% CI 0.80, 0.99) vs ≤300 g per day were associated with reduced CRC risk. However, these risk factors did not account for the differences in CRC risk between geographical areas of low and high CRC incidence. This was further confirmed by the KHB method using baseline and follow-up measurements (b=0.02, 95% CI −0.02, 0.06, p=0.26).ConclusionLifestyle-related CRC risk factors did not explain the geographical variations in CRC incidence among Norwegian women. Possible residual explanations may lie in heritable factors.

Temporal and geographical variations in colorectal cancer incidence in Northern Iran 2004–2013

Introduction: Colorectal cancer (CRC) is one of the most common cancers in the Golestan province, Northern Iran. The purpose of this study is to describe colorectal cancer incidence patterns and trends in the province 2004–2013.Methods: Data on CRC cases were obtained from the Golestan Population-based Cancer Registry (GPCR). The GPCR is a high-quality cancer registry that collects data on primary cancers according to internationally accepted standard protocols. Age-standardized Incidence rates (ASR) were calculated and the 10-year trend quantified using the average annual percentage change (AAPC) from Joinpoint regressions.Results: The overall ASR of CRC were higher in men (14.8 per 100,000 person-years) and the urban populations (35.4), relative to women (11.5) and the rural populations (17.1), respectively. The overall incidence rate was observed to significantly increase 2004–2013 in men (AAPC = 7.3; 95%CI: 2.9–11.8) and women (AAPC = 6.6; 95%CI: 2.7–10.6). The analysis also showed that urban areas (AAPC = 8.1; 95%CI: 2.4–14.1) had a relatively more rapid increase in rates compared to rural areas (AAPC = 6.9; 95%CI: 2.2–11.7).Conclusions: CRC incidence rates in Golestan have been rising during the most recent decade, with a higher incidence and more rapid increases among men and the urban populations. The underlying risk factors should be assessed in the context of developing CRC prevention interventions in Golestan.

Geographic Variation in Colorectal Cancer Incidence and the Disparities in the Prevalence of Modifiable Risk Factors Across Canada

Background: Colorectal cancer is the third most common cancer worldwide. There is wide geographic variation in incidence with rates varying ten-fold between high- and low-income countries. This heavy burden can be mitigated given previous research has estimated that nearly half of all colorectal cancer cases could have been prevented through healthier diets and physically active lifestyles. In Canada, there is considerable geographic variation in age-adjusted incidence rates for colorectal cancer between jurisdictions, greater than that seen for many other cancers. These wide variations likely reflect differences in the prevalence of risk factors across provinces and territories. Aim: To describe the extent of the variation in colorectal cancer incidence rates across Canada and the disparities in the prevalence of modifiable risk factors across jurisdictions known to contribute to this burden. Methods: Colorectal cancer incident cases were obtained from the Canadian Cancer Registry; 2014 was used for provinces (except Quebec where 2010 was the most recent year available) and years 2012 to 2014 were combined to achieve more stable rates for the territories, which are much smaller in population. Data on four known modifiable risk factors for colorectal cancer (excess weight, physical inactivity, alcohol intake and low fruit and vegetable consumption) were obtained from the 2015-16 combined Canadian Community Health Survey. Results: Findings suggest that there is a north-south and east-west gradient in colorectal cancer modifiable risk factors in Canada. For instance, the percentage of adults with excess body weight ranged from 56.8% in British Columbia (west) to 73.1% in New Brunswick (east) and the percentage of adults not meeting physical activity guidelines ranged from 31.8% in Yukon (north) to 50.3% in New Brunswick (east). Generally, this pattern also reflects colorectal cancer incidence rates. The highest prevalence of modifiable risk factors and rates of colorectal cancer are typically in the northern (territories) and eastern provinces of Canada. Conclusion: The global burden of colorectal cancer is expected to increase by nearly 60% by 2030; therefore, targeted interventions are needed to ensure there is not a widening gap in colorectal cancer burden worldwide. Based on current knowledge, the most effective approaches to reduce the burden of colorectal cancer include: 1) adopting public policies that make healthy choices easier and create healthier environments where people live, work and play, and 2) continuing emphasis on screening and early detection. Strategic approaches to addressing modifiable risk factors, as well as mechanisms for detecting colorectal cancer before it develops, have the potential to translate into positive effects on population health and less people developing and dying from cancer.

Trends of Colorectal Cancer Incidence in Thailand by Age, Gender, and Region

Background: Colorectal cancer (CRC) is the third most common cancer in the world. While CRC incidence has decreased in many western countries over the last decades, largely thanks to screening, it is increasing in low and middle-income countries, including Thailand. However, it is unclear if these increases are consistent across different regions, gender and age groups. Aim: To understand the age-, gender- and region-specific temporal variation in CRC incidence in Thailand since the 1990s. Methods: We analyzed CRC incidence data from the Thailand National Cancer Network (TCIN) cancer registries, which include Chiang Mai (1990-2012), Lampang (1993-2014), Lopburi (2000-2014), Khon Kaen (1990-2014) and Songkhla (1990-2014) cancer registries. Trends in age-adjusted incidence (measured by annual percentage change (APC)) were assessed using Joinpoint regression. Trends by birth-year and calendar-year were assessed using age-period-cohort models. All analyses were done by region, gender, and age group (30-49, 50-84, 30-84). Results: CRC incidence has been increasing significantly in all regions, gender, and age groups; Overall, the APC was 3.82 for men and 3.84 for women (Chiang Mai, 4.34 for men & 3.26 for women; Khon Kaen, 2.69 for men & 3.68 for women; Lampang, 2.13 for men & 3.37 for women; Lopburi, 5.31 for men & 4.67 for women; Songkhla, 4.67 for men & 4.32 for women). The increase in incidence was higher for ages 50-84 (APC = 3.99 for men & 4.04 for women) compared with ages 30-49 (APC=2.97 for men & 3.09 for women). Test of parallelism suggests that increases are consistent between gender (P-value=0.97). The age-period-cohort analysis suggests that both calendar-year and birth-year are strongly correlated with CRC incidence trends, with a stronger relationship with birth-year than calendar-year for both genders. Conclusion: In contrast to western countries such as the US, CRC incidence is increasing across all age groups in Thailand, with faster increase in older ages. This highlights the needs for establishing population-wide screening programs to reduce the burden and stop the rise of CRC in Thailand and low-middle income countries.

Region-specific differences in colorectal cancer: Slovakia and Hungary have highest incidence in Europe.

Epidemiological data on colorectal cancer (CRC) exhibit high incidence in Central East Europe. Hungary, Slovakia and Croatia represent the lead. For decades it was the Czech Republic but it attained the fourth rank after the mid-2000. Remarkably, the Ashkenazi Jews who imigrated to the USA from Central Europe have the highest incidence of CRC among US minorities. They also have high incidence of inflammatory bowel disease, a risk for CRC. Notably, countries surrounding the Central European focus of CRC, Austria, Germany, Poland, Romania, Ukraine and Russia have substantially lower incidence. CRC in Central Europe has higher incidence than CRC among the highest at-risk cohort in the USA, the elderly blacks. Research and the genome wide screening identified genetic mutations associated with CRC in Ashkenazis from Central Europe. Some risk factors for CRC are non genotypic as evidenced by wide variation in CRC incidence in the course of only a few decades. Recent trends offer hope that identification of the non-innate pathogenic mechanisms would potentially reduce the burden of this third most lethal malignancy (Tab. 1, Fig. 4, Ref. 40).

Rak jelita grubego. Czy dieta ma znaczenie?

Colorectal cancer (CRC) is the most common malignancy of the gastrointestinal tract and one of the most common malignancies among men and women in Western countries. The role of dietary factors in CRC development seems to be significant, however, showing the relation of dietary factors in CRC remains challenging. Data supporting the interaction between diet and malignancy development come from: studies with an animal model of the disease, observations regarding geographical variation in CRC incidence, and different studies in people, especially long-term prospective investigations. The most important factor seems to be fiber. Additionally, recently published studies have shown that the diet-related disease obesity is also a risk factor of CRC. Adipokines, substances produced and secreted by adipose tissue, are proposed as a link between obesity and carcinogenesis. Genetic studies will possibly elucidate the complex interactions lying in the background of the development of the malignancy. Moreover, the gut microbiome seems to also play a role. Our paper discusses the current knowledge regarding CRC and diet.

Abstract A105: The extracellular calcium sensing receptor regulates the proliferation of colonic epithelial cells

Abstract The progression of colorectal cancer (CRC) from normal colonic epithelium to the malignant phenotype is associated with diverse genetic and epigenetic changes, including mutations of APC or beta-catenin genes. Extensive experimental and epidemiological evidence also suggest that differences in diet contribute to more variation in CRC incidence than any other factor. For example, several animal experimental studies support the notion that dietary Ca2+ prevents the development of CRC. The precise mechanism(s) mediating the chemopreventive properties of Ca2+ remain incompletely understood. The extracellular Ca2+-sensing receptor (CaR), a GPCRs originally cloned from parathyroid chief cells, plays a major role in the control of extracellular Ca2+ concentration by regulating parathyroid hormone secretion. However, subsequent studies demonstrated that the CaR is also expressed in other tissues and organs, including the entire gastrointestinal (GI) tract. Interestingly, CaR expression in colonic carcinomas is greatly reduced or lost, suggesting that the suppression of its expression may be associated with abnormal differentiation and malignant progression. Here, we assessed the role of the CaR in colonic epithelial cells proliferation. In order to elucidate the mechanisms involved, we examined in vitro changes in beta-catenin phosphorylation and intracellular distribution and cellular proliferation triggered by CaR stimulation. We found that CaR stimulation promotes, in human epithelial cells derived from normal colon and from colorectal adenocarcinoma, a decrease of up to 60% in beta-catenin Ser-552 phosphorylation, a residue involved in beta-catenin nuclear import and transcriptional activity regulation. This change in phosphorylation was accompanied by a redistribution of beta-catenin from the cytoplasm and nuclei to the plasma membrane and by a marked proliferation inhibition. To determine the role of the CaR in the proliferation of colonic cells in vivo, we employed a novel mouse model where the expression of the CaR was specifically knocked out in the GI tract. The results show that the crypts in the distal colon are deeper in knock out (KO) mice (389 ± 7.39 Arbitrary Units, mean ± SEM) than controls littermates (268 ± 6.35 AU) P < 0.0001. Similarly, the crypts in the proximal colon are deeper in KO mice (289 ± 7.02 AU) than controls (232 ± 5.36 AU) P < 0.0001. We also found significant morphological differences in the crypt’ structure of several regions in the proximal colon of CaR KO mice, including the absence of a well-organized surface layer of epithelial cells and the presence of disorganized crypts and numerous enlarged globet cells. Further analysis of the colon of KO mice showed that the number of proliferating cells, as revealed by Ki-67 proliferation marker immunostaining, was significantly larger than control littermates. Specifically, proliferating cells in the KO mice were detected in the base of the crypt and up to 60% of the crypt column. In contrast, in control littermates the proliferating cells were fewer and present mostly at the base of the crypt. We hypothesize that pathways emanating from the CaR lead to proliferation inhibition of colon-derived epithelial cells by a mechanism that involves beta-catenin Ser-552 dephosphorylation and that the genetic ablation of this receptor promotes hyperproliferation of colonic crypts. Citation Information: Cancer Epidemiol Biomarkers Prev 2010;19(10 Suppl):A105.

Abstract B128: Geographic and socioeconomic variations in colorectal cancer incidence in the prospective NIH-AARP Diet and Health study

Abstract Background: Persons from lower socioeconomic backgrounds have higher exposure to risk factors for, and higher mortality rate from, colorectal cancer (CRC), but there is a paucity of published population-based studies on the relationship between neighborhood socioeconomic context and CRC incidence. In this study, we used national prospective data to determine: 1) whether CRC incidence varied according to area-level socioeconomic context; and 2) if area-level differences in incidence are explained by clustering of CRC risk factors. Methods: We used data from the NIH-AARP Diet and Health Study, a prospective cohort of 566,402 persons residing in 6 US states and 2 metropolitan areas who were 50–71 years of age at baseline (1995–1996). Detailed data on diet, lifestyle and medical history were collected using questionnaires. Cancer incidence was ascertained from tumor registries through December 31, 2003. Participants were linked to the 2000 US Census data at the tract level. We used principal component factor analyses to derive an index of neighborhood socioeconomic deprivation from 10 census variables about education, poverty, employment and occupation. We restricted the analyses to 319,057 men and 214,298 women who did not have history of CRC at baseline and had complete data including valid geocoded information. Results: In single predictor Cox models with frailty, compared to persons residing in the lowest quintile of the deprivation index, those in the most deprived census tracts had a higher incidence of CRC (HR=1.27; 95% confidence interval [CI]: 1.16–1.40 for men and HR=1.32, CI: 1.15–1.52 for women). This increased risk was robust to adjustments for age, race-ethnicity and family history of colon cancer, body mass index, physical activity and dietary variables including calcium intake, smoking and a history of diabetes (HR: 1.13, CI: 1.03–1.24) for men and HR: 1.17, CI: 1.01–1.34 for women) and to further adjustment for use of non-steroidal inflammatory agents (HR=1.18; CI 1.05–1.34) for men; and HR= 1.19, CI: 0.99–1.42 for women). Significant heterogeneity was observed for the incidence of CRC among census tracts for both men and women (likelihood ratio test p-value <0.001). Conclusion: Our study found significant variation in the incidence of CRC by neighborhood of residence and neighborhood socioeconomic conditions after adjusting for recognized individual risk factors. Further studies are needed to explore other factors that may be associated with area-level differences in CRC incidence such as the use of screening. Citation Information: Cancer Prev Res 2010;3(1 Suppl):B128.

Spatial analysis of colorectal cancer incidence and proportion of late-stage in Massachusetts residents: 1995–1998

BackgroundThe aims of this study were to determine if observed geographic variations in colorectal cancer incidence are simply random or are statistically significant deviations from randomness, whether statistically significant excesses are temporary or persistent, and whether they can be explained by risk factors such as socioeconomic status (SES) or the percent of the population residing in an urban area rather than a rural area. Between 1995 and 1998, 6360 male and 6628 female invasive colorectal cancer cases were diagnosed in Massachusetts residents. Cases were aggregated to Census tracts and analyzed for deviations from random occurrence with respect to both location and time.ResultsSix geographic areas that deviated significantly from randomness were uncovered in the age-adjusted analyses of males: three with higher incidence rates than expected and eight lower than expected. In the age-adjusted analyses of females, one area with a higher incidence rate, and one area with a lower incidence rate than expected, were found. After adjustment for SES and percent urban, some of these areas were no longer significantly different.ConclusionPublic health practitioners can use the results of this study to focus their attention onto areas in Massachusetts that need to increase colorectal screening or have elevated risk of colorectal cancer incidence.

Can resistant starch and/or aspirin prevent the development of colonic neoplasia? The Concerted Action Polyp Prevention (CAPP) 1 Study.

Loss of function of the adenomatous polyposis coli (APC) tumour suppressor gene through truncating mutations or other means is an early event in most colo-rectal cancer (CRC). The APC gene encodes a large multifunctional protein that plays key roles in several cellular processes, including the wnt signalling pathway where an intact APC protein is essential for down regulation of beta-catenin. The APC protein also plays a role in regulation of cell proliferation, differentiation, apoptosis, cell-cell adhesion, cell migration and chromosomal stability during mitosis. Acquisition of a non-functional APC gene can occur by inheritance (in the disease familial adenomatous polyposis (FAP)) or by a sporadic event in a somatic cell. Whilst there is strong epidemiological evidence that variation in diet is a major determinant of variation in CRC incidence, conventional adenoma recurrence trials in sporadic cases of the disease have been relatively unsuccessful in identifying potentially protective food components. Since the genetic basis of CRC in FAP and in sporadic CRC is similar, intervention trials in FAP gene carriers provide an attractive strategy for investigation of potential chemo-preventive agents, since smaller numbers of subjects and shorter time frames are needed. The Concerted Action Polyp Prevention (CAPP) 1 Study is using a 2 x 2 factorial design to test the efficacy of resistant starch (30 g raw potato starch-Hylon VII (1:1, w/w)/d) and aspirin (600 mg/d) in suppressing colo-rectal adenoma formation in young subjects with FAP. Biopsies of macroscopically-normal rectal mucosa are also being collected for assay of putative biomarkers of CRC risk.

Colorectal cancer incidence and mortality in Texas 1990-1992: a comparison of rural classifications.

Although cancer incidence and mortality rates are known to be higher in urban populations, more unstaged tumors and later staged cancer are diagnosed in rural populations. Most investigators have used a dichotomous definition of urban and rural in studying these populations, and they have not considered whether a more detailed categorization of rural areas could influence their findings. The objective of this study was to evaluate colorectal cancer incidence and mortality rates in Texas from 1990 to 1992 by using a dichotomous definition (Metropolitan Area vs. Nonmetropolitan Area [MA/non-MA]) and two more detailed rural classifications (the Rural-Urban Continuum Code [RUCC] and the Urban Influence Code [UIC]). Cancer data were obtained from the Texas Cancer Registry for 1990 to 1992 and supplemented with data from the Texas State Department of Vital Statistics (mortality), the US Census Bureau (age, gender, race) and the Area Resource File (rural and urban definitions). Incidence and mortality rates, age-adjusted to the 1970 US standard population, were calculated for non-Hispanic White, African American, and Hispanic males and females. Results revealed a nonlinear relationship between rural category and colorectal cancer incidence or mortality for all races. Applying the MA definition yielded rates in the middle of the ranges obtained with using RUCC or UIC classifications and most closely reflected the result for non-Hispanic Whites using the more detailed scales. Our results suggest that a dichotomous definition of rural and urban may mask important variation in colorectal cancer incidence and mortality rates within rural areas.

The annual report to the nation on the status of cancer, 1973-1997, with a special section on colorectal cancer.

This annual report to the nation addresses progress in cancer prevention and control in the U.S. with a special section on colorectal cancer. This report is the joint effort of the American Cancer Society, the National Cancer Institute (NCI), the North American Association of Central Cancer Registries (NAACCR), and the Centers for Disease Control and Prevention (CDC), including the National Center for Health Statistics (NCHS). Age-adjusted rates were based on cancer incidence data from the NCI and NAACCR and underlying cause of death as compiled by NCHS. Joinpoint analysis was based on NCI Surveillance, Epidemiology, and End Results (SEER) program incidence rates and NCHS death rates for 1973-1997. The prevalence of screening examinations for colorectal cancer was obtained from the CDC's Behavioral Risk Factor Surveillance System and the NCHS's National Health Interview Survey. Between 1990-1997, overall cancer incidence and death rates declined. Joinpoint analyses of cancer incidence and death rates confirmed the declines described in earlier reports. The incidence trends for colorectal cancer have shown recent steep declines for whites in contrast to a leveling off of the rates for blacks. State-to-state variations occurred in colorectal cancer screening prevalence as well as incidence and death rates. The continuing declines in overall cancer incidence and death rates are encouraging. However, a few of the top ten incidence or mortality cancer sites continued to increase or remained level. For many cancer sites, whites had lower incidence and mortality rates than blacks but higher rates than Hispanics, Asian and Pacific Islanders, and American Indians/Alaska Natives. The variations in colorectal cancer incidence and death rates by race/ethnicity, gender, age, and geographic area may be related to differences in risk factors, demographic characteristics, screening, and medical practice. New efforts currently are underway to increase awareness of screening benefits and treatment for colorectal cancer.

Diet and colorectal cancer

Studies of migrants to Australia indicate that the risk of colorectal cancer (CRC) can be influenced by environment during adult life. Under a gene x environment interaction model for the risk of CRC, it is postulated that a high proportion of the variation in CRC incidence among populations is attributable to differences in diet, and that the average genetic susceptibility of populations to dietary carcinogenic components is similar. The possible relevance within populations of individual susceptibility to dietary components is supported by studies showing that the risk of CRC, compared with that of the general population, is not increased in the spouses of cases. It is postulated that, conditional upon a relevant dietary exposure, the level of susceptibility to diet is a major determinant of variation in individual risk. Despite high correlations of meat and fat with CRC among populations, the results of case-control studies have been inconsistent. Inability to stratify subjects by susceptibility may explain the lack of association of intake of fat and meat with CRC in many studies. A new generation of case-control and cohort studies of diet and CRC may extend the limits of epidemiology. Prevention trials with beta-carotene and other compounds have not protected against colorectal neoplasia, and may have exerted adverse effects. This possibility challenges the philosophy of chemoprevention trials in favor of trials of changes in diet towards patterns that are associated with lower risk.

Variation in colorectal cancer incidence in the united states by subsite of origin

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