Variation In Cancer Incidence Research Articles

Social inequality and incidence of and survival from cancer in a population-based study in Denmark, 1994–2003: Background, aims, material and methods

The purpose of this register-based study was to identify variations in cancer incidence and survival after cancer in Denmark on the basis of a range of socioeconomic, demographic and health-related indicators. The indicators were level of education, disposable income, affiliation to the work market, social class, housing tenure, size of dwelling, cohabitation status, type of district, ethnicity, Charlson comorbidity index, depression and schizophrenia measured at the individual level on an annual basis. The study population comprised all Danish residents born between 1925 and 1973 and aged ⩾30 years, who were followed up for cancer incidence in 1994–2003 and for survival in 1994–2006. The study was based on 3.22 million persons, yielding almost 26 million person-years and 147,973 cancers. In this paper, we provide a detailed description of the indicators and the statistical methods, and we discuss the strengths and limitations of our approach.

Social inequality in incidence of and survival from cancer in a population-based study in Denmark, 1994–2003: Summary of findings

The purpose of this nationwide, population register-based study was to describe variations in cancer incidence and survival by social position in a social welfare state, Denmark, on the basis of a range of socioeconomic, demographic and health-related indicators. Our study population comprised all 3.22 million Danish residents born in 1925–1973 and aged ⩾30 years, who were followed up for cancer incidence in 1994–2003 and for survival in 1994–2006, yielding 147,973 cancers. The incidence increased with lower education and income, especially for tobacco- and other lifestyle-related cancers, although for cancers of the breast and prostate and malignant melanoma the association was inverse. Conversely there was a general increase in incidence among early retirement pensioners, persons living in rented housing and those living in the smallest dwellings. Also incidence rates were generally higher in persons living alone compared to those living with a partner and in the capital area compared to the rural areas. Social inequality in the prognosis of most cancers was observed, despite the equal access to health care in Denmark, with poorer relative survival related to fewer advantages, regardless of how they were measured, often most pronounced in the first year after diagnosis. Also living alone and having somatic or psychiatric comorbidity negatively impacted the relative survival after most cancers. Our study shows that inequalities in cancer incidence and survival must be addressed in all aspects of public health, with interventions both to reduce incidence and to prolong survival.

Variations in cancer incidence among UK ethnic groups

Variations in cancer incidence among UK ethnic groups

Cancer Incidence, Mortality, and Associated Risk Factors Among Asian Americans of Chinese, Filipino, Vietnamese, Korean, and Japanese Ethnicities

Many studies demonstrate that cancer incidence and mortality patterns among Asian Americans are heterogeneous, but national statistics on cancer for Asian ethnic groups are not routinely available. This article summarizes data on cancer incidence, mortality, risk factors, and screening for 5 of the largest Asian American ethnic groups in California. California has the largest Asian American population of any state and makes special efforts to collect health information for ethnic minority populations. We restricted our analysis to the 4 most common cancers (prostate, breast, lung, colon/rectum) and for the 3 sites known to be more common in Asian Americans (stomach, liver, cervix). Cancer incidence and mortality were summarized for 5 Asian American ethnic groups in California in order of population size (Chinese, Filipino, Vietnamese, Korean, and Japanese). Chinese Americans had among the lowest incidence and death rate from all cancer combined; however, Chinese women had the highest lung cancer death rate. Filipinos had the highest incidence and death rate from prostate cancer and the highest death rate from female breast cancer. Vietnamese had among the highest incidence and death rates from liver, lung, and cervical cancer. Korean men and women had by far the highest incidence and mortality rates from stomach cancer. Japanese experienced the highest incidence and death rates from colorectal cancer and among the highest death rates from breast and prostate cancer. Variations in cancer risk factors were also observed and were for the most part consistent with variations in cancer incidence and mortality. Differences in cancer burden among Asian American ethnic groups should be considered in the clinical setting and in cancer control planning.

Time trends in socioeconomic differences in incidence rates of cancers of gastro-intestinal tract in Finland.

BackgroundThe magnitude of socioeconomic differences in health varies between societies, and over time within a given society. We studied the association between social class and incidence of cancers of the gastro-intestinal tract over time in a large cohort in Finland.MethodsWe studied social class variation among 45–69 year-old Finns during 1971–95 in incidence of cancers of the gastro-intestinal tract by means of a computerized record linkage of the Finnish Cancer Registry and the 1970 Population Census, which included social class data.ResultsThere were 2.3 million individuals in the cohort under follow-up, with 1622 cases of cancer of the esophagus, 8069 stomach (non-cardia), 1116 cardia, 408 small intestine, 6361 colon, 5274 rectum, 1616 liver, 1756 gallbladder, and 5084 pancreas during 1971–1995. Cancers of the esophagus, stomach, cardia, gallbladder and pancreas were most common among persons belonging to a low social class. Cancers of the small intestine in males only, colon in both genders, and rectum in females were most common in the higher social classes. Incidence of stomach cancer decreased and incidence of colon cancer increased over time in both genders in all social classes, and the large differences between social classes remained unchanged over time. Incidence rates of cardia cancer did not change substantially over time.ConclusionThere is a large variation in incidence of cancer of the gastrointestinal tract by social class in Finland. Although much of the observed social class differences probably could be explained by known etiological factors such as diet, physical exercise, alcohol consumption, smoking and exogenous hormone use, part of the variation is apparently attributable to largely unknown factors.

Third Annual World Congress on the Insulin Resistance Syndrome

This is the third of three articles reviewing presentations at the 3rd Annual World Congress on the Insulin Resistance Syndrome, San Francisco, California, 17–19 November 2005. Pamela Goodwin (Toronto, Canada) introduced the topic of insulin resistance and malignancy, pointing out that there is variation in cancer incidence around the world, with variations in diet and obesity as important determining factors, and perhaps with the insulin resistance syndrome (IRS) as the underlying state leading to both increased cancer risk and worse outcomes of cancers of breast, prostate, colon, and many other tissues. Mediators may include activation of tyrosine kinase signaling pathways of premalignant and malignant cells via the insulin, insulin-like growth factor (IGF)-1, and IGF-2 receptors. Insulin receptors are present on normal breast, colorectal, and other cells, and in cancer cell lines, binding of the insulin receptor activates the mitogen-activated protein kinase pathways, and insulin stimulates cell-cycle progression, with the potential to increase epithelial cell proliferation in colon and other tissues. Hormone receptor negative breast cancers, particularly those not expressing the progesterone receptor, may have increased signaling through the insulin receptor. There are two forms of the insulin receptor. The A form is mainly seen in the fetal state, and also in the adult central nervous system (CNS), with the B form seen in the adult. The A form has high-affinity IGF-2 binding, has mitogenic and antiapoptotic effects, and hybridizes with the IGF-1 receptor; therefore, a fruitful area of research in carcinogenesis may be the expression of this form of the insulin receptor. Gerald Reaven (Stanford, CA) noted that differential tissue insulin sensitivity may be important in the relationship between the IRS and malignancy. The dose-response curve of adipose tissue to insulin shows a greater degree of insulin effect than that seen in skeletal muscle. Similarly, in the IRS not every …

Rural‐Urban Differences in Colon Cancer Risk in Blacks and Whites: The North Carolina Colon Cancer Study

Geographic and racial variations in cancer incidence have been observed. Studies of colorectal carcinoma indicate a higher incidence and mortality rate for blacks than for whites in the United States. We evaluated the effect of rural versus urban residence on colon cancer risk and stage of disease at diagnosis in blacks and whites. Interviews were conducted with 558 colon cancer cases and 952 controls enrolled in the North Carolina Colon Cancer Study, a population-based case-control study of blacks and whites residing in 33 contiguous counties. Residence in a rural area was associated with increased colon cancer risk (odds ratio, 1.4; 95% confidence interval, 1.1-1.8). This association was no longer significant after controlling for recent use of colorectal cancer screening tests (odds ratio, 1.2; 95% confidence interval, 0.9-1.6). Risk estimates were not modified by race nor were they markedly different for extent of disease at diagnosis. However, colorectal cancer screening rates were lower for blacks than for whites. Our findings suggest that rural blacks and whites are at increased risk of colon cancer regardless of stage of disease at diagnosis than their urban counterparts; this relationship may be mediated by screening behavior.

Cancer Map Patterns: Are They Random or Not?

Maps depicting the geographic variation in cancer incidence, mortality or treatment can be useful tools for developing cancer control and prevention programs, as well as for generating etiologic hypotheses. An important question with every cancer map is whether the geographic pattern seen is due to random fluctuations, as by pure chance there are always some areas with more cases than expected, or whether the map reflects true underlying geographic variation in screening, treatment practices, or etiologic risk factors. Nine different tests for spatial randomness are evaluated in very practical settings by applying them to cancer maps for different types of data at different scales of spatial resolution: breast, prostate, and thyroid cancer incidence; breast cancer treatment and prostate cancer stage in Connecticut; and nasopharynx and prostate cancer mortality in the U.S. Tango's MEET, Oden's Ipop, and the spatial scan statistic performed well across all the data sets. Besag-Newell's R, Cuzick-Edwards k-NN, and Turnbull's CEPP often perform well, but the results are highly dependent on the parameter chosen. Moran's I performs poorly for most data sets, whereas Swartz Entropy Test and Whittemore's Test perform well for some data sets but not for other. When publishing cancer maps we recommend evaluating the spatial patterns observed using Tango's MEET, a global clustering test, and the spatial scan statistic, a cluster detection test.

Nutritional “Omics” Technologies for Elucidating the Role(s) of Bioactive Food Components in Colon Cancer Prevention

Evidence continues to implicate dietary components and genetic susceptibilities as important determinants of cancer risk and tumor behavior. Variation in cancer incidence among and within populations with similar dietary patterns suggests that an individual's response may reflect interactions with genetic factors, which may modify gene, protein, and metabolite expression patterns. Nutrigenomics, defined as the interaction between nutrition and an individual's genome, will likely provide important clues about responders and nonresponders. In this symposium, the role of bioactive food components in colon cancer susceptibility was used to exemplify the application of "omic" technologies for cancer prevention. Topics that were addressed included dietary changes and gene polymorphisms (nutrigenetics), DNA methylation (nutritional epigenomics), gene expression (nutritional transcriptomics), altered formation or bioactivation of proteins (proteomics), and characterizing how the quantity and timing of exposure influence small molecular weight cellular constituents (metabolomics). The final presentation focused on exfoliated cells as a surrogate sample for the evaluation of bioactive food components in cancer prevention. The goal of the symposium was to provide an example of each of the "omic" technologies as they relate to nutrition, cancer risk, and tumor behavior, and to help the participants understand that an integrated framework that simultaneously examines all of the "omic" technologies is needed.

Behaviour partly explains educational differences in cancer incidence in the south-eastern Netherlands: the longitudinal GLOBE study.

Cancer morbidity and mortality vary among socio-economic groups. We investigated whether educational differences in behaviour could explain the variation in cancer incidence. In 1991, a postal questionnaire on socio-economic status, exposure variables, health and health-related behaviour was filled out by 18,973 participants (response rate 70.1%) of the longitudinal GLOBE study. Participants were followed and linked with the regional population-based Eindhoven Cancer Registry. Between 1991 and 1998 a total of 760 new tumours were found. The risk of cancer (all sites combined) was higher in the three quartiles of lower educational level compared with the highest educational level, odds ratios (ORs) varying from 1.25, 1.34, 1.27 to 1.00 from the lowest to the highest category, respectively (P=0.14). The relative risk (RR) for lung cancer for low versus high education was 2.7 [95% confidence interval (CI) 1.3-5.3]; adjustment for smoking, alcohol intake and physical activity decreased the risk to 1.6 (95% CI 0.8-3.3). Smoking alone explained 39% of the association, when alcohol intake and physical exercise were added to the model 61% of the effect was explained. In conclusion, a lower education is associated with increased cancer risks, which can be explained partly by behavioural factors.

Local clustering in breast, lung and colorectal cancer in Long Island, New York

BackgroundAnalyses of spatial disease patterns usually employ a univariate approach that uses one technique to identify disease clusters. Because different methods are sensitive to different aspects of spatial pattern, an approach employing a battery of techniques is expected to describe geographic variation in human health more fully. This two-part study employs a multi-method approach to elucidate geographic variation in cancer incidence in Long Island, New York, and to evaluate spatial association with air-borne toxics. This first paper uses the local Moran statistic to identify cancer hotspots and spatial outliers. We evaluated the geographic distributions of breast cancer in females and colorectal and lung cancer in males and females in Nassau, Queens, and Suffolk counties, New York, USA. We calculated standardized morbidity ratios (SMR values) from New York State Department of Health (NYSDOH) data.ResultsWe identified significant local clusters of high and low SMR and significant spatial outliers for each cancer-gender combination. We then compared our results with the study conducted by NYSDOH using Kulldorff's spatial scan statistic. We identified patterns on a smaller spatial scale with different cluster shapes than the NYSDOH analysis did, a consequence of different statistical methods and analysis scale.ConclusionThis is a methodological and comparative study to evaluate whether there is substantial benefit added by using a variety of techniques for geographic pattern detection at different spatial scales. We located significant spatial pattern in cancer morbidity in Nassau, Queens, and Suffolk counties. These results broadly agree with the results of other studies that used different techniques, but differ in specifics. The differences in our results and that of the NYSDOH underscore the need for an exploratory, integrative, and multi-scalar approach to assessing geographic patterns of disease, as different methods identify different patterns. We recommend that future studies of geographic patterns use a concordance of evidence from a multiscalar integrative geographic approach to assure that 1) different aspects of spatial pattern are fully identified and 2) the results from the suite of analyses are logically consistent.

Socio-economic differences in incidence rates of cancers of the male genital organs in Finland, 1971-95.

We studied social class variation in the incidence of cancers of the prostate, testis, penis and scrotum among 1.1 million Finnish men (45-69 years of age) during 1971-95. The incidence of prostate cancer (6,972 cases) was increasing during the study period; the highest at all the times occurred in Social Class I (highest social class), 40-50% higher than in Social Class IV (lowest). The social class gradient was strongest in localized disease but there was some variation in incidence of non-localized prostate cancer. A total of 174 testicular cancer cases were diagnosed during the study period. In the early 1970s, the incidence of testicular cancer in Social Class I was 5-fold compared to Social Classes III and IV. Thereafter, the incidence rate decreased in Social Class I, but increased in the lower classes. The positive social class gradient was similar for seminomas and non-seminomas. For penile cancer (n = 128), the incidence decreased over time and social class variation was small. Only 6 cases of scrotum cancer were observed. In testicular cancer the strong positive social class association in the early 1970s is disappearing along with converging incidence trend slopes in different social classes. The difference diminished to less than 2-fold in the 1990s. Reasons for this observation remain open.

Evolution of Cancer Epidemiology

As the 20th century passes into history, it seems timely to reflect upon current directions and progress in epidemiologic studies of cancer. The most important legacy of cancer epidemiology to date is the general recognition that an array of exogenous exposures are responsible for most cancer occurrence (1). Evidence supporting this conclusion includes: 1) the notable variation in cancer incidence internationally, 2) migrants' and/or their descendants' frequent development of cancer rates characteristic of the new area of residence, and 3) etiologic studies demonstrating a substantial fraction of cancer arising from exogenous exposures. An important watershed was a 1981 article by Doll and Peto estimating the proportion of US cancer deaths due to major categories of exposures (1). The two most important categories were nutritional factors (estimated to be responsible for approximately 35 percent of cancer occurrence) and tobacco use (30 percent); others included reproductive factors/sexual behavior (7 percent); occupation (4 percent); alcohol drinking (3 percent); geophysical factors, including ionizing radiation and ultraviolet radiation from sunlight (3 percent); pollution (2 percent); iatrogenic exposures (1 percent); food additives (<1 percent); industrial products (<1 percent); and other and unknown factors. In an ongoing debate, some epidemiologists have questioned the entire premise of these estimates; others proclaim their continuing accuracy, while a few suggest rigorous reevaluation at periodic intervals to direct cancer epidemiologic research priorities. Differences as well as similarities between cancer epidemiology and other areas of epidemiology have changed over time. Prior to the second half of the 20th

Cancer and Low Levels of Plasma Cholesterol: The Relevance of Cholesterol Precursors and Products to Incidence of Cancer

Background. It is proposed that the mechanism responsible for the low plasma cholesterol–cancer associations reported in the literature is related to blood and tissue levels of cholesterol precursors and products, reflecting rates of cholesterol synthesis rather than the plasma cholesterol level itself.Methods. Data have been collated from Japanese and Northern European studies on plasma levels of a cholesterol precursor, lathosterol, and one product, cholestanol, each a marker of cholesterol metabolism. Situations in which the rate of cholesterol synthesis is altered have also been examined for their relationship to cancer incidence.Results. The data though minimal suggest that lathosterol and cholestanol may be higher in the blood of the Japanese compared with the Northern Europeans, despite lower plasma cholesterol levels in the Japanese. In accord with the hypothesis the Japanese have a low incidence of many cancers. Cholesterol synthesis is lowered when dietary cholesterol and fat intake are increased and incidence of cancer is increased in these states. Conversely cholesterol synthesis is raised in vegetarianism, the Mediterranean diet, pregnancy, and lactation, and incidence of some cancers is lowered.Conclusions. At least some of the variation in cancer incidence with plasma cholesterol levels and also with dietary saturated fat and cholesterol, as well as vegetarianism, the Mediterranean diet, pregnancy, and lactation, can be accounted for by their effects on the rate of cholesterol synthesis and the level of cholesterol precursors and/or products so generated.

An Analysis of the Geographic Variation in Cancer Incidence and its Determinants in Ontario

Cancer incidence data for the Ontario Public Health Units in 1980-91 were examined to investigate regional patterns and the existence of outlier values after adjustment for known risk factors. Candidate risk factors were derived from the Ontario Health Survey and the census. Weighted regressions were fit to the data, and the spatial pattern of the residuals was analyzed. The number of outlier data points with significant elevations or reductions in risk was close to that expected by chance. They were dispersed geographically, and occurred in a variety of cancer types. We conclude that, in general, most of the geographic variation in cancer risk can be associated with variation in known risk factors, and that there appear to be no broad regional effects remaining after adjustment for these factors. A few cancer sites provide limited evidence of regional effects that may warrant further investigation.

The relationship between population density and cancer mortality in Taiwan.

Many investigators have examined urbanization gradients in cancer rates. The purpose of this report was to identify urban‐rural trends in cancer mortality rates (1982–1991) for municipalities in Taiwan. For this purpose, Taiwan's municipalities were classified as rural, suburban, urban, or metropolitan, using population density as an ordinal indicator of the degree of urbanization. Average annual age‐adjusted, site‐specific cancer mortality rates were calculated for both sexes within each population density group. Significant increasing trends with more urbanization were observed in mortality rates for cancers of the lung, pancreas, and kidney among both males and females, as well as male prostate cancer, and female breast and ovary cancer. In addition, this study revealed a significant rural excess for nonmelanoma skin cancer among both males and females, as well as male non‐Hodgkin's lymphoma, and cancers of the female bone, and female connective tissue. Analytic studies for sites with consistent urban‐rural trends may be fruitful in identifying the aspect of population density, or other unmeasured factors, that contribute to these trends.

Cancer incidence of Hispanics and non-Hispanic whites in Cook County, Illinois.

Variations in cancer incidence and mortality rates between Hispanics and non-Hispanic whites have been reported in several regions in the United States. This report describes the ethnic variation in selected cancer sites in Cook County, Illinois. Cancer incidence, age-specific, and age-standardized relative rates, and 95% confidence intervals were estimated among Hispanics and non-Hispanic whites in Cook County, Illinois, for 1986-1987. Hispanics were identified using surnames and maiden names with the Generally Useful Ethnic Search System (GUESS). Rates of lung cancer in Hispanics were approximately half of those observed for non-Hispanic whites. Hispanics also had lower rates of colon, breast, and bladder cancer. Hispanic females had rates of invasive cervical cancer that were approximately two times higher than those of non-Hispanic whites. These results are consistent with previous studies and suggest that Hispanics residing in the United States may retain some of the risk profile of those living in their home country.

Childhood malignancies in the south‐west region of England, 1976–1985

The incidence and pattern of childhood cancer in the South-West Region of the United Kingdom was studied in the period 1976-1985 to see if there was any unevenness in distribution. This region consists of five counties with considerable variation in radon exposure and urbanisation. Cases were identified from multiple sources and the basis of the diagnosis reviewed. Internationally accepted diagnostic categories were used. Six hundred seventy-eight cases were found, giving an age standardised incidence rate of 114.2 per million childhood years. The incidence of different cancers by sex was strikingly similar to the Manchester Children's Tumour Registry, from a noncontiguous region, with three exceptions. In the South-West, there was a higher rate of soft tissue sarcoma in boys (P = 0.01) and lower rates of sympathetic nervous system and germ-cell tumours in girls (P = 0.01 and P = 0.04, respectively). There was no significant variation in cancer incidence among the five counties or with time. The incidence rate in counties of high radon exposure was not higher than with low radon exposure. The overall incidence in counties with urban districts was not significantly increased compared to those without, although there was a nonsignificant trend towards a higher incidence of leukaemia (P = 0.08). The incidence and type of childhood cancer are similar to those in a noncontiguous region. Geographical and temporal incidence are remarkably stable. Local environmental variation may not play a major role in the causality of childhood cancer.

Dietary non-nutritive cancer protective factors.

It has been widely believed that the majority of cancers in humans were caused by exposure to environmental carcinogens. The pronounced variation in incidence rates of specific cancers from one country to another was explained by a variation in the load of carcinogens to which people were exposed from the sea of carcinogens in which they lived. This native and simple point of view can no longer be upheld. It is becoming evident that this theory cannot quantitatively explain the observed occurrence of cancer. Variations in the intake of compounds with anticarcinogenic effects might just as well be made responsible for a major part of the variation in cancer incidence. A review is given of this emerging field and it is argued that the study of anticarcinogens may allow us to reach a more balanced concept of the causative network in human cancer. It should also equip us with better means for more effective cancer prevention.

Occurrence of carcinogens in the external environment: epidemiological investigations.

The variation in cancer incidence between European populations indicates that at least 50% of the cancer incidence in Denmark may be attributable to environmental factors, including factors related to living conditions and lifestyle, and, hence, in principle are avoidable. Based on data from epidemiological studies of cancer causes, it is estimated that 30-40% of the total cancer burden in Denmark could be prevented by application of already available knowledge. Epidemiological studies of cancer occurrence in relation to arsenic in drinking-water, chlorination of drinking-water, nitrates in drinking-water and ambient air pollution are briefly reviewed. Although the causal associations between these factors and cancer in humans are hypothetical and unproven, the available data allow a rough calculation of the maximum proportion of cancer cases which possibly can be caused by these factors. At most, a few percent of the total cancer incidence is attributable to these external environmental factors.