Trends in colorectal cancer incidence and histologic findings in Maori and Polynesian residents of New Zealand

Disparities in Early-Onset Colorectal Cancer

The incidence and mortality of early-onset colorectal cancer (CRC) are increasing in the United States (US) and worldwide. In the US, there are notable disparities in early-onset CRC burden by race/ethnicity and geography. African Americans, Hispanic/Latinos, and populations residing in specific regions of the Southern U.S. are disproportionately affected with CRC diagnosed at younger ages, while less is known about disparities in other countries. Reasons for these disparities are likely multi-factorial and potentially implicate differences in health determinants including biology/genetics, diet/environment, individual health behaviors, and access to high-quality health services, as well as social and policy factors. This review summarizes current understanding of early-onset CRC disparities and identifies specific research areas that will inform evidence-based interventions at individual, practice, and policy levels to reduce the global burden of this disease.

Trends in colorectal cancer mortality by ethnicity and socio-economic position in New Zealand, 1981-99: one country, many stories

BACKGROUND

Ethnicity and socio-economic position are important determinants of colorectal cancer (CRC) mortality. In this paper, we determine trends in colorectal cancer mortality by ethnicity and socio-economic position in New Zealand.

METHODS

Cohort studies of the entire New Zealand population for 1981-84, 1986-89, 1991-94 and 1996-99 (linking Census and mortality datasets) allowed direct determination of trends in CRC mortality by income and education. For ethnicity, we used routine unlinked Census and mortality data, but with correction factors applied for undercounting of Mâori and Pacific deaths.

RESULTS

ETHNICITY: CRC mortality trends varied markedly. There were small (10-20%) decreases among non-Mâori non-Pacific people, a 50% increase among Mâori, and up to 10-fold increase among Pacific people. By 1996-99, all three ethnic groups had similar CRC mortality. SOCIO-ECONOMIC POSITION: For females, differences in CRC mortality by education and income increased over time e.g. poor females had a 40% higher CRC mortality than rich females in 1996-99, compared with no difference in 1981-84 (p for trend 0.04). In men, increases in inequality were seen by income but not education.

CONCLUSION

The observed ethnic trends probably reflect differential trends in exposure to etiological risk factors. Social inequalities in colorectal cancer mortality appear to be increasing.

Age and time as factors in the left-to-right shift of the subsite of colorectal adenocarcinoma: a study of 213,383 cases from the California Cancer Registry

GOALS

Using a data set of more than 200,000 cases, we can measure the effects of age, time, sex, and race/ethnicity on the shift of the site of origin of colorectal adenocarcinoma from the left to the right side.

BACKGROUND

As people become older, there is a shift of the site of origin of adenocarcinoma of the colorectum from the left to the right side. Although some studies do show some relationship of this shift, in addition to age, to race/ethnicity and to sex, there are no large, total population-based data studying the effects of these factors and time trends in this shift.

STUDY

213,383 cases of adenocarcinoma of the colorectum for the years 1988 to 2003 from the California Cancer Registry have been studied.

RESULTS

The left-to-right shift increases significantly with increasing age and year of diagnosis, and is greater in women than in men and is greater in whites than in other racial/ethnic groups. The time-related shift is a reflection of a lesser decrease in the incidence of colorectal adenocarcinoma on the right side than on the left.

CONCLUSIONS

The most attractive hypothesis is that a greater likelihood of prior polypectomy, and thus prevention of more cancers, occurs on the left side than on the right.

A population-based study of colorectal cancer histology in the United States, 1998-2001

BACKGROUND

Histology is an important factor in the etiology, treatment, and prognosis of cancer. The purpose of this study was to descriptively characterize colorectal cancer (CRC) histology in the United States population.

METHODS

Data from cancer registries in the National Program of Cancer Registries (NPCR) or Surveillance, Epidemiology and End Results (SEER) program, representing 88% of the U.S. population, were used in the study. The analysis included 522,630 microscopically confirmed CRC cases diagnosed from 1998-2001.

RESULTS

About 96% of CRCs were adenocarcinomas, approximately 2% were other specified carcinomas (including carcinoid tumors), about 0.4% were epidermoid carcinomas, and about 0.08% were sarcomas. The proportion of epidermoid carcinomas, mucin-producing carcinomas, and carcinoid tumors was greater among females. Several histologic patterns with regard to race and ethnicity existed, including a higher percentage of carcinoid tumors among most non-white populations. With respect to age, higher percentages of sarcomas, mucin-producing adenocarcinomas, signet ring cell tumors, and carcinoid tumors were found in individuals under age 40. Overall, adenocarcinomas were more likely to be diagnosed at regional stages with moderate differentiation. Compared with other adenocarcinomas, signet ring cell tumors were more often poorly differentiated and were at distant stage at diagnosis. Carcinoid tumors and sarcomas were mainly poorly differentiated and were at localized stage at diagnosis. Small cell carcinomas were more likely undifferentiated and were at distant stage at diagnosis.

CONCLUSIONS

To date, this is the largest population-based study to analyze CRC histology in the United States. Distinct demographic and clinical patterns associated with different histologies may be helpful for future epidemiologic, laboratory, and clinical studies.

Time trends of incidence of digestive system cancers in changle of China during 1988-2002

AIM: To analyze the incidence of digestive system cancer in Changle of China over a 15-year period.

METHODS: The datasets were presented as time-series of China-standardized annual incidence during

1988-2002. Linear regression model was used to analyze the incidence of stomach, liver, esophagus and colorectal cancers.

RESULTS: Linear regression models for the time-series of stomach and esophagus cancer incidences for both men and women were statistically significant (P < 0.05); Regression models for liver cancer and for colorectal cancer were statistically significant for men (P < 0.05).

CONCLUSION: The incidence rates of stomach and esophagus cancers for both men and women had down tendencies. For men, liver cancer had a down trend of the incidence and colorectal cancer had an upward trend of the incidence rate.

Meat consumption, cancer risk and population groups within New Zealand

In comparison with other OECD countries with good cancer registries, New Zealand has the highest mortality rate of colon cancer, second highest of breast cancer and third highest of prostate cancer. A possible association with heterocyclic amine consumption has been suggested for each of these cancers. Studies of locally cooked meat suggest that the main contributors to heterocyclic amines in the New Zealand diet would be well-cooked beef, chicken and pork. Well-cooked beef steak, and the specific heterocyclic amine, IFP, showed a weak positive correlation with prostate cancer risk in the New Zealand population, but no studies thus far have considered the role of meat cooking practices or heterocyclic amines in the development of other cancers. The Maori and Pacific Island people, despite a superficially similar diet, have a substantially lower incidence of colon cancer than people of Caucasian origin. These differences are particularly intriguing in view of a report that a very high percentage of these people have a fast acetylator phenotype-a factor suggested to augment the effect of well-cooked red meat in other populations. The three population groups are known to differ in their preferences for meat type (including processed meats), and there are anecdotal suggestions that they may differ in preferred cooking methods. More detailed population studies are warranted to establish the role of meat, meat processing, cooking methods and the interaction with food plants and/or with genotype and phenotype in New Zealand.

Developing areas in cancer in New Zealand

New Zealand has a cancer profile similar to those of Western developed countries, with a high rate of melanoma, similar to Australia. Statistics separating the Maori from the non-Maori population, although open to difficulties in interpretation, show higher rates in Maori of liver, stomach, lung and cervix uterine cancer and lower rates of colorectal cancer and of melanoma. Screening and prevention programmes are limited by resource constraints; there is population screening for cervical cancer and breast cancer screening is being developed. Screening for hepatitis B and liver cancer is proposed, despite conflicting scientific opinions, while screening for colorectal cancer is not planned, despite randomized trial evidence of benefit. There is no clear national cancer control programme at present. Investigation of stomach cancer in Maori families had identified a new gene.

Micronutrients, dietary questionnaires and cancer

There is increasing evidence that many chemicals, although present in the diet at only low levels, play an important role in protection against cancer. Micronutrients are defined as nutrients present in the body in amounts less than 0.005% of body weight. Some micronutrients suggested to play a protective role in cancer are beta-carotene, vitamin E and vitamin C. In addition to those chemicals with an established role in nutrition, there is also a less well-defined group of chemicals, often referred to as phytochemicals, which may prove even more important. Examples here are a group of sulphur-containing chemicals present in brassicaceous vegetables, such as broccoli and cabbage, that appear to be very effective anticarcinogens. Epidemiology will be essential in accurately defining the role of phytochemicals and micronutrients in cancer. However, the large prospective studies that would be most desirable increasingly utilize food frequency questionnaires containing a limited number of questions. Such an approach has been well validated for macronutrients. However, there is often less accurate information available on micronutrients and phytochemicals, and the food combinations necessary (and acceptable) for macronutrients may be inappropriate for these other factors. It would be most desirable that fruits and vegetables are individually itemized or grouped according to plant families rather than macronutrient status. This may be the most appropriate way of identifying potentially novel protective factors in the diets of countries such as Morocco or New Zealand.

Changes in the localization of colorectal cancer: implications for clinical practice

A hospital-based study was performed in order to examine the subsite distribution of colorectal cancer diagnosed in 1992-93 in the Zaanstreek region. The localization was compared with tumours diagnosed in the years 1972-73 and 1982-83. The number of colorectal cancers has markedly increased, and a significant rise in localization of tumours proximal to the splenic flexure has occurred (32% in 1972-73 to 43% in 1992-93). There also appears to be greater incidence of colorectal cancer in women. A trend towards an increase of proximal localization of tumours in women was noted. Possible explanations for this phenomenon are discussed. The results of this study suggest the importance of improved diagnostic accuracy in colorectal cancer and, in addition, may have consequences for screening programmes.

Using central cancer-registry data to monitor progress in early detection of breast and cervical cancer (Illinois, United States)

Cases of breast and cervical cancer account for almost 40 percent of all cancers diagnosed in Illinois (United States) women. Information on screening rates, however, is not collected routinely for the populations at risk. This paper reports on surveillance indicators designed to identify target populations and evaluate programs. All cases of cancers of the breast (n = 38,824, including in situ) and invasive cervix (n = 2,763) with a known stage, among women aged 40 to 74, were identified through the population-based Illinois State Cancer Registry for 1986 to 1992. The proportion of breast cancer cases with in situ disease-stage and cervical cancer cases with a late invasive stage were selected as surveillance indicators. Differences by age and race were evaluated, as were age- and race-specific trends. The data suggest that Black women, aged 40 to 74 years, and White women, aged 65 to 74 years, should be targeted for breast-cancer-screening interventions. All women, aged 40 to 74, should be targeted for enhanced cervical-cancer-screening interventions. Significant trends in in situ breast cancer diagnoses were apparent in all age-race groups, however no significant decline in invasive cervical cancer was found for any age-race group. The indicators identified the age- and race-specific disparities among potential target populations for breast and cervical cancer screening.

Insulin and colon cancer

Some factors related to Westernization or industrialization increase risk of colon cancer. It is believed widely that this increase in risk is related to the direct effects of dietary fat and fiber in the colonic lumen. However, the fat and fiber hypotheses, at least as originally formulated, do not explain adequately many emerging findings from recent epidemiologic studies. An alternative hypothesis, that hyperinsulinemia promotes colon carcinogenesis, is presented here. Insulin is an important growth factor of colonic epithelial cells and is a mitogen of tumor cell growth in vitro. Epidemiologic evidence supporting the insulin/colon-cancer hypothesis is largely indirect and based on the similarity of factors which produce elevated insulin levels with those related to colon cancer risk. Specifically, obesity--particularly central obesity, physical inactivity, and possibly a low dietary polyunsaturated fat to saturated fat ratio--are major determinants of insulin resistance and hyperinsulinemia, and appear related to colon cancer risk. Moreover, a diet high in refined carbohydrates and low in water-soluble fiber, which is associated with an increased risk of colon cancer, causes rapid intestinal absorption of glucose into the blood leading to postprandial hyperinsulinemia. The combination of insulin resistance and high glycemic load produces particularly high insulin levels. Thus, hyperinsulinemia may explain why obesity, physical inactivity, and a diet low in fruits and vegetables and high in red meat and extensively processed foods, all common in the West, increase colon cancer risk.

Differences in intake of specific food plants by Polynesians may explain their lower incidence of colorectal cancer compared with Europeans in New Zealand

Epidemiological studies have implicated obesity; high intakes of alcohol, fat, and energy; and low intakes of food plants as risk factors for colorectal cancer. In New Zealand, Polynesians (including Maoris and people from several Pacific Islands) are more likely to be overweight and have higher intakes of fat and energy than Europeans, and they are likely to have similar total intakes of food plants. Yet, in New Zealand, Polynesians have a significantly lower incidence of colorectal cancer than the Europeans. It is possible that the difference in incidence of colorectal cancer is due to differences in consumption of specific food plants by Polynesians and Europeans in New Zealand. Here we have compared the consumption of specific food plants by 429 Maoris, 643 Pacific Islanders, and 4,451 Europeans in paid employment in New Zealand. Of the 51 food plants eaten by New Zealanders, 6 were eaten significantly more frequently and 17 significantly less frequently by the two Polynesian groups than by Europeans. The quantity of any protective chemical components (or other as yet unknown protective factors) in food plants is likely to be related to their botanical classification. Differences in the intake of specific food plants may at least partly explain differences in the incidence of colorectal cancer between Polynesians and Europeans.