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Cancer is a varied group of diseases that have in common the uncontrolled proliferation and spread of abnormal cells, which may invade other tissues of the body. The different types of cancer vary not only in their site or tissue of origin, but also in other factors including cell morphology, rate of growth, and method of spread. Through January 16, 2003, the Indiana State Cancer Registry has recorded 27,133 cases of cancer that were newly diagnosed in 1997. (Note: basal and squamous cell carcinomas of skin are not reported.) Excluding in situ cancers except urinary bladder (n = 1,943: 2,326 total in situ cases minus 383 in situ urinary bladder cases), 25,190 cancer cases are included in the incidence tables. The exclusion of in situ cases allows comparisons with national data and is based on the major differences in prognosis and treatment between in situ and invasive cancers. Interpreting the pathologist's description of invasion for urinary bladder tumors has proven difficult for coders and, since patients generally receive the same treatment for in situ and microinvasive tumors, in situ bladder tumors have traditionally been included in incidence rates.
Cancer incidence increases with age, though cancer can occur in infants as well as the elderly. Table IV presents information on the distribution of cancer cases by age and Table V presents age-specific incidence rates. In 1997 there were 113 new cases of invasive cancer in children less than 10 and an additional 144 cases in those ages 10 - 19. Less than 1% of cancers occurred in children, whereas approximately 60% occurred in those ages 65 and over. Those 70 - 79 years of age had the largest number of new diagnoses (7,604). The lowest incidence rate* for invasive cancer was in children ages 5 - 9 (9.4 per 100,000). The incidence rates increased steadily with age to 2,220.4 for those 80 - 84.
Nationwide African-Americans have a higher risk of cancer than does the white population. In 1997, the all-sites cancer incidence rate for Indiana's black population was somewhat higher than the rate for the white population (388.6 vs. 367.1) but this difference was not statistically significant. The 1997 lung cancer incidence rate was significantly higher in African-Americans than in whites (77.2 vs. 63.2), and the incidence rate for prostate cancer was almost 60% higher for black males in Indiana than for white males (160.8 vs. 101.2). In addition, blacks are more likely to be diagnosed at a later stage than are whites, leading to a higher cancer mortality rate for blacks than for whites.
In general, men are more likely to be diagnosed with cancer than are women. The Indiana 1997 cancer incidence rate was 27% higher for men than for women (421.2 vs. 332.7). However, since cancer incidence increases with age and since, due to the longer life span of women, there are more elderly women than men, more women were diagnosed with cancer in Indiana in 1997 than were men (12,732 vs. 12,458). There are a few cancers that occur more frequently in women. For example, the rate of thyroid cancer in Indiana females is more than 2 ½ times that of males (5.8 vs. 2.2).
The most frequently diagnosed cancer in Indiana in 1997, as in the United States (US) as a whole, was lung cancer. The next most common cancer was breast cancer, followed by prostate, colon (excluding rectum), and urinary bladder cancers. Table I lists the most commonly diagnosed cancers by sex. For men, the most commonly diagnosed cancer was prostate, followed by lung, colon, bladder, and non-Hodgkin's lymphoma.
For Indiana women, breast cancer was most commonly diagnosed, followed by lung, colon, uterine body, and ovarian cancers. For both men and women, mortality from lung cancer (3,738 deaths in Indiana in 1997) was greater than that from either prostate (734 deaths) or breast cancer (917 deaths). Colon cancer (1,148 deaths) was the second leading cause of cancer death for the total Indiana population.
The 1997 cancer incidence was lower in Indiana than in the US as a whole, though cancer mortality was higher (Table I and SEER Cancer Statistics Review). It is unclear whether the lower incidence rate in Indiana reflects incomplete reporting to the Indiana State Cancer Registry or whether the SEER data from 11 population-based registries, representing approximately 14% of the US population, is not representative of the country as a whole.
Illness and death from cancer are increasingly preventable by decreasing modifiable risk factors, increasing early detection through improved screening, and developing more effective treatments. Current estimates indicate that at least 75% and perhaps more than 90% of cancers are due to factors external to the patient, i.e., factors other than the patient's heredity, endogenous hormones, and immunologic status. More than two-thirds of these external or "environmental" factors are associated with personal lifestyle and behavior. Tobacco use accounts for approximately 30% of US cancer deaths. Numerous scientific studies have shown that involuntary exposure of nonsmokers to environmental tobacco smoke increases their risk of lung cancer and other illnesses. Another estimated 30% of cancer deaths can be attributed to dietary factors, particularly those associated with obesity, such as high dietary saturated fat and low consumption of fruits and vegetables. An estimated 5% of cancer deaths are associated with low physical activity, and an additional 3% - 7% with personal choices in the areas of sexual contacts, and childbearing.
Table III compares Indiana State incidence rates for all sites and the most common cancers with the incidence rates for the individual counties. Table VII presents information on the numbers of cases diagnosed and incidence rates by county. In Indiana with its numerous small counties (and in the case of less common cancers), there are often many counties with only a few or no cases of a specific cancer type. To avoid compromising the confidentiality of individuals in those counties, the actual number of cases for a county is not reported if it is less than 5, and in cases where the number for any one sex is less than 5, the number for the opposite sex is not reported either. Rates based on less than 20 total cases are very unstable and can be misleading, hence no comparison with the state is made when there are less than 20 cases in a county and those rates are flagged in Table VII. Appendix B (Technical Notes) gives information on rates, confidence intervals, and how to interpret them.
* In general, incidence rates are the number of new cases per 100,000 persons in the population and, except for age-specific rates, are age-adjusted to the 1970 US standard million population. See Appendix B. Age-specific incidence rates are the number of new cases occurring in persons of that age per 100,000 persons of that age in the population.
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