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About Cancer Data

about cancer

Cancer surveillance is the most well-established and extensive disease surveillance network in the United States. Centralized cancer registries in the United States conduct population-based surveillance of cancer incidence and mortality.

This page provides general information about cancer data and measures developed by the Iowa Public Health Tracking program. Contact Us for more information about these data.

Information on this page:

What do these data tell us?

  • The incidence of cancer in Iowa residents by year. Incidence is the number of new cases of illness occurring within a specific population over a period of time.
  • The incidence of some cancers in Iowa residents by age group, race/ethnicity, gender, or region of the state.
  • If a measure is going up or down over time.
  • If a segment of a population is at higher risk for cancer or a specific type of cancer.

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How can we use these data?

  • To inform the public about cancer incidence in Iowa.
  • For program planning and evaluation by state and local partners.

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What can these data not tell us?

  • What causes cancer or what causes specific types of cancer.

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What are the sources of the data?

  • Iowa Cancer incidence data is collected by the State Health Registry of Iowa (SHRI)/Iowa Cancer Registry (ICR).
  • The ICR is a population-based cancer registry that has served the State of Iowa since 1973. The ICR has been a member of the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) Program since its inception in 1973.
  • Since 1982 cancer has been a reportable disease in Iowa and the ICR has been delegated the responsibility for collecting data on cancer. In the Iowa Administrative Code (IAC) under Public Health (641), Chapter 1, Reportable Diseases, Poisonings and Conditions, and Quarantine and Isolation covers the reporting of cancer.

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What time period of data is available?

  • The Iowa Public Health Tracking portal displays cancer data from the year 2000 through the most recent year of data available.
  • There is usually a three or four-year lag period before cancer incidence data are available on the Iowa Public Health Tracking portal.

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How is a cancer case identified?

  • Cancer patient data are collected from hospitals, pathology laboratories, cancer treatment centers, dermatology clinics and Iowa death certificates. The ICR also collects data from targeted physicians who send their pathology specimens to out-of-state laboratories. Data are collected by 20 field representatives who are responsible for case finding in their assigned coverage areas.

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What is the difference between a number, rate, age-adjusted rate, and age-specific rate and how to use them?

Number:

  • The number indicates the total number of newly diagnosed cancer cases.
  • To understand the magnitude or how large the overall burden is, use the number.
  • To protect an individual's privacy, counts of 5 or less are suppressed.

Crude Rate:

  • If you want to understand the probability or what is the underlying risk in a population, then use a rate.
  • In our analysis a rate is calculated using a numerator, the number of newly diagnosed cancer cases during a period of time, divided by a denominator, the number of people in a population during the same period of time. This fraction is then multiplied by 100,000 or 1,000,000 to provide a more recognizable value.
  • To protect an individual's privacy, rates based on counts of 5 or less are suppressed.

Age-adjusted rate:

  • Age-adjusted rates are useful when comparing the rates of two population groups that have different age distributions.
  • A weighted average, called the direct method, is used to adjust for age in this analysis. Age specific rates in a given population are adjusted to the age distribution in a standard population by applying a weight. The U.S. 2000 Standard population is used as the basis for weight calculations.
  • To protect an individual's privacy, rates based on counts of 5 or less are suppressed.

Age-specific rate:

  • A rate of an event (such as disease or death) measured within a particular age group. It is similar to a crude rate but is calculated within an age group (e.g. an age-specific rate of cancer in children under the age of 15).
  • To protect an individual's privacy, rates based on counts of 5 or less are suppressed.

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What are the limitations of the data?

  • Counts and rates are calculated based upon residential address at time of diagnosis. No information is available on prior residences.
  • Geocoding accuracy, level of geocoding, and geocoding completeness may vary by time and space. This could potentially create geographically non-random errors in calculated rates of cancer.
  • No personal exposure information will be available, including smoking history, diet, lifestyle, or history of cancer.
  • No information will be available on the latency of cancer cases.
  • Rates based on 10 or fewer cases of cancer are unstable (i.e. unstable rate or UR) and caution should be exercised in interpreting these rates.
  • Counts presented here are number of cancers, not number of people with cancer. A person can contribute more than one case of cancer for the purposes of these data.

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Where can I find more technical information about the data?

More detailed documentation of the cancer data can be found in the following documents:

Indicator Profiles

All Ages Cancer Incidence
Childhood Cancer Incidence

Descriptive Metadata

Cancer Incidence

Contact Us to learn more about cancer data, or any of the measures displayed on the Iowa Public Health Tracking Portal.

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