Cancer Prevalence Statistics Overview
Prevalence is a statistic of primary interest in public health because it identifies the level of burden of disease or health-related events on the population and health care system. Prevalence represents new and pre-existing cases alive on a certain date, in contrast to incidence which reflects new cases of a condition diagnosed during a given period of time. Prevalence is a function of both the incidence of the disease and survival.
- Limited-Duration Prevalence represents the proportion of people alive on a certain day who had a diagnosis of the disease within the past x years.
- Complete Prevalence represents the proportion of people alive on a certain day who previously had a diagnosis of the disease, regardless of how long ago the diagnosis was, or if the patient is still under treatment or is considered cured.
We used the counting method to estimate prevalence from incidence and follow-up data from the SEER cancer registries. The counting method estimates prevalence by counting the number of persons who are known to be alive at a specific calendar time and adjusting for those lost to follow-up. Prevalence estimates obtained using the counting method are generally limited-duration prevalence due to the length of registration time. For example, incidence data collected from 1975 through 2009 yields a maximum of 35-years prevalence, in other words, prevalence of people diagnosed in the previous 35 years. Because people can be diagnosed with more than one tumor, there are different methods that can be used to determine which tumors to include in the counting method (Tumors Included in Prevalence Estimates).
The completeness index method (Capocaccia & De Angelis, 1997) is used to estimate complete (unlimited) prevalence from limited-duration prevalence. Other approaches to estimate complete prevalence are cross-sectional population surveys, the transition method rate, and back calculation (all are defined in Approaches to Estimation).