Cancer Incidence Rates Adjusted for Reporting Delay

Timely and accurate calculation of cancer incidence rates is hampered by reporting delay, the time elapsed before a diagnosed cancer case is reported to the NCI. Currently, the NCI allows a standard delay of 22 months between the end of the diagnosis year and the time the cancers are first reported to the NCI in November, almost 2 years later. The data are released to the public in the spring of the following year. For example:

• Cases diagnosed in 2005 were first reported to the NCI in November 2007 and released to the public in April 2008.
• In each subsequent release of the SEER data, all prior diagnosis years (e.g., diagnosis years 2004 and earlier in the 2007 submission to the NCI) are updated as either new cases are found or new information is received about previously submitted cases.
• The submissions for the most recent diagnosis year are, in general, about two percent below the number of cancers that will be submitted for that year in the future, although this varies by cancer site and other factors.

The idea behind modeling reporting delay is to adjust the current case count to account for anticipated future corrections (both additions and deletions) to the data. These adjusted counts and the associated delay model are valuable in more precisely determining current cancer trends, as well as in monitoring the timeliness of data collection -- an important aspect of quality control (Clegg et al., 2002; Midthune et al., 2005). Reporting delay models have been previously used in the reporting of AIDS cases (Brookmeyer & Damiano, 1989; Pagano et al., 1994; Harris, 1990).