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 cancer registries. The NCI’s Surveillance Epidemiology and End Results program (SEER) 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 two years later. The data are released to the public in the spring of the following year. For example, cancer cases diagnosed in 2015 were first reported to the NCI in November 2017 and released to the public in April 2018. In each subsequent release of the SEER research data, all prior diagnosis years (e.g., diagnosis years 2014 and earlier in the 2017 submission to the NCI) are updated as either new cases are found or new information is received about previously submitted cases (e.g., two separate cases are consolidated after they are found to be for the same person, a case is determined to have a different primary cancer site than originally determined, the race is changed from unknown to a specific race). The submissions for the most recent diagnosis year are, in general, about four percent below the number of cancers that will be submitted for that year eventually, 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).
Changes in the Delay-Adjustment Incidence Model
In the April 2018 data release (based on the 2017 submission with data through diagnosis year 2015), the reporting of SEER delay-adjusted incidence rates are derived from NAACCR submission data. This is the fourth year that delay factors for SEER have been based on NAACCR submission data. The statistical model is based on the same model used in the 2015 submission data. The details are available in the Development of the Delay Model.