Cancer incidence trends using American Community Survey estimates are not consistent with SEER for small populations

• Cancer incidence rates estimated using American Community Survey and SEER population estimates rarely differ significantly.
• Interpretations of cancer incidence trends over time vary depending on the source of population estimates.
• Comparisons of cancer incidence rates among groups may yield opposing conclusions depending on the population estimate used.

BackgroundAmerican Community Survey (ACS) estimates are said to be uncertain for small areas and small population groups. The Surveillance, Epidemiology and End Results (SEER) database uses a decennial census extrapolation methodology to yield population estimates used by cancer researchers across the country. We compared metropolitan Detroit cancer incidence estimates calculated using ACS data to those using SEER population estimates, which we considered to be the gold standard.MethodsWe generated age-adjusted cancer incidence rate estimates for 1-year, 3-year and 5-year time periods (2005–2010) using SEER and ACS population estimates for four racial/ethnic groups by sex and cancer type for residents in the tri-county Detroit area. We calculated incidence rate ratios (IRRs) with corresponding 95% confidence intervals (CIs), and compared trends.ResultsWhile the IRRs were rarely significant, there were significant differences in incidence rate estimates for Hispanic males. Additionally, interpretation of trends varied by the estimate source: the ACS-based lung cancer incidence rate estimate for Hispanic females increased from 70.59 (95% CI 44.85, 110.67) to 86.13 (95% CI 54.83, 132.44) per 100,000 women from 2007 to 2010, while the SEER incidence rate estimate decreased from 80.76 (95% CI 53.36, 119.24) to 73.54 (95% CI 49.24, 106.62).ConclusionsInconsistencies were found when comparing incidence rate estimates for small population groups using the two population estimate sources. This finding has potential implications for health disparities research.