Background: Incidence rates of endometrial cancer are routinely calculated without removing women who have had a hysterectomy from the denominator, which leads to an underestimate. Furthermore, as the number of women who have had a hysterectomy (hysterectomy prevalence) varies by race, the estimate of racial difference in endometrial cancer incidence is incorrect.
Methods: Data from 1992 to 2008 from the SEER Program were used to calculate incidence rates of endometrial cancer (corpus uterus and uterus, NOS) for 67,588 women 50 years and older. Data from the Behavioral Risk Factor Surveillance System were used to estimate hysterectomy prevalence. SEER area populations were reduced by hysterectomy prevalence, and corrected incidence rates were calculated.
Results: For women 50 years and older, the corrected incidence rate of endometrial cancer was 136.0 per 100,000 among whites and 115.5 among blacks, a 73% and 90% increase respectively compared with the uncorrected rate. The increase was greater for black women because hysterectomy prevalence was higher among black women (47%) than white women (41%). The corrected incidence among black women significantly increased 3.1% per year compared with a 0.8% significant decrease among white women resulting in higher rates among black women toward the end of the study period.
Conclusion: Correcting the incidence rate for hysterectomy prevalence provides more accurate estimates of endometrial cancer risk over time.
Impact: Comparisons of rates of endometrial cancer among racial groups may be misleading in the absence of denominator correction for hysterectomy prevalence.