Endometrial cancer (EC) is the most common gynecologic malignancy and is the fourth most common cancer seen in U.S. women. It is the only major cancer that has continued to see a rise in incidence and mortality for the past 2 decades, and it is anticipated that nearly 66,000 new cases of EC will be diagnosed this year with 12,550 deaths.1 Given that the well-established risk factors for developing EC including obesity, diabetes, and insulin resistance, the obesity epidemic is indisputably playing a significant role in the increasing incidence.
Historically, White women were thought to have the highest incidence of EC; however, this incidence rate did not account for hysterectomy prevalence, which can vary widely by numerous factors including age, race, ethnicity, and geographic region. When correcting EC incidence rates for prevalence of hysterectomy, Black women have had the highest incidence of EC since 2007, and rates continue to climb.2 In fact, the average annual percent change (APC) in EC incidence from 2000 to 2015 was stable for White women at 0.2% while Black women had a near order of magnitude greater APC at 2.1%.2
Dr. Wesley Burkett
Differing incidence rates of EC can also be seen by histologic subtype. Endometrioid EC is the more common and less lethal histology of EC that often coincides with the type I classification of EC. These tumors are estrogen driven; therefore, they are associated with conditions resulting in excess estrogen (for example, anovulation, obesity, and hyperlipidemia). Nonendometrioid histologies, primarily composed of serous tumors, are more rare, are typically more aggressive, are not estrogen driven, and are commonly classified as type II tumors. Racial differences between type I and type II tumors are seen with White women more commonly being diagnosed with type I tumors while Black women more typically have type II tumors. White women have the greatest incidence rate of endometrioid EC with an APC that remained relatively unchanged from 2000 to 2015. Black women’s APC in incidence rate of endometrioid EC has increased during this same period at 1.3%. For nonendometrioid tumors, an increasing incidence is seen in all races and ethnicities; however, Black women have a much higher incidence of these tumors, with a rate that continues to increase at an APC of 3.2%.2
EC incidence is increasing with a particularly concerning rise in those who report Black race, but are these same disparities being seen in EC mortality? Unfortunately, drastic disparities are seen in survival data for Black women afflicted with EC. Black patients are more likely to be diagnosed with advanced or metastatic EC and less likely to be diagnosed with localized tumors. While being diagnosed with a more advanced stage of disease does affect survival in EC, Black patients have worse survival regardless of stage of disease at the time of diagnosis.1 As discussed earlier, the more aggressive type II tumors are composed of nonendometrioid histologies and are more common in Black women. This could lead to the false assumption that these higher-risk tumors are why Black women are disproportionately dying from EC; however, when examining survival by histologic subtype, Black women are more frequently dying from the lower-risk endometrioid EC regardless of stage of disease. The same disparate survival outcomes are also seen in nonendometrioid histologies.2 Thus, Black patients have the lowest survival rates irrespective of stage at diagnosis or histologic subtype.
The disparities seen in EC mortality are not new. They can be seen in data for over 30 years and are only widening. While there has been an increase in mortality rates from EC across all races and ethnicities from 2015 to 2019 compared with 1990 to 1994, the mortality rate ratio for Black women compared with White women has increased from 1.83 in 1990-1994 to 1.98 in 2015-2019.3 In the early 1990s, the risk of death from ovarian cancer was twice that of EC. The mortality of EC is now similar to that of ovarian cancer. This threshold in mortality ratio of EC to ovarian cancer has already been seen in Black women, who have experienced greater mortality in EC compared with ovarian cancer since 2005. In fact, the EC mortality of Black women in 2019 was similar to the mortality of White women with ovarian cancer nearly 30 years ago.3
Decades of data have demonstrated the glaring racial disparities seen in EC, and yet, no significant progress has been made in addressing this inequity. Oncology research is now beginning to move beyond describing these differences to a strategy of achieving equitable cancer care. While the study frameworks and novel investigations aimed at addressing the disparities in EC is outside the scope of this article, disparities in clinical trial enrollment continue to exist.
A recent example can be seen in the practice-changing KEYNOTE-775 trial, which led to the Food and Drug Administration approval of lenvatinib plus pembrolizumab in EC treatment.4 A total of 827 patients with EC that progressed or recurred following treatment with platinum-based chemotherapy were enrolled in this multinational, multicenter trial. Thirty-one (3.7%) of the patients enrolled were Black. Of those who were enrolled in the United States, 14% were Black. The authors report that this proportion of Black patients in the United States is consistent with 2020 census data, which reported 13.4% of people identified as Black. However, using census data as a benchmark for equitable enrollment is inappropriate. Certain demographic groups are historically more difficult to count, and the COVID-19 pandemic exacerbated the challenge in obtaining an accurate count through job loss, government distrust, and access restrictions resulting in an estimated net undercount of 2.45% in those who report Black race.5 Composition of trial enrollment should mirror the population that will be affected by the study results. As advanced EC disproportionately affects Black patients, their enrollment must be higher in these pivotal trials. How else are we to know if these novel therapeutics will work in the population that is most afflicted by EC?
Future studies must account for socioeconomic factors while acknowledging the role of social determinants of health. It is imperative that we use the knowledge that race is a social construct created to control access to power and that there are biologic responses to environmental stresses, including that of racism, affecting health and disease. Changes at every level, from individual practitioners up to federal policies, will need to be enacted or else the unacceptable status quo will continue.
Dr. Burkett is a clinical fellow in the division of gynecologic oncology, department of obstetrics and gynecology, at the University of North Carolina at Chapel Hill.
References
1. Siegel RL et al. CA Cancer J Clin. 2022;72:7-33.
2. Clarke MA et al. J Clin Oncol. 2019;37:1895-908.
3. Giaquinto AN et al. Obstet Gynecol. 2022;139:440-2.
4. Makker V et al. N Engl J Med. 2022;386:437-48.