Uterine fibroid tumors (leiomyomas) are the most common benign pelvic tumors in women and are the major indication for hysterectomy. Fibroid tumors are more common and more severe among African American women. Although this disease disproportionately affects the African American population, we understand little about what causes the disparity. Fibroid tumors should be considered a public health issue, given the magnitude of the problem and the costs of health care for this disease. In this review, we examine the burden of disease from fibroid tumors in the African American population and review the natural history, diagnosis, and treatment of uterine fibroid tumors, with emphasis on how these can differ, depending on race. We also focus on the socioeconomic burden caused by the disease and describe the anticipated influence of new health care reforms and funding mechanisms for fibroid tumor research.
Uterine fibroid tumors, also termed leiomyomas or myomas , are the most common benign gynecologic tumors; ultrasound evidence shows that >80% of African American women and approximately 70% of white women will have uterine fibroid tumors by age 50. However, because only 20-50% of all women with fibroid tumors experience related symptoms and because screening for fibroid tumors is not performed routinely, the true incidence is difficult to ascertain. In fact, the reported incidence of fibroid tumors in most studies likely is underestimated because they include only symptomatic women with clinical diagnoses that have been confirmed ultrasonographically. For women in their 40s and 50s, abnormal uterine bleeding is the most common reason to seek gynecologic consultation, and fibroid tumors are among the most common causes of this symptom. Pelvic pain, another common reason for gynecologic consultation, is a symptom often associated with fibroid tumors. These symptoms markedly alter the quality of life and reproductive health in affected women. Treatment options include many alternatives to hysterectomy, including medical therapies, minimally invasive surgery, uterine artery embolization, and magnetic resonance–guided focused ultrasound surgery. Hysterectomy, however, remains the most common intervention, and in the United States, fibroid tumors are the leading indication for hysterectomies.
Disproportionate impact of fibroid tumors in African American women
In addition to a having greater lifetime incidence of fibroid tumors, African American women have a 3-fold increased age-adjusted incidence rate and a 3-fold increased relative risk of fibroid tumors when adjusted for other confounding factors. Some investigators suggest a doubling of risk for Hispanic women, whereas others suggest that only African American women have increased risk. African ancestry is considered a key risk factor for the development of fibroid tumors. African American women have fibroid tumors diagnosed at earlier ages, are more likely to be symptomatic, and are likely to have different responses to medical treatment than white women. The size and growth rates of fibroid tumors are greater in African American women, who are more likely to undergo surgical intervention than other racial groups. Approximately 42 per 1000 women are hospitalized annually because of fibroid tumors, but African American women have higher rates of hospitalization, myomectomies, and hysterectomies compared with white women (relative risk, 3.5, 6.8, and 2.4, respectively).
Taran et al published a systematic review detailing the limited racial diversity in high-quality fibroid tumor studies that were published from 2000-2006 and attempted to determine the factors that encouraged the reporting of race and ethnicity. The investigation showed that >75% of fibroid tumor studies did not report the patients’ race, and most of the studies that reported race were those exclusively of African American women (eg, reports from the Black Women’s Health Study). Of the remaining studies that reported race, African American women represented 15% of the studied population.
Biologic studies of racial differences
Despite the racial differences in symptoms and incidence, relatively little data have been published regarding the biologic basis of fibroid tumors in African American women. The few existing studies that examined large numbers of African American and white women (eg, the Nurses’ Health Study) did not show that risk factors that traditionally differed by race accounted for the increased burden of fibroid tumors in African American women. Some data suggest that fibroid tumor growth differs by race, especially as women approach menopause. Although some evidence links environmental factors such as diet and history of abuse to this increased risk, most of this information comes from studies such as the Black Women’s Health Study. A recent study has linked vitamin D insufficiency with increased fibroid tumor risk in African American women. This study is important not only because of the biologic plausibility of the mechanism (ie, darker skin inhibits the production of biologically active vitamin D) but also because it opens a potential pathway to prevention.
Information on the genetic basis of fibroid tumors in African American women has been sparse for several reasons. First, many of the important genetic studies of fibroid tumors using exome sequencing or genome-wide association studies have come from countries such as Finland and Japan, where there are few women of African descent. The Finding Genes for Fibroid Tumors study, which began in 1999, aimed to recruit both African American and white women in the United States for genome-wide association studies ; however, the published reports have all been limited to the genetics of white women because participation by African American women has been limited. The historic issues of unethical treatment of African American medical study participants (eg, the Tuskegee syphilis studies) potentially has limited enrollment in these important studies.
Additional studies have demonstrated racial differences in fibroid tumors at the molecular level, with differential gene expression of genes, proteins, and micro-RNAs. Based on these biologic differences, it is reasonable to hypothesize that fibroid tumors in African American women may respond differently to medical therapy. If the pathophysiologic condition of fibroid tumors differs by race, there is a need for trials that will compare fibroid tumor therapies in African American vs white women.
Biologic studies of racial differences
Despite the racial differences in symptoms and incidence, relatively little data have been published regarding the biologic basis of fibroid tumors in African American women. The few existing studies that examined large numbers of African American and white women (eg, the Nurses’ Health Study) did not show that risk factors that traditionally differed by race accounted for the increased burden of fibroid tumors in African American women. Some data suggest that fibroid tumor growth differs by race, especially as women approach menopause. Although some evidence links environmental factors such as diet and history of abuse to this increased risk, most of this information comes from studies such as the Black Women’s Health Study. A recent study has linked vitamin D insufficiency with increased fibroid tumor risk in African American women. This study is important not only because of the biologic plausibility of the mechanism (ie, darker skin inhibits the production of biologically active vitamin D) but also because it opens a potential pathway to prevention.
Information on the genetic basis of fibroid tumors in African American women has been sparse for several reasons. First, many of the important genetic studies of fibroid tumors using exome sequencing or genome-wide association studies have come from countries such as Finland and Japan, where there are few women of African descent. The Finding Genes for Fibroid Tumors study, which began in 1999, aimed to recruit both African American and white women in the United States for genome-wide association studies ; however, the published reports have all been limited to the genetics of white women because participation by African American women has been limited. The historic issues of unethical treatment of African American medical study participants (eg, the Tuskegee syphilis studies) potentially has limited enrollment in these important studies.
Additional studies have demonstrated racial differences in fibroid tumors at the molecular level, with differential gene expression of genes, proteins, and micro-RNAs. Based on these biologic differences, it is reasonable to hypothesize that fibroid tumors in African American women may respond differently to medical therapy. If the pathophysiologic condition of fibroid tumors differs by race, there is a need for trials that will compare fibroid tumor therapies in African American vs white women.
Differences in surgical procedures and outcomes
Surgical treatment for fibroid tumors is especially prevalent among African American women because of both an earlier age of onset and more symptomatic disease. African American women are 2-3 times more likely to undergo hysterectomy for fibroid tumor tumors than are other racial groups. As reported in the National Hospital Discharge Survey, the total rates of hysterectomy for African American and white women were similar from 1988-1990 (61.7 and 56.5 per 10,000 women, respectively). However, fibroid tumors as the primary indication for hysterectomy was much higher for African American women (61% vs 29% for white women). This pattern was confirmed in another large cohort of 80,000 women that again showed that African American women had significantly higher rates of fibroid tumor surgery than white women. Comparisons of the rates of hysterectomies and myomectomies in African American and white women indicate that African American women are more likely than white women to undergo both myomectomy and hysterectomy ( Figure ). Myomectomy appears to be even more common in African American women, with almost a 7-fold increased relative risk. With the increasing racial diversity in the United States, this means that, if surgical rates are stable, fibroid tumor–related surgical procedures and hospitalizations are projected to increase by 20-31% by 2050.
Fibroid tumors tend to be more numerous and larger among African American women who undergo hysterectomy, which increases their risk of blood transfusion and postsurgical complications such as infection and bleeding. However, there are no corresponding data on racial differences in disease burden before other fibroid tumor therapies or at the time of diagnosis.
Postoperative complications after myomectomy were twice as high in African American women compared with white women (odds ratio [OR], 2.5; 95% CI, 1.5–4.8). Also, perioperative blood transfusions were significantly higher among the African American patients (OR, 2.3; 95% CI, 1.1–5.0). The issue of blood transfusions is further complicated by the overrepresentation of African American women among Jehovah’s Witnesses, which is a group with a religious prohibition against blood transfusion. Published data estimated Jehovah’s Witness congregations to be 22% African American, whereas the general US population is 12% African American. Because some gynecologic services and physicians insist that transfusion remain a medical option or decline to provide care for women who refuse transfusion, this can affect disproportionately African American women who avoid or delay needed medical care out of fear that their religious beliefs will not be respected.
Fibroid tumors in pregnancy and obstetric outcomes
Uterine fibroid tumors, especially submucosal fibroid tumors, have an adverse impact on fertility and pregnancy. Furthermore, many studies have shown that the removal of submucosal fibroid tumors and large intramural fibroid tumors (>5 cm) improves pregnancy outcome and live birth rates in patients who undergo in vitro fertilization and in those who achieve spontaneous pregnancy. Pregnancy loss during the first trimester and spontaneous abortion are also twice as common in patients with fibroid tumors. One metaanalysis evaluated the effect of uterine fibroid tumors on the rate of pregnancy loss in women who undergo in vitro fertilization and found that patients in the leiomyoma group had twice the miscarriage rate as patients without fibroid tumors (15.3% vs 7.7%). Also, uterine fibroid tumors have been associated with various obstetric complications such as preterm labor, fetal malposition, placenta previa, postpartum hemorrhage, and neonatal morbidity. Studies have shown that women with fibroid tumors more commonly have cesarean delivery than women without fibroid tumors (48.8% vs 13.3%), mostly because of fetal malpresentation and abnormal placentation that is caused by enlarged uterine fibroid tumors.
A large retrospective cohort study by Lai et al compared neonatal outcomes of women with and without leiomyoma. They found an increased risk of preterm birth, low birth rate, and intrauterine fetal death in women with fibroid tumors, regardless of maternal age, ethnicity, or parity.
Fibroid tumors and assisted reproductive technology
A recent review of fibroid tumors and reproductive outcomes compared women with and without fibroid tumors and documented lower cumulative birth rates (36.9% vs 41%), more miscarriages (20.4% vs 12.9%), and an increased rate of preterm delivery (OR, 1.5; 95% CI, 1.3–1.7) in women with fibroid tumors. Disparities have been noted in the incidence and outcomes of fibroid tumors with the comparison of white and African American women who undergo assisted reproductive technology (ART) (incidence of leiomyoma, 30.8% and 10.7% for African American and white women, respectively). The higher prevalence of uterine fibroid tumors among African American women potentially may lead to worse ART outcomes.
Feinberg et al examined minority outcomes and the use of ART in the US Department of Defense and compared it with minority use of ART in the US population. They compared the implantation rate, clinical pregnancy rate, spontaneous abortion rate, and live birth rate for African American and white women. First, they found that African American women used ART services more often when access to care was improved (eg, for employees of the military and their dependents). Second, they reported a decrease in the live birth rate for African Americans (29.6% vs 35.8%; risk ratio [RR], 0.83; 95% CI, 0.67–1.02) and a significant increase in spontaneous abortion rate in African American women (25% vs 15.9%; RR, 1.57; 95% CI, 1.05–2.36). Third, they determined that fibroid tumors reduced ART success, regardless of race. In their study, fibroid tumors were 3 times more prevalent in African American women (30.8% vs 10.7%; RR, 2.85; 95% CI, 2.06–3.95). For all women, ultrasonographic identification of fibroid tumors at baseline was associated with reduced clinical pregnancy rates (35% vs 43.2%; RR, 0.74; 95% CI, 0.51–0.98), reduced live birth rates (26.2% vs 36.0%; RR, 0.63; 95% CI, 0.44–0.90), and reduced implantation rates (25.6% vs 31.1%; RR, 0.82; 95% CI, 0.69–0.98). This study suggests that differences in ART outcomes by race in an environment that offers equal access to care might, to some extent, be explained by the increased incidence of fibroid tumors in African American women.
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