Abstract
While the incidence of ovarian cancer is lower in African-American women compared to European-American women, African-American women have much poorer survival. Five-year relative survival for African-American women is 36.4% compared to 44.3% in European-American women. However, factors affecting risk and survival of ovarian cancer are under-studied among African Americans despite notable differences in incidence and survival, histological subtype distribution and age at diagnosis compared to European-American women. Although there are a limited number of studies, many of the currently known risk factor associations appear similar in African-American versus European-American women with noted differences in the prevalence of reproductive and lifestyle characteristics. This indicates that the risk factor profile for ovarian cancer among African-American women may be distinct and may explain the lower incidence but poorer survival compared to European Americans. It has been suggested that lower socioeconomic status, co-morbidities, and access to care are in part responsible for poorer ovarian cancer outcomes among African-American women. In this presentation published results are reviewed to highlight gaps in epidemiologic research through the presentation of data from two population-based case-control studies, the multi-center African American Cancer Epidemiology Study (AACES) and the North Carolina Ovarian Cancer Study (NCOCS) and a large international consortium, the Ovarian Cancer Association Consortium (OCAC). The data presented help to establish the rationale for pooling existing datasets to achieve a larger sample size.
The following are highlighted in this presentation:
In both the AACES and NCOCS we observed a high proportion (15%) of women who were deceased at ascertainment among African-American ovarian cancer cases compared to 4% in European-American ovarian cancer cases in the NCOCS study. This, in part, may be a result of late stage at diagnosis among those deceased at ascertainment.
A higher prevalence of obesity associated with increased risk in both AACES and NCOCS illustrates differences in the risk profile of African-American women compared to European-American women.
Further exploration of genetic association may uncover novel SNP associations due to differences in allele frequencies of SNPs in African-American women compared to European Americans. Analyses if the NCOCS show genetic associations with short CAG repeat length polymorphisms in the androgen receptor (AR) gene and associations between several SNPs in the vitamin D receptor (VDR) gene in African-American women. Confirmation in a larger study is required because of small sample sizes.
The exclusion of African-American women from GWAS studies because of small numbers underscores the need for increased sample size.
OCAC includes over 70 member studies of which only 7 have a more than 20 ovarian cancer cases in women of African Ancestry. Of the ∼ 30,000 cases and ∼37,000 controls enrolled in OCAC, only 508 cases and 605 controls are African American.
Associations with several risk factors among those of African Ancestry in OCAC are comparable to those of European ancestry, although some differences are seen.
Fully elucidating epidemiologic factors that contribute to the development of ovarian cancer in African-American women will require the pooling of existing epidemiologic data and biospecimens from many studies. We have identified approximately 1,500 cases and 1,900 controls from existing studies conducted in the U.S over the past twenty years.
There is strong rationale to pool epidemiologic data on ovarian cancer in AA women which has led to the formation of the Ovarian Cancer in Women of African Ancestry (OCWAA) consortium. Goals of OCWAA include harmonization of epidemiologic and genomic data from existing data from AACES, OCAC, the Ovarian Cancer Cohort Consortium (OC3) and the African American Cancer Cohort (A2C2) consortia to conduct pooled analyses to assess the impact of lifestyle and genetic factors on ovarian cancer risk and prognostic factors in African American women. These extensive epidemiologic datasets including clinical, reproductive and lifestyle factors will be an invaluable resource for achieving these aims. OCWAA promises to begin to fill in gaps in our understanding of risk factors and survival among this understudied group of women. In the longer term, findings will be incorporated into our ongoing effort in developing a clinically useful risk prediction model that incorporates risk factors in African American women; our current model is limited to European American women. Although data harmonization and pooled analyses will enhance statistical power for assessing factors for risk and survival the existing sample sizes will fall short to address disease heterogeneity of histologic and molecular subtypes and genetic association.
Listed below are research objectives that will address important gaps in the epidemiology of ovarian cancer in African American women:
Harmonize existing epidemiologic data for risk factor associations
Evaluate the relationship between socioeconomic status, stage at diagnosis, co-morbidities and disease outcomes
Evaluate associations with lifestyle and reproductive factors in major histologic subtypes
Assess genetic determinants of disease risk and survival
Determine molecular subtypes among African-American women
Incorporate assessment of ovarian cancer risk of African Americans in risk prediction models
Develop evidence-based interventions to reduce risk and increase survival
Citation Format: Joellen Schildkraut. Risk factors and ovarian cancer in African American women: Contributors to disparities. [abstract]. In: Proceedings of the Seventh AACR Conference on The Science of Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; Nov 9-12, 2014; San Antonio, TX. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2015;24(10 Suppl):Abstract nr IA42.
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