The Epidemiology of Ovarian Cancer: Different Prognoses for Different Populations

Ovarian cancer (OC), the third most common gynecologic cancer after cervical and uterine cancer, was diagnosed in 295,414 women worldwide in 2018, constituting 3.4% of all women’s cancers and 4.4% of all women’s cancer-related deaths.¹ Among the cancers affecting women, OC has one of the highest fatality rates, despite its relatively low prevalence, which falls below that of breast cancer.^1,2 The 5-year survival rate of 45.6% increases to 70% if OC is detected at an early stage; however, early diagnosis occurs in only about 20% of cases.² The more common late-stage diagnosis of OC is a consequence of its asymptomatic characteristic; it has a survival rate of 35%.^2,3

There are 3 histologic types of OC, with epithelial OC (EOC) composing 90% of OC cases, while germ and follicular cell types are therefore significantly less common.^2,4,5 For this reason, literature references to OC generally concern EOC, which is considered a postmenopausal disease, and studies have shown diagnosis occurring at a median age of 50 to 79 years.¹ A rarer histologic variety of OC, ovarian carcinosarcoma (OCS), also referred to as mixed malignant Müllerian tumors, accounts for 1% to 4% of OC cases and carries a worse prognosis than EOC.⁴ OCS is diagnosed in an older patient population, is diagnosed at more advanced stages, and has a 5-year survival rate of 29.8%.⁴ Most patients diagnosed with OCS experience relapse within 1 year after their first course of treatment.⁴ There are a couple of proposed factors for the poorer prognosis of OCS: One is the later stage of disease at diagnosis and the other is the older age of the patient, who is usually an inappropriate candidate for aggressive chemotherapy, which can improve outcomes in younger patients.¹

Globally, OC prevalence varies among regions and groups. The highest rate of prevalence occurs in white non-Hispanic women at 12 cases per 100,000, with 30% of these cases occurring in Europe.¹ The prevalence decreases in Hispanic women to 10.3 cases per 100,000, then in black women to 9.4 per 100,000, and finally in Asian/Pacific Islander women to 9.2 per 100,000.1 However, the mortality trend does not reflect this pattern, with African groups sustaining the highest mortality rate.¹ In terms of geographic distribution as reported for 2012, the United States had the highest rate of new cases at 81.8%, followed by China at 14.60%, and India at 11.33%.¹ Within the United States, racial disparity was found to result in a shorter overall survival rate in black women (21.7 months) than in white women (42.6 months), according to a recent study.⁶ This may be due in part to disparities in comorbidities and in treatment. Black women with OC had greater body mass index scores than white women and received less optimal surgical cytoreduction procedures and fewer intraperitoneal chemotherapy treatments than did white women.⁶ Disparities in wealth and in time available for treatment may contribute to the differences in treatment received, as postulated by the study’s authors, since intraperitoneal chemotherapy entailed more frequent trips to the administering institution.⁶ It remains to be clarified which mortality disparities might occur secondary to histologic differences in OC between groups and which are strictly socioeconomic.

References

1. Momenimovahed Z, Tiznobaik A, Taheri S, Salehiniya H. Ovarian cancer in the world: epidemiology and risk factors. Int J Womens Health. 2019;11:287-299.
2. Chandra A, Pius C, Nabeel M, et al. Ovarian cancer: current status and strategies for improving therapeutic outcomes. Cancer Med. 2019;8(16):7018-7031.
3. Lheureux S, Gourley C, Vergote I, Oza AM. Epithelial ovarian cancer. Lancet. 2019;393(10177):1240-1253.
4. Boussios S, Karathanasi A, Zakynthinakis-Kyriakou N, et al. Ovarian carcinosarcoma: Current developments and future perspectives. Crit Rev Oncol Hematol. 2019;134:46-55.
5. La Vecchia C. Ovarian cancer: epidemiology and risk factors. Eur J Cancer Prev. 2017;26(1):55-62.
6. Dilley S, Erickson BK, Phillips CE, et al. Do differences in medical comorbidities and treatment impact racial disparities in epithelial ovarian cancer? Gynecol Oncol. 2018;149(1):49-52.