Greater Bay Area Cancer Registry

Cervical Cancer Incidence and Mortality in the Greater Bay Area, 1988-2016

Cancer of the cervix is currently the 12^th most common cancer diagnosed among females in the Greater Bay Area, and the 14^th leading cause of cancer deaths. This cancer typically develops slowly and as a result, regular screenings (“Pap” testing) can detect changes that occur in the cells before cancer develops. Undetected, abnormal cells may become cancerous and start to grow more deeply into the cervix and to surrounding areas [1]. The most common risk factor (i.e., characteristic associated with a disease) for cervical cancer is human papillomavirus (HPV) infection [1-4].

Incidence and Mortality

The number of newly diagnosed cases each year per 100,000 women (incidence rate) has declined substantially since 1988 in all racial/ethnic groups (Figure 1) and in the year 2016, just over 200 cases were diagnosed in the Greater Bay Area. The annual rate of newly diagnosed cancers decreased by an average of -3.5% to -4% per year for Asian/Pacific Islanders, Hispanics, and non-Hispanic (NH) black women, and less significantly (-1.6% per year) for NH whites (Figure 1). 

Compared to all other racial/ethnic groups, Hispanic women have the highest rate of cervical cancer (Figure 2). This may, in part, be due to low rates of cervical cancer screening in this population [5]. The most recent incidence rates (2012-2016) show that NH whites and Asian/Pacific Islander women have statistically significantly lower rates than Hispanic women (Figure 2).

The number of annual deaths per 100,000 women (mortality rate) has also declined among all racial/ethnic groups since 1988, but particularly among NH blacks and Asian/Pacific Islanders. Hispanic women have the highest mortality rate when compared to all other racial/ethnic groups (Figure 2). In the year 2016, just over 50 cervical cancer deaths occurred among Greater Bay Area residents.

In comparison to incidence and mortality rates in California, Greater Bay Area rates are significantly lower (Figure 2).

Figure 2: Racial/ethnic group disparities in incidence and mortality by geographic area

Cervical Cancer and Human Papillomavirus (HPV) Infection

HPV is the most common sexually transmitted infection in the US. There is no treatment for HPV infection, but typical HPV infections are resolved within just a few months without any intervention, and are about 90% clear within two years. There are many HPV types, and most do not cause any long-term complications. However, a small proportion of infections with certain types of HPV (types 16 and 18) can persist and progress to cancer over the course of 15 to 20 years [2]. In the U.S. About 70% of cervical cancers and precancerous lesions on the cervix are caused by infection with these two HPV types [4, 6]. In developed countries such as the U.S., screening for pre-cancerous lesions is commonly performed, making most pre-cancerous lesions identifiable at a stage where they can be easily treated; this is estimated to prevent up to 80% of cervical cancers [4].

Potential Effects of HPV Vaccination

Cervical cancer screening has undoubtedly contributed significantly to the overall decline in cervical cancer incidence and mortality over the past two decades [1, 2, 7, 8]. In 2006, three highly effective vaccines against HPV strains most often associated with cervical cancer were approved by the Food and Drug Administration (FDA) for the prevention of HPV-caused cancers [9]. In combination with continued cervical cancer screening, these vaccines are now recommended by the Centers for Disease Control and Prevention for girls ages 11 to 12 (since 2006) and boys ages 11 to 12 (since 2009). And, the most recent data show that vaccination uptake is increasing [10]. Data from 2017 show that roughly half of adolescents were up to date on the HPV vaccine. In addition, adolescents who started the HPV vaccine series increased by an average of 5% each year from 2013-2017. However, there are disparities in vaccination uptake; adolescents in urban areas have significantly higher vaccination rates than in rural areas [10]. In addition, concerns about the vaccine's effect on sexual behavior, low perceived risk of HPV infection, cultural influences, irregular preventive care, and vaccine cost were identified as potential barriers to vaccination [11]. There are significant nation- and state-wide efforts to increase awareness and availability of obtaining the vaccine.

In addition to screening, vaccination may also be starting to contribute to the declines in the proportion of HPV16/18-positive cervical cancers [7]; a recent study showed that from 2008-2014, the greatest declines occurred in vaccinated women [12]. However, because of the long interval between HPV infection and the development of cancer, it will take time to continue to assess the impact of vaccination on HPV-associated cervical cancers.

References

1. National Cancer Institute, Cervical Cancer Screening (PDQ®)–Patient Version. Available at: https://www.cancer.gov/types/cervical/patient/cervical-treatment-pdq#link/_117. U.S. Department of Health and Human Services, National Cancer Institute, Bethesda, MD.

2. American Cancer Society, Cervical Cancer: Detailed Guide. Available from: http://www.cancer.org/cancer/cervical-cancer/causes-risks-prevention/risk-factors.html. .

3. Jemal, A., et al., Annual Report to the Nation on the Status of Cancer, 1975-2009, featuring the burden and trends in human papillomavirus(HPV)-associated cancers and HPV vaccination coverage levels. J Natl Cancer Inst, 2013. 105(3): p. 175-201.

4. World Health Organization, Human papillomavirus (HPV) and cervical cancer. Available at http://www.who.int/news-room/fact-sheets/detail/human-papillomavirus-(hpv)-and-cervical-cancer. 2018.

5. Zhou, J., et al., Trends in cancer screening among Hispanic and white non-Hispanic women, 2000-2005. J Womens Health (Larchmt), 2010. 19(12): p. 2167-74.

6. Centers for Disease Control and Prevention, Genital HPV Infection - Fact Sheet. Available at https://www.cdc.gov/std/hpv/stdfact-hpv.htm. 2017.

7. Van Dyne, E.A., et al., Trends in Human Papillomavirus-Associated Cancers - United States, 1999-2015. MMWR Morb Mortal Wkly Rep, 2018. 67(33): p. 918-924.

8. National Cancer Institute, Cervical Cancer Screening (PDQ®)–Health Professional Version. Available at: https://www.cancer.gov/types/cervical/hp/cervical-screening-pdq. U.S. Department of Health and Human Services, National Cancer Institute, Bethesda, MD.

9. American Cancer Society, HPV vaccines. Available at: https://www.cancer.org/cancer/cancer-causes/infectious-agents/hpv/hpv-vaccines.html.

10. Centers for Disease Control and Prevention, HPV Vaccination Coverage Data. Available at: https://www.cdc.gov/hpv/hcp/vacc-coverage/index.html.

11. McClung, N.M., et al., Trends in Human Papillomavirus Vaccine Types 16 and 18 in Cervical Precancers, 2008-2014. Cancer Epidemiol Biomarkers Prev, 2019. 28(3): p. 602-609.

12. Holman, D.M., et al., Barriers to human papillomavirus vaccination among US adolescents: a systematic review of the literature. JAMA Pediatr, 2014. 168(1): p. 76-82.

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