HPV monograph series: latin american and caribbeanRisk factors for Human Papillomavirus Exposure and Co-factors for Cervical Cancer in Latin America and the Caribbean
Introduction
The incidence of cervical cancer in Latin America and the Caribbean (LAC) is among the highest in the world (average regional estimate: 29.2 cases per 100,000 women) [1]. Although human papillomavirus (HPV) infection is a necessary cause of cervical cancer, the presence of certain co-factors in combination with infection will significantly increase the risk of developing cervical cancer [2]. Because HPV infection is sexually transmitted, sexual behaviour (age at first sexual intercourse, number of sexual partners and sexual behaviour of the partner) is associated with an increased risk of acquisition. Most women in LAC will be infected with HPV sometime during their sexual life, however only a small proportion of them with persistent infection will develop cervical pre-cancer and cancer. Long-term use of oral contraceptives (OC), high parity and smoking are established factors for cervical cancer among HPV DNA positive women. Paradoxically, many studies that have largely contributed to establishing the causal link between HPV and cervical cancer, to the understanding of the natural history of HPV infection and cervical cancer, and to the evaluation of HPV vaccines, have been carried out in LAC (Appendix and Fig. 1) where many women still die from the disease. This article summarises the current patterns of risk factors for HPV infection and co-factors for cervical cancer in the region using national statistics, national demographics, socio-economic and health surveys, and specific data reported in the region.
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Cervical cancer in the Latin America and Caribbean region
Cancer of the cervix uteri is the second most common cancer among women in the LAC region. In 2002, 72,000 new cases and 33,000 deaths were estimated, however there is an estimated 75% increase in the number of cases predicted for 2025, if current incidence rates remain constant [1]. Three major demographic shifts are happening in LAC countries: population growth, urbanisation and aging. Fertility rates have decreased in the past decades from 3.9 between 1980–85 to 2.5 in 2000-2005 [3], [4], at
HPV infection in LAC countries
HPV infection is a necessary cause of cervical cancer and is sexually transmitted. In a recent meta-analysis including 14,586 women with negative cytology from studies in Costa Rica, Honduras, Mexico, Argentina, Brazil, Chile, Colombia, Paraguay and Peru, the prevalence of HPV (any type) was 12.3% (95% confidence interval (CI): 11.2–13.4%) in South America and 20.4% (95% CI: 19.3–21.4%) in Central America, substantially higher than worldwide prevalence estimates (10.4%; 95% CI: 10.2–10.7%) [11]
HPV variants in Latin America and the Caribbean
During the last decade several studies have found that certain HPV-16 and -18 variants may be more strongly associated with an increased risk of persistent infection, high-grade squamous intraepithelial lesions (HSIL), histologically confirmed cervical intraepithelial neoplasia (CIN) and cervical cancer [21], [22], [23], [24]. The prevalence of HPV variants and its association with cervical cancer has been reported in two case-control studies [25], [26] and four cross-sectional studies in LAC
Risk factors for HPV exposure
Data from three sources are used to describe the current patterns of sexual behaviour and their effect on HPV infection acquisition: (1) national statistics from the World Health Organization (WHO)/Catalan Institute of Oncology (ICO) Information Centre on HPV and cervical cancer [15]; (2) national socio-demographic surveys; and (3) data from epidemiological studies carried out in LAC. As a result of recall bias, some caution is needed when interpreting sexual behavioural data because women
HPV co-factors for the development of cervical cancer
The majority of cervical cancer cases in the region are squamous cell carcinomas, but it seems that they share the same risk factors with adenocarcinomas of the cervix, except for smoking [62]. Data from the WHO/ICO Information Centre, the United Nations Joint Programme on HIV / acquired immune deficiency syndrome (AIDS) (UNAIDS) and epidemiological studies are used to describe the current patterns of reproductive health factors and sexually transmitted diseases.
Protective factors for cervical cancer
It is clear that well-organised cervical screening programmes or widespread good quality cytology can reduce cervical cancer incidence and mortality. Although rates have declined substantially over the last 30 years in LAC, cervical cancer rates are still among the highest in the world. Cytological screening has been widely offered opportunistically for several decades but has failed to prevent the many cervical cancer deaths currently occurring in LAC.
The introduction of HPV vaccination could
Conclusions
HPV infection is a necessary cause of cervical cancer; other co-factors have been shown to contribute significantly to the increased risk for developing CIN or cervical cancer among women persistently exposed to HPV. Lifetime number of male sexual partners and the sexual behaviour of the male sexual partners are associated with an increased risk of HPV infection. LAC women tend to remain monogamous once married or cohabiting, while men do not, thus increasing the risk of cervical cancer in
Disclosed potential conflicts of interest
MM: Research Grants (GlaxoSmithKline). GP: Advisory Board (Merck Sharp & Dohme); Consultant (Merck Sharp & Dohme); Speakers Bureau (Merck Sharp & Dohme); Steering Committee (Merck Sharp & Dohme); Travel Grants (Merck Sharp & Dohme).
Acknowledgements
We thank Merck, Sharp & Dohme (MSD) for kindly providing baseline information specific of Latin American participants in their trials. We also thank Laia Bruni for her graphical support.
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