EPIDEMIOLOGY AND CONTROL OF CERVICAL CANCER IN BRAZIL – ROLE OF HPV GENOTYPES
02. Epidemiology and natural history
J.E. Levi, Virology Lab., Instituto de Medicina Tropical da Universidade de Sao Paulo – Sao Paulo (Brazil)
Background / Objectives
The estimated age-adjusted incidence of cervical cancer (CC) in Brazil is approximately of 18⁄100,000 women/year, with large regional differences. Apart from epidemiological interest, recognizing the role of each individual HPV genotype in cervical malignancy became more important after the introduction of HPV vaccines against HPV 16 or 18 infections, showing limited cross protection to other high-risk genotypes non-16/18. Not surprisingly, a new generation of vaccines including another 5 high-risk HPV genotypes have recently been launched. Surveillance with extended genotyping platforms is necessary to identify an eventual emergence of a non-vaccine genotype that may occupy this, to be vacant, ecological niche. However, it is clear that the current vaccines are highly effective on naïve populations but not appropriate to previously and current infected subjects. This translates into the need to screen for CC for the next 50 years. Concerning CC screening, several studies have shown that testing for HPV-DNA is more advantageous than by cytology. Therefore, many countries are remodeling their CC screening program, placing HPV testing as the primary tool and referring to cytology only the HPV+ samples. The objective of this work is to investigate the differential role of HPV genotypes in the epidemiology of cervical cancer in Brazil.
Brazilian studies investigating the distribution of HPV genotypes in the general population and cervical cancer specimens were reviewed and compiled.
Prevalence of high-risk HPVs in Brazil is similar to countries presenting a low incidence of CC, indicating inefficiencies in the national screening program, which relies on cytology. HPV genotyping in large scale has depicted a frequency of HPV genotypes in the general Brazilian female population that is similar to the global 122⁄490 distribution; HPV 16 being the commonest followed by other genotypes according to the study population and geographical region, but not HPV 18. In contrast, on CC cases HPV 18 is the second, being present on 10–15% of all CCs, far after HPV 16 which accounts for 50–70%.
Large studies with prolonged follow-up revealed that among HPV genotypes, classified as of high-risk, there are significant differences in their oncogenic potential. Consequently, in the age of personalized medicine, it makes sense to have management strategies according to the genotype or group identified in the sample. Several biomarkers are under evaluation in order to identify on HPV positive cervicovaginal samples, those that present a higher diagnostic or prognostic risk of neoplasia, thus justifying more costly and invasive procedures.