Reference Manual - IARC Screening Group

IntroductionDespite these problems, at least two vaccines are available that canprotect women from cancer-linked papillomaviruses (HPV types 16 and18): bivalent (Cevarix®) and quadrivalent (Gardasil®) vaccines. Both areconsidered prophylactic vaccines and preferably given prior to naturalexposure to HPV types 16 and 18 (Wright et al. 2006). It will most likelybe several years, however, before either vaccine will be affordable indeveloping countries. There have also been attempts to produce atherapeutic vaccine, which would boost the immune system of someonewho is already infected and cause the cancer to regress or even disappear.This vaccine is targeted to inactivate the E6 and E7 proteins, those viralproteins that block the action of the cell growth regulating proteins (Rband p53) (Massimi and Banks 1997).Until a protective vaccine is widely available, primary prevention mustfocus on reducing the behaviors and risks that increase a person’s risk ofbecoming infected. Risk reduction counseling related to the risk factorslisted above should be incorporated into all levels of the healthcaresystem, especially those dealing with young people, and should informadolescents that practices designed to minimize the risk of STI or HIVexposure (e.g., the use of male or female condoms) may not be aseffective for HPV prevention. In addition, vigorous efforts to discourageadolescents, especially young girls, from starting smoking and initiatingsexual activity should be widely and continually disseminated.Secondary PreventionScreeningWomen who are already infected with HPV should be screened todetermine whether they have early, easily treatable precancerous lesions(i.e., screening). If lesions are found, they should be treated before theyprogress to cancer. Although the Pap smear is the most well-establishedmethod of screening women for precancerous lesions, other approachesto screening women at risk for cervical cancer have been investigated.These include visual screening, HPV tests and automated cytologyscreening. Appendix A lists a number of cervical cancer screening testsand their technical components, benefits and limitations.For screening programs to have an impact on the incidence of cervicalcancer, they need to screen as many women as possible. Ideally, theprograms would screen 80% of the population at risk. Then, those womenwho are identified as having precancerous lesions need to have thoselesions treated before they progress to cancer. When coverage is high, itis not necessary to screen women annually to have an impact on diseaseincidence. For example, if all women ages 35–64 who have had onenegative Pap smear were to be screened every 5 years (and all those withdysplasia treated), the estimated incidence of cervical cancer could bereduced by about 84% (Table 1-2). Screening these women even every10 years would reduce the incidence by an estimated 64%.1-6 Cervical Cancer Prevention Guidelines for Low-Resource Settings