‘Australia defeats cervical cancer’ was announced on newspaper headlines this week. Around the world, the initial results of the Australian government initiative to introduce HPV vaccination to high school age students suggested that cervical cancer instances may have reduced by up to 70%.
While countrywide HPV vaccination programs may deal a significant blow to cervical cancer incidence, the war is far from won.
HPV and cervical cancer
The primary cause of cervical cancer is unregulated cellular proliferation on the cervix as a result of HPV infection. Largely transmitted through sexual contact, HPV (Human papillomavirus) l can lead to a variety of clinical manifestations ranging from warts to cancer. Cervical cancer is the most common HPV related cancer, but HPV has also been associated with anal, vulvar, penile and oropharyngeal cancers. In most cases, however, the body clears the virus without the recipient ever experiencing any symptoms.
As the second most common female cancer, after breast cancer, cervical cancer causes 266,000 deaths annually worldwide. HPV leads to 90% of cervical cancer cases. Therefore, a reduction in HPV infections could significantly reduce the number of cervical cancer diagnoses. Current cervical cancer screening programs include either testing for the presence of the cancerous cell using the Pap test or the presence of the HPV virus, or a co-test of both procedures. In the event of finding a concerning abnormality, colposcopy (magnified visualization of the cervix) is conducted with biopsies being taken to confirm any potential precancerous or cancerous lesions.
The limitations of the HPV vaccination
The HPV vaccine is not a ‘magic bullet’ that eradicates the need for cervical cancer screening. As with any medical intervention, the HPV vaccination contains inherent limitations.
The HPV virus has multiple genotypes/strains. HPV-16 and HPV-18 represent 71% of cervical cancer cases globally. The three types of HPV vaccination available all vaccinate against these genotypes. Two of the vaccines also vaccinate against additional genotypes. However, none of the available vaccines cover all of the known cancer-causing forms of HPV. HPV vaccination does not provide full protection against HPV linked cancers. From a health education standpoint, women must clearly understand that the HPV vaccination does NOT equal immunity to cervical cancer. Other forms of cervical cancer can develop unrelated to the HPV virus or HPV strains.
All forms of the HPV vaccine require at least two doses to be effective. These should be administered before the onset of sexual activity to create immunity before a potential HPV infection. This proves especially true in low resource settings where there might exist financial, social or geographic barriers to healthcare, and it may be infeasible to achieve the population coverage needed.
Reliance on vaccination has its limitations. At the recent IPVC (International Papillomavirus Conference) conference in Sydney, Australia, Dr. Doug Lowy, deputy director of the US National Cancer Institute in the US, addressed the issue of global vaccine shortages. Given the limited supply and related cost of vaccines, addressing HPV infection and cervical cancer requires a broad global health strategy.
Non-vaccinated populations must be considered
Vaccination programs have only recently been introduced leaving a large section of the population uncovered. Public education must clearly promote the continued need for cervical cancer screening both because of the limitation in the effectiveness of vaccination programs and to cover any unvaccinated populations.
The World Health Organization Position Paper on HPV vaccines stresses that the introduction of the HPV vaccine “should not undermine or divert funding from developing or maintaining effective screening programs for cervical cancer.”
Cervical cancer screening must continue for the benefit of those who have not received or qualified for the HPV vaccination.
Australian officials agree: Cervical cancer screening is still essential
While the Australian vaccination program is being lauded in the press as ‘ending cervical cancer,’ figures within the Australian cancer world are more remain circumspect. In her interview in the New York Times, Dr. Karen Canfell, the Director of the Cancer Research at Cancer Council NSW, the organization that led the study into the Australian vacation program, stressed the importance of continued cervical cancer screening. “If we only focused on vaccination… we wouldn’t be able to address this issue for hundreds of millions of women.”
Even in Australia, caution should persist along with continued cervical cancer screening. Leisa Ashton, the spokeswoman for the Australian Cervical Cancer Foundation, was quoted as saying, “We are thrilled with this news, however, we don’t want women to get complacent.”
As so often the case with popular medical developments, the medical and scientific world must temper the grand promises made in the media. Physicians should vocally support solid evidence-based treatment plans and the implications explained to patients. In this case, the HPV vaccination does have many benefits. The community should promote the HPV vaccine for adolescents while also maintaining regular cervical cancer screening programs for all women.
Photo credit: Drew Hayes