Vaccination and Screening Down Under Shows Cervical Cancer the Door
News Oct 03, 2018
Image credit: Pixabay
Australia is set to become the first country to eliminate cervical cancer as a public health issue, thanks to the early adoption of both HPV vaccination and HPV-based cervical screening. The age-standardized annual incidence of cervical cancer is predicted to decrease, and cervical cancer could effectively be eliminated as a public health problem in Australia within the next 20 years.
Comprehensive modeling of HPV vaccination, HPV natural history and transmission and cervical screening has led to estimates of cervical cancer incidence in Australia from 2015 to 2100. It is predicted that cervical cancer in Australia will achieve ‘rare cancer status’ by 2020, if the existing vaccination and screening protocol continues. In Australia and Europe, a rare cancer is defined as a cancer which has an annual age-standardized incidence of six new cases per 100 000 women. The findings were published yesterday in The Lancet.
The authors summarized the implications of their findings:
‘To our knowledge, this study represents the first estimation of the time to elimination of cervical cancer at a country level… Our findings imply that the elimination of cervical cancer could be on the horizon for high-income countries, such as Australia.’A well-established and validated platform called ‘Policy1-Cervix’ was used to account for different parameters, such as vaccine uptake, date at which boys started getting vaccinated and vaccine efficacy, to predict the incidence of cervical cancer and mortality rates in Australia from 2015 to 2100.
Two screening scenarios were considered, based on different assumptions:
Scenario 1: Screening continues in all cohorts
Scenario 2: Cervical screening stops in cohorts offered the nonavalent vaccine as preadolescent girls, but assumes HPV screening continues for older, unvaccinated cohorts and cohorts given the quadrivalent vaccine
|Year||Predicted number of cases of cervical cancer per 100,000 women/year|
|Before organized cervical screening||1990||13.5|
|Before quadrivalent vaccine||2006||6.66|
|Scenario 2||2090||Cervical cancer and associated mortality rates would achieve a steady state|
|Scenario 2||2100||2.31 (overall)|
Age 15-29: 0.23
Age 30-49: 3.23
Age 50-84: 4.64
The study is one of several recent reports which demonstrate the efficacy and safety of the HPV vaccine. In July this year, the UK announced that adolescent boys will be offered the HPV vaccine to protect them from cancer. Ensuring that boys are vaccinated against HPV is a move that is supported by sensitivity analysis data from the current study:
‘In a sensitivity analysis, we found that, had boys not been included in the NHPV (National HPV Vaccination Program) in Australia, the elimination of cervical cancer would have been delayed by 2 years.’Mortality rates are expected to drop to fewer than < 0.15 per 100 000 women each year, or < 3 per 1 million women in 2100. However, the authors caution that as with any modeling study, the results are dependent on several assumptions. For example, they assumed that one dose of the vaccine would have no efficacy (a conservative assumption), and did not account for immigration effects in the model (non-vaccinated and non/screened immigrants may delay the time to elimination). However, the future looks promising, as summarized in the paper:
'If high-coverage vaccination and screening is maintained, and if an elimination threshold of four cases per 100 000 women is chosen, cervical cancer is on track to be eliminated as a public health problem in Australia within the next 20 years. However, screening and vaccination initiatives would need to be maintained thereafter to continue to achieve very low incidence of, and mortality from, cervical cancer.'More about cervical cancer:
Cervical cancer develops from the uncontrolled growth of cells that comprise the cervix. It is the eighth most common cancer worldwide. Almost all cervical cancers are linked to the papilloma viruses (HPV), however, not all women with HPV develop cervical cancer.
The most commonly experienced symptom is unusual vaginal bleeding between periods or during/after sexual intercourse. Numerous other symptoms include unusual vaginal discharge, pain after sex, and general discomfort within the pelvis area. A large proportion of cervical cancer cases (~70%) are caused by two particular strains of HPV (HPV 16 and HPV 18). Women infected with HPV don’t experience symptoms during the early stages, so they are usually unaware that they have contracted the virus.
HPV can cause several other types of cancer. Approximately 95% of anal cancers are caused by HPV 16 and they are associated with other cancers of the genital area, for example:
Hall, M. T., Simms, K. T., Lew, J., Smith, M. A., Brotherton, J. M., Saville, M., . . . Canfell, K. (2018). The projected timeframe until cervical cancer elimination in Australia: A modelling study. The Lancet Public Health. doi:10.1016/s2468-2667(18)30183-x