Cervical cancer screening shouldn't start until 25
20 February 2013
Women in England, Scotland, Wales and Northern Ireland will all soon be advised to start screening for cervical cancer at 25 years, and those aged between 50 and 64 years to screen every five years rather than every three. And a review of the Australian National Cervical Screening Program is considering whether it should make the same recommendations.
The Australian review is considering evidence on the screening starting age and the interval between Pap smears, as well as different screening technologies such as Liquid Based Cytology (LBC) and primary HPV testing. It coincides the with major changes in similar programs in the United Kingdom based on recommendations by the UK National Screening Committee (NSC).
The policy change was made in England in 2003 and Northern Ireland in 2010. And following a recent review, the protocol has been recommended for extension to both Scotland and Wales.
The changes are based on evidence that screening women under 25 offers little benefit. In fact, screening this age group arguably causes "more harm than good" with little or no health benefit, and potential physical, psychological, and economic harms. Cervical cancer is extremely rare in young women and the efficacy of screening drops as age decreases.
In a large UK population-based study, researchers found evidence that screening women aged 20 to 24 "has little or no impact on cervical cancer" and that there was virtually no difference in cancer incidence between women who were screened within that age range and those who were not.
These findings are supported by a better understanding of the cause and natural history of cervical cancer. Human papillomavirus (HPV) is the primary cause of cervical cancer and cervical abnormalities detected at screening. HPV infection in young women represents a transient or short-term infection that can be spontaneously cleared by the immune system. It's only persistent infection that causes severe or clinically significant cervical abnormalities and cancer, and it's this kind of HPV infection that is important to detect and treat.
Screening young women results in the detection and over-treatment of transient infections, which would otherwise clear naturally. Detection and treatment of inconsequential disease has important negative consequences for young women, with evidence of psychosocial harm (worry, anxiety, guilt and concerns about infertility and relationships), economic costs (treatment and sick leave) and potential physical harm because the treatment of the cervix is linked to perinatal mortality and adverse pregnancy outcomes.
The UK NSC also highlighted the impact of the HPV vaccine program on reducing infection and cervical abnormalities in young women, suggesting vaccination would further reduce any benefit of screening found in the younger age group.
The policy change is consistent with the International Agency of Research on Cancers (IARC) 2005 review of cervix screening, which states that "organised programs should not include women aged less than 25 years in their target populations". The IARC also recommends a three-year screening interval for women aged 25 to 49 years and five years for women between 50 and 65.
The recommendation for longer screening intervals by both IARC and the UK NSC is based on evidence that the benefit of screening every two years, rather than three, is small. Similarly, screening every three years (rather than five years) from age 50 onwards offers little health benefit with a increase in protection of 4 percent (from 83 percent five yearly to 87 percent three yearly), yet a substantial increase in program costs of around 60 percent to 66 percent.
In Australia, two-yearly cervical screening begins at 18 or two years after the start of sexual activity, whichever is later. Approximately 450,000 women under 25, and 1.1 million women over 50 were screened in 2008-2009.
Australia has a high-quality and very effective cervical screening program and has taken a leading role in providing HPV vaccination in school-based programs. Cervical cancer incidence and mortality (nine in every 100,000 and two in every 100,000 women aged 20 to 69, respectively) are low by international standards, and the numbers have halved since the introduction of a national organised screening program in 1991.
Continuing this leading role, while minimising unnecessary harm, particularly the over-treatment of young women, should be a priority.
Nevertheless disparities remain. Cervical cancer incidence and mortality are significantly higher among Aboriginal and Torres Strait Islander women compared to the rest of the Australian population, and are also higher in women living in remote and very remote areas. Women in the highest fifth of the social strata have the lowest cervical cancer incidence and mortality.
The current review offers an opportunity to renew the Australian cervical screening program to maximise benefit, while minimising harm and redirecting resources in beneficial and cost-effective ways. It's an opportunity to deliver a cervical screening program that is beneficial, accessible and acceptable to all Australian women.
Associate Professor Kirsten McCaffery and Professor Alexandra Barratt are from the School of Public Health in Sydney Medical School. Jane Williams is a PhD student in the Centre for Values, Ethics and the Law in Medicine.
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