Cervical screening changes queried

A LEADING pathologist has suggested plans to upgrade the National Cervical Screening Program could inadvertently lead to a fall in participation rates and a rise in invasive disease.

The Medical Services Advisory Committee (MSAC) has recommended raising the age to start screening from 18 to 25 years and replacing the current system of 2-yearly Pap tests with 5-yearly human papillomavirus (HPV) testing. (1)

The proposed changes are being considered by the federal Department of Health as part of the program’s scheduled renewal, and take into account the impact of widespread HPV vaccination and the evolution of HPV testing. The changes have strong support as being in line with the best available evidence.

However, Adjunct Professor Annabelle Farnsworth, medical director of Douglass Hanly Moir Pathology in Sydney, warned this week in an MJA editorial that “changing one aspect of a public health program may have unwanted consequences on another aspect”. (2)

Professor Farnsworth was commenting in light of new research published in the Journal confirming reports that there had been a decrease in participation in the screening program since the introduction of the HPV vaccine in Australia in 2007. (3)

The study of linked data from the Victorian Cytology Registry and the National HPV Vaccination Program Register found that over a 2-year period to 2011 vaccinated women aged 20‒24 years and 25‒29 years were significantly less likely to be screened than unvaccinated women (37.6% v 47.7% and 45.2% v 58.7%).

This was despite widespread patient education about the need for vaccinated women to have Pap smears as the vaccine does not prevent all HPV types that cause cervical cancer and cannot protect women already infected with HPV.

Professor Farnsworth suggested that raising the screening age could lead to a further fall in participation rates.

She noted that in England, changing the age to start screening from 21 to 25 years in an unvaccinated cohort in 2003 had been linked with a significant decrease in screening participation and a significant increase in cervical cancer in the 25‒29-year age group. (4)

Although UK researchers suggested an increase in HPV infections was to blame, Professor Farnsworth said changing the screening age may also have been a factor.

“It is hoped that in a vaccinated population [as in Australia today], raising the age for commencing cervical screening to 25 years will not have the same consequences as in England”, she said.

Professor Farnsworth also raised concerns about quality assurance measures under the proposed changes in Australia, predicting that as the number of cervical samples taken for cytological testing fell, fewer laboratories would be able to perform the tests optimally.

She said invalid HPV test results were “not rare”, saying that at her laboratory she had observed a 1% rate of invalid test results in 2013.

Professor Ian Hammond, chair of the Renewal Steering Committee for the National Cervical Screening Program, hit back at several aspects of the editorial, claiming Professor Farnsworth had misinterpreted the experience in England and mistakenly implied that MSAC had ignored issues of implementation.

“She fails to mention that the UK study found that screening women under the age of 25 years does not reduce the incidence of cervical cancer at ages 25‒29 years”, he told MJA InSight.

He noted that similar cancer trends were seen in Scotland and Wales over the period, indicating the impact of factors other than screening age.

Professor Hammond stood by the MSAC’s proposals, saying the current regimen of starting screening at 18 years of age and screening every 2 years was “too intensive when compared with other countries with similar outcomes”.

He agreed that it would be “very, very important that women do start being screened at age 25 in the new National Cancer Screening Program, and that there should be no significant delay”. This was why the MSAC had stressed that there should be an invitation and recall for 5-yearly HPV screening.

The authors of the MJA study also said their research emphasised the “imperative” to use direct invitations to commence screening.

They warned their results were likely to be limited by incomplete and unlinked data. However, they said this would not wholly explain their finding that vaccinated women were under-screened.

Dr Julia Brotherton, medical director of the National HPV Vaccination Program Register and a coauthor of the study, told MJA InSight she agreed that careful attention and commitment to organisation and quality assurance would be critical to the success of the program’s renewal.

However, she expressed confidence that this was achievable, saying “we have a long history of success in these areas”.

“Vaccination is undoubtedly superior to Pap testing in its ability to prevent those fortunately rare but rapidly occurring cervical cancers in very young women ... but we do need both and our research is a call to action for young women who have not yet attended screening to find the time to do so.”

1. Australian Government: National Cervical Screening Program Renewal
2. MJA 2014: 201: 245-246
3. MJA 2014; 201: 279-282
4. J Med Screen 2012: 127-132

(Photo: BSIP / Science Photo Library)