Co-authored by Associate Professor Marion Saville
As Australia prepares to transition to a new National Cervical Screening Program in December, a research study has found that Human Papillomavirus (HPV) screening is more effective at detecting high-grade cervical abnormalities than Pap tests.
The study, called Compass, is a timely confirmation of just how effective the new cervical screening program is expected to be, not only in unvaccinated women, but also in those who have had the HPV vaccine. It is providing early insight into the performance of the new cervical screening program.
What is Compass?
Compass is the largest clinical trial in Australia and is being conducted by the Victorian Cytology Service, in collaboration with Cancer Council NSW.
The trial compares 2.5-yearly Pap smear screening with 5- yearly HPV screening. A Pap smear tests for the presence of abnormal cells in the cervix, while a HPV test looks for the Human Papillomavirus, which is the cause of most cases of cervical cancer. If HPV is found, further testing for abnormal cells (precancerous lesions) is carried out.
The first phase of the trial (the results of which are presented in this study) recruited around 5000 women aged 25-64. They attended routine cervical screening at 47 participating medical practices in Victoria, Australia, and their samples were then randomly assigned to one of three possible test pathways.
Why is this study important?
Compass is the first large scale clinical trial internationally, to assess cervical screening in an HPV vaccinated population. The free national HPV vaccination program was introduced in Australia in 2007, with a free vaccination program for 12-13 year old females (and males since 2013).
We found that the HPV test was substantially more effective at picking up high-grade cervical abnormalities (precancerous lesions) compared to the Pap test. The increased detection of precancerous lesions and earlier treatment leads to longer term protection against developing cervical cancer.
The trial adds to existing evidence about how much more accurate and effective HPV screening is. We now have a superior method for detecting not just the virus that causes cervical cancer, but also high-grade abnormalities.
What is the new National Cervical Screening Program?
The screening program will change from conducting Pap smear tests (which look for abnormal cells) to a test that looks for HPV (the human papillomavirus – a virus that causes almost all cervical cancers). This means that we are catching what could eventually turn into cervical cancer one step earlier.
The procedure to collect cells from the cervix for testing will stay the same. The changes will happen in how the test is done in the lab.
A second important change is that women will only need to be tested every five years, instead of every two years. The new HPV test is more accurate and effective, and for that reason, women don’t need to have it as frequently as a Pap smear test. This means most woman will only need to have about 10 cervical screening tests over their lifetime, compared to about 25 Pap smears.
The new screening program will come into place in December this year.
It is expected to lower cervical cancer incidence and mortality by at least 20 per cent – thanks to the more accurate, effective and safe test.
Adjunct Professor Karen Canfell, Director of Cancer Research at Cancer Council NSW, is a Principal Investigator on the Compass trial, in conjunction with Associate Professor Marion Saville, Executive Director of Victorian Cytology Service Inc.