At present, the standard way screen women for cervical cancer is a Pap smear alone, or co-testing using both a Pap smear and a human papillomavirus (HPV) test.
There is, however, new interim guidance about the health advantages of instead using the HPV test alone as the primary screen to find cervical cancer or its precursors. Under the new guidance, the Pap smear, which dates back more than 80 years, would still be used for follow-up tests if an HPV test is positive. The Pap smear will still be used for primary screening of women under age 25.
The need for guidance about using the HPV test was triggered last April when the US Federal Drug Administration approved one existing HPV test for use in primary cervical cancer screening. The guidance is written by a group of cervical cancer screening experts led by University of Alabama, Birmingham gynaecologic oncologist Dr Warner Huh. "Although FDA approval is critically important for introducing a new screening test or algorithm, providers ultimately rely on guidance or guidelines to help them make the best decisions for their patients and want to understand advantages, disadvantages and unknowns associated with a new screening approach," said Huh, who is a senior scientist for the UAB Comprehensive Cancer Centre, director of the UAB division of gynaecologic oncology.
Overall, the panel said, "While there continue to be numerous practical and research questions, primary HPV testing has the potential to further reduce morbidity and mortality of cervical cancer in the U.S. However, what is most important is that women need to be screened with any strategy, as many women in the US with cervical cancer are either unscreened or under-screened."
"The scientific evidence clearly demonstrates that primary HPV testing out-performs cytology or Pap as a screening test," said Huh. "This has been confirmed from numerous European and Canadian studies as well as the ATHENA trial. There are going to be fewer false negatives with HPV, and arguably, we have been using a less sensitive test for screening for a while now." Huh added, "Pap smears miss a fair number of adenocarcinomas. We don’t want a test that will miss disease."
From the patient’s point of view, the experience of getting an HPV test will be the same as getting a Pap smear. The difference is how the sample is then screened: Instead of a technician looking for abnormal cells (Pap), the HPV sample is put into an automated machine to detect HPV DNA.
As the new advance of primary HPV screening enters into clinical practice, there will be a number of additional questions and concerns, the panel said. First, clinicians need to be aware that false negative tests will still occur – that is, some women will still develop invasive cancer, even though their HPV tests were negative. Second, at present there are four commercially available, FDA-approved HPV tests; but only one of them is FDA-approved for primary screening. While the panel hopes that there will be other tests that will be rigorously validated and approved for primary screening sometime in the near future, clinicians should not use a test that lacks a specific primary HPV screening indication. Third, the panel noted a need for comparative effectiveness studies "that consider projected lifetime number of screening tests, colposcopies and follow-up visits," as well as direct cost comparisons between primary HPV testing vs Pap smears and co-testing. Further information is also needed about the cancer risks if the interval between HPV tests is extended from three years to five years.
While the guidance applies to women who receive regular screening for cervical cancer, the panel also noted the continuing need to identify women who are still unscreened or under-screened.
"One major aspect of cervical cancer prevention that needs to be discussed in light of screening is HPV vaccination," said Huh. "Particularly with the recent FDA approval of the new 9-valent HPV vaccine and evidence that the vaccine decreases HPV and disease prevalence, I have concerns that this will put an additional strain on the performance of cytology. We will need to look at other tests like HPV as a more appropriate screening test as disease rates decrease over time."
[link url="http://www.uab.edu/news/focus-on-patient-care/item/5625-new-recommendation-for-cervical-cancer-screening-using-hpv-test-alone"]University of Alabama release[/link]
[link url="http://journals.lww.com/jlgtd/Abstract/publishahead/Use_of_Primary_High_Risk_Human_Papillomavirus.99692.aspx"]Journal of Lower Genital Tract Disease abstract[/link]
[link url="http://www.gynecologiconcology-online.net/article/S0090-8258(14)01549-2/abstract"]Gynaecologic Oncology end-of-trial abstract[/link]