NEW YORK (GenomeWeb) – A collection of new studies suggest that it may be time to rethink cervical cancer screening methods, moving away from cytology-based testing on Pap smear samples and toward direct screening for DNA from human papillomavirus (HPV).
Because the vast majority of cervical cancer cases can be traced back to persistent HPV infection — particularly infections involving HPV16 or HPV18 types — methods have emerged for directly detecting as a means of identifying individuals at risk of the disease who might require enhanced screening.
As part of a special issue of the journal Preventive Medicine, several independent investigators and research teams outlined the available evidence related to HPV DNA testing, along with barriers and considerations that should be taken to account for those thinking of rolling out widespread HPV testing.
"I believe that, among experts, there is an emerging consensus that HPV testing is theoretically the optimal available primary screening testing, but that optimal implementation is far from settled," Mark Schiffman, a clinical genetics researcher at the National Cancer Institute and guest editor for the special issue, said in a statement.
"It turns out that detailed implementation of HPV primary screening to replace cytology reveals many choices reliant on value judgments and not risk assessment, particularly when resources are limited," Schiffman added. "Controversial areas include acceptable costs and effort, choices of safety and action thresholds, and the role of the clinician in the integration of test data [versus] apps and guidelines."
In an editorial accompanying the studies, McGill University researchers Sandra Isidean and Gayle Shinder highlighted the Pap test's role in reducing cervical cancer rates, while looking ahead to new technologies that are starting to take hold for cervical cancer prevention, including both automated cytology methods and HPV testing.
In his own introduction to the issue, Schiffman pointed to the importance — and limitations of — epidemiological data for helping select appropriate cervical cancer screening strategies in a given setting. He noted that "epidemiology has just one seat at a crowded table when discussing health care policy and the practical management of screen-positive women."
"Local policy concerns, varying views and tolerances of safety, patient and clinician advocacy, funding constraints, and many other non-scientific factors outweigh epidemiological data in deciding which prevention programs are created and supported," Schiffman wrote.
For their part, researchers from Canada and the US discussed findings from clinical trials using HPV molecular testing as a primary screening method, including findings from two large randomized controlled trials of the approach. They cautioned that the data may be most relevant to places with relatively robust resources available for such screening.
Indeed, the authors noted that the review "summarizes a report recently distributed to Canadian policy makers and other relevant agency/organization representatives to provide an overview of the current state of evidence regarding HPV-based screening for cervical cancer and describe the benefits of introducing molecular HPV testing as the primary screening technique."
Some members of the same team also took a look at potential triage strategies for women who test positive for HPV in another Preventive Medicine paper, based on findings from a community study in Montreal. Because molecular testing is a less specific method for finding cervical cancer or precancerous lesions, for example, positive tests may require additional genotyping, follow-up cytology, and/or cervical examination.
Still other teams considered controversies that remain around HPV testing, the applicability of cervical cancer screening in populations that have received HPV vaccination, and addressed the applicability of HPV testing in South Africa or other resource-limited settings.