Is newer better when it comes to cervical cancer screening programs?

The Pap test has been the centre of cervical cancer screening programs in the developed world for decades. Now, another test that promises more accurate results and less frequent screening is vying to take its place.

Unlike Pap tests, which look for abnormal cellular changes in the cervix that could pose a cancer risk, the newer test looks for the presence of the human papillomavirus (HPV), a common sexually transmitted infection that can lead to cervical cancer. If the virus is found, a woman can then undergo more comprehensive and sometimes invasive tests to see whether the virus poses a cancer threat.

Proponents say the new HPV test is more reliable, is less prone to human error and could make cervical screening simpler. Lobbying efforts are under way to persuade some provinces to publicly fund HPV testing as the primary cervical cancer screening tool.

But the head of the task force that wrote Canada's national cervical screening guidelines says this new test has not been adequately studied and that the push to embrace HPV testing is being fuelled by manufacturers of the test.

Is the new test the way of the future? Or an unnecessary threat to a well-functioning screening program that is being promoted by commercial interests?

The Canadian Cancer Society estimates that last year, 1,500 women were diagnosed with cervical cancer, while 380 died from the disease.

Until recently, regular Pap smears were a woman's best defence against cervical cancer. If doctors could spot abnormal cell changes early, they could intervene before they turned cancerous.

A sample of cells is taken from the cervix, put on a slide and examined under a microscope by a cytologist working in a laboratory. If abnormalities are detected, the woman is typically referred for follow-up testing, which could include a colposcopy, during which a doctor uses a magnifying tool to look more closely at the cervix, or a biopsy. This helps doctors determine whether the abnormality is likely to develop into cancer and, if so, take steps to remove those cells.

The arrival of the HPV vaccine about a decade ago – arguably one of the most important public-health breakthroughs in recent memory – gave women a major new weapon in cervical cancer prevention. The vaccine protects against several strains of HPV that commonly lead to cervical cancer.

While highly effective, the vaccine doesn't protect 100 per cent against cervical cancer, so screening programs will still be necessary even after all young women are vaccinated in the decades to come.

But as more women are vaccinated against HPV and the virus becomes much less common, it's going to be increasingly difficult to spot cellular abnormalities under a microscope, said Eduardo Franco, director of the division of cancer epidemiology at McGill University. That's because the cellular changes could be more subtle in women who have been vaccinated, or because lab workers will have a hard time spotting the one abnormal cell in a sea of normal ones, Franco said.

As a result, he said, it's time to look for other, more reliable methods of detecting the presence of HPV. Franco is a staunch supporter of the move to adopt HPV testing as a primary screening tool and wrote an article promoting its benefits on Healthy Debate, a website dedicated to a variety of health-care topics. Unlike Pap tests, which are prone to human error and misinterpretation, HPV testing is much more accurate because it relies on a machine to detect the presence of the virus, he said.

"We need to change the whole screening infrastructure," Franco said.

He believes that, eventually, Pap screening will become obsolete because the number of cervical cancer cases will dwindle and the HPV test will be there to help spot the remaining ones.

One major body that advises on and implements cancer screening program agrees with the move to HPV testing. Cancer Care Ontario now recommends that HPV testing be used as the primary cervical cancer screening tool. Because there is no publicly funded HPV testing program in the province, the recommendations state that Pap tests should be used until such a program is created.

Dr. Linda Rabeneck, vice-president of prevention and cancer control at Cancer Care Ontario, said the recommendations reflect "the growing evidence to support HPV testing" and that the organization hopes that HPV testing will be funded.

"We have been working diligently to achieve that," she said.

But Dr. James Dickinson, head of a working group that created Canada's national cervical cancer screening guidelines, is not convinced.

While HPV testing has potential, more work needs to be done to determine how it works in women at different ages and how to properly implement the new test, said Dickinson, chair of the Canadian Task Force on Preventive Health Care's cervical cancer working group.

He said he also has concerns over the fact support for the move to HPV testing seems to originate from the company that makes one of the tests, as well as medical professionals who have been involved with the company.

For instance, Qiagen, one of the companies selling an HPV test in Canada, has hired health-care consultancy Santis Health to lobby some provinces to adopt the HPV test as the primary screening tool for cervical cancer. Last year, three Santis employees registered in British Columbia to lobby the Health Minister on the government's "future policy direction" on HPV testing. And a lobbyist registration record filed last December with Ontario's Office of the Integrity Commissioner states that HPV testing is unequivocally better than Pap testing and that provinces "have been very slow to shift to and publicly insure HPV screening for women."

The registration goes on to say that "leading clinicians and researchers" are "educating the government, the public and cancer agencies" about the need to move to primary HPV testing.

Franco is one of those experts. He has also served as a consultant to Qiagen and other companies involved in HPV diagnostics and is listed as an author of an industry-sponsored report touting the benefits of HPV testing.

Three other authors on that report also wrote Cancer Care Ontario's recommendations to adopt HPV testing, including Dr. Joan Murphy, clinical lead of the CCO's Ontario Cervical Screening Program. The report was published last December by Santis Health, the lobby firm that has represented Qiagen since 2014, and concludes that HPV testing should be the primary cervical cancer screening tool.

Dickinson said this is a potentially serious conflict of interest that highlights the need for caution. "There's a balance here," he said. "If people are going to be setting public policy, they've got to look at both sides."

Franco said in an interview that it is "ludicrous" to think Qiagen is influencing expert opinion on HPV testing. He said he does not have a close relationship with the company and that the report was written without any input from the company.

He argues that Dickinson has a conflict of interest and that there is resistance to moving away from Pap testing because it will cost many lab workers their jobs. He also rejects the idea that there is not enough evidence to support a shift to primary HPV testing.

Rabeneck said the three authors of the report are not CCO employees and that the organization does not constrain experts from working with commercial entities. She added that many countries are moving toward HPV testing and that it is clearly the way of the future.

Irma Alfaro-Beitz, vice-president of global health for Qiagen, said the company works with experts in the field because it wants to disseminate information about an important public-health initiative.

"To say we are just pushing because we are focused on sales is just not an accurate statement," she said. "It is unfortunate that people perceive that we are pushing this. I wouldn't see it as a push, I would see it as support."

Dickinson said a shift to HPV testing would probably have only a small benefit because it doesn't address the biggest challenge facing cervical screening in Canada, namely the fact that a large subset of women simply do not get tested. For instance, a 2012 study in the journal Canadian Family Physician found that women living in the lowest-income neighbourhoods in Ontario were half as likely to be screened as their peers in other areas.

"Doing a better test for those who are already getting Pap tests provides a marginal benefit," Dickinson said. "The big benefit would come from getting to those who currently are not getting tested at all or tested infrequently. That's where the big problem is."

As for what the future holds, Kathleen Decker, an epidemiologist with CancerCare Manitoba, said she believes that HPV testing will play a prominent role. But not until more research is done. "No province currently offers primary HPV testing because we're not quite there yet," she said.