New And Better Testing Keeps Cervical Cancer At Bay
Prevention and Treatment In the mid-20th century, three decades after Greek doctor Georgios Papanicolaou discovered that inspecting cells from the cervix could detect cancer, his test was adopted on a widespread basis.
Since then, the Pap test has cut the rate of cervical cancer deaths in North America by more than 70 percent.
The Pap test has evolved in recent years. Rather than being transferred directly to a microscope slide, the cells are now deposited into preservative liquid where mucus and other elements are removed from them. They are then transferred to a slide for examination. This method, called liquid-based cytology, has decreased the number of unsatisfactory samples and is well regarded even though not all Canadian health care providers have yet gained access to it.
The Pap test still plays a pivotal role in screening for cervical cancer and is sometimes used in conjunction with a test that detects the human papillomavirus virus (HPV), which causes nearly 100 percent of all cervical cancers.
While the Pap test can detect pre-cancerous cells and help prevent this cancer, it can also give a false-positive result when the cells look abnormal for other reasons. In that scenario, something looks like a precancerous condition, but actually isn’t. A false-positive result can lead not just to anxiety for the patient but also to unnecessary follow-up tests and procedures that could have negative side effects, including problems with future pregnancies.
How much is too much?
For this reason, there has been an ongoing debate about when a woman should start getting Pap tests and how often she should get them.
Two years ago, the Canadian Task Force on Preventive Health Care concluded that women should start getting regular Pap tests when they are 25 years old; a growing body of scientific evidence indicates that the benefits of screening younger women don’t outweigh the risks. Most cervical cancer cases are diagnosed among women in their forties or older.
“If more women go for regular testing, more lives will be saved.”
The Task Force also determined that when women start getting the Pap test, they should do so every three years rather than annually. Evidence indicates that it takes an average of 10 to 20 years from the time a woman is infected with HPV until the time cervical cancer might appear.
Benefits of ‘co-testing’
Dr. Vladimir Iakovlev, Director of cytopathology at St. Michael’s Hospital in Toronto, feels that when a woman in her late twenties gets an atypical but not conclusively precancerous Pap test result, she could benefit from undergoing another test, one that checks for high-risk HPV infection.
Traditional HPV tests work by checking for the virus in one kind of cell (DNA) while newer tests work by checking for the virus in another kind of nucleic acid (RNA) in cells. Iakovlev views the introduction of the latter test as a “significant development” because in addition to indicating when the virus is present it also indicates when the virus is active.
Iakovlev adds that women 30 years and older could benefit from regular co-testing — that is, both the Pap test and the HPV test. If combined with the HPV test, a Pap test could be conducted every five years instead of every three without any detriment to the patient, he says.
Dr. Terence Colgan, head of gynaecological pathology and cytopathology at Mount Sinai Hospital, says there are a few drawbacks to HPV testing in general because many women harbor HPV without having any cervical disease. However, he praises the HPV test for its “sensitivity in detecting cervical preinvasive disease and cancer.”
Most health care providers see the benefit in using both tests, but some believe that the HPV test should be the first one used in screening for cervical cancer.
That being said, the HPV test is not part of regular cervical cancer screening anywhere in Canada — at least, not for the time being — and patients have to pay for it out of pocket.
Colgan advises females to stick to the screening guidelines, which he describes as “quite reasonable,” and participate in the HPV vaccination programs that have been introduced. Dr. Scott Boerner, Director of cytopathology at the University Health Network, agrees. “The most important message to convey to women is that they should get vaccinated,” he says, adding the HPV vaccination coverage rate among females in Canada is only about 70 percent.
Sadly, about 1,500 Canadian women are diagnosed with cervical cancer each year and almost 400 die from it. “If more women go for regular testing,” Iakovlev says simply, “more lives will be saved.”