Most women should be routinely screened for cervical cancer starting at age 25 and then every three years, according to new Canadian guidelines that leave open the question of testing for the virus that causes the disease.

Cervical cancer is a preventable sexually transmitted infection. In 2011 in Canada, an estimated 1,300 new cases of cervical cancer were diagnosed and there were about 350 deaths, according to the Canadian Cancer Society.

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In a Pap test, cells are taken off the cervix and examined under a microscope to check for abnormalities from cancer precursors. (Bizuayehu Tesfaye/AP Images for College of American Pathologists)

Most of those deaths were among women who never had screening or had a long gap between Pap tests, the main cervical cancer screening tool, say guidelines published in Monday's issue of the Canadian Medical Association Journal. The guidelines were developed by Dr. James Dickinson, the Calgary-based chair of the task force on preventive health care's cervical screening working group, and his co-authors.

In a Pap test, cells are collected from the cervix and looked at under a microscope to check for abnormalities from cancer precursors caused by human papilloma virus (HPV) infection. Since Canadian women originally started receiving Pap smears annually decades ago, other countries have achieved similar declines with less frequent testing and starting screening at later ages, the panel said.

Compared with the task force's previous guidelines for doctors and policymakers from 1999, the major change is increasing the starting age for screening from 18 to 25, with an emphasis on women 30 to 69.

The new recommendations include:

  • No routine screening for women under age 25, including sexually active women.
  • A strong recommendation for screening women aged 30 to 69 every three years.
  • Ending screening for women aged 70 and over who've had three successive negative Pap test results.

Women whose initial Pap test result is abnormal may be asked to have a repeat test or a closer exam called a colposcopy. If an unusual area of cells are found in a biopsy, then the area may be treated, although this can cause short-term pain, bleeding and discharge as well as early loss of future pregnancies or premature labour.

Guidelines balance screening benefits, harms

The task force said many of these procedures can be considered overtreatment or excessive because fewer than one-third of high-grade abnormalities progress to cancer.

"Our recommendations aim to balance the benefits of screening for cervical cancer with its potential harms for women of different ages," the authors concluded. As in the U.S., the panel said women who have had a hysterectomy for benign disorders no longer need to be screened for cervical cancer.

But women with impaired immune systems may benefit from more frequent screening, the authors said.

"Practitioners should be aware of women's values, preferences and beliefs about screening, and discuss these in the context of the potential benefits and harms of the screening process."

They also noted that certain groups such as aboriginal women, immigrants and women with very low socioeconomic status are less likely receive adequate screening, according to previous research. Evidence from other countries suggests that organized screening programs are the most effective approach.

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By using HPV testing, cervical cancer screenings can be less frequent with equal effectiveness, said Dr. Joan Murphy. (CBC)

Dr. Lora Cruise, medical director of the Bridgepoint Family Health Team in Toronto, performs physical exams on four women a day on average.

"I would say that many have misinformation that they need a Pap test every year," Cruise said. "But most women if you clearly explain that they don't require it every year are happy to accept that."

In Canada, uptake of both Pap testing and HPV vaccination as well as access to colposcopy all vary by community, Dr. Janet Dollin of the department of family medicine at the University of Ottawa said in a journal commentary accompanying the guidelines.

"Improving uptake and access to HPV vaccination and cervical screening would do more to lower the rates of cervical cancer than deciding at what age to start Pap testing and how frequently it should be done," wrote Dollin, a member Cancer Care Ontario's cervical cancer advisory committee.

HPV testing recommended before Pap

Cancer Care Ontario recommended that starting this year, HPV tests should be done first, followed by Pap testing only if the viral test is positive, Dollin said. Ontario is still considering whether to fund the HPV test. 

HPV DNA tests take a sample of mucous from the cervix and check for the presence of the human papilloma virus, including if it is a high-risk strain. Unlike the Pap test, the HPV test can detect the virus before precancerous cells appear, Dollin said.

"Because of the nature of the test and the nature of the disease, we know that by using HPV we can screen less frequently with equal effectiveness," said Dr. Joan Murphy, who headed the Cancer Care Ontario.  

For women, the process feels the same way for both tests. 

Dollin called Pap testing just one tool in the kit to prevent cervical cancer, along with vaccination to prevent HPV and HPV testing.

"We can envision a future where this cancer can either be prevented as a sexually transmitted viral infection or screened for less frequently with better tools," Dollin concluded.

But the panel said it was premature to make a recommendation on HPV tests, which are not currently offered in all provinces.

HPV tests cost more than traditional tests, and it's not yet clear which HPV testing technology is best to use in screening programs, Dickinson said, adding the panel will revisit the issue as new data becomes available.

With files from CBC's Laura MacNaughton and Pauline Dakin