Cervical cancer screening re-examined
Studies find little benefit from tests for young women
Are young Canadian women undergoing too many Pap tests? New research suggests they probably are. And the findings provide strong hints that change may be in the wind when the Canadian Task Force on Preventive Health Care issues new recommendations in January on who, when, how often and how to screen for cervical cancer.
The two new studies look at what has happened to rates of invasive cervical cancer and deaths since Canada got into the cervical cancer screening business in 1949.
This country was actually a pioneer in cervical cancer screening, and the benefits of that work are clear, the graphs and charts in the papers show.
In the decades since women started getting annual Pap smears — now generally done at a two -or three-year interval — new cases of invasive cervical cancer, and deaths due to the disease, have plummeted.
Cervical cancer deaths fell to 2.2 per 100,000 women from a peak of 13.5 per 100,000 between 1952 and 2006 — an 83-per-cent drop, reports one of the studies, published in the online journal BMC Public Health.
In other words, what was a rare cancer has become rarer still. The Canadian Cancer Society estimates 1,350 Canadian women will have been diagnosed with cervi- cal cancer this year, and 390 will die from the disease in 2012.
But the research shows that most of the gains — the cancers averted, the deaths prevented — have been in women in their 40s and beyond.
There are so few cervical cancer cases diagnosed in women in their teens and 20s that there appears to be little benefit in screening women that young, the papers suggest.
And there are some risks, mainly from requiring women to undergo treatment for abnormal test findings that would never have become cancer, but which, once found, had to be treated.
“Discontinuing the practice of routine screening of women under the age of 25 could be given consideration due to the absence of theoretical basis and the clear harms caused by the treatment of lesions largely destined to regress,” concludes one of the studies, published this month in the Journal of Obstetrics and Gynecology Canada.
Both studies were written by the same team of researchers, some of whom are from the Public Health Agency of Canada.
They were done to inform the discussion on the new cervical cancer screening recommendations, says Dr. James Dickinson, the lead author on one of these studies and a secondary author on the other. Dickinson is chair of the group drawing up the cervical cancer screening guidelines.
The Canadian Task Force on Preventive Health Care weighs medical evidence to advise doctors on what preventive healthcare tests they should offer their patients.
With these guidelines, they are expected to tell doctors when women should have their first cervical cancer screening test, how often they should be tested and at what age they should stop. The guidelines will also likely deal with the type of test to be used in screening programs.
The January document will be the first updated recommenda- tions on cervical cancer screening in years from the task force, which was inactive from 2005 to 2010 when the federal government stopped funding its work for a period.
Dickinson, a professor of family medicine at the University of Calgary, says the studies point to substantial benefit of screening for women who are in their 30s and beyond. But the benefits are much less evident below that, and especially for women younger than 20.
“Certainly for women under the age of 20, there is almost no cancer at all. So yes, that’s really pointless,” he says. “For women 20 to 25, yes, the incidence (of cervical cancer) is very low. And we don’t really seem to have made much difference to that (through screening). So we haven’t lowered the incidence very much despite very intensive screening for those women.”
In the absence of updated guidance from the task force, policy has evolved on a province-byprovince basis.
About three years ago Alberta changed its approach, telling doctors to stop screening women before the age of 21 and to re-screen every three years after that if their Pap tests are normal. For women who’ve had normal Pap test results, screening stops at 70. Other provinces followed.
And while some devised variations of the Alberta policy — Ontario says women who aren’t sexually active by age 21 should wait until they are active to have their first Pap test.
In most parts of the country the starting age is 21 and the interval is three years.
These new studies suggest the starting age for screening might well be pushed out even further.