In 2011, an estimated 1300 new cases of cervical cancer were diagnosed in Canada, with about 350 deaths.1 The number of cases of diagnosed cervical cancer increases among women aged 25 years and older, peaking during the fifth decade of life (Figure 1). The incidence of and mortality due to cervical cancer in Canada have decreased substantially in the past 50 years,2,3 and long-term survival rates after treatment are high. Lifetime incidence was 1.5% in 1972, and is now 0.7%; risk of death from cervical cancer is now 0.2%.3 Most advanced cervical cancer (and associated mortality) occurs among women who have never undergone screening or who have had a long interval between Papanicolaou (Pap) tests.2
Screening for cervival cancer using the Pap test detects precursor lesions, thereby allowing earlier and potentially less invasive treatment than is required for disease that causes symptoms. The benefits of such screening on the incidence of invasive disease4 and death due to cervical cancer5 have been consistently shown in cohort and case–control studies.6
It is likely that much of the change seen in the incidence of cervical cancer in Canada is due to screening, but early and frequent (often annual) cervical screening is unnecessary: other countries have achieved similar outcomes with less frequent testing and starting screening at older ages.7 The similar levels of success with different approaches highlights uncertainties regarding the best ages at which to start and stop screening, screening intervals and screening methods. Furthermore, the benefits of screening must be balanced against its potential harms, such as additional follow-up tests for abnormal results and unnecessary treatment (e.g., owing to false-positives and overdiagnosis).
The likelihood of abnormal Pap test results is highest for young women, and decreases with increasing age.8 Because the prevalence of high-grade abnormalities declines steadily with age, although the incidence of cancer is higher, the proportion of abnormal results that represent serious abnormalities is greater among older women.8
Women whose initial Pap test result is abnormal may be asked to undergo a repeat test or have a colposcopy. The colposcopist may then biopsy the cervix. If the biopsy shows cervical intraepithelial neoplasia, the colposcopist may then treat the cervix by excising the transformation zone using various methods. These procedures cause short-term pain, bleeding and discharge,9 and may cause early loss of future pregnancies or premature labour.10 It is likely that many of these procedures can be considered overtreatment,11 because fewer than one-third of even high-grade abnormalities progress to cancer.12–14
This guideline provides updated recommendations for screening for cervical cancer in Canada based on new information about the epidemiology and diagnosis of cervical cancer and a new systematic search of the literature.11 This guideline updates the recommendations of the Canadian Task Force on Preventive Health Care that were last revised in 1994.15
Recommendations are presented for the use of Pap tests for women with no symptoms of cervical cancer who are or who have been sexually active, regardless of sexual orientation. Separate recommendations are provided for screening in women in the following age categories: younger than 20 years, 20–24 years, 25–29 years, 30–69 years and 70 years or older. Recommendations do not apply to women with symptoms of cervical cancer or previous abnormal test results on cervical screening (unless they have been cleared to resume normal screening); to women who have had complete surgical removal of the cervix; to women who are immunosuppressed by HIV, organ transplantation, chemotherapy or chronic use of corticosteroids; or to women who have limited life expectancy such that they would not benefit from screening. The recommendations do not address the management of abnormal test results or cervical cancer. Furthermore, they do not address screening through testing for human papilloma virus (HPV), either alone or in combination with Pap testing. The Canadian Task Force on Preventive Health Care felt that it was premature to make recommendations on such screening until the evidence in this area is further developed.