[Previous] [Table of Contents] [Next]

Cancer of the Uterine Cervix

Eliane Duarte-Franco, MD, MPH and Eduardo L. Franco, MPH, DrPH (McGill University)

Health Issue

Cervical cancer is one of the most common malignant diseases of women: it is diagnosed in almost half a million women every year, and half as many die from it annually. Although Canada has been one of the pioneer countries in reducing the incidence of cervical cancer through the adoption of Pap smear screening, the disease remains an important problem for the Canadian health care delivery system, both because of the numbers of invasive cancer cases that escape surveillance and the high costs of maintaining the quality and coverage of screening programs. Cervical cancer is a particularly important problem for immigrant groups and for Aboriginal women. Cervical cancer consists of two general histological varieties: squamous cell carcinomas and adeno-carcinomas. Although prevalence of the former has decreased in response to screening, the proportion of the latter among all cervical cancers has increased, because Pap cytology is generally ineffective to detect these adenocarcinomas and their precursor lesions.

Key Findings

In Canada, it is estimated that there were 1,450 new cases of and 420 deaths from cervical cancer in 2002. Cervical cancer incidence and mortality have declined during the last 50 years as a result of the increased availability of Pap smear screening programs worldwide and, likely, the decline in fertility rates during the last half-century in several countries. Canada was one of the first countries to adopt organized screening for cervical cancer, but most provinces have yet to follow national guidelines calling for the implementation of program-based cytology screening. In most provinces, early detection still depends on opportunistic screening that relies on cytology tests done at the discretion of family physicians. A woman with a diagnosis of cervical cancer is, on average, at least two decades younger than a woman with other female genital cancers. An average 26 years of life are lost per female patient dying of cervical cancer. It is estimated that each year in Canada, cervical cancer causes an estimated 11,000 person-years of life lost.

Unlike most other cancers, cervical cancer has a central causal factor: human papilloma virus (HPV) infection, which may in fact be a necessary cause of this disease and of its precursor lesions. Other risk factors are specific sexual behaviours, smoking, parity, oral contraceptive use, diet, and HIV infection. Primary prevention can be achieved through health education (sexual behaviour modification) and vaccination to prevent HPV infection. Two main types of HPV vaccines are currently being developed: (i) prophylactic vaccines to prevent HPV infection, and (ii) therapeutic vaccines to induce regression of precancerous lesions or remission of advanced cervical cancer. Such vaccines are under evaluation in different populations. The initial results appear to be very promising, but wide-scale use as a preventive strategy is still more than a decade away.

Data Gaps and Recommendations

The authors identified the following data gaps and made the following recommendations:

• Most progressive cases of cervical cancer occur because of a false-negative Pap test result, because a woman did not receive a Pap test at all, or was not tested often enough. Well-developed recommendations and guidelines exist as part of a succession of national consensus reports concerning the implementation and maintenance of cytology-based screening programs. However, most Canadian women do not yet have access to organized, centralized cervical cancer screening.
• Despite the availability of some excellent Canadian surveys of Pap test utilization among women who developed the invasive form of the disease, we still lack critical information concerning the appropriate management of precursor lesions from audit studies. Various automated systems, aimed at improving the performance of the cytology test, are currently being tested. Large-scale prospective studies are still needed to evaluate these systems.
• Several studies have assessed the relative utility of HPV testing in addition to or compared with the Pap test as a cervical cancer-screening tool. These have been cross-sectional or short-term follow-up investigations, and no randomized controlled trials have yet been published. Testing for HPV seems to be a promising screening approach, but definitive evidence of efficacy is still needed from long-term follow-up studies with invasive cancer as an outcome and from randomized, controlled trials.
• One other screening application for HPV testing is in the secondary triage of equivocal Pap smears. Results from large-scale studies have indicated that HPV testing has greater sensitivity than a repeat Pap test for detecting hidden precursor lesions or cancer among women referred because of an equivocal Pap smear; such testing also reduces costs in terms of colposcopy referrals. However, taking into account the totality of the evidence, we still lack Canadian data to justify augmenting or modifying current screening programs.

Download Full Chapter (PDF)

[Previous] [Table of Contents] [Next]