Ovarian Cancer in Canada (October 1999) Breast Cancer in Canada (April 1999) Cervical Cancer in Canada (March 1998)

Cervical Cancer in Canada

• 1,300 new cases and 390 deaths from cervical cancer were estimated for 1997.
• Regular screening can prevent almost all cases of invasive cervical cancer.
• Not all provinces have organized screening programs.
• 15% of women have never been screened; 30% haven't been screened in the last 3 years.
• 5-year survival rate is 74% overall.

Cancer of the cervix is the eleventh most frequently diagnosed cancer among Canadian women (in contrast, it is the second most common form of cancer in women worldwide) and, despite being almost completely preventable through regular screening, continues to be an important cause of morbidity and mortality. It was estimated that, in 1997, approximately 1300 women would develop cervical cancer and 390 women would die from this disease⁽¹⁾. A study by Miller et al⁽²⁾ revealed that mortality estimates based on information from death certificates were underestimates, since a large number of cervical cancer deaths were incorrectly coded as uterine cancer deaths. Regional variation in the incidence of and mortality from cervical cancer is considerable, with higher rates in the Atlantic and Northern regions and lower rates in Western Canada (Figures 1 and 2, data supplied by the Canadian Cancer Registry, formerly the National Cancer Incidence Reporting System).

Trends

Incidence rates decreased steadily in the 1970s and early 1980s and showed a more moderate decline since about 1985 (Figure 3). This attenuated decline in incidence occurred in all age groups (Figure 4), reflecting either a plateau in screening activity or a change in the prevalence of risk factors, the former being the more likely explanation. Over the past two decades, mortality from cervical cancer also decreased, from a rate of 11 per 100,000 in 1951 to 2.39 per 100,000 in 1995 (Figure 5)⁽²⁾. The rate of decline in incidence and mortality was similar for all age groups but varied provincially, more rapid reductions being observed in Newfoundland and New Brunswick. The highest incidence and mortality rates have consistently been found in women above the age of 65.

Squamous cell carcinomas make up about 80% of all types of cervical cancer and are reasonably well detected with the Pap smear. Adenocarcinomas, which account for another 15% of subtypes, are unfortunately less easily detected using this test. A recent analysis of incidence trends according to cervical cancer subtypes⁽³⁾ revealed that while the incidence of squamous cell cancers declined by 3.2% per year between 1984 and 1992, the incidence of adenocarcinomas increased by 4% during the same period. An increase in the incidence of the adenocarcinoma subtype has also been reported in the United States, Australia and Taiwan and emphasizes the importance of surveillance according to cellular subtype as well as the development of newer, more sensitive screening methods for this particular form of cervical cancer.

Until quite recently, little was known about morbidity and mortality from cervical cancer in Aboriginal women. A study from Saskatchewan linking the health insurance system with the provincial cancer registry found that the incidence of cervical cancer in status Indians was 10 times higher than the provincial average⁽⁴⁾. These data reinforce the need for establishing a formal national Aboriginal cancer surveillance system, along with strategies for cancer prevention and control that are sensitive to the culture and traditions of Canada's Aboriginal population.

Figure 1
Cervical Cancer Incidence by Province/Territory, 1984-1993

Figure 2
Cervical Cancer Mortality by Province/Territory, 1984-1995

Figure 3
Cervical Cancer Incidence and Mortality

Figure 4
Cervical Cancer Incidence, by Age Group, 1969-1993

Figure 5
Cervical Cancer Mortality, by Age Group, 1950-1995

Primary Prevention

The main risk factors for cervical cancer include early age at first intercourse, greater number of sexual partners, increasing age, infection with human papilloma virus (HPV), smoking and low socioeconomic status. The relationship between cervical cancer and other possible risk factors such as oral contraceptive use and nutritional deficiencies (folate, vitamin A and vitamin C) is presently unclear. Some reports suggest a familial predisposition to cervical cancer, although the etiology of this disease is likely multifactorial with both genetic and environmental influences⁽⁵⁾. The primary prevention of cervical cancer is therefore closely linked to ongoing public health initiatives targeting behaviour change of the population, particularly in the areas of smoking cessation and safer sex practices.

Secondary Prevention

Early detection using the Pap smear remains the best currently available method of reducing the incidence and mortality of cervical cancer. The Canadian Task Force on the Periodic Health Examination⁽⁶⁾ recommends annual screening with the Pap smear after initiation of sexual activity or at age 18. If an organized screening program is in place with appropriate quality control measures and information systems, the screening frequency may be reduced (for women with two previous normal smears) to every 3 years until age 69. The Walton Report⁽⁷⁾ and a series of national workshops^(8-10) on cervical cancer screening urged the establishment of organized, provincial screening programs with centralized laboratory and information systems. To date, three provinces (British Columbia, Nova Scotia and Prince Edward Island) have adopted these recommendations in whole or part.

Cost of Screening: The cost of performing a Pap smear is low in comparison to other cancer screening tests and is largely offset by savings to the health care system from prevented cases of cervical cancer⁽¹¹⁾. The implementation of organized screening programs should also result in long-term savings from reduced laboratory expenses and lower morbidity and mortality from this disease⁶.

Utilization of Screening: In an analysis of the 1994 National Population Health Survey (NPHS)⁽¹²⁾, 82% of women who participated reported ever having had a Pap smear (self-reported data can affect population estimates of screening). Almost half of the respondents (46%), had had a Pap smear in the previous 12 months, and 68% had been given this test within 3 years of the survey. (Estimates adjusted for hysterectomy status increased to 55% and 81%, respectively⁽¹³⁾.) There was little variation in Pap smear utilization by province.

Approximately 15% of women had never been screened. These women were poorer, less educated and tended to be either young (31% were 18-24 years) or older (28% were older than 65). Unfortunately, the NPHS did not assess screening rates for high risk groups, such as immigrants, Aboriginal women and women living in the Territories and northern regions. The 1990 Ontario Health Survey⁽¹⁴⁾, however, found that recent immigrants, women who spoke neither English nor French and rural residents were less likely to have had a Pap smear.

Factors known to affect the use of cervical cancer screening include access to screening (especially in Northern and rural areas), awareness of the benefits of screening and anxiety about the procedure itself⁽¹⁵⁾.

Treatment

Survival rates provide a direct indication of disease severity and the impact of cancer treatment. For cervical cancer the 5-year survival rates are generally high, at 74% for all ages, 87% for 0-44 years, 72% for 45-54 years, 67% for 55-64 years, 57% for 65-74 years and 47% for age 75 and above⁽¹⁶⁾.

Treatment of this cancer depends on the stage of the disease, size of the tumour as well as the patient's age, overall condition and desire to have children⁽¹⁷⁾. The earliest form of cervical cancer is carcinoma in situ (stage 0), a non-invasive cancer that can be treated by loop electrosurgical excision procedure (LEEP), conization (removing a cone-shaped piece of the cervix), cryotherapy, laser therapy or hysterectomy. In stage 1 cervical cancer, the tumour invades into the normal tissue but has not spread beyond the cervix itself. Treatment options for this stage include hysterectomy, conization, and internal or external radiation therapy. Cancers that extend beyond the cervix but are still limited to the pelvis (stage 2) may be treated with internal and external radiation combined, hysterectomy followed by radiation, or by radiation and chemotherapy. Treatment of cancers that have spread throughout the pelvis (stage 3) usually involve a combination of internal/external radiation therapy plus chemotherapy. In stage 4 disease, the cancer has spread to other parts of the body and treatment usually consists of radiation, chemotherapy or a combination of the two.

Current Initiatives

The Cervical Cancer Prevention Network, an informal association of provincial, territorial and federal representatives and clinical professional bodies, shares information on program development, organization and data collection and strongly supports the development of organized screening programs in Canada. Through this network stakeholders in five provinces (Alberta, Saskatchewan, Manitoba, Ontario and Newfoundland) are considering or planning to implement organized screening programs in their jurisdictions.

Future Directions

Recent advances in understanding the mechanistic action of HPV through molecular biology techniques have provided insight into methods for vaccine development that may help to control HPV in the future. Until such a vaccine becomes available, regular use of condoms and Pap-smear testing continue to be the main strategies for prevention.

The collection of cervical cancer data according to stage of disease at diagnosis by all provincial/territorial cancer registries, would provide stage-specific survival rates and aid in the evaluation of the success of existing screening programs.

Summary

Screening for cervical cancer using the Pap smear has been effective in reducing morbidity and mortality from this disease. Over the past two decades, however, the decline in incidence has stabilized somewhat, suggesting a plateau in screening activity and bringing into question the usefulness of an ad hoc approach to cervical cancer prevention. Data from the 1994 NPHS confirmed that women who were poor or less educated were less likely to have had a Pap smear. Special efforts are needed to understand factors affecting Pap smear utilization in high risk groups and to then recruit these groups for screening. The evidence strongly supports the National Workshop's recommendations for full implementation of comprehensive cervical cancer screening programs in all provinces in order to reduce the occurrence of this preventable disease in Canada.

Acknowledgement

Data were provided to Health Canada from the Canadian Cancer Registry, formerly the National Cancer Incidence Reporting System, at Statistics Canada. The cooperation of the provincial and territorial cancer registries which supply the data to Statistics Canada is gratefully acknowledged.

References

1. National Cancer Institute of Canada. Canadian cancer statistics 1997. Toronto, 1997.

2. Miller AB, Lindsay J, Hill GB. Mortality from cancer of the uterus in Canada and its relationship to screening for cancer of the cervix. Int J Cancer 1976;17(5):602-12.

3. Probert A, Fung Kee Fung M, El Atebi F, Faught W, Senterman M, Semenciw R et al. Trends in the incidence of the histological subtypes of cervical cancer in Canada and Ontario. Cancer Bureau, Laboratory Centre for Disease Control, Health Canada and the Gynecological research group, Ottawa General Hospital, University of Ottawa.

4. Gillis DC, Irvine J, Tan L, Liu L, Robson D. Cancer incidence and survival of Saskatchewan northerners and registered Indians, 1967-1986. 8th International Congress on Circumpolar Health. Whitehorse, Yukon. May 23, 1990.

5. Schottenfield D, Fraumeni J. Cancer epidemiology and prevention. Second Edition. New York: Oxford University Press, 1996.

6. The Canadian Task Force on the Periodic Health Examination. The Canadian guide to clinical preventive health care. Ottawa: Supply and Services Canada, 1994: Health Canada Cat H21-1117/1994E.

7. Task Force on Cervical Cancer Screening Programs. Cervical cancer screening programs (The Walton Report). Can Med Assoc J 1976;114:1003-33.

8. Miller AB, Anderson G, Brisson J et al. Report of a national workshop on screening for cancer of the cervix. Can Med Assoc J 1991;145:1301-25.

9. Berkel J. Proceedings of the second national workshop on cervical cancer screening. Chronic Dis Can 1992;13(4S);S1-S41.

10. Mills CJ. Workshop Report. Cervical cancer: toward the implementation of organized screening. Chronic Dis Can 1993;14(3):110-112.

11. Miller AB. Advances in cancer screening. Massachusetts: Kluwer Academic Publishers, 1996:46.

12. Snider J, Beauvais J, Levy I, Villeneuve P, Pennock J. Trends in mammography and pap smear utilization in Canada. Chron Dis Can 1996;17:108-17.

13. Snider JA, Beauvais JE. Pap smear utilization in Canada: estimates after adjusting the eligible population for hysterectomy status. Submitted for publication to Chronic Dis Can.

14. Goel V. Factors associated with cervical cancer screening: results from the Ontario Health Survey. Can J Public Health 1994;85:125-7.

15. Austoker J. Screening for cervical cancer. BMJ 1994:309;241-8.

16. National Cancer Institute of Canada. Canadian cancer statistics 1995. Toronto, 1995.

17. U.S. National Cancer Institute. PDQ information for health professionals. Cervical Cancer October 1997.

Contributors: Maureen Carew, Dena Schanzer, Judy Snider and Laura Villeneuve.