The widespread use of Pap smears has resulted in a remarkable change in the amount of cervical cancer and deaths. Since 1977, even without an organized program, the Canadian incidence of cervical cancer has dropped by half. The death rate has declined by 60 per cent. However, cervical cancer has not been cured. A disturbing number of women still get the disease and die from it.
Failing to be screened with a regular Pap smear or under-screening (not being screened in the recommended way) is still a major risk factor for cervical cancer. Statistics suggest about 30 per cent of women have not been screened in the previous three years.
Risks also come from over-screening. Too many tests can be done, with the accompanying discomfort and cost. Over-screening can also lead to more invasive, unnecessary therapies that may harm women.
We now have a better understanding of risk factors for developing this cancer. Almost all cervical cancers and abnormal pap smears come after infection with human papilloma virus (HPV). This viral infection is very common. About half of women get it within four years of starting sexual activity.
Most infections (over 90 per cent) clear fully and are of no further concern to the woman. However, a number resolve more slowly, and some create abnormal Pap smears and cancer. The development of an abnormal smear or abnormal cells on the cervix is visible from the time of infection. Most cases resolve completely with no further risk. In a very small number of women it gets worse over time and develops into cancer.
Cervical cancer evolves over many years and follows the same pattern:
Other factors can increase a woman’s risk of persistent HPV infection. For instance, smoking doubles the risk. Certain conditions also affect a woman’s ability to fight the infection completely.
Guidelines exist on appropriate screening for cervical cancer in women who have never had an abnormal test.
When to start: In most provinces, screening begins within three to four years of starting sexual activity. In Alberta, screening begins at age 21, based on a 15 year review of the incidence of cancer.
How often: All provinces agree on a two to three year interval for screening once a woman has had three negative smears one year apart.
When to stop: Screening ends at age 69, or if the cervix is removed for other reasons unrelated to cervical cancer.
If abnormal cells are found at any time in the screening process, clear procedures are in place. Appropriate follow-up and treatment are done. As well, if there are symptoms of disease, a Pap smear can be scheduled earlier.
The link between HPV infection and development of cervical cancer is now better understood. As a result, many provinces are introducing HVP vaccine to prevent the disease, and HPV testing to see if it is present. Often, this test helps decide on further therapy for women who have abnormal Pap smears. Currently, testing and vaccination programs are not fully underway.
Tips for the test
As most provinces have an active recall program, many women receive letters reminding of the need for Pap smear. If you believe that you need one done, you can take steps to ensure quality test results.
Pap smear guidelines have changed. Screening starts later in a woman’s life, and is done less often for women at low risk. The changes have been made for good reason. They support better health for all women, a higher identification of disease, and a lower rate of inappropriate interventions.