Why does cancer of the cervix still occur?

Posted by Alex

Underscreened populations. Women are inadequately screened for several reasons. For women to enjoy the benefits of screening, they must first undergo the test. In Prince Edward Island, 57% of women diagnosed with invasive cancer of the cervix had not previously been screened. Eighty-six percent of women older than 60 diagnosed with invasive cancer had never been screened. Despite a population-based screening program in British Columbia since 1955, 15% of all women in that province have never had a Pap test. Nationally, twice as many women between the ages of 25 and 44 were not screened in 1990 as were not screened in 1985.

Many of the unscreened women are from immigrant communities, aboriginal communities, or core areas of our cities. Other groups shown to be under-screened include those living in remote areas; single, unemployed women; low-income earners; and older women.1213 The challenge these groups of women present to family physicians is more than a lack of compliance with cervical cancer screening. They frequently feel uncomfortable and unwelcome in physicians’ offices and thus attend infrequently.

There are both physician-specific and patient-specific barriers to cervical screening. To overcome these barriers, family physicians need to make preventive care a priority. When patients attend for any reason, family physicians need to encourage all women due for screening to undergo Pap tests, especially those who have never been screened. This requires effective communication of the purpose of screening as well as of the mechanics of the test.

Underscreened women have been shown to respond to culturally sensitive education initiatives. An organized system of patient reminders has-proven effective in increasing screening rates.14,17 Ensuring adequate follow up of abnormal test results requires office organization as well as good communication skills. This begins with adequate explanation of the procedure before the test as well as preparing patients for possible outcomes of the initial screening test.

Using a patient-centred approach, which involves addressing patients’ concerns as well as preparing them for possible outcomes (family physician’s agenda) has been shown to increase patient compliance with follow-up appointments. Women also appreciate choices as to where they have the test. Those with established, trusting relationships with family physicians often prefer to see them for their Pap smears, while others prefer the option of a dedicated Pap test clinic run by women practitioners. Women’s Health

Smear quality. The second reason for inadequate screening is that, when a test is performed, the quality of the smear must be high enough to allow appropriate interpretation. The high false-negative rate of smears has been attributed to two problems: inadequate specimens for cytopathologists to evaluate and smear interpretations that miss or misinterpret abnormal cells on the slide. As providers of most of the material for interpretation, family physicians need to provide the best possible samples.

To ensure an adequate sample, it is essential to view the cervix clearly. Much research in this area has concentrated on the instruments available for obtaining the smear. Randomized controlled trials have compared various methods. The best results are obtained with a combination of the extended tip spatula scraping the ectocervix followed by a Cytobrush to obtain an optimum endocervical sample. Both specimens are placed together on the same slide.

Level III evidence suggests that the specimen should not be contaminated with lubricant, so the sample should be taken before the bimanual examination. The sample should be rapidly fixed holding the aerosol 25 cm from the slide to avoid cell damage or loss from the pressure of the spray. Table 1 summarizes the technique currently recommended to ensure an adequate sample. Evista online

Table 1 • Technique for Pap smears
Collect sample before bimanual examination
Do not contaminate sample with lubricant; warm speculum in water for lubrication and comfort
View entire cervix
First collect ectocervical scraping (extended tip wooden spatula) then endocervical sample (Cytobrush)
Fix rapidly; hold spray 25 cm from slide
Data from Thompson.

Laboratory error. As family physicians, we are not responsible for the quality of cytopathology reporting we receive, but we are responsible for ensuring that we send our specimens to the best available laborato¬ry. Retrospective analysis of Pap smears reported as normal has revealed problems in interpretation of the slides. Resulting litigation in the United States has caused a crisis in the cytopathology industry.

False-negative results attributable to laboratory error fluctuate from laboratory to laboratory; smaller commercial laboratories generally provide poorer results. The Canadian response has been to centralize the process at publicly funded and accredited laboratories where quality control can be adequately monitored. Raloxifene 60 mg

We should inquire about the false-negative rates, quality control measures, and reporting systems of potential providers of the service. It is important that reports indicate the adequacy of specimens submitted for interpretation. Feedback from cytopathologists to clinicians provides an important mechanism for quality control of adequate sampling. Current literature suggests that a false-negative rate of between 5% and 10% is both achievable and acceptable.

Frequency of sampling. Perhaps the most controversial question is the optimum frequency of screening. The various guidelines available are contradictory, and the evidence upon which they are based is weak. We do not know how long it takes for the first detectable abnormality on screening to develop into invasive cancer. Various expert panels that have addressed the frequency of testing used mathematical models of data from screened populations, some screened as long as 20 years ago. Despite the limitations of these data, the results demonstrate useful principles for understanding the rationale behind the recommendations.

Canadian experts consistently argue that more frequent testing should continue to compensate for the lack of population-based programs with centralized laboratories and a registry. These measures are expected to ensure adequate quality of smears and interpretation to reduce the false-negative rate. In addition, a registry would ensure that women are aware of the need for testing and that follow up of inadequate or abnormal smears is appropriate. Female Viagra

Rather than expressing frequency in terms of years between tests (eg, every 3 years), the models have looked at the number of tests per lifetime (Table 2). The mortality expressed per 10 000 tests clearly drops as the penetration of screening improves. Thus, when 80% of the population is screened, mortality is only 7.1/10000 tests when 10 tests are performed over women’s lifetimes. Increasing the number of tests per lifetime to 23 from 10 (ie, increasing the frequency of testing) results in 7.4/10000 mortality rate with only 50% of the population screened. This is due to the marked decrease in false-negative rates by repeatedly screening the same women.

Table 2. Mathematical model of test frequency, based on level II evidence

NO. OF TESTS	ELIGIBLE POPULATION UNDERGOING TESTING (%)	MORTALITY*
10 tests	50	19.5
10 tests	80	7.1
10 tests	90	5.0
23 tests	50	7.4

Data from Shun-Zhang et al
* Cause-specific mortality from cancer of cervix per 10000 tests.

Interpreting the same models using incidence reduction results in a slightly different picture (Table 3). While annual testing results in a 93.5% reduction of cancer of the cervix, only 33 cases are identified per 100000 smears. Screening every 3 years results in 90.8% reduction, but 96 cases are identified per 100000 smears, resulting in a more cost-effective approach. The policy proposed by the Society of Obstetricians and Gynaecologists of Canada compensates for Canada’s current shortcomings in not having a centralized registry or laboratory by recommending annual screening. Canadian Fosamax

Table 3. Mathematical model of screening effectiveness

TEST INTERVAL	INCIDENCE REDUCTION (%)	CASES*
1 year	93.5	33
2 years	92.5
3 years	90.8	96
5 years	83.6

Data from Soost et al.28
* Cases identified per 100′000 smears.

While the models support this policy statistically, they do nothing for women who are not screened. The time, energy, anpl resources used in screening the same women three times in 3 years should be diverted to screening more women every 3 years, as suggested by the Canadian Task Force on the Periodic Health Examination. Family physicians have a responsibility in this area. We should resist the temptation to screen the same low-risk women annually even though they might have become accustomed to this frequency of testing. Family physicians need to introduce the necessary office systems into their practices to provide reminders when Pap tests are due. As a group, we should advocate for a central registry, such as the registry that has proven effective in British Columbia.