Population Screening for Cervical Cancer - Essay Example

Population Screening For Cervical Cancer Cervical cancer and its cytologic precursors are conditions that affect sexually active women, especially in their reproductive years (Hartman et al, 2002).This condition, also known as squamous cell carcinoma of the cervix, is one of the most frequent cancers worldwide. An estimated 470,000 new cases occur worldwide each year, with the bulk of these coming from the developing countries (Boking, 2003, p.6). In the United States alone approximately 12,800 new cases of cervical cancer are diagnosed and almost 4,800 deaths recorded annually (Hartman et al, 2002). For the UK, the NHS Cancer Screening Programme reports that 900 women lose their lives annually due to cervical cancer (Cervical Screening Facts, 2006). Epidemiology studies have identified a number of risk factors associated with the development of cervical cancer and its precursor lesions. The most important of these has been found to be with a variety of sexually transmitted diseases, especially the Human Papillomavirus (HPV). Other risk factors include early initiation to sexual intercourse, age at first pregnancy, number of lifetime sexual partners, cigarette smoking, oral contraceptive use, and within the black population, low socioeconomic status and parity (Boking et al, 2003, p.7; Hartman et al, 2002). However, cigarette smoking has been shown to be the strongest and single most consistent non-sexual factor related to cervical cancer, increasing the risk by a two-four fold (Hartman et al, 2002). The detection of cervical cancer in its early stages is life saving, as survival of cancer of the cervix depends largely on the stage of progression of the condition at diagnosis. It is estimated that 91.5% of patients will survive 5years when the cancer is localized at diagnosis, but only about 12.6% can survive distant diseases (Hartman et al, 2002). Screening for cancer thus constitutes a significant contribution to the prevention of cancer and the reduction of both mortality and morbidity due to the condition. Population screening for cancer involves "the early detection of cancer, precursors of cancer or susceptibility to cancer, including genetic, in individuals who do not have a symptom of cancer. These interventions are directed to entire population or to large and easily identifiable groups within the population" (Population cancer Screening, 2002). It is an effective method of preventing cancer by detecting and treating early abnormalities which if left untreated, could lead to cancer in the women's cervix (What is Cervical Screening, 2006). Population screening for cervical cancer started in the UK in the 1960s, and on a whole, there have been considerable consensus regarding its effectiveness as a preventive strategy. However, by the mid 1980s, though, many women were having regular test, there was considerable concern that people at greater risk were not being tested, and perhaps, those with positive results not being adequately followed up. This concern led to the establishment of the NHS Screening Programme in 1988 and all health institutions instructed to operate computerized call-recall systems and inviting eligible women for the test at scheduled periods. Recently, it is estimated that about 4million women are screened annually (Howson, 2001, p.167, Hartman et al, 2002). According to Boking (2003), cervical exfoliative cytology or Papanicolaou smear (Pap smear), which is the basic procedure for cervical screening, is a highly effective screening and diagnostic test in pathology. Its efficiency and effectiveness has been demonstrated in detecting various pathologic conditions of the female genital tract, particularly the preneoplastic lesion of the uterine cervix. The discovery of the causal role of HPV in cervical dysplasia and invasive cancers, have prompted the development of several methods for detecting the viral presence during screening and to differentiate them into high risk and low risk types (p.10). However, numerous and varied systems of nomenclature abound for describing the various cytological and histological findings regarding cervical dysplasia and squamous cell carcinomas. The generally accepted Bethesda system uses the following classification system - Low grade squamous intraepithelial lesion (LSIL) and High grade intraepithelial lesions (HSIL) for cytological findings, while cervical intraepithelial neoplasia (CIN) refers to histological findings and usually categorized into CIN 1-3 (Hartman et al, 2002). Normally, the specimens for cervical cancer screening are obtained at the time of pelvic examination; a speculum is used to hold the vagina open and visualize the cervix, while obtaining samples with spatula or cervical brush for cytological study. The objective of sampling is to pick cells from the cervical transformation zones; this is the area of the cervix where physiological transformations from columnar cell lining the endocervical canal to the squamous cells covering the ectocervical occurs. This is because it has been shown that cervical dysplasia and cancers occur in this zone. It is easier to collect samples from younger women than the elderly, since the transformation zone is more towards the surface of the cervix, but with increasing age, it becomes more difficult as this zone is likely to be higher in the endocervix (Hartman et al, 2002). For conventional cervical cytology, the sample in the sampling tool is 'smeared' onto a glass microscope slide. Two slides or two distinct areas of the same slide are prepared to represent the ectocervical and endocervical samples. Immediately, the slides are then sprayed with or placed in fixatives (Hartman et al, 2002), for about 15mins (What is cervical screening, 2006) and then passed to a cytology laboratory to be read under microscope by a technician who will usually review the slides at a 10x magnification, systematically in 2mm sections. Another variation of the conventional cervical cytology is the method called the Thin Layer Cytology or Liquid Based Cytology (LBC). Here the specimen sample is collected in similar way to the conventional smear method, using special device which brush up cells from the cervix, but rather than smearing the sample onto the glass slides, the samples are suspended in a fixative inside a small vial containing preservative fluid by breaking the head of the sampling brush into the fluid or stirring the specimen collection tool in the fluid. The vial is sealed and sent to the laboratory. Theoretically, this is believed to improve the probability of transferring true representative samples to the slide. In the laboratory, the technicians disperse the sample in the fixative and collect the cells on a filter and then transfer the cells to a microscope slide in a single layer. Immediate fixation and uniform spread of the cells are aimed at reducing detection errors by assuring that cells are well preserved, not obscured and more easily assessed by the cytology technicians. The specimens are deposited on the slide and are examined in the same way under a microscope at the same magnification (Hartman et al, 2002; what is cervical screening, 2006). The goal of cervical cancer screening is to achieve a significant reduction in the mortality and morbidity associated with squamous cell carcinoma of the cervix. However, the screening system used must be acceptable to both patient and the healthcare provider; it must also be able to detect cellular abnormalities that are amenable to interventions (Hartman et al, 2002). According to these authors, the wide spectrum of cervical abnormalities detected by cytological and histopathological examinations, from low grade changes to carcinoma in situ is a particular challenge. They further assert that HSIL requires immediate evaluation by biopsy and endocervical curettage, patients with CIN 3/CIS requires definition intervention such as conization by loop electrosurgical excision procedure (LEEP), laser or cold knife to get rid of the cervical transformation zone and be sure no invasive discuss is present. However, patients with CIN 2 may be treated with conization or ablative procedures to remove or destroy the transformation zone (Hartman et al, 2002). The Atypical Squamous Cell of Undetermined Significance (ASCUS), a term coined to describe the broad spectrum separating morphologically normal or benign changes of epithelial from definite squamous intraepithelial lesions (Boking, 2003,p.7) and the low grade intraepithelial squamous lesions (LSIL) are a particularly active part of research focused on determinant of progression, stability and regression (Hartman et al, 2002). Moreover, numerous epidemiological, clinicopathological and molecular studies have linked the presence of specific types of HPV to development of anogenital cancer and its precursors (Boking, 2003, p.8). It is estimated that more than 90% of cervical carcinomas worldwide show HPV presence. In addition cellular changes associated with HPV infection can be seen on visual examination of cervical cytologic or biopsy specimens and at times colposcopy. Therefore, direct HPV testing methods for assessing the presence and types of HPV, which rely on identification of HPV viral DNA are more promising for cervical cancer screening (Hartman et al, 2002; Boking, 2003). Although, these tests vary; some are quantitative, estimating the viral burden, while others allow assessment of the degree of integration of HPV into the host genome. Because the family of HPV viruses is large and also because only a small group of these types are associated with cervical dysplasia and cervical cancer, tests that identify specific viral types or panel of high risk viral types are far more preferable to detection of all HPV types. Stressing the benefits of cervical cancer screening, Boking (2003) explains that cytological and histological investigations have played crucial role and contributed a lot to the fight against cancer, but the most successful screening programmes ever carried out is the early detection of cervical cancer and its precursors using exfoliative cytology (p.16). The introduction of the screening programme to nave population has resulted in cancer reduction rates of 60%-90% within a period of 3years. And this reduction, in both mortality and morbidity is found to be consistent and dramatic across populations. Furthermore, Hartman et al (2002) opine that the benefits and success achieved in cancer prevention reflects three factors: i. Progression from early cellular abnormalities, called low grade dysplasia, through more severe dysplasia, to carcinoma in situ and then invasive cancer is generally slow, thus allowing time for detection ii. Associated cellular abnormalities can be identified and iii. Effective treatment for pre-malignant lesions have been developed Putting all these together, one would conclude that invasive squamous cell carcinoma is a highly preventable disease once detection is effective (Hartman et al, 2002). To further buttress the benefits of cervical screening for the population, Hartman et al (2002) argue that between 50%-70% of cervical cancer cases occur among women who have never been screened or who have missed screening for the past 5years. However, like every other screening programme, the cervical screening programme is not perfect and thus suffers some limitations. The first among such limitation is what is referred as screening failures, and involves cancer occurring in properly screened persons. This could occur as a result of three different factors. First, cervical cellular abnormalities may be identified by appropriately scheduled screening but not properly treated as a result of patient or provider's failure to follow up the abnormalities. This is estimated to occur in 22%-63% of cases. Second, serious abnormalities may be absent at the time of screening, and progression occurs between recommended screening intervals. This is rare for annual screening but for a 3year interval, this may occur in up to 50% of diagnosed cases. Such progression is more common among women under 45years of age. Third, abnormalities may be present at the time of screening but not detected by the screening test. This occurs in approximately 14%-33% of cases and can be further sub divided into two categories: Those that represent sampling errors i.e. cells from the abnormal area were not obtained and so could not be identified in the specimen, and those that reflect detection errors i.e. the abnormal cells were included in the specimen and were not identified as abnormal (Hartman et al, 2002). Another limitation of cervical cancer screening programme as reported by Boking (2003) is that reproducibility of cytological and histological diagnosis of pre-cancerous lesions has been greatly insufficient and causes clinical problems. He attributed this to be partly due to the absence of validated morphological criteria upon which pathologist and cytologist are united (p.16). Also, Hartman et al (2002) argue that because women are now screened at younger ages and in larger numbers, coupled with the fact that tests are increasingly sensitive for detecting low grade changes such as ASCUS, the potential harms of screening is becoming more pronounced. He cited the psychological effects of labelling young women with anxiety-provoking, possibly pre-cancerous, the associated individual, health care system and societal costs of the screening programmes as some of the areas deserving attention. References Bcking, Med. A (2003). Identification Of Progressive Cervical Squamous Intraepithelial Lesions Using DNA-Image-Cytometry A Study On Diagnostic Validity And Reliability. Aus dem Institut fr Cytopathologie der Heinrich-Heine Universitt Dsseldorf, p.3-35 Cervical Screening; The Facts (2006).NHS Cancer Screening Programmes Educational Leaflet. Available at viewed Mar 14 2006 Hartmann, Katherine E Susan A. Hall, MS Kavita Nanda, MHS John F. Boggess, Dennis Zolnoun (2002). Screening for Cervical Cancer Systematic Evidence Review.Paper Prepared for U.S. Department of Health and Human Services Agency for Healthcare Research and Quality. Available at Viewed Mar 14 2006 Howson, Alexandra (2001). Locating uncertainties in cervical screening. Routledge Publishers, Volume 3, Number 2, pp167 - 179 Population Cancer Screening in Canada: Strategic Priorities (2002). Final Report: Canadian Strategy for Cancer Control: Screening Working Group What is cervical screening Cancer Research UK. Available online at viewed Mar 14. 2006 Read More