Policy analysis of cervical cancer screening strategies in low-resource settings: clinical benefits and cost-effectiveness

Costs and benefits of different strategies to screen for cervical cancer in less-developed countries

BACKGROUND

About 80% of cervical cancers occur in less-developed countries. This disproportionate burden of cervical cancer in such countries is due mainly to the lack of well-organized screening programs. Several cervical cancer screening strategies have been proposed as more cost-effective than cytology screening. We compared the costs and benefits of different strategies and their effectiveness in saving lives in a less-developed country.

METHODS

We used a population-based simulation model to evaluate the incremental societal costs and benefits in Thailand of seven screening techniques, including visual inspection of the cervix after applying acetic acid (VIA), human papillomavirus (HPV) testing, Pap smear, and combinations of screening tests, and examined the discounted costs per year of life saved (LYS).

RESULTS

Compared with no (i.e., not well-organized) screening, all strategies saved lives, at costs ranging from 121 US dollars to 6720 US dollars per LYS, and reduced mortality, by up to 58%. Comparing each strategy with the next least expensive alternative, VIA performed at 5-year intervals in women of ages 35-55 with immediate treatment if abnormalities are found was the least expensive option and saved the greatest number of lives, with a cost of 517 US dollars per LYS. HPV screening resulted in similar costs and benefits, if the test cost is 5 US dollars and if 90% of women undergo follow-up after an abnormal screen. Cytology (Pap smear) was a reasonable alternative if sensitivity exceeds 80% and if 90% of women undergo follow-up. Compared with no screening, use of a combination of Pap smear and HPV testing at 5-year intervals in women of ages 20-70 could achieve greater than 90% reduction in cervical cancer mortality at a cost of 1683 US dollars per LYS, and VIA could achieve 83% reduction at 524 US dollars per LYS.

CONCLUSIONS

Well-organized screening programs can reduce cervical cancer mortality in less-developed countries at low costs. These cost-effectiveness data can enhance decision-making about optimal policies for a given setting.

Oncogenic human papillomavirus (HPV) infection and uterine cervical cancer: a screening strategy in the perspective of rural India

The predominance of cervical cancer in India can mostly be attributed to the lack of early screening. The objective of the present study has been, therefore, to determine a cost-effective oncogenic human papillomavirus (HPV)-based cervical cancer screening plan for rural Indian women. The results showed that in normal women, highest prevalence of HPV 16/18 infection was in the age group < or =23 years and lowest in > or =44 years with an insignificant change in between. HPV 16/18 infection was significantly associated with cervical erosion at age < or =23 years, but not with cytology or visual inspection with acetic acid testing at any age. The low-grade cytological lesions, however, increased only with increase in age. Fourteen per cent of the cervical malignancy was also found to be present in the age group 24-33 years with an 87% HPV infection. Here we proposed a cost-effective screening scheme in which HPV testing must be performed in women (a) < or =23 years with cervical erosion and (b) 24-43 years, as an adjunct to Pap smears (both HPV and cytology were prevalent in this group). For women > or =44 years, HPV testing might not be useful, since abnormal cytology was more prominent over the viral infection. We infer that by not performing HPV test in the group < or =23 years, approximately 76% of the high-risk HPV-infected individuals potentially "at risk" for developing cervical cancer might be missed.

Present standards for cervical cancer screening

Survival rates for cancer of the uterine cervix have improved over the last 40 years largely because of the impact of screening measures such as the Pap smear. The ability to screen and treat women for preinvasive disease, cervical dysplasia, is the key factor leading to the reduction in the incidence of invasive cervical cancer. More recently, the ability to test women for the causative agent, the human papilloma virus, has emerged as a potential screening tool. New research has focused on new technologies for Pap smear screening such as thin layer technology, the appropriate intervals for screening, and the appropriate methods of incorporation of human papilloma virus testing into the screening protocols. Reviews of published studies evaluating the efficacy of new technologies suggest that there is still insufficient information to confirm improved outcome; however, results to date suggest that thin layer Pap smear technology may improve sensitivity in the detection of cervical dysplasia. Automated rescreening technologies in use may decrease the number of false-negative Pap smears and are an option for laboratories. Various professional groups and countries have differing recommendations on the interval for screening, primarily on the basis of cost-effectiveness. Some of the most important new information this year regarding cervical cancer screening includes the new Bethesda System for the reporting of Pap smears and the new guidelines for the management of the abnormal Pap smear by the American Society of Colposcopy and Cervical Pathology. These guidelines incorporate human papilloma virus testing based on a multicenter trial documenting its efficacy in the triage of women with atypical squamous cells on Pap smear. These recommendations are reviewed along with the current literature on cervical cancer screening.

Determinants of cervical cancer rates in developing countries

Although cervical cancer (CC) is a leading cause of cancer-related deaths in developing countries, incidence rates vary considerably, ranging from 3 to 61 per 10(5) females. Identifying determinants of high vs. low rates may suggest population-level prevention strategies. CC rates for 175 countries were obtained from the IARC. Country-specific behavioral, health, economic and demographic measures were obtained from United Nations agencies and other international organizations. Regression analyses performed for 127 low or medium developed countries identified both geography and religion as independently associated with high CC rates. Among behavioral measures, high fertility rates, early age at birth of first child and high teenage birth rates were significantly associated with high CC rates. Countries with high CC rates had fewer doctors per capita, less immunization coverage, more HIV infections and shorter life expectancies. CC rates also tended to be higher in countries with more spending on health and younger, less educated populations. Patterns of CC rates suggest that programmatic approaches, such as promoting delayed childbearing and sexual monogamy, may be appropriate interventions. For countries with high CC rates and some flexibility in their health-care budgets, a once-in-a-lifetime screen of women 30-50 years of age, using Pap smears, direct visual inspection and/or HPV DNA testing, may be cost-effective. Finally, relatively low immunization rates and a shortage of health-care workers in countries with high CC rates suggest potential challenges for introducing prophylactic HPV vaccines.

The causal relation between human papillomavirus and cervical cancer

The causal role of human papillomavirus infections in cervical cancer has been documented beyond reasonable doubt. The association is present in virtually all cervical cancer cases worldwide. It is the right time for medical societies and public health regulators to consider this evidence and to define its preventive and clinical implications. A comprehensive review of key studies and results is presented.

Direct visual inspection for cervical cancer screening: an analysis of factors influencing test performance

BACKGROUND

The authors evaluated direct visual inspection of the cervix after the application of 5% acetic acid (DVI) as a cervical cancer screening test for use in low-resource settings.

METHODS

Four tests were used to screen 2754 previously unscreened women: DVI with and without x4.5 magnification and differentiating between all lesions and well-circumscribed lesions; testing for high-risk types of human papillomavirus DNA using the Hybrid Capture II assay, cervical cytology, and Cervicography. Women with positive results on any of the four screening tests were referred for colposcopy and histologic sampling. All women were tested for N. gonorrhea, C. trachomatis, T. vaginalis, and human immunodeficiency virus 1.

RESULTS

Histologically confirmed carcinoma was diagnosed in 21 women (0.8%), high-grade squamous intraepithelial lesions (SILs) were diagnosed in 96 women (3.5%), and low-grade SILs were diagnosed in 102 women (3.7%). The estimated sensitivity of DVI when performed without magnification for high-grade SILs was 70%, with an estimated specificity of 79%. Magnification did not significantly improve sensitivity for high-grade SILs (74% with magnification) but significantly reduced specificity (77%). Restricting the definition of a positive DVI test to a well-defined acetowhite lesion reduced sensitivity and significantly improved specificity. Infection with T. vaginalis, N. gonorrhea, and C. trachomatis did not alter sensitivity or specificity.

CONCLUSIONS

This study confirmed the utility of DVI as a primary screening test. Evaluation of the clinical effectiveness of screening with this low-cost and simple test in low-resource settings is necessary.

Human papillomavirus in cervical cancer

Epidemiologic studies supported by molecular technology have provided sufficient evidence of the causal role of some human papillomavirus (HPV) infections in the development of cervical cancer. The finding is consistent universally, and HPV has been proposed as the first identified necessary cause of cervical cancer. Such recognition translates into the concept that cervical cancer does not develop without persistent presence of HPV DNA. In the developed parts of the world, cytologic screening programs could benefit from the addition of HPV testing to their protocols. Controlled studies and one randomized trial have shown that HPV testing is helpful in solving the ambiguous cases generated by cytology reading. In populations where cytology programs are not functional or efficient, HPV testing is being evaluated as an alternative means of primary screening. Prevention of exposure to high-risk HPV types, either by prophylactic vaccination or by combined prophylactic and therapeutic immunologic intervention, may prove to be the most efficient and logistically feasible option for the prevention of cervical cancer in developing populations.

Will New Human Papillomavirus Diagnostics Improve Cervical Cancer Control Efforts?

With the causal link between specific types of human papillomavirus (HPV) and cervical cancer firmly established, efforts have turned to assessing the relative merits of offering HPV testing in screening, triage, and posttreatment management. Many unanswered questions remain, but a growing body of evidence supports a role for HPV testing in cervical cancer prevention programs. Already, clinical centers that serve thousands of women in Europe and the United States have incorporated HPV DNA tests in triage algorithms.