Effective Screening Programmes for Cervical Cancer in Low- and Middle-Income Developing Countries. (Theme Papers)

Article excerpt

Voir page 960 le resume en francais. En la pagina 961 figura un resumen en espanol.

Introduction

Cervical cancer is an important public health problem for adult women in developing countries in South and Central America, sub-Saharan Africa, and south and south-east Asia, where it is the most or second most common cancer among women. The vast majority of cervical cancer cases are caused by infection with certain subtypes of human papilloma virus (HPV), a sexually transmitted virus that infects cells and may result in precancerous lesions and invasive cancer (1). Developing countries accounted for 370 000 out of a total of 466 000 cases of cervical cancer that were estimated to occur in the world in the year 2000 (2). Worldwide, cervical cancer claims the lives of 231 000 women annually, over 80% of whom live in developing countries. A conservative estimate of the global prevalence (based on the number of patients still alive 5 years after the diagnosis) suggests that each year there are 1.4 million cases of clinically recognized cervical cancer. It is also likely that 3-7 million women worldwide may have high grade dysplasia.

Some of the developing countries that have data on cancer incidence and/or mortality have registered either a stable or slowly declining trend in cervical cancer incidence, most likely due to sociodemographic changes rather than to early detection/ prevention efforts (3). On the other hand, some regions in sub-Saharan Africa have registered an increased incidence in recent years (4). Despite the declining trends in incidence observed in some regions, the total burden of cervical cancer is rising in high-risk developing countries, mostly due to increasing populations.

In developed countries, initiation and sustenance of cervical cytology programmes involving the screening of sexually active women annually, or once in every 2-5 years, have resulted in a large decline in cervical cancer incidence and mortality (Fig. 1 and Fig. 2) over the last 40-50 years (5-8). The aim of these programmes is to detect precancerous lesions and treat them before they progress to invasive cancer. In contrast, the risks of disease and death from such lesions have remained largely uncontrolled in high-risk developing countries, mostly because of the lack of screening programmes or because of their ineffectiveness. This paper reviews existing experiences, achievements, constraints, and lessons learned in community-based, cervical cancer intervention programmes in developing countries. The sensitivity and specificity values that we report for various screening tests correspond to the detection of high-grade lesions (cervical intraepithelial neoplasia II and III) and invasive cancer.

[FIGURES 1-2 OMITTED]

Cervical cytology screening programmes worldwide

To date, cervical cancer prevention efforts worldwide have focused on screening sexually active women using cytology smears and treating precancerous lesions. It has been widely believed that invasive cervical cancer develops from dysplastic precursor lesions, progressing steadily from mild to moderate to severe dysplasia, then to carcinoma in situ, and finally to cancer. It now appears that the direct precursor of cervical cancer is high-grade dysplasia, which in about a third of instances may progress to cervical cancer over a period of 10-15 years, while most low-grade dysplasias regress spontaneously (9, 10).

Even though the impact of cytology screening has never been proved through randomized trials, it has been shown to be effective in reducing the incidence and mortality from cervical cancer in developed countries (5-8). The incidence of cervical cancer can be reduced by as much as 80% if the quality, coverage, and follow-up of screening are high. In most developed countries, women are advised to have their first smear test soon after becoming sexually active and subsequently once every 1-5 years. …