IARC Confirms Efficacy of Cervix Cancer Screening for Women 25-65 in Reducing Mortality
Cancer of the cervix uteri is the second most common cancer among women worldwide, with about 500,000 new patients women diagnosed and 250,000 deaths every year. Almost 80% of the cases occur in developing countries and in many regions, cervix cancer is the most common cancer in women.
IARC, a key player in cancer prevention around the world
"One of the key missions of the International Agency for Research on Cancer (IARC)", says Dr Peter Boyle, the recently appointed Director of the WHO cancer research Agency, "is to provide preventive tools and methods particularly to those countries that lack proper resources of their own." A Working Group of the IARC, chaired by Professor Nicholas Day of Cambridge, was convened in Lyon, France, from 20 to 27 April 2004, in order to evaluate the effectiveness of cervix cancer screening in reducing incidence of and mortality from the disease.
Organized cytology screening programmes are effective
The Working Group concluded that there is sufficient evidence that screening for cervical cancer by cytological examination of Pap smear cell samples does prevent death. The experts, however, emphasized that in order to achieve this goal optimally, an organized programme with quality control of every key step of the entire process is a prerequisite. In such circumstances, it was estimated that an 80% reduction in mortality can be achieved. Such a screening programme should cover women aged 25-65 years; women need not undergo screening more often than once every 3 years up to the age of 49 and every 5 years thereafter. The Working Group also concluded that advances such as improved handling of the cell samples and use of computers for cytological analysis could also reduce the incidence of invasive cervix cancer and death from the disease.
Cervical cancer is a rare outcome of human papilloma virus (HPV) infection, a common and mainly sexually transmitted infection, which accounts for over 95% of all cervix cancer cases. This infectious pathway opens new avenues for control by means of screening and vaccination. In this context, tests for the presence of viral DNA in a sample of epithelial cells have been established as a step toward identifying potentially precancerous conditions. The Group concluded that there is sufficient evidence that the human papilloma virus test can reduce mortality from cervix cancer. "Identification of the role of HPV in the aetiology and now the prevention of cervix cancer has been a major contribution of epidemiological and biological science to cancer control", said Dr Boyle. "However," he added, "much requires to be done to have an affordable, simple and reliable test available for widespread use around the world. This is the next major challenge in cervix cancer prevention."
Screening in developing countries
Since most of the burden of cervix cancer rests on the developing world, experts look also into methods of control that can be applied in low-resource settings, yet with high efficacy, to reduce incidence of and mortality from the disease. Of course, if cytological screening can be implemented with good participation and quality control, this should be encouraged. Visual inspection of the cervix after application of acetic acid (VIA) or iodine (VILI) is of high promise in low-resource countries. At present its effects in reducing mortality from cervix cancer at the epidemiological level is still unclear, and the evidence for efficacy of this method was therefore regarded as limited. Large-scale population-based research projects are in progress, with the aim of validating this screening method for large-scale application.
Screening, a component of health policy
The Working Group identified several areas of research that will improve our understanding of screening modalities and their applicability as a component of a public health policy.
"The message for women in the developed world and of 25 to 65 years of age is that screening for cervix cancer is useful, it is safe, and it will remove most of their risk of dying from cervix cancer" said Dr Nicholas Day, Chairman of the Group. "Furthermore, it is not necessary to undergo the test more than once every 3 to 5 years." This is consistent with the European Code Against Cancer that reads "Women from 25 years of age should participate in cervical screening. This should be conducted within programmes with quality control procedures in compliance with European Guidelines for Quality Assurance in Cervical Screening" .(1)
In the developing world, few countries have the resources or infrastructure needed to use existing proven methods for screening. Within the next few years, evidence from on-going research will hopefully make low-cost, low-technology screening methods a valid option for use in these settings, pending the availability of HPV vaccines on an industrial scale.
World Health Organization
International Agency for Research on Cancer
Organisation mondiale de la Sant