Cervical cancer screening aims to detect pre-cancerous lesions when curative treatment is still possible and before (invasive) cancer has developed. Nordic countries were among the first to implement organized cervical cancer screening between the 1960 and 1970. Today, many European countries have some form of cervical cancer screening. In most of countries screening is opportunistic, indicating that women come on their own initiative for screening or that screening is offered by a physician when the women visits the clinic for other reasons. In other countries, organized screening programmes exist where women of certain ages are regularly invited for screening. Screening programmes in European countries show considerable variation in both design and performance. The variation in screening efforts is reflected in the cancer incidences. In countries with a well-organized screening programme and high screening participation, cervical cancer incidence rates have shown a substantial decrease in the last decades of the 20th century. Currently, in those countries a disproportionally large number of cancer cases are observed in poorly screened and unscreened women. In contrast, in countries that rely on opportunistic screening or that have a programme with low screening participation, cervical cancer incidences have remained high and in some countries, have even increased.
Traditionally, screening is cytology-based using so-called PAP smears. A PAP smear involves the collection of cervical cells by a medical doctor or a trained nurse during a gynaecologic examination. Specialized laboratory personnel assess the smears for specific cellular (cytological) changes that may indicate the presence of (pre)cancer. Women with abnormal PAP smear are referred to a gynaecologist for further diagnostic evaluation and, if necessary, treatment. Because the proportion of abnormalities that are detected by a single PAP smear is only 50-75%, and performance varies across population, organized screening programmes use short screening intervals, with the number of screening tests per woman ranging from 6 to over 50 in some countries. As an alternative to cytology, HPV DNA testing is currently being implemented in several European countries. The proportion of (pre-)cancerous lesions detected by HPV DNA testing is considerably higher than cytology (90-95%) and shows less variability across populations. Studies have shown that women who receive an HPV test have a lower incidence of high-grade precancerous abnormalities in the next screening round compared to women who receive cytology. However, the proportion of women without abnormalities that have a positive HPV test, is somewhat higher than with cytology, especially in women under 30 years of age. This has slowed down the implementation of primary HPV-based screening in several countries. Stakeholders have demanded additional evidence on follow-up strategies for HPV-positive women in order to optimally weigh the additional safety of a negative HPV test and the increase in the number of women unnecessarily referred for further gynaecological examination.
An important aspect of a successful screening programme is to attain high screening participation. Currently, most cervical cancer cases are observed in poorly screened and unscreened women. To increase participation, “self-sampling” has been proposed. During self-sampling women collect their own (cervico-) vaginal sample. It is considered as a friendly and acceptable alternative to sampling by the physician. Several studies have indicates that self-sampling may be an effective way to reach marginalized/poorly screened populations.
Finally, the first vaccinated cohorts will reach screening ages soon and it can be anticipated that the screening programmes must be adapted to remain cost-effective. Integrated prevention strategies that optimize both vaccination and screening in country-specific settings need to be developed.