Human papillomavirus and cervical cancer. Global epidemiological update

Historically speaking, cervical cancer has been the most widespread form of cancer among women. In spite of the opportunities offered by early diagnosis programmes, it is still the second most common form of cancer among women throughout the world, with an estimated 493,000 new cases and 274,000 deaths in 2002. 80% of cases of cervical cancer (which represent 15% of all cancers affecting women) take place in developing countries. In developed countries, cervical cancer has also been more present in the strata of population with lower socio-economic levels, while the lack of suitable early diagnosis policies is highlighted as one of the main determining factors in the appearance of the invasive stages of the disease.

Cervical cancer adenocarcinomas represent 10% of all forms of cancer, and their variability and relative importance are increasingly visible in those countries in which early diagnosis is taken more seriously. Conventional cytology frequently forgets to sample lesions in their earliest stage in the cervix.

Human papillomavirus (HPV) infections are the most common types of sexually transmitted infections. Among women with normal cytology in the age range included in early detection programs, the average HPV viral load detected is estimated to be about 10%, with significant geographical variations.

In most studies, HPV-16 is predominant. In contrast, when lesions develop in the cervix, the presence of the DNA corresponding to the HPV increases to 75-85% in LSIL (low-grade squamous intraepithelial lesions) and up to 85-100% in HSIL (high-grade squamous intraepithelial lesions) and in invasive carcinoma.
In cervical cancers, the number of different types of HPV is reduced to 12-15, most of which are of a single type and with a clear distribution profile.

At the global level, it is estimated that HPV-16 is clearly the most common type, affecting approximately 50% of all cases, followed by HPV-18, HPV-45, HPV-31 and HPV-33. In the subgroup of cervical cancer adenocarcinomas, HPV-16 and HPV-18 are found in similar proportions, followed by HPV-45, while other types are found to be quantitatively inferior in terms of contribution. These three types combined (16, 18 and 45) represent 75% of carcinomas in squamous skin cells and almost 90% of adenocarcinomas.