The human papillomavirus (HPV) is a virus whose family consists of more than 100 types. Of these, there are at least 14 that are considered causative agents of various types of cancer that affect both men and women.
Globally, HPV is the cause of one in twenty human cancers (one in ten in women). It is responsible for practically all cervical cancers, as well as a variable proportion of cancers of the vagina, vulva, anus, penis, and oropharynx : around 60% of vaginal neoplasms, 40% of vaginal cancers. vulva and penis, up to 85% of anal canal cancers and between 30% and 70% of oropharyngeal carcinomas.
Of the implications of HPV with different cancers, the best defined is cervical cancer. Cervical cancer is the fourth most common type of cancer in women.
In the world, more than 550,000 new cases of cervical cancer are diagnosed annually and more than 300,000 women die from this disease. The natural history of HPV infection in anatomical regions other than the cervix is less well known.
How is HPV spread?
Genital HPV infection is extremely common. HPVs are spread primarily through sexual contact. It is estimated that approximately 50-80% of sexually active women come into contact with HPV at some point in their life.
Although most people acquire this virus shortly after starting their sex life, the infection can occur at any time in life. Several factors, such as the early initiation of sexual intercourse or the number of sexual partners, increase the risk of infection, while others, such as the HPV vaccine or the use of a condom, reduce it.
From HPV infection to cancer
HPV infection does not cause symptoms and generally clears up spontaneously. The defenses of each individual will be responsible for eliminating the virus. Therefore, most infections will last only a few months (or a few years) and many of them will go unnoticed.
However, between 10 and 15% of cases HPV will not be eliminated and will persist for decades. Viral persistence is the necessary condition for premalignant lesions to appear. If these lesions are not diagnosed early and left untreated, cancer can develop.
The persistence capacity of HPV depends on multiple factors : viral factors (the type of HPV or viral load), factors of the infected individual (if they have a disease or take medication that weaken their defense system) and environmental factors (such as tobacco, the type of contraceptives you use, the number of sexual partners …).
Prevention tools
Primary prevention (vaccines) and secondary prevention (screening) are the main tools we have to avoid infection and the development of premalignant lesions and cancer.
In 2006, two vaccines capable of preventing infection by HPV types 16 and 18 began to be marketed, the two types of HPV responsible for 70% of cervical cancers and most cancers related to it. HPV in other locations (vagina, vulva, penis, anal canal, and oropharynx). Currently, there are three vaccines marketed to prevent HPV that have shown extremely high safety and efficacy (close to 100%) in preventing infection and, therefore, also the appearance of lesions.
With them, it is possible to prevent the development of about 90% of cancers caused by this virus. For this reason, the World Health Organization (WHO) recommends routine administration of HPV vaccines and most countries, following its guidelines, have incorporated the vaccine into their immunization programs.
In fact, in Spain it is included in the vaccination schedule for girls and adults considered “at risk” (men and women with HIV infection, men who have sex with men, men and women who have received a bone marrow transplant, women treated for a premalignant cervical lesion, etc.).
Vaccines and screening, tools for cancer elimination
In the case of cervical cancer, there is also a secondary prevention (screening) whose objective is to reduce the number and mortality of this neoplasm by detecting premalignant lesions.
Treating these lesions (usually by removing part of the cervix or conization) can prevent their progression and the development of cancer. Until now, cervical cancer screening has been based on cytology.
However, recently, cervical HPV tests have been shown to be more helpful in preventing cancer than cytology. For this reason, screening strategies based on HPV detection rather than cytology are currently being organized. There are no secondary prevention programs for other HPV-related neoplasms.
Combining correct primary and secondary prevention, that is, obtaining high vaccination coverage and adequate screening of the population, is an essential requirement to achieve the future goal set by the WHO: the elimination of cervical cancer worldwide. .
In addition, recently, the European Cancer Organization (ECO) has proposed to go one step further and, within the European plan to fight cancer, the initiative has been launched to achieve the elimination of all HPV-related cancers in Europe.
Marta del Pino, Associate Professor. Consultant in the Oncological Gynecology Unit of the Hospital Clínico de Barcelona, Universitat de Barcelona
This article was originally published on The Conversation. Read the original.
