“I recommend using a condom for stable couples, because papilloma can be acquired at a young age and appear at 40 years old”

How can a virus cause cancer?

Viruses are DNA or RNA particles and require human cells to reproduce. When a cell is infected with papilloma, part of the virus interacts with cellular DNA. In many cases this resolves the infection, but sometimes a chronic infection occurs. Since the origin of tumors lies in errors in cell replication, the presence of a virus increases the likelihood of errors occurring.

What types of cancer are most often caused by viruses?

Anogenital cancer, including cervical cancer caused by the human papillomavirus, liver cancer caused by hepatitis B and C, and lymphomas and leukemias caused by the Epstein-Barr virus.

Specifically, what exactly is the human papillomavirus that causes cancer?

Many HPV infections resolve spontaneously and disappear. But a small proportion, about 10%, become persistently infected, so they interact repeatedly with cellular DNA and can initiate tumor transformation and become cancer of the anus, cervix, vulva, vagina, penis or pharynx. There are cofactors that can speed up this process, for example, smoking, taking long-acting tablets and others of a hormonal nature.

What is the prevalence of HPV infection in Spain and cancer caused by HPV?

It is a very common infection among young people, with an estimated incidence of 30%. In middle age and adult women it is 5%. And the number of HPV-related cancers can be estimated at about 2,500 per year, with about 2,000 occurring on the cervix, which is the fourth most common cancer in women worldwide. In Spain it ranks 15th in terms of cancer statistics.

How can a person know if he is infected?

There are more than 40 types of HPV. The low cancer risk group – papillomas 6 and 11 – cause the appearance of warts, so a person notices them immediately. But those who are in the high-risk group have no symptoms, which is why the situation has reached the point where 12% of women in the world are carriers of papilloma. For the infection to spread so widely, it is necessary that there be a lot of sexual contact and that these infections do not lead you to a doctor or treatment that interrupts transmission.

To avoid this, the best remedy is a condom. Do you recommend its use even for long-term stable couples?

A condom provides partial protection because it only covers part of the genital tract, sometimes breaks, etc. But it is perhaps the only option we have to prevent sexually transmitted diseases. The problem with stable couples is that you will never be safe because infections can be acquired in youth and appear in your 40s. Therefore, I recommend using a condom.

How can you prevent a high-risk virus from degenerating into cancer after infection?

Since most infections are silent, progress has been made in diagnostics: we now have very good technology that detects whether a person is infected before a tumor appears. For this reason, WHO recommends replacing conventional cytology with a virus detection test. The sample is taken in the same way, but molecular biology is used to detect the papilloma DNA. This is very significant progress, since in case of a negative result we can easily postpone the next control for several years. However, if the cytology is negative, there is still a 50% risk that the tumor is present but not detected, so it is repeated more often.

What is the treatment if a high-risk papilloma is detected?

If it is detected by screening, there is no specific viral treatment, but it can be determined whether the process of transformation into cancer cells has already begun and early treatment, usually a small surgical incision, can be offered. If the process has not started, the patient is monitored periodically to see if the virus disappears or progresses. And in these cases, we are exploring the possibility of vaccinating the person to reduce transmission to their partners.

How is screening implemented in Spain?

The Interterritorial Council approved the gradual implementation of the HPV screening program, but it is much more complex than we expected, implementation is slow, and in some localities it has not yet begun. It is recommended that the test be performed on women aged 30 years and older. Screening is quite developed in Catalonia. There is a pilot program in Baix Llobregat, and the laboratories that will carry out the screening are equipped with the technology to analyze hundreds of samples per day. It is also being introduced in the Basque Country and will become a routine form of cervical cancer screening in the future.

Another big achievement is the vaccine, which has been included in the vaccination schedule for 12-year-old boys and girls. How effective will this be?

This is an extremely good and safe vaccine; which has the ability to protect against infection, so it is expected to stop all tumors associated with papilloma. If we have any option to eliminate this cancer, it is through mass, sustained vaccination and screening of unvaccinated women. We can achieve the same thing that happened with smallpox, polio or measles, when the number of cases fell sharply while vaccinations continued. Cervical cancer is the first cancer against which WHO launched an eradication campaign, which has prompted countries to introduce vaccination and screening among both rich and poor.

Would you recommend the vaccine to other groups?

There are clearly defined risk groups, such as homosexual men, sex workers, immunocompromised patients or transplant patients, who should be included in vaccination programmes.

This vaccine, like the coronavirus vaccines, has met with resistance.

Indeed, the introduction of a new vaccine, especially against sexually transmitted infections, has generated a backlash of resistance, uncertainty and a scenario in which the politicization of medical indications has led to a public health issue of confrontation between parties in some countries. But after receiving more than 300 million doses, we have accumulated evidence that it is effective and has no safety concerns or serious side effects over a follow-up period of up to 15 years.