by Xavier Bosch He is one of the leading experts in Spain on human papillomavirus (HPV), a pathogen that can go unnoticed but is widespread: it affects 30% of the young population. His work, mainly at the Institut Català d’Oncologia and at IDIBELL, has contributed to identifying the role of the virus as the cause of, among others, cervical cancer, which was the starting point for the development of the vaccines. which is expected to eradicate the disease in the future. On the occasion of Human Papillomavirus Day, he explains what the progress and pending challenges are.
How can a virus cause cancer?
Viruses are DNA or RNA particles and they need human cells to reproduce. When a cell is infected with papilloma, a part of the virus interacts with the cellular DNA. Many times this ends up eliminating the infection but sometimes a chronic infection occurs. Since the beginning of tumors is in cell replication errors, having a virus increases the probability of errors occurring.
What cancers are most frequently caused by viruses?
Anogenital cancers, including cervical cancer, caused by the human papillomavirus, liver cancers caused by hepatitis B and C, and lymphomas and leukemias derived from the Epstein-Barr virus.
Specifically, what does the human papillomavirus cause cancer?
Many HPV infections resolve spontaneously and disappear. But a small fraction, around 10%, becomes persistent infection, so repeated interaction with cellular DNA can initiate tumor transformation and become cancer of the anus, cervix, vulva, vagina, penis or pharynx. . . There are cofactors that can accelerate the process, such as tobacco, the use of long-acting pills, and others of a hormonal nature.
Many strains of the virus do not cause symptoms, which is why the situation has reached that globally 12% of women carry papilloma.
What is the prevalence of HPV infection in Spain and of cancer caused by HPV?
It is a very common infection in young people, where an incidence of 30% is estimated. In intermediate ages and in adult women it is 5%. And the number of cancer cases associated with HPV can be estimated at around 2,500 per year, about 2,000 of the cervix, which is the fourth most common neoplasm in women worldwide. In Spain it is in 15th place in cancer statistics.
How can a person know if they are infected?
There are more than 40 types of HPV. A low oncological risk group, papillomas 6 and 11, cause warts, so the person notices them immediately. But in those at high risk there are no symptoms, which is why the situation has reached that globally 12% of women carry papilloma. For it to spread so widely, it is necessary that there be a lot of sexual relations and that these infections do not lead you to the doctor or a treatment that interrupts transmission.
Xavier Bosch, expert in human papillomavirus and member of the Catalan Institute of Oncology / ZOWY VOETEN
To avoid this, the best tool is a preservative. Do you recommend its use even in long-term stable couples?
The preservative offers partial protection because it only covers part of the genital tract, sometimes it breaks, etc. But it is perhaps the only option we have to interrupt sexually transmitted diseases. The problem with stable couples is that you are never safe, because the infections could have been acquired in youth and manifest themselves at 40 years of age. So I do advise the use of the preservative.
As most infections are silent, progress has come in diagnosis: the WHO recommends replacing cytology with a viral detection test
Once infected with a high oncological risk virus, how can you prevent it from turning into cancer?
As most infections are silent, progress has come in the field of diagnosis: we now have very good technology that detects if a person is infected before the tumor appears. For this reason, the WHO recommends replacing conventional cytology with a viral detection test. The sample is taken in the same way, but molecular biology is used to detect DNA from the papilloma. It is a very significant progress because if the result is negative, we can easily delay the next control for a few years. However, if a cytology is negative, there is still a 50% risk that there is a tumor but it is not detected, which is why it is repeated more frequently.
What is the treatment once a high-risk papilloma is detected?
If it is detected in a screening, there is no specific viral treatment but it can be investigated whether the process of transformation into cancer cells has already begun and an early treatment can be proposed, generally a small surgical incision. If the process has not started, the patient is monitored periodically to see if the virus disappears or if it progresses. And, in these cases, we are studying vaccinating the person, to reduce transmission to their partners.
The vaccine is extraordinarily good and safe; It has the ability to protect against infection, so the expectation is that it will stop all tumors associated with papilloma.
How is the introduction of screening going in Spain?
The Interterritorial Council approved the gradual introduction of the HPV screening program, but it is much more complicated than we anticipated, implementation is slow and in some communities it has not started. The recommendation is to perform the test on women aged 30 and older. In Catalonia, screening is quite developed. There is a pilot program in Baix Llobregat and the laboratories that will do the screening have been identified with technology that analyzes hundreds of samples a day. It is also being implemented in the Basque Country and in the future it will be the routine form of control to detect cervical cancer.
Xavier Bosch, expert in human papillomavirus and member of the Catalan Institute of Oncology / ZOWY VOETEN
The other great advance is the vaccine, which has been introduced into the calendar for 12-year-old boys and girls. How effective will you get?
This is an extraordinarily good and safe vaccine; which has the ability to protect against infection, with which the expectation is that it will stop all tumors associated with papilloma. If we have any option to eliminate this cancer, it is with massive, sustained vaccination and screening of unvaccinated women. We are in a position to achieve what happened with smallpox, polio or measles, where the number of cases has been greatly reduced while vaccination is maintained. Cervical cancer is the first for which the WHO has launched an elimination campaign, which has encouraged countries to introduce vaccination and screening, in both the rich and the poor.
Would you recommend the vaccine to other groups?
There are well-defined risk groups such as homosexual men, sex workers or immunosuppressed or transplant patients who must participate in vaccination programs.
This vaccine, as occurred with the covid vaccines, generated opposition.
Indeed, the introduction of a new vaccine, particularly against a sexually transmitted infection, generated reactions of rejection, uncertainty and a scenario in which the politicization of health indications introduced a public health issue into the confrontation between parties in some countries. But, with more than 300 million doses administered, we have consolidated evidence that it is effective and has no safety concerns or severe side effects in follow-ups of up to 15 years.
