Genital warts tied to range of cancers
The vast majority remained cancer-free during the study period. In all, 2,363 people - or less than 5 percent of the study group - developed some form of cancer. And only 305 were diagnosed with any of the cancers known to be linked to HPV.
Still, some of those risks were higher than average.
Men with a history of genital warts had a 21 times higher-than-average risk of anal cancer, for instance. Among women, the risk was eight times higher than the norm.
How do high-risk HPVs cause cancer?
HPVs infect epithelial cells. These cells, which are organized in layers, cover the inside and outside surfaces of the body, including the skin, the throat, the genital tract, and the anus. Because HPVs are not thought to enter the blood stream, having an HPV infection in one part of the body should not cause an infection in another part of the body.
Once an HPV enters an epithelial cell, the virus begins to make proteins. Two of the proteins made by high-risk HPVs interfere with normal functions in the cell, enabling the cell to grow in an uncontrolled manner and to avoid cell death.
Many times these infected cells are recognized by the immune system and eliminated. Sometimes, however, these infected cells are not destroyed, and a persistent infection results. As the persistently infected cells continue to grow, they may develop mutations that promote even more cell growth, leading to the formation of a high-grade lesion and, ultimately, a tumor.
Researchers believe that it can take between 10 and 20 years from the time of an initial HPV infection until a tumor forms. However, even high-grade lesions do not always lead to cancer. The percentage of high-grade cervical lesions that progress to invasive cervical cancer has been estimated to be 50 percent or less.
The rates of cervical, penile, vaginal, and mouth and throat cancers were anywhere from 50 percent to eight-times higher, compared with the general population.
There was also some evidence tying genital warts to non-melanoma skin cancers, the researchers say.
Overall, 440 study participants, or less than 1 percent, developed non-melanoma skin cancer - which is somewhat higher than expected, the researchers say.
Complications of HPV
Certain strains of HPV are associated with a number of serious health risks. In particular, some HPV strains appear to increase your risk of developing specific types of cancers, including vulvar, penile, and cervical cancer. Women with prolonged HPV infection are at particular risk for developing cervical cancer. In fact, more than 80% of women with cervical cancer have a history of HPV infection. For this reason, it is essential that every woman who is sexually active have regular pap smears. The pap smear can help detect any irregular cells in the cervix. With early detection, the vast majority of cervical cancer sufferers can be treated. It is important to note, though, that those HPV strains associated with cervical cancer generally do not cause any outward symptoms and rarely are associated with genital warts.
HPV and Pregnancy
HPV infection can also prove problematic during pregnancy. The strains of HPV that cause genital warts are particularly problematic, because genital warts can grow to large sizes during pregnancy. These large genital warts can make urination difficult or they can sometimes block the birth canal during delivery. This can necessitate a cesarean section delivery. Rarely, babies contract genital warts during the delivery process. Genital warts can develop in the throats of these babies, making breathing difficult. This can be potentially life-threatening and requires immediate treatment.
It’s possible there is some type of connection between HPV and non-melanoma skin cancer, Kjaer told Reuters Health in an email. Since the immune system fights both infections and cancer, it’s possible that impaired immune function could underlie persistent HPV infection and skin cancer in some people.
But that’s all “speculative” for now, Kjaer stressed.