Human papillomavirus (HPV) can cause several types of cancer, including cervical cancer. It is important to understand how this common sexually transmitted infection (STI) may lead to a cancer diagnosis.
There are over 200 types, or strains, of HPV, some of which are spread through direct sexual contact. The strains can be divided into two categories of HPV:
- Low-risk- rarely associated with cancer, but some can cause issues like genital warts.
- High-risk- can cause certain types of cancer such as cervical, head and neck, and anal cancers. Out of the 14 high-risk strains of HPV, two types (HPV16 and HPV18) are responsible for most HPV-related cancers.
Nearly all sexually active people are infected with HPV at some point during their lifetime. This is normal. Although about half of these infections are with a high-risk HPV type, most infections do not lead to cancer because the immune system is usually able to fight them off.
How does HPV cause cancer?
Sometimes the immune system is unable to fight off an HPV infection. When a high-risk HPV infection is persistent (does not go away over time), it can lead to cell changes (dysplasia) that, if left untreated, may develop into cancer. It takes about 10-20 years (or longer) for HPV-infected cervical cells to develop into cancer.
There are risk factors for HPV persistence and the development of cervical cancer, which include:
- HPV-type (having a high-risk type, like HPV16 or HPV18)
- Weakened immune system (e.g., those living with HIV or taking medicines to suppress the immune system)
- Co-infection with other STIs
- Smoking tobacco
Aside from cervical cancer, HPV can also lead to other types of cancer such as vaginal, vulvar, penile, anal, and oropharyngeal.
While HPV is the most common cause of cervical cancer, it is important to note that another cause of cervical cancer (though much more rare) is exposure to diethylstilbestrol (DES) in utero. DES is a synthetic form of the female hormone estrogen. There are some other rare types of cervical cancer that are not due to HPV.