Cancer caused by the sexual strains of HPV
Vaccination against HPV can protect you from getting cancer. When unvaccinated, the majority of cancer cases are caused by HPV strains that normally don’t cause warts. Most people do not know they have even been infected until the later stages of the cancer as symptoms are not shown in the early stages. The virus can cause cancer of the cervix, vulva, anus, penis or oropharynx (middle of the throat).
Over a period of time, the repeated infection of specific strands of HPV can result in cancerous lesions. If these are not treated, they can become cancerous.
High-risk HPVs cause about 5% of cancer cases worldwide. High-risk HPVs are known to cause several different types of cancer:
- Cervical cancer – all cervical cancer is caused by HPV. The HPV types 16 and 18 are responsible for roughly 70% of all reported cases of cervical cancer.
- Anal cancer – 95% of all anal cancers are the result of HPV type 16.
- Cancers of the mid throat, soft palate, tonsils and base of the tongue (oropharyngeal cancers) – 70% of these are caused by HPV and more than half of these cancers are a result of HPV type 16.
- Rarer cancers – 65% of vaginal cancers are caused by HPV, as well as over 50% of vulvar cancers and 35% of penile cancers. Most of these types of cancers are also caused by HPV type 16.
How does HPV cause cancer?
HPV causes cancer when the epithelial cells, which are found in layers covering the outside surfaces of the body, including the genital tract, throat, anus and skin become infected with the virus. Once infected, the virus begins to produce encoded proteins which interfere with the functions of the cells, disrupting their ability to control their growth.
In some cases, these cells are detected and destroyed by the immune system. In others, the cells continue to grow and multiply in an uncontrollable manner. As they continue to grow, they begin to form cell mutations leading to pre-cancerous cells being formed and ultimately, if left untreated, a cancerous tumour.