HPV and Cervical Cancer

Human Papillomavirus (HPV) is a common sexually transmitted infection. If you are sexually active, there is a 50% chance that you have already infected with HPV at some point of time. Most of the time HPV infection will not produce any symptoms and our body immune system can cure it by itself within 2 years time without any treatment (median 8 months). However, some infected people may have genital warts and for female, it may lead to pre-cancerous changes in the cervix. The pre-cancerous changes need further monitoring and possibly treatment.

           Human Papillomavirus

HPV has been widely discussed now because of its link to cervical cancer, though the risk is very small. Besides, HPV is also related to other types of cancer around genital area such as vagina, vulva, penis and anus. 

There are more than 100 types of different HPVs, however, only about 40 has clinical significance to human. Base on their risk to cause cancer, they can be divided into "high risk" type and "low risk" type. HPV type 16 and 18 are the most well known high risk type and both are associated with almost 70% of cervical cancer.

HPVs can infect both male and female equally. It can be transmitted from a person to another through direct contact during sexual intercourse. So if you start to have sex at early age, have multiple sexual partners or if your partner has multiple sexual partners, your risk of getting HPV infection is higher.

Most HPV infection is transient, but about 10% of women may have persistent infection. If the persistent HPV type is HPV 16/18, then the risk of developing cervical pre-cancerous changes is higher. It may progress to cervical cancer if left untreated.

Since long time ago Pap smear has been available as a screening tool for cervical cancer in female. Now Pap smear is still the most important screening test that save lives. Its accuracy is improved with the new liquid base cytology test, which is better than the conventional "scrape and spread on slide" test.

Not long ago, HPV DNA test is recommended as as "add-on" to Pap smear to further help the decision making for doctors in patients with abnormal pap smear result. HPV DNA test is not recommended routinely for women <30 years old unless the Pap smear shows abnormality. It cannot substitute Pap smear as the main cervical cancer screening tool. If the HPV DNA test is positive for high risk HPV type in a patient with "borderline" Pap smear result, then it may prompt further investigation.

      

    Changes in cervix caused by HPVs

HPV infection can be prevented through vaccine. Currently there are 2 types of vaccines available: Gardasil (HPV 6, 11, 16, 18) and Cevarix (HPV 16, 18). HPV 16 & 18 are the most common high risk HPV that account for almost 70% of cervical cancer. HPV 6 & 11 are low risk HPV that can only lead to genital warts.

These vaccines are given in 3 separate intramuscular doses (0, 1-2, 6 months apart). They are found to be 100% effective in preventing pre-cancerous cervix lesion caused by HPV 16 & 18. Thus it should be able to prevent 70% of cervical cancer (as HPV 16 & 18 cause 70% of cervical cancer). It is not 100% prevention from cervical cancer. There are other types of high risk HPVs and many other possible causes for cervical cancer. So Pap smear is still mandatory even after you have received Gardasil or Cervarix vaccination.

Vaccination is best given to girls/women before they are infected with HPV 16 & 18, or in other words, before having their first sex. It can be given as early as 9 years old up to over 40 years old. However, the earlier the better it is.