Progression of Cervical Disease after HPV infection

Cervical cancer does not happen over night or out of sudden.  Many studies have shown that it may take 10 - 15 years from the exposure of persistent HPV infection before it progress to become an invasive cervical carcinoma. That is why it is said that cervical cancer is 100% preventable and curable. This is because the stages of cervical disease caused by the HPV infection can be easily detected and treated if a woman comes for her routine cervical smear screening.

Following the HPV infection, the virus get embedded into the DNA of the cervical epithelium and cause changes into the genetic material of the normal epithelium. After a certain period, the normal cervical epithelium will be replaced by the abnormal cells and this cervical disease is called Cervical Intraepithelial Neoplasia (CIN) or Squamous Intraepithelial Neoplasia (SIL). There are 3 grades of CIN, depending on the thickness of the abnormal cell replacing the normal cervical epithelium.
CIN 1- 1/3 of the normal epithelium is replaced; CIN 2 - 2/3 of the normal epithelium is replaced;
CIN 3- whole thickness of the cervical epithelium is replaced. Once the abnormal cells invade the deeper layer below the basement membrane of the cervical epithelium it become an invasive cervical carcinoma. It is not clear whether there is a progression from a lower grade CIN to a higher grade before it becomes an invasive cancer but many studies have shown that higher grade SIL (CIN 2 &CIN 3) has a higher tendency to progress into invasive cancer at a shorter period of time compared to the lower grade SIL (CIN 1).

Most of women infected by HPV would clear the infection naturally but women infected by HPV type 16, 18 and other oncogenic HPV types are likely to have persistent infection. The good news is almost all of these condition are curable. Hence, the role of pap smear is to detect HPV infected cervical epithelium and cervical pre-cancerous lesion before it progress into an invasive cancer.

HPV Infection and HPV Types

There are plenty of evidences that showed Human Papilloma Virus (HPV) is the sole agent that cause cervical cancer. HPV infection is the most common sexually transmitted disease in the world. It is estimated that up to 50 - 80% of women will acquire HPV infection in their lifetime.  The woman can also get infected by a multiple HPV types at one time.  As the infection carry no symptom, most women often not aware that they have acquired the infection. 

To date, there are about 72 types of Human Papilloma Virus (HPV) identified. Not all HPV types but HPV 16, 18, 31, 33, 45, 52, 58 are oncogenic and associated with cervical cancer. Globally, almost 70 % of cervical cancers cases are caused by HPV 16 and 18 while another 30% are due to HPV 31, 33, 45, 52, and 58.  Hence, by vaccinating against HPV 16 and 18, over 70% of cervical cancer cases can be prevented.

Most women who acquired HPV infection cleared or recovered from it spontaneously without any treatment. Those who have persistent HPV infection may eventually develop cervical cancer over period of time. Infection with HPV 16 and 18 and other oncogenic type HPV are more likely to persist than infection with other low-risk HPV types. In younger women aged 15-25 years, almost 80% of HPV infection are transient but in older women, cervical HPV infection are more likely to persist.

Almost all HPV infection are acquired through sexual intercourse either through genital to genital, finger to genital or oral to genital contact. Condom used may help to reduced risk but not fully protective against contact with HPV infected male organ.

Hence, we can conclude that all women who are or have been sexually active are at risk of exposure to HPV infection at any time of their lifetime unless they and their sexual partner/spouse have a lifetime mutual monogamous relationship.

Referrences:
1. Munoz N, et al. Int J Cancer 2004; 111: 278-285
2. Trottier H & Franco El. Am J Manage Care 2006;12;462-472
3. Parkin DM & Bray F. Vaccine 2006;24:11-25
4. Anhang R, et al. CA Cancer J Clin 2004;54:248-259
5. Lee SK et al. Am J Epidemiol. 2003;157:218-226

What Causes Cervical Cancer?

In the past, we are not so clear of what is a cause of cervical cancer. There was a link between Human Papilloma Virus (HPV) and cervical cancer but it was not very clear whether there was some other factors involved. After an extensive research and studies by the scientist for many years, we are now certain that the sole culprit that cause cervical cancer is HPV, and no other.

If cigarette smoking is a hazard as it brings 10 times increase risk of lung cancer, the study has shown that woman infected with HPV has 300 -500 times chances to develop cervical cancer (Wallboomers JH, et al. J Pathol 1999). Scientists has identified many types and strains of HPV, however not all HPV types cause cervical cancer. The type of HPV that causes cervical cancer is HPV 16, 18, 45, 33, and 31. This type of HPV not only cause cancer of the cervix but also anus, vagina, vulva, mouth and oro-pharynx.

But the question is how does a woman get HPV infection? HPV infection is acquired through skin to skin contact, largely through sexual intercourse. It is sexually transmitted like any other sexually transmitted diseases. Any sexually active woman is at risk of HPV exposure in their life time but the following group of women are at high risk of acquiring the HPV infection.

1. Sexually active young women (20 - 24 years old)
2. Women with multiple sex partners
3. Women with partner who has multiple sex partners (including polygamous man with many wives)
4. Women who had sexual intercourse at very young age
5. Women who smoke
6. Women who use contraceptive pill for longer term

How does HPV causing cervical cancer? Cervical cancer does not happen overnight but it takes 10 - 15 years after a woman is infected with HPV to develop cancer. It causes pre-cancer lesion of the cervix that can be detected by pap smear and can be treated.

The Burden Of Cervical Cancer

Let us talk about cervical cancer for this month. Since the availability of HPV immunization to young women in effort to prevent cervical cancer, there are so much confusion, misunderstanding and scare about the vaccination programme. People especially parents are sceptical about the benefits of vaccinating young girls. Some people say it might encourage promiscuity and some say it is harzardous.

In order to get the correct information one must refer to the best available evidences that support or refute the practice or recommendation for vaccination. Before we come to that, let us understand the burden of cervical cancer on our population and the rationale of it prevention.

Worldwide, every two minutes a woman dies of cervical cancer. In another word in one hour 30 women die of cervical cancer. Up to 80%, it occurs in less developed regions where there is lack of effective cervical screening programme (Ferlay J et al Globocan 2002). For comparison, in developed country like USA, there are about 14500 new cases of cervical cancer diagnosed annually and 6000 deaths due to cervical cancer. Where as in Asia including Malaysia about 266 000 new cases detected and 143 000 deaths annually. Why is such a big different? This is because a developed country like USA, has an effective cervical cancer screening programme that pap smear is compulsory for every sexually active women annually. Therefore, most of the cervical infection and pre cancerous conditions are treated before it progress to become a cancer.
On the other hand, in Malaysia and most of Asian countries has no proper screening programme and cervical smear is done as an opportunistic test. It means that whenever the woman come to see gynae doctor for some reason, it is an opportunity to offer/do pap smear. If not, it is up to the woman's level of awareness to request for a pap smear. WHO health survey in 2001/2002 reported only 20 % of Malaysian women have had a regular pap smear and the majority of them are from a low risk group of getting cervical cancer.

What Causes Cervical Cancer?

Cervical cancer is the only cancer that is sexually transmitted. How? Follow my next posting.

Welcome to SHJ Women's Health Specialist Blog!

Welcome to my blog. This blog is specially set up to provide a platform to educate my patient and improve their understanding on various women health condition and at the same time sharing my experiences as a practising gynaecologist to other audiences as well. I usually spend some time talking to my patient in the clinic trying to give them as much knowledge as I can of their gynaecological condition and answering all their questions but time is always a limiting factor. Thank you to the modern Information Technology that we are now have many other means and alternative to communicate more effectively. Despite living in the Information Era where knowledge and information is available before our eyes by just a click of our finger, however not all these information are readily digestable and reliable as there are plenty from various sources. I think people still need a confirmation of what they read from the website from their own doctor. Evidence based practice has become a core and integral part of any medical practice nowadays where the opinion of doctor and the treatment they offer are not only supported by their experience but largely by the facts derived through the best quality research/evidence available at that time of practice. What is written theoretically is not necessarily proven in reality thus it requires a series of experimens/trials to confirm what is claimed. Furthermore, medical practice are changing from time to time. What is practice before may become obsolete and no longer acceptable when new reliable evidence surface. Doctors have to keep updating their knowledge in order to provide their patient the best advice.