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Prevention of Cervical Cancer
 
Introduction
 
Worldwide, cervical cancer is the second most common cancer among women, with only breast cancer occurring more commonly. About 500,000 new cases of cervical cancer are reported annually with 250,000 deaths. In another word, one woman is diagnosed with cervical cancer every minute and one woman died of cervical cancer every two minutes. Out of these, 80% of cervical cancer was diagnosed in the developing countries with 50% among Asian countries.
 
Aetiology
 
Virtually all cases of cervical cancer are caused by Human Papilloma Virus (HPV) as HPV DNA is identified in 99.7% of cervical cancer biopsies. HPV is a double-stranded, non-enveloped DNA virus belonging to the Papilloma virus genus of the family Papillomaviridae. Nearly 120 HPV types are identified. About 15 to 20 types are highly oncogenic (cause cancer). HPV virus may cause dysplasia (abnormal cell changes) on the cervix and may progress to cervical cancer if left untreated.
 
Risk Factors
 
The risk factors for cervical cancer are mainly surrogates for sexual activity. Among the major risk factors are :
icon Early age of sexual activity
icon Multiple sexual partners or if the male partners have multiple sexual partners
icon Cigar smoking
icon Low socio-economic class
icon High parity
icon Sexually transmitted disease
icon Immunocompromise
 
Prevention of Cervical Cancer
 
Cervical cancer is the most preventable gynaecological cancer. It is disheartening to note that it is still the second most common cancer among women in developing countries including Malaysia. A lot more needs to be done to reduce the incidence of cervical cancer.

The medical dictum“Prevention is better than cure” could not be more appropriate in this situation. Prevention can be divided into primary and secondary prevention. Primary prevention means measure is being taken prior to the onset of disease process. Secondary prevention means that measure is being taken after the onset of disease process but prior to the development of cancer.
 
Healthy Life Styles
 
It is important to educate the public regarding healthy life styles such as:
icon Delay onset of sexual activity
icon Maintain monogamous relationship or reduce the number of sexual partners.
icon The use of condoms to reduce the incidence of transmission of HPV virus
icon Stop smoking
icon Sex education: in school and community to provide correct information about sexual relationship and risk of sexually transmitted disease including HPV infection.
 
Secondary Prevention
 
I will discuss on secondary prevention first as it has been available for the last 6 decades. Pap smear was first introduced by Mr Papanicolaou (hence the name of the test) in 1940. It involves taking a sample of cells from the cervix and viewing them under a microscope to check for dysplatic cells (abnormal cell changes)

The natural history of cervical cancer is such that the cervical cells undergo dysplasia, initially mild, to moderate and then severe before developing into cervical cancer. The rationale of the screening programme is to detect the abnormal cell before it becomes cancerous and treat it appropriately.

With the establishment of a successful screening programme, pap tests have been proven to reduce the incidence of cervical cancer and mortality by 50%.

The conventional method involves using a speculum to insert into the vagina and visualize the cervix, a sample of cells is collected from inside and around the cervix using a small brush and spatula. The sample is smeared onto a glass slide and fixed with alcohol to send to the laboratory for screening.

 
Cervical Cancer photo Cervical Cancer photo
 
The efficacy of a cervical screening method is measured by its ability to diagnose precancerous lesions. The false negative rates (the test is negative even though the patient has the disease) of conventional pap smears have been reported to range from 10 to 50%. These are due to the limitations of sampling or slide preparation. Accurate interpretation can be adversely affected by the presence of blood, mucus, obscuring inflammation and air-drying artifact.

To address the problems of false negative rates of conventional pap test, a new liquid-based, thin-prep Pap test has been approved by the US Food and Drug Administration in 1996. It has only been introduced in Malaysia in the last couples of years. With this method, the cervical sample is taken from the patient in the usual manner. A cytobrush is used to collect the sample. However, instead of smearing onto a glass slide, the cells are rinsed into a small vial containing preservative solution. Sample is later processed and screened in the laboratory. Studies have proved that this method to be more sensitive to detect the precancerous lesions than the conventional pap test.

Our national cervical screening programme recommends every sexually active woman or who has previously been sexually active, to be screened from the age of 20 to 65. Annual smear is taken for first 2 years. If both smears are negative, then she can be screened once every 2 years.

If the pap smear shows abnormal result, the patient should be referred to a gynaecologist for colposcopic examination and further treatment if necessary.
 
Primary Prevention
 
HPV vaccine
 
A lot of research has been done to develop the HPV vaccine as 99.7% of cervical cancer is caused by the HPV virus. There are 2 vaccines available: Gardasil, a quadrivalent vaccine that helps protect against HPV types 6, 11, 16 & 18. HPV type 6 & 11 are responsible for 90% of genital warts whereas HPV types 16 & 18 are responsible for 70% of cervical cancer. The other vaccine, Cervarix, a bivalent vaccine that helps protect against HPV types 16 & 18.

The vaccine is recommended for young women from 9 to 26 years old. It should be administrated in 3 doses, 0, 2 and 6 months. The vaccine is very well tolerated, with few adverse effects such a pain, swelling, erythema and pruritis at the injection-site. It is only contraindicated in those who are hypersensitive to the components of the vaccine.
 
HPV DNA testing
 
The role of HPV DNA testing in prevention of cervical cancer is unclear at this stage. The test involves the same process as when a liquid-based thin prep pap smear is being done. It can detect the 13 high-risk HPV types.

In Western countries, it has been proposed as part of the screening programme. If the DNA testing does not reveal any high-risk types, then the woman may have less frequent pap smear screening eg once every 5 years. It has been found to be cost-effective as it involves higher cost to see a doctor for yearly pap smear. However, more research still needs to be done to assess its effectiveness.

Currently, it is useful in cases of management of recurrent mild dysplasia or follow-up after treatment for dysplasia. If the HPV DNA testing exclude high risk type, it is probably safe to manage patient conservatively by regular pap smear. On the other hand, in the presence of HPV high risk type, more aggressive treatment should be instituted. It has complimentary role to pap test screening but definitely is not a replacement tool for pap test at this stage.
 
Conclusion
 
With the advancement of liquid-based pap test and the introduction of HPV vaccine, the incidence and mortality from cervical cancers will be reduced. However, due to the limited resources in developing countries, it is still the simple conventional pap smear that will make a major impact on the reduction of incidence and mortality from cervical cancer. The success of an effective screening programme depends on its wide coverage screening of at least 85% of the at-risk population.
 
Cervical Cancer photo
Cervical cancer
 
Dr Ng Siew Eng
Consultant O&G Specialist
 
Timberland Medical Centre @ 2015 Lembaga Iklan Ubat no : KKLIU 2353/2015