Cervical cancer is considered to be the most preventable cancer and yet it is still the 4th most commonly diagnosed cancer in women around the world with an estimated 604,000 cases diagnosed annually1. About 311,000 women die from this deadly cancer each year. In Singapore, it is the 10th most common cause of cancer among women with an incidence of 7.1 per 100,000 women2.
What causes Cervical Cancer?
Cervical cancer is a type of cancer that develops from the cervix (the entrance into the womb). We know today that most of this type of cancer (about 96 to 99%) is due to an infection by high-risk types of human papilloma viruses (HPV). The HPV virus is extremely common and it has been estimated that 1 in 2 women might be infected in their lifetime. Fortunately, most infections resolve spontaneously and cause no symptoms.
However, in a small group of women, persistent infection with the virus may lead to cervical cancer. Cervical cancer is highly treatable and can be cured if detected early. Fortunately, there are 2 clinically proven methods to prevent cervical cancer – through vaccination and screening.
HPV Vaccination – what is it and where can I take it?
Primary prevention of cervical cancer can be achieved through HPV vaccination. The first generation of HPV vaccines have been available in Singapore since 2007 and is used in school vaccination programs as well as polyclinics. This particular vaccine targets types 16 and 18 which account for up to 70% of all cervical cancers. They have been shown to be highly efficacious in numerous studies and have been incorporated in many national screening programs around the world3.
The second generation 9-valent vaccine was approved by the FDA in 2014 and has been available in Singapore since 2017. This newer vaccine targets 7 high-risk types (16,18,31,33,45,52,58) and 2 low-risk types (6,11) and has a reported prevention coverage of up to 90%. It is mainly used in hospitals and private clinics. A large clinical trial showed that more than 99% of girls and women aged 9 to 26 years old develop antibodies to all 9 types of the HPV and the vaccine was not inferior to the first generation vaccines4. Subsequent studies showed that the vaccination can be extended to women up to the age of 45 years old.
The vaccine does not contain the HPV virus and is made from proteins that only resemble the external look of the high-risk HPV viruses. The body triggers the production of antibodies in response to the vaccine, offering protection from future infections caused by the virus. The vaccine has been shown to be safe and there is no good evidence of association with any major side effects or significant medical conditions5. The vaccine provides long lasting protection without the need for any booster.
The Ministry of Health, Singapore has been recommending HPV vaccination for girls and women aged 9 to 26 years since 20106. MediSave can be utilised for HPV vaccination at all polyclinics and eligible clinics for women up to age 26 years. In 2019, a national school-based vaccination program was made available and all Secondary One female students can opt in to receive a free HPV vaccination to protect against cervical cancer. For girls aged 9 to 14 years, two doses are sufficient, whereas those 15 years or older will need 3 doses of the vaccine.
What type of Cervical Screening should I go for?
Screening for cervical cancer allows for early detection of changes in the cervix before cancer develops. These precancerous changes are termed as CIN (Cervical Intraepithelial Neoplasia). With time, CIN can progress and become invasive cancer if left untreated.
1. Pap Smear
The introduction of the pap smears to detect these changes has saved many women’s lives. However clinical studies suggest that the pap smear has a poor sensitivity of between 48.6% to 57.4% and a specificity of 96.1 to 96.5%.7
2. High-Risk (HR) HPV Test
Fortunately, a new test has been developed and it has now replaced the traditional pap smear as the standard screening method for cervical cancer. The new test is called high-risk (HR) HPV test and it detects whether a woman harbours high risk strains of the human papilloma virus on the cervix. This test is highly effective in early detection and is more sensitive than pap smear in identifying women with CIN2+ lesions but is less specific than pap smears. However, the HPV test has a very high negative predictive value of 96% which means that the chance of a woman having precancerous lesions on the cervix is very low if a test is negative. Women with a negative HPV test has shown to have less than half the risk of developing the disease compared to the pap smear.
In Singapore, screening for cervical cancer with the HR HPV test is highly recommended by the Health Promotion Board through the National Cervical Cancer Screening Program for sexually active women from the age 30 years to 69 years since 20198. On the other hand, women from age 25 years to 29 years are encouraged to have the pap smear as the chances of detecting transient HPV infections are higher in this group.
If the HR HPV test is negative, the chance of having cancer is less than 1% and the next screen can be conducted 5 years later. For a negative pap smear, the subsequent screening can be done every three years. Screening is available at a subsidised cost under the Screen for Life National Health Screening Program for Singapore citizens and Permanent residents.
In conclusion, healthy individuals are strongly recommended to go for regular cervical screenings. If you have not received any HPV vaccination, please consult a doctor or medical professional to assess if you are indeed suitable for it as vaccination is a crucial step in protecting you from the risks of cervical cancer. Lastly, avoid smoking, practice using barrier contraception and limit the number of sexual partners to help reduce the incidence of this deadly disease.
This article was contributed by Dr Timothy Lim Yong Kuei, AIA Preferred Provider, and President of The Society for Colposcopy & Cervical Pathology of Singapore. To request an appointment with Dr Timothy Lim, please click here.
2. Singapore Cancer Registry 50th Anniversary Monograph ((1968-2017)
3. HPV vaccination and cancer prevention. A. Athanasiou et al. / Best Practice & Research Clinical Obstetrics and Gynaecology 65 (2020) 109-124
4. A 9-valent HPV vaccine against infection and intraepithelial neoplasia in women. Joura et al. N Engl J Med. 2015 Feb 19;372(8):711-23. doi: 10.1056/NEJMoa1405044.
5. GACVS. Safety update of HPV vaccines. https://www.who.int/vaccine_safety/committee/topics/hpv/June_2017/en/; 2017.
6. FAQs on HPV Vaccination 9/2010. Health Promotion Board, Singapore. MOH Clinical Practice Guidelines on cervical cancer screening. February 2010
7. Overview of the European and North American studies on HPV testing in primary cervical cancer screening. J. Cuzick, C. Clavel, K.U. Petry, C.J. Meijer, H. Hoyer, S. Ratnam, et al. Int J Canc, 119 (2006), pp. 1095-1101