References

Cervical cancer is almost 100% cured when diagnosed early.

It is estimated that in 2007 there were 1,350 new cases of cervical cancer detected in Canada and 390 deaths associated with the disease.  The lifetime probability of a woman dying from cervical cancer is 1 in 437.¹  Almost all of these deaths could be prevented, if the diagnosis is made in the pre-cancerous phase.

Until recently, the best way to detect cervical cancer was through the Papanicolaou (Pap) smear test - a diagnostic test available in Canada for the past 50 years.  Unfortunately, Pap smears have a sensitivity rate of only 50 per cent.²  A Pap test is a visual examination for any abnormal cell changes in the cervix. However, results from a Pap test require interpretation by a laboratory professional, which can sometimes result in false negatives. There are factors unrelated to cervical cancer that can occasionally cause an abnormal Pap test result (e.g. a yeast infection or other causes of vaginal irritation).

Scientists now know that virtually all cervical cancers are related to infections from a family of viruses known as the Human Papilloma Virus (HPV).  Infections with these viruses are very frequent and are sexually transmitted. The majority of infections go away on their own without causing any lesions.  There are two kinds of HPV: the low-risk HPV types, which may cause genital warts and the high-risk HPV types, which may lead to pre-cancers and cancer.

Detection of these viruses can now be used as an early warning system to screen women prior to the development of cervical cancer.

The HPV test is a sensitive, non-invasive method that can detect the presence of high-risk HPV that can cause cervical cancer, even before any changes can be seen on the cells of the cervix. Cells are scraped from the cervix, as for a Pap test, collected into a liquid and sent to a lab to look for the genes (DNA) of the HPV virus at the molecular level. Once this HPV test result indicates that the virus is present, another test can be performed to identify which of the 37 sub-types of the virus are present. This test is called the Linear Array HPV test. Using the same sample of cells, this test is a genotyping process that identifies the individual sub-types of the virus. Once identified, the treatment can be tailored to the patient's need, since certain types such as 16 and 18, appear to require a tighter follow-up.   

HPV testing is not recommended for women under 30 since the HPV infection is very frequent in younger women and most often clears without causing any health problems.  However, they should still have a Pap test. For women 30 and over, the HPV testing is recommended in the event of an equivocal Pap result. 

"For women who receive an equivocal Pap smear result, HPV testing is a better option than waiting six months to repeat the smear.  It can immediately reassure women who will not need further investigation (colposcopy), while making sure that those who need this investigation will get it in a timely manner," says Dr. Marie Helene Mayrand, Assistant Professor with the Departments of Obstetrics Gynecology and Social and Preventive Medicine at the Université de Montréal.

Using the HPV test could save costs estimated at $50 million annually in Canada, of additional colposcopies and biopsies made necessary by abnormal Pap test results.  The precision of the HPV test also reduces the number of non-required colposcopies and hospital waiting lists for such procedures also alleviating associated system costs and healthcare workload.³

In addition, the screening test complements the use of the HPV vaccine, as the current vaccine only protects against two high risk types of the HPV virus, and is inefficient against the other eleven known to be linked to cervical cancer.  Screening and vaccination should thus be used in tandem.

The HPV test improves cervical cancer screening and provides physicians with an efficient tool for identifying women at risk at an early stage of the cancer development, while significantly facilitating the management of treatment and reducing the healthcare costs related to this disease.

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