CANCER PREVENTION INSTITUTE OF CANADA

Last updated: 15-Jan-2007

Newsletter Excerpts

HPV: High Priority Virus

The story about the infectious causes of cancer continues to be uncovered. One constantly expanding chapter of the story concerns the human papillomoavirus (HPV).

HPV appears to have a special affinity for the epithelial cells in skin and mucosal tissues. There are a wide variety of cancers and non-malignant diseases where HPV has been detected.

Cancer of the cervix stands out as the first cancer discovered where a virus is always detected in disease tissue. At the same time, it is important to note that all cases of cervical HPV infection do not lead to cancer. Thus researchers have concluded that HPV is a necessary (but not always sufficient) cause of cervical cancer. The understanding of the role of HPV in cancer makes this type of cancer particularly amenable to preventive vaccination.

A minimum of 100 HPV subtypes exist, with at least 20 of these being oncogenic. Furthermore, and estimated 80% of sexually active individuals will contract a genital HPV infection during their lifetime. HPV is a “high priority virus” in health care. Basic approaches to preventing cancer with an infectious origin (notably cervical cancer) include:

We will briefly examine each of these approaches.

Exposure prevention. Exposure prevention means eliminating transmission of viruses and other pathogens. What is the main transmission route for genital HPV? Simply, it is sexual contact. “Contact” is the key word here. Skin-to-skin transfer occurs in the case of HPV so, unlike fluid-borne pathogens such as hepatitis C and HIV, there is evidence that condoms are not very effective in exposure prevention – skin to skin contact may occur before condom application or after it is removed. Regardless of its ultimate impact on HPV transmission, consistent and proper condom usage is vital when engaging in high-risk sexual behaviour. The bottom line is that HPV is “easily transmitted”. Indeed, HPV is the most common sexually transmitted infection in North America. The only “full-proof” way to eliminate the risk for HPV infections is to refrain from genital contact with another person. The next most certain approach is to be sexually active only within a long-term, mutually monogamous relationship with an uninfected partner. Primary prevention. The best “real world” hope for primary prevention is an HPV vaccination program. Several HPV vaccines are under investigation, with two companies poised to launch a vaccine within the next year or so. Clinical studies to date have shown a remarkable efficacy for the tested vaccines. The feasibility of establishing a population based vaccination program for teens is being examined in many jurisdictions.  Secondary prevention screening. The cornerstone of HPV management has been screening women for signs of early disease. The B.C. Cancer Agency’s Cervical Cancer Screening Program, implemented in 1960, was the first organized population program in the world. The program is credited with an 85% reduction in the incidence of cervical cancers and a 75% reduction in mortality due to cervical cancer, a result hailed as a triumph of public health. Each year BCCA / PHSA assesses more than 500,000 cervical smears.

(PreventCancer.ca Newsletter, Issue 1)

How do Individuals Respond to Positive HPV Test Results

The testing of cervical tissue for the presence of human papilloma virus (HPV) is going to be increasingly available in Canada. While most provinces do not at present make it available as a benefit of the medical plan, in other jurisdictions it has been shown to be a useful and cost-effective tool in determining the frequency of future cervical tests. As with many lab tests, there can be consequences beyond the simple test results. A physician giving the result to the patient should be aware of these potential consequences.

The response of individuals to learning of a positive HPV test result can vary but it usually includes a mixture of anger, concern and distress (McCaffery et al. British Journal of Gynaecology, 2004, Vol. 111). Increased anxiety tends to be associated with younger age, a higher perceived risk of cervical cancer and not understanding the meaning of test results. On occasion, individuals react with an expression of relief, particularly if they believe that discovery of an abnormal test result could allow them to take the steps necessary to prevent cervical cancer. Whether positive or negative, the attendant feelings tend to dissipate within six months (Maissi et al. British Journal of Cancer, 2005, Vol. 92). Naturally, the more serious diagnosis of genital warts or cervical intraepithelial neoplasia can have an adverse impact on mood, self-image, and sexual functioning in adult women.

HPV test results can also generate considerable interpersonal consequences (Kahn et al. Journal of Women’s Health, 2005, Vol. 14). Disclosure to a partner is viewed by many women as a responsibility. Their reasons include proving to their partners that they were monogamous (if the test results are negative) or assigning blame (if the results are positive). The knowledge or disclosure of positive test results can be seen as adversely impacting sexual relationships because of the stigma and shame associated with a sexually transmitted infection. Women who test positive tend to report feeling worse about both past and future sexual relationships than women who test negative.

(PreventCancer.ca Newsletter, Issue 3)