Preventing cervical cancer through vaccination
Dr. Ricardo Manalastas, Jr., professor of obstetrics and gynecology, University of the Philippines’ College of Medicine, spoke about human papillomavirus at a lunch symposium organized by research-based pharmaceutical company Merck Sharp & Dohme (MSD) in connection with the 2008 Annual Convention of the Philippine Obstetrical and Gynecological Society (POGS) held at the Philippine International Convention Center last Nov. 11-14.
Over 100 types of HPV have been identified, about 40 of which infect the anal and genital areas with approximately 15 to 20 types proven to cause cancer. HPV has been implicated in cancer of the cervix, vulva, vagina, anus, penis, oropharynx (tongue and tonsils), low-grade dysplasia (abnormal changes in cells lining the cervix), genital warts, recurrent respiratory papillomatosis (RRP, warty growths in the larynx of children and young adults).
One hundred percent of cervical cancer cases worldwide (almost 500,000 cases); 40 percent of vulvar and vaginal cases; 90 percent of anal cancer cases; 40 percent of penile cancer cases; 12 percent of oropharynx cancer cases; and three percent of mouth cancer cases can be attributed to cancer-causing HPV types.
“From 1980 to 1995, the incidence rate of cervical cancer in the country — a relatively high 22 per 100,000 women — has remained unchanged. Almost seven out of 10 of cervical cancer cases are diagnosed in the advanced stage when the chance of dying of the disease is high. About six out of 10 Filipino women with cervical cancer will die within five years,” lamented Dr. Manalastas.
Dr. Manalastas underscored the importance of prevention in the light of the high cost of cervical cancer treatment. Treatment for cervical cancer costs between P150,000 and P500,000.
“HPV infection is transmitted mainly through sexual contact. However, note that sexual contact is not limited to penetrative sex alone but also includes any direct skin-to-skin contact such as oral sex, anal sex, or any other contact involving the genital area, including hand-to-genital contact,” Dr. Manalastas explained.
The virus can also be spread from mother to newborn (vertical transmission) and, experts theorize, through “fomites,” any object or substance contaminated with germs which can transfer them from one individual to another. Examples of fomites are undergarments, surgical gloves, and biopsy forceps. Moreover, most infected individuals are unaware that they are infected and may unknowingly spread the virus.
The most effective way to prevent infection with HPV is total abstinence from all genital contact. “Unfortunately, this strategy may be quite impractical for most people,” Dr. Manalastas said. If practiced strictly, lifetime mutual monogamy would be equally effective; however, if one partner has not been monogamous, both partners are at risk. Using a condom may help reduce infection risk but does not provide full protection. Circumcised men have a lower risk of HPV infection.
Dr. Manalastas stressed that preventive HPV vaccines are most effective when given before a woman reaches the age when she is at greatest risk of getting infected. Studies have shown that HPV infection is most prevalent during adolescence and among people in their 20s. As such, experts strongly believe that young adolescents represent an ideal population for HPV vaccination.
To highlight the importance of HPV vaccination among young adolescents, Dr. Manalastas cited results of the 2003 Young Adult Fertility and Sexuality Survey, which revealed that almost one in four Filipino adolescents,15 to 24 years old, has engaged in pre-marital sex.
“Giving an HPV vaccine to adolescent, adult, and mid-adult women could dramatically reduce the incidence of low- and high-grade cervical dysplasias, conditions that can progress to cervical cancer — and genital warts,” Dr. Manalastas said.
