HPV and cervical cancer: causes and treatments
By Barry C. Fox, MD, University of Wisconsin
The human papillomavirus, or HPV, is a ubiquitous virus in the United States. It is estimated that 6 million people are newly infected each year. Most HPV infections are not only asymptomatic, they are too small to be clinically noticeable. On the outside, however, infections can be visible as warts.
History of HPV
In the 1950s, at least 15,000 women died each year from cervical cancer. Henrietta Lacks was one of those women diagnosed with cervical cancer. However, many women chose not to get tested and Henrietta Lacks was one of them. Henrietta Lacks died in October 1951, less than a year after her diagnosis. Years later, scientists discovered that her cervical cancer was caused by an infection known as the human papillomavirus or HPV.
These Henrietta tumor cells were also found to be immortal, paving the way for the study of genes that turn cancer cells on and off and test different drugs for their effectiveness.
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Prevalence and link to cervical cancer
HPV has the highest prevalence rate of 45 percent in girls and women aged 14 to 26 and an overall prevalence of 27 percent in this gender. The virus also causes genital warts in one percent of men. The prevalence gradually decreases with age, as 90 percent of new HPV infections actually decrease over 6 to 18 months.
The most significant concern about the infection is that it is involved in over 99 percent of cervical cancers. Cervical cancer is one of the top ten causes of cancer death in women.
Persistent infection is a prerequisite for progression to cervical cancer. Out of the hundred types of HPV, there are about 13 types that can cause cervical cancer.
About 70 percent of cervical cancer cases are caused by genotypes 16 and 18, while 90 percent of genital warts are caused by genotypes 6 and 11. It was not until 1984 that the HPV 18 strain of the virus, which Henrietta Lacks had, was actually discovered. These are the types that are targeted in vaccination.
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The mechanism causing cancer
HPV DNA can insert into the DNA of the host cell. HPV has the potential to cause oncogenes, which cause the host cell to develop malignant characteristics. In addition, it is also responsible for 5 percent of all cancers worldwide, including throat and anal cancer, in both men and women.
A cervical Pap test is used to check women for cervical cancer. It is ideal to check for cervical cancer once every three years. Nonetheless, there are newer and more sophisticated molecular diagnostic tests available to look for high-risk variants of HPV associated with cancerous transformation, which could eventually replace the smear.
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Vaccinations against HPV infections
Vaccines are generally immunogenic for the creation of antibodies that protect against chronic HPV infection. Immunity is expected to last for at least 10 years and at this time no booster vaccination is recommended.
The vaccine should be given before exposure to HPV infections because there is no protection against HPV disease for infections acquired before vaccination.
The FDA approved a vaccine for women aged 9 to 26 in 2006. This vaccine provides protection against infection with genotypes 6, 11, 16 and 18 of HPV, which cause the most incidence of cancer of the breast. cervix and genital warts. A second HPV vaccine was also approved in 2009, but only contains genotypes 16 and 18.
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Vaccine and ethics
National organizations target girls aged 11 to 12, but also recommend vaccination for women aged 13 to 26 as this age group is still at risk. Naturally, this young age of vaccination has generated some ethical controversy.
Some parents may object to the administration of an STD vaccine before the child is sexually active. Conservative religious groups strongly opposed a mandate, arguing it would condone premarital sex and violate parental rights.
Despite these potential objections, immunization committees have also recommended that boys and young men also receive the vaccine. This is based on the hypothesis that vaccination would help reduce the prevalence of HPV in men and, therefore, reduced transmission to their sexual partners.
Common questions about HPV and cervical cancer
Most HPV infections are not only asymptomatic, but they are also too small to be clinically noticeable. On the outside, however, infections can be visible as warts.
A cervical Pap test is used to screen women Cervical cancer. There are also newer and more sophisticated molecular diagnostic tests available to look for high-risk variants of HPV, which could eventually replace the smear.
The FDA has approved a HPV vaccine for use in women 9 to 26 years of age that provides protection against infection for HPV genotypes 6, 11, 16 and 18. A second HPV vaccine that contains only genotypes 16 and 18 was approved in 2009.
National organizations target girls in the 11-12 age group for HPV vaccination. This young age of vaccination has generated some ethical controversy as parents and conservative groups oppose the administration of a vaccine before the child is sexually active, tolerate premarital sex and infringe parental rights.