As I’ve written before, there are just a handful of ways to reduce your risk of cancer. Don’t smoke. Stay out of the sun. Keep a healthy weight. Don’t drink alcohol. And get vaccinated with the HPV vaccine to prevent HPV-associated cancers (see Note 1).
Too many people who discuss the HPV vaccine, especially among the anti-vaccine religion, tend to focus on HPV-related cervical cancer. But HPV is linked to several dangerous and deadly cancers, and a new report examines the details of those cancers.
What is HPV?
Human papillomavirus (HPV) infections are the most common sexually transmitted infections (STI) in the USA. HPV is generally transmitted from skin-to-skin contact especially during vaginal, anal or oral sex.
Very rarely, it can spread from a mother to the baby during delivery. The newborn may develop recurrent respiratory papillomatosis (RRP), a dangerous condition where warts caused by HPV (similar to genital warts) grow inside the throat.
Most HPV infections cause no symptoms and resolve spontaneously. That doesn’t mean it’s not a concern. In many people, the HPV infection can persist and may result in warts or precancerous lesions. These precancerous lesions increase the risk of HPV-associated cancer.
There are no effective treatments for HPV infections.
There are at least 147 strains or subtypes of HPV that can infect humans – however, only 40 of these strains are linked to one or more different cancers. Of those 40 strains, most are fairly rare.
According to current medical research, here are some of the HPV-associated cancers:
In addition, there is some evidence that HPV infections are causally linked to skin and prostate cancers. The link to skin cancer is still preliminary, but there is much stronger evidence that HPV is linked to many prostate cancers.
HPV-associated cancers are believed to constitute nearly 5% of all new cancers across the world, making it almost as dangerous as tobacco in that respect. According to the CDC, roughly 79 million Americans are infected with HPV – approximately 14 million Americans contract a new HPV every year. Most individuals don’t even know they have the infection until the onset of cancer.
There were two HPV vaccines on the world market before 2014. GSK, also known as GlaxoSmithKline, produced Cervarix, a bivalent (protects against two HPV strains) vaccine. It has been withdrawn from the US market (although available in many other markets), because of the competition from the quadrivalent (immunizes against four different HPV strains) and 9-valent (against nine HPV strains) Gardasil vaccines.
Merck manufactures Gardasil, probably the most popular HPV vaccine in the world. The first version of the vaccine, quadrivalent Gardasil, targets the two HPV genotypes known to cause about 70% of cervical cancer and two other HPV genotypes that cause genital warts. In Europe and other markets, Gardasil is known as Silgard.
The newer Gardasil9, approved by the FDA in 2014, is a 9-valent vaccine, protecting against HPV Types 6, 11, 16, 18, 31, 33, 45, 52, and 58 (with HPV16 and HPV18 the most prevalent, by far, of the types found in HPV-associated cancers). The vaccines target the four HPV strains found in the older quadrivalent version, along with five additional ones that are linked to cervical and other HPV-related cancers.
Both versions of Gardasil are prophylactic, meant to be given to females or males before they become exposed to possible HPV infection through intimate contact. Gardasil is one of the easiest and best ways to prevent HPV-associated cancers.
Currently, in the United States, the Advisory Committee on Immunization Practices (ACIP) recommends that preteen girls and boys aged 11 or 12 are vaccinated against HPV. The immunization is also recommended for teenage girls and young women up to the age of 26 who did not receive it when they were younger, and teenage boys and young men up to the age of 21.
HPV vaccines are not contraindicated for men and women older than 26, and many individuals request the vaccine since it’s improbable that anyone would be infected by all 9 strains of HPV covered by Gardasil9.
USA statistics of HPV-associated cancers
In a recent article published in the Centers for Disease Control and Prevention (CDC) Morbidity and Mortality Weekly Report, CDC researcher Elizabeth A Van Dyne, MD et al. examined the incidence of HPV-associated cancers in the USA from 1999 to 2015. Their results are surprising and should make us redouble our efforts to increase the uptake of the HPV vaccine.
The researchers found that oropharyngeal squamous cell carcinoma (SCC) (see Note2) is now the most common of the HPV-associated cancers in the USA. SCC incidence rates, from 1999 through 2015, increased by 2.7% per year for men and 0.8% per year among women.
Oropharyngeal cancer has now replaced cervical cancer as the number 1 in the list of HPV-associated cancers. In 2015, there were a total of 11.788 cervical cancers compared to 18,917 oropharyngeal SCC’s.
According to the report, the decline in cervical cancer is part of a long-term trend, since the 1950s, has resulted from better guidelines and attention to cervical screening. On the other hand, the increase in oropharyngeal SCC may be due to changing sexual behaviors over the past 15-20 years, including unprotected oral sex, especially among white men, who report having the highest number of sexual partners and performing oral sex at a younger age.
The study also stated that in 1999, there were a total of 30,115 new cases of HPV-associated cancers. However, in 2015, there were 43,371 cases. The rate of HPV-associated cancers dropped by 0.4% annually during the study period, whereas it increased by 2.4% annually among men.
To obtain this data, the CDC analyzed data from their own National Program of Cancer Registries and the National Cancer Institute’s Surveillance, Epidemiology, and End Results (SEER) program for all years from 1999 to 2015.
There is a limitation to these registries – they track the incidence of invasive cancers, but they do not track the HPV status of individual cases cancer. The researchers adjusted the data using published statistics on the percentage of each cancer that are linked to HPV. In the United States, HPV DNA was found in 91% of cervical, 91% of anal, 75% of vaginal, 70% of oropharyngeal, 69% of vulvar, and 63% of penile cancers.
The researchers observed these annual changes in HPV-associated cancers over the 1999-2015 study period:
|Cancer Type||Average Annual Change (%)|
|Oropharyngeal in men||2.7|
|Oropharyngeal in women||0.8|
|Anal in men||2.1|
|Anal in women||2.9|
Note: penile cancer rates remained stable during the study period.
In the USA in 2015, there were over 43,000 new cases of HPV-associated cancers. The vast majority of these cancers can be stopped with a simple prevention – the Gardasil9 HPV vaccine.
There are so few ways to actually prevent cancer. Why would any parent not take their children to the pediatrician to get the vaccine that could protect against 43,000 HPV-associated cancers every year? Why is this even a question?
- Although this article focuses on the HPV vaccine, the hepatitis B vaccine is also important for the prevention of some cancers. The vaccine prevents hepatitis B viral infections, and chronic hepatitis B infections can lead to liver cirrhosis or cancer. Liver cancer is actually one of the few cancers in the USA where the incidence has increased over the past few years. And if you follow the anti-vaccine rhetoric, you know the hepatitis B vaccine is almost as controversial as the HPV vaccine.)
- Oropharyngeal squamous cell carcinoma is sometimes called “throat cancer,” but it actually includes cancers at the base of tongue, pharyngeal tonsils, anterior and posterior tonsillar pillars, glossotonsillar sulci, the anterior surface of soft palate and uvula, and lateral and posterior pharyngeal walls. So it’s a broad name of a number of closely related cancers.
- Bzhalava D, Guan P, Franceschi S, Dillner J, Clifford G. A systematic review of the prevalence of mucosal and cutaneous human papillomavirus types. Virology. 2013 Oct;445(1-2):224-31. doi: 10.1016/j.virol.2013.07.015. Epub 2013 Aug 5. Review. PubMed PMID: 23928291.
- Ljubojevic S, Skerlev M. HPV-associated diseases. Clin Dermatol. 2014 Mar-Apr;32(2):227-34. doi: 10.1016/j.clindermatol.2013.08.007. Review. PubMed PMID: 24559558.
- Saraiya M, Unger ER, Thompson TD, Lynch CF, Hernandez BY, Lyu CW, Steinau M, Watson M, Wilkinson EJ, Hopenhayn C, Copeland G, Cozen W, Peters ES, Huang Y, Saber MS, Altekruse S, Goodman MT; HPV Typing of Cancers Workgroup.. US assessment of HPV types in cancers: implications for current and 9-valent HPV vaccines. J Natl Cancer Inst. 2015 Apr 29;107(6):djv086. doi: 10.1093/jnci/djv086. Print 2015 Jun. PubMed PMID: 25925419; PubMed Central PMCID: PMC4838063.
- Van Dyne EA, Henley SJ, Saraiya M, Thomas CC, Markowitz LE, Benard VB. Trends in Human Papillomavirus-Associated Cancers – United States, 1999-2015. MMWR Morb Mortal Wkly Rep. 2018 Aug 24;67(33):918-924. doi: 10.15585/mmwr.mm6733a2. PubMed PMID: 30138307.
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