Can Oral Sex Cause Cancer?

Dr Ho Kean Fatt, MBBChBAO (Belfast), MRCP (UK), FRCR (UK), MD (Manchester)

2nd October 2017

Dr Ho Kean Fatt

Can oral sex cause cancer?

Yes, one can get cancer of the throat from oral sex.  It’s not oral sex, per se, that causes cancer, but the human papillomavirus (HPV), which can be passed from person to person during sex, including oral sex.

Change in types of people affected by mouth cancer

In the last 30 years, head and neck cancer has changed dramatically, especially in the developed countries. Research has found that patients diagnosed with cancer of the oropharynx – the middle part of the throat that includes tonsil, soft palate and the base of the tongue, was increasingly younger in their 40s and more frequently, non-smokers. Previously, most cancers of the oropharynx affected older adults who smoked and drank alcohol regularly.

Association between HPV and oropharyngeal cancer

Researchers have found that these cancers of the oropharynx are probably caused by a certain type of human papillomavirus (HPV). Human papilloma virus (HPV) is an infection that causes genital warts. HPV comes in more than 100 different strains and some can trigger cancers, including cancers of the penis, cervix, vulva, vagina, anus, and throat. HPV does not directly give you cancer, but it causes changes in the cells it has infected (for example, in the throat or cervix), and these cells can then become cancerous.

In the early 2000s, scientists were able to use advanced DNA testing to find HPV in many of these newer mouth cancers. But how do we become infected by HPV? The virus is transmitted during sex, including oral sex. HPV can lead to cervical cancer in females and cancer of the oropharynx in both males and females. It is not sex that causes cancer but the transmission of the virus during sex which passes the HPV from person to person. A study published in The New England Journal of Medicine (NEJM) in 2007 showed a greater risk for oropharyngeal cancer in people that had had oral sex with at least six different partners. The DNA of HPV type 16 was often found more often in the cancers of people who had multiple oral sex partners.

How high is my risk of oropharyngeal cancer?

HPV is common, but it doesn’t always cause cancer. If you aren’t exposed to HPV during oral sex, you’re not at risk for cancer. Most sexually active people (about 90%) will have been exposed to HPV. If you do get infected by HPV, in 90% of cases, the infection is cleared naturally by the body within two years. Furthermore, very few people infected with HPV will develop cancer. However, people who smoke are much less likely to clear the virus from their body. This is because smoking damages special protective cells in the skin called immune surveillance cells, allowing the virus to persist. Overall, most of us have been infected, but very few are affected.

More research is still being carried out as it is still unclear how many people get HPV throat infections by oral sex, or how many of them get oropharyngeal cancer eventually. A study carried out in 2009-10 concluded that the prevalence of oral HPV infection in American men was 10%, and in women 3.6% (Gillison et al 2011). Those who have HPV detected in their mouth had a 22-fold increase in the risk of oropharyngeal cancer (Rollison et al 2016).

Because of the decreased incidence of smoking in the United States, HPV-negative, smoking-related oropharyngeal cancer is decreasing and HPV-associated oropharyngeal cancer is increasing in incidence. The prevalence of HPV in oropharyngeal cancers has increased by 225% from 1988 to 2004, and the HPV-negative cancers have declined by 50% according to the SEER database (Chaturvedi et al).

Cancer of the oropharynx is still relatively uncommon in Malaysia (<5%) and falls outside the top 10 most frequent cancer site in the Malaysian Cancer Registry. However, the incidence is predicted to increase in the future due to changes in sexual behavior, rise in oral HPV transmission and increase income. In economically developed countries like the United States, HPV probably cause 60-70% of oropharyngeal cancers compared to 10% in less economically developed countries. 

Should I change my sexual behavior?

Currently, there is very little research that has looked at the possible risks from giving oral sex to a man compared to giving oral sex to a woman. But we do know that HPV-related oropharyngeal cancer is twice more common in men than women, and is most common in heterosexual men in their 40s and 50s (compared to the rates in homosexual men).

This indicates that performing cunnilingus (oral sex on a woman) is more risky that performing fellatio (oral sex on a man). This may be because the concentration of HPV in the thinner, moist skin of the vulva is much higher than the amounts of virus shed from the thicker, dry skin of the penis, and this affects how easy it is to pass the virus on. Other research indicates that HPV can be present in semen and passed on at ejaculation.

Can I reduce my risk of HPV infection?

You can make oral sex safer by using a condom on a man’s penis, because it acts as a barrier between the mouth and the penis. A dam (a square of very thin, soft plastic) across a woman’s genitals can protect against infection. Although condoms do not offer complete protection against HPV, it is still advisable to use them to minimise the risk of infection.

There is a vaccine that protects against some of the high-risk strains of HPV, but it must be given before there is any chance that you have been exposed to HPV infection. Malaysia was among the first countries in Asia to introduce a national HPV vaccination programme for 13-year-old girls in schools about five years ago. This is because it is known that nearly all cervical cancers are HPV-related and that the vaccine offers protection in women. Boys are not routinely given the HPV vaccine in Malaysia. This is because they do not need to be protected against cervical cancer. However, emerging evidence on the impact of HPV vaccination on cancers is being reviewed and the need for boys to be vaccinated too is being considered.

References:

Chaturvedi AK, Engels EA, Pfeiffer RM, et al.: Human papillomavirus and rising oropharyngeal cancer incidence in the United States. J Clin Oncol 29 (32): 4294-301, 2011.

Gillison ML, Broutian T, Pickard RL, et al. Prevalence of Oral HPV Infection in the United States, 2009-2010. JAMA. 2012;307(7):693-703.

Rollison DE, Gillison ML. The Alpha, Beta, Gammas of Oral Human Papillomavirus Infection and Head and Neck Cancer Risk. JAMA Oncol. 2016;2(5):606-607.