What are the risk factors for penile cancer?
A risk factor is anything that affects your chance of getting a disease such as cancer. Different cancers have different risk factors. For example, exposing skin to strong sunlight is a risk factor for skin cancer. Smoking is a risk factor for many cancers.
But risk factors don't tell us everything. Having a risk factor, or even several, does not mean that you will get the disease. On the other hand, some men who develop penile cancer have no known risk factors. Even if a man does have one or more risk factors for penile cancer, it is impossible to know for sure how much that risk factor may have contributed to causing his cancer.
Scientists have found certain risk factors that make a man more likely to develop penile cancer.
Circumcision removes all (or a part) of the foreskin. This procedure is most often done in infants but it can be done later in life. Circumcision seems to protect against penile cancer when it is done during childhood. Men who were circumcised as children have a lower chance of getting penile cancer than those who were not, but studies looking at this issue have not found the same protective effect if the foreskin is removed as an adult. Some studies even suggested a higher risk of penile cancer in men who were circumcised as adults. The reasons for this are not entirely clear, but may be related to other known risk factors.
For example, men who are circumcised cannot develop the condition called phimosis, and cannot accumulate material known as smegma (see next section). Men with smegma or phimosis have an increased risk of penile cancer. The later a man is circumcised the more likely it is that one of these conditions will occur first. Also, circumcised men are less likely to get and stay infected with the human papilloma virus (HPV), even after accounting for differences in sexual behavior. Again, the later a circumcision is done, the more likely that a man will be infected with HPV before the procedure.
In weighing the risks and benefits of circumcision, doctors consider the fact that penile cancer is very uncommon in the United States, even among uncircumcised men. Neither the American Academy of Pediatrics nor the Canadian Academy of Pediatrics recommends routine circumcision of newborns. In the end, decisions about circumcision are highly personal and depend more on social and religious factors than on medical evidence.
Phimosis and smegma
Uncircumcised men with certain conditions may be at higher risk for penile cancer.
In men who are not circumcised, the foreskin can sometimes become tight and difficult to retract. This condition is known as phimosis. Penile cancer is more common in men with phimosis. The reason for this is not clear. Phimosis can often be prevented by retracting the foreskin when washing the penis.
Sometimes secretions can build up underneath the intact foreskin. If the area under the foreskin isn't cleaned well, these secretions build up enough to become something called smegma. Smegma is a thick, sometimes smelly substance found under the foreskin. It is made up of oily secretions from the skin, along with dead skin cells and bacteria. It is more common in men with phimosis, but can occur in anyone with a foreskin, if the foreskin is not regularly retracted to clean the head of the penis.
Some older studies have suggested a link between smegma and penile cancer, and in the past some experts were concerned that smegma may also contain compounds that can cause cancer. Most experts now believe that smegma itself probably doesn't cause penile cancer, but it can irritate and inflame the penis, which may increase the risk of cancer. It may also make it harder to see very early cancers. Men can prevent smegma from building up simply by washing the penis with the foreskin retracted.
Human papilloma virus infection
Human papilloma virus (HPV) is a group of more than 100 related viruses. They are called papilloma viruses because some of them cause a type of growth called a papilloma. Papillomas are not cancers, and are more commonly called warts. Different HPV types cause different types of warts in various parts of the body. Some types cause common warts on the hands and feet. Other types tend to cause warts on the lips or tongue.
Certain HPV types can infect the outer female and male genital organs and the anal area, causing raised, bumpy warts. These warts may barely be visible or they may be several inches across. The medical term for genital warts is condyloma acuminatum. Two types of HPV, HPV 6 and HPV 11, cause most cases of genital warts. These 2 types are seldom linked to cancer, and so are called low-risk types of HPV. However, other HPV types have been linked with cancers and are known as high-risk types of HPV. These include HPV 16, HPV 18, HPV 31, as well as others. Infection with a high-risk HPV may produce no visible signs until pre-cancerous changes or cancer develops.
HPV infection is found in about half of all penile cancers. Researchers believe that infection with HPV is an important risk factor for penile cancer. HPV infection is also linked to many other cancers, including cancers of the cervix, vagina, and vulva in women and cancers of the anus in men and women. It is also a factor in some throat cancers (in men and women).
HPV is passed from one person to another during skin-to-skin contact with an infected area of the body. HPV can be spread during sex -- including vaginal intercourse, anal intercourse, and oral sex – but sex doesn't have to occur for the infection to spread. All that is needed is skin-to-skin contact with an area of the body infected with HPV. Infection with HPV seems to be able to be spread from one part of the body to another, for example, infection may start in the penis and then spread to the anus. The only way to completely prevent anal and genital HPV infection may be to never allow another person to have contact with those areas of the body.
HPV infection is common. One study found that about half of men 18 and older have a genital HPV infection at any point in time. In most people, the body is able to clear the infection on its own. In some, however, the infection does not go away and becomes chronic. Chronic infection, especially with high-risk HPV types, can eventually cause certain cancers, including penile cancer.
Men who smoke are more likely to develop penile cancer than those who do not smoke. Smokers who have HPV infections have an even higher risk. Smoking exposes your body to many cancer-causing chemicals. These harmful substances are inhaled into the lungs, where they are absorbed into the blood. While in the bloodstream, they can travel throughout the body to cause cancer in many different areas. Researchers believe that these substances damage the DNA of cells in the penis, which can lead to the development of penile cancer. Smoking also increases the risk of HPV infection, likely due to effects on immune function.
UV light treatment of psoriasis
Men who have a skin disease called psoriasis are sometimes treated with drugs called psoralens, followed by exposure of the body to an ultraviolet A (UVA) light source. This is known as PUVA therapy. Men who have received this treatment have been found to have a higher rate of penile cancer. Because of this risk, men being treated with PUVA now have their genitals covered during treatment.
The risk of penile cancer goes up with age. About 4 out of 5 cases of the disease are diagnosed in men over age 55.
Men with AIDS (acquired immunodeficiency syndrome) have a higher risk of penile cancer. This higher risk seems to be related to their lowered immune response, but lifestyle factors may also play a role. In some studies, men with penile cancer who were HIV-positive were more likely to smoke and to be infected with HPV than HIV-negative men with penile cancer.
Last Medical Review: 05/02/2012
Last Revised: 01/17/2013