Screening for HPV-caused Cancers
Before diving in to the questions below, you might want to read What Cancer Screening Tests Really Tell Us. This information from the National Cancer Institute clearly explains some of the challenges involved, and how misleading some cancer screening statistics can be.
Is screening recommended to find HPV-caused cancers?Open or CloseFor many years, the only screening tests recommended by the U.S. Preventive Services Task Force (USPSTF) for HPV-caused cancers was the Pap test for cervical malignancies. This test has been the gold standard for detecting precancerous cells of the cervix that may develop into cancer. Recently, however, it has been proposed that the Pap test can be replaced by molecular tests that screen for the presence of the HPV virus. The USPSTF issued its latest recommendations in 2018 for cervical cancer screening, which now say that women 30 and older can drop the traditional Pap tests every 3 years in favor of testing for human papillomavirus (HPV) every 5 years, if they choose to.
Here are the details:
Women 21-29 should receive a pap test every 3 years to check the cervical lining for abnormal cells.
Women 30-65 should receive either a pap test every 3 years, an HPV test every 5 years, or a combination of both every 5 years.
Healthy women younger than 21 most likely don't need any screening.
Women older than 65 who've had normal testing in recent prior years likely don't need any screening.
Healthy women who've had a hysterectomy with cervix removal likely do not need screening.
If you’re interested in the details of these molecular tests for HPV, the Pan American Health Organization has published a review detailing how the tests work in their Summary of Commercially Available HPV Tests, or look at this Powerpoint presentation from Prof. Dr. Elizaveta Padalko from 2015 HPV Diagnosis: Current HPV Tests published by the International Centre for Reproductive Health.
A 2015 paper in Science Translational Medicine suggests that tumor DNA (somatic mutations or human papillomavirus genes) in the saliva and plasma could be a potentially valuable biomarker for detection of head and neck cancers caused by HPV. Wang Y et al Detection of somatic mutations and HPV in the saliva and plasma of patients with head and neck squamous cell carcinomas Sci Transl Med. 2015 June 24; 7(293): 293ra104. doi:10.1126/scitranslmed.aaa8507.
Why aren’t there other screening tests for HPV?Open or CloseThere are several reasons. It would be technically possible to test various other tissues (e.g. the oral cavity, or the anus) to see if one has been infected with a cancer causing strain of HPV. However, it’s very clear that only a very small percentage of people infected with these strains will actually develop cancers (see the Epidemiology of HPV Cancers page). Most won’t because their immune system will successfully fight off the virus, a process that can take months to several years. Because of the expenses involved in testing, and the real dangers of scaring people by telling them they have a cancer causing virus (even though the chances of them actually developing cancer are very low), this type of screening is not generally done.
Random detection of HPV DNA in an oral/ oropharyngeal swab or saliva sample has no known utility as a screening test, because most patients will clear the infection without long-term consequences, and a positive saliva test is unlikely to direct a clinician to the anatomical site of an early (silent) cancer.
Reference: Pytynia KB et al Epidemiology of HPV-associated oropharyngeal cancer Oral Oncol. 2014 May ; 50(5): 380–386. doi:10.1016/j.oraloncology.2013.12.019.
A more recent trend is to have dental offices screen patient for visible signs of oral cancer, which is not a bad idea. Tumors caught this way could then be treated in a standard way. However, the fact that your dentist might not find anything doesn’t mean that you don’t have an oral tumor. It could be hidden in your throat past what your dentist can observe. Tonsillar HPV tumors start out in the tonsillar crypts, which are deeply buried at the back of the throat and are not visible in the mouth at an early stage. If you’re going to the dentist, they should really be vigilant in looking for oral cancers, whether those caused by HPV, or caused by something else.
You can read what the US Preventative Services Task Force has to say about oral cancer screening (i.e. the pros and cons) here. Here’s a short version of their conclusions:
“In the current recommendation, the USPSTF found inadequate evidence that the oral screening examination accurately detects oral cancer. It also found inadequate evidence that screening for oral cancer and treatment of screen-detected oral cancer improves morbidity or mortality. The evidence for screening for oral cancer remains insufficient; therefore, the USPSTF is unable to make a recommendation in favor of or against screening.”
There are no frequently used screening tests for cancers of the penis, vagina, vulva, or anus.
Should I be screened to see if I’ve been infected by HPV?Open or CloseThis would not only be difficult to do, it wouldn’t be terribly helpful in most cases. It’s possible to detect the virus using tissue swabs combined with molecular diagnostics, but you would need to test a number of tissues (for example, women would need to have their mouths, vulva, vagina, rectum, and cervixes tested). If you test negative, it’s possible that the swabbing could have missed a small area where the infection has taken hold. If you test positive, especially for one of the more common cancer causing strains (e.g. 16 and 18), then you are still highly unlikely to develop an HPV caused cancer (see the question and answer below). Being told that you are carrying a cancer causing virus can have significant negative psychological effects on people, even though in most instances these infections will not develop into cancer.
It’s for these reasons that screening tests are focused on checking for cancer, not merely for the presence of the virus. The one exception is cervical cancer screening, as explained in the answer to the first question above.
If you’re HPV positive, does that mean you will develop cancer?Open or CloseNot at all. In fact, the vast majority of people who are infected will never show any signs of the infection at all. Their immune systems will fight and eventually eliminate the virus. Consider that the number of people in the US infected with HPV is estimated to be about 79 million, with 14 million more infected every year. High-risk genital HPV infections affect about 25 percent of men and 20 percent of women. The prevalence of any type of oral HPV infection among adults ages 18-69 in 2011-2014 was about 7 percent, while the prevalence of high-risk oral HPV infection was 4 percent.
Now lets do some calculations.With 79 million people infected, about 20 million men and about 16 million women will have the high risk genital HPV infections. But the number of men who were diagnosed with any HPV associated cancers in 2015 was 18,939 (less than 0.1%), and the number of women diagnosed with any HPV-associated cancer that same year was 24,432 (about 0.15%). This means that less than 1 in a thousand infected men, and less than 2 in a thousand infected women, will be diagnosed with an HPV cancer each year.
This data has also been broken down by various ethnic/racial groups (white, Asian, hispanic, and black). Here are some of the findings:
The prevalence of oral high risk HPV strains was lower in Asians than other groups.
The prevalence of high-risk oral HPV was higher among men than women in all race and Hispanic groups, although the difference was not significant among non-Hispanic Asian adults.
The prevalence of any genital HPV was lowest among non-Hispanic Asian adults and highest among non-Hispanic black adults.
How are HPV-caused cancers discovered? What are the symptoms?Open or CloseThese cancers are generally found once symptoms present themselves, except for cervical cancer, where abnormal cells (that have not yet become cancer) are often first detected by the Pap smear (or now, by swabs that look for the presence of HPV DNA or RNA). Details about the rational for using HPV testing in place of the Pap test can be found here.
Cancers caused by HPV are found in a variety of tissues. These include the cervix, vagina, and vulva in women, the penis in men, and the oral cavity and anus in both men and women. Samples of tissue are generally removed and then tested using a variety of molecular techniques to determine if the tissue contains the HPV virus, and, if so, what strain of the virus it is. Knowing if a cancer is positive or negative for HPV can make a significant difference in choosing treatment options and in calculating the potential outcomes for the patient following treatment. This is because the virus actually plays a primary role in the process by which the normal cells are transformed into cancer cells.
Here are some of the symptoms of oral cavity and oropharyngeal cancer:
- A sore in the mouth that doesn't heal (common).
- Pain in the mouth that doesn’t go away (also very common).
- A lump or thickening in the cheek.
- A white or red patch on the gums, tongue, tonsil, or lining of the mouth.
- A sore throat or a feeling that something is caught in the throat that doesn’t go away.
- Trouble chewing or swallowing.
- Trouble moving the jaw or tongue.
- Numbness of the tongue or other area of the mouth.
- Swelling of the jaw that causes dentures to fit poorly or become uncomfortable.
- Loosening of the teeth or pain around the teeth or jaw.
- Voice changes.
- A lump or mass in the neck (most common, see below).
- Weight loss.
- Constant bad breath.
The most common symptom (for people who are later diagnosed with an HPV-caused cancer) that brings them to the doctor’s office are lumps in the neck.These lumps are caused by the migration of cancer cells from the oropharynx into the lymph nodes located there.
Here are some of the symptoms of anal cancers:
- Rectal bleeding.
- Rectal itching.
- A lump or mass at the anal opening.
- Pain or a feeling of fullness in the anal area.
- Narrowing of stool or other changes in bowel movements.
- Abnormal discharge from the anus.
- Swollen lymph nodes in the anal or groin areas.
Here are some of the symptoms of vaginal cancer:
- Unusual vaginal bleeding, for example, after intercourse or after menopause.
- Watery vaginal discharge.
- A lump or mass in your vagina.
- Painful urination.
- Frequent urination.
- Pelvic pain.
Here are some of the symptoms of vulvar cancer:
- An area on the vulva that looks different from normal – it could be lighter or darker than the normal skin around it, or look red or pink.
- A bump or lump, which could be red, pink, or white and could have a wart-like or raw surface or feel rough or thick.
- Thickening of the skin of the vulva.
- Pain or burning.
- Bleeding or discharge not related to the normal menstrual period.
- An open sore (especially if it lasts for a month or more).
Here are some of the symptoms of cervical cancer:
- Abnormal vaginal bleeding, such as bleeding after vaginal sex, bleeding after menopause, bleeding and spotting between periods, and having (menstrual) periods that are longer or heavier than usual. Bleeding after douching or after a pelvic exam may also occur.
- An unusual discharge from the vagina − the discharge may contain some blood and may occur between your periods or after menopause.
- Pain during sex.
Here are some of the symptoms of penile cancer:
- An area of skin becoming thicker.
- Changes in the skin color.
- A lump.
- An ulcer (sore) that might bleed.
- A reddish, velvety rash under the foreskin.
- Small, crusty bumps.
- Flat, bluish-brown growths.
- Smelly discharge (fluid) or bleeding under the foreskin.
What are the guidelines for determining if a head and neck cancer tumor is positive for HPV?Open or CloseThere are updated guidelines that were published in Sept. 2018 by the American Society of Clinical Oncology (ASCO). They are:
- HPV tumor status should be determined for newly diagnosed oropharyngeal squamous cell carcinomas.
- HPV tumor status testing may be performed by surrogate marker p16 immunohistochemistry either on the primary tumor or from cervical nodal metastases only if an oropharyngeal primary tumor is present.
- The threshold for positivity is at least 70% nuclear and cytoplasmic expression with at least moderate to strong intensity.
- Additional confirmatory testing may be done at the discretion of the pathologist or treating clinician.
- Pathologists should not routinely determine HPV tumor status in non-squamous carcinomas of the oropharynx or non-oropharyngeal squamous cell carcinomas of the head and neck.
- When there is uncertainty of histologic type or whether a poorly differentiated oropharyngeal tumor is non-squamous, HPV tumor status testing may be warranted and at the discretion of the pathologist or treating clinician.
Additional information is available from ASCO.