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.
1) 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.
2) 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.
3) 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.
4) 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.
5) 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.
6) How do they determine 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.
7) What’s the link between failure to find oropharyngeal tumors via screening programs, and “cancers of unknown origin” aka “cancers of unknown primary (CUP)”?Open or CloseThe most common symptom that leads patients with HPV-caused oral cancers to visit their doctors is a lump in the neck. This lump may be caused by the growth of cancer cells in the lymph nodes in the neck. It can also be caused by other things that are NOT cancer. The lump will often be biopsied by doing a fine needle aspirate, which can reveal if cancer cells are actually present, and if they are HPV positive or not. The finding of a lump will lead your doctor to look for the place where a cancer might have actually started (again, if it is cancer) before it spread to the lymph nodes. Common places to look would be the tonsils, base of the tongue, and back of the throat. Sometimes, however, no source of the cancer can be readily found in these locations, in which case the tumor may be classified as being of unknown origin. About 3 to 5 percent of head and neck cancers are classified as cancers of unknown origin. To learn more about cancers of unknown origin, look at this page on the website of Beyond Five - The Face of Head and Neck Cancer.
As to what percentage of these “cancers with unknown origins” are actually HPV positive, well, that answer is complicated. Results have varied in a number of different studies for reasons explained in the paper listed below. Here’s an important observation: as with other oropharyngeal cancers, having a cancer of unknown origin that is HPV positive is generally associated with a better outcome (i.e. it responds better to treatment) than those that are HPV negative.
Reference: Sivars et al Human Papillomavirus as a Diagnostic and Prognostic Tool in Cancer of Unknown Primary in the Head and Neck Region Anticancer Research 36: 487-494 (2016) FREE ARTICLE
8) Does HPV play a role in the development of cervical “pre-cancers”?Open or CloseYes. Changes to cells in the cervix caused by the virus may be classified as pre-cancerous, and may lead to outright cervical cancer over time. These changes to the cervix can be detected early, leading to treatment that prevents the development of cervical cancer. Keep in mind that most women who have abnormal cervical screening test results do NOT have cervical cancer.
Details can be found on the Understanding Cervical Changes: Next Steps After an Abnormal Screening Test page of the National Cancer Institute website.
A number of studies have been conducted to determine if at-home HPV tests may be useful for cervical cancer prevention. These studies are designed specifically for screening of women who, for a variety of reasons, have difficulty visiting their doctors to be tested for cervical pre-cancers. Programs have been tested in Norway, Sweden, the Netherlands, and in the US. The study in the US found that 78% of the women used the testing kits they were sent, and that 12.4% of women who swabbed their vaginas (close to the cervix) were found to harbor high risk (i.e. cancer causing strains) of HPV. This percentage is nearly the same as what is observed in doctors offices. These women were informed that they should visit their doctors for follow up care.
You can read about this study here, or look at the original paper: Des Marias et al
Home Self-Collection by Mail to Test for Human Papillomavirus and Sexually Transmitted Infections. Obstetrics and Gynecology Nov. 5, 2018.
9) Is there a blood test that can be used to screen head and neck cancer patients and determine if they are likely to have a recurrence?Open or CloseI don’t know of any such test on the market, but there is one in development from researchers at the University of North Carolina Lineberger Comprehensive Cancer Center. It’s designed to measure HPV fragments that have been released into the blood by dead or dying cancer cells. It can distinguish these HPV fragments from HPV that may be present from an active infection. The test is being developed as an alternative way of following patients after their treatments have concluded. If it works, it may enable doctors to begin treatment earlier for tumors that were not eradicated on previous treatments. It would also save money on CT scans, and by avoiding these scans patients would be spared excess radiation exposure. Since the test is measuring HPV fragments, it would not be appropriate for patients who have head and neck cancers that are HPV negative. In theory this test could also work on other HPV positive cancers such as cervical and anal cancers.
Details can be found at HPV blood test shows promise for tracking head and neck cancer after treatment.
10) What’s the story on efforts to develop a new type of screening test for cervical cancer that’s not based on either cytology (like the Pap test) or on HPV status, but is instead based on epigenomics i.e. a measure of DNA methylation? Is this new test promising?Open or CloseThis is an interesting development that may lead to a less expensive and more accurate test than a combination of standard Pap smears with HPV testing. The idea is to look for a “signature” methylation pattern in the DNA of cells scraped from the cervix that indicates the presence of cervical precancers that are likely to develop into outright cancers. Pap smears can detect only about half of cervical precancers, and HPV tests only determine if a cancer causing form of the virus is present, not whether or not it will cause cancer. The new test, called 5S, should be cheaper if it proves out than existing tests, and require fewer visits to the clinic. That’s because it detects a greater proportion of high-grade disease with a high short-term risk of cervical cancer during an initial screen than the other approaches.
Here’s the paper:
Cook et al Evaluation of a validated methylation triage signature for human papillomavirus positive women in the HPV FOCAL cervical cancer screening trial. Int. J. Cancer: 9999, 1–9 (2018) (FREE DOWNLOAD).
11) What was learned from a study in which people were screened for oral cancers? Isn’t it easy to find cancer this way?Open or CloseWhile it would seem that cancer screening programs should be easy to run, in practice they turn out to be more problematic than most people would think. In one study, otolaryngologists (doctors who specialize in head and neck diseases) were asked to screen individuals who came to a free community clinic. 761 people were screened by being asked about symptoms (medical history) as well as being given a physical exam. Amazingly, 47% of the people (356) screened had one or more symptoms that could be indicative of oral cancer. The most frequent symptoms were hoarseness and difficulty swallowing. It was suspected that 41 of these 356 people actually had cancer. Despite being told this, 22 never returned for a follow up visit. Twelve individuals had a negative workup, and seven were actually confirmed to have either pre-malignant changes or cancer. Four cases of squamous cell carcinoma were found in this group. Interestingly, these four were in the vocal folds, the supra glottis, or the pharyngeal wall.
The data illustrates the problem with screening programs. Most oral cancer screenings are done by dentists, but in this report it was otolaryngologists who did the study. Lots of people had one or more cancer symptoms, but many people never returned for follow up care. While many people had broad cancer symptoms, in the end less than 1 in 100 people actually had cancer. And only one of those four cancers might have been seen in a screen by dentists.
Shuman et al Demographics and Efficacy of Head and Neck Cancer Screening. Otolaryngol Head Neck Surg. 2010 September ; 143(3): . doi:10.1016/j.otohns.2010.05.029.
While cancer screening programs in general sound good, the results do not always meet up with expectations. In a recent review, looking at breast, colon, prostate, and lung cancer screening programs, the percentage of deaths prevented by the screen ranged from 9 to 27 percent (that is, the screen failed to prevent 73 to 91 percent of the deaths). Often glossed over is the harms that the screening programs can inflict, including radiation exposure, colon puncturing, infections following prostate cancer biopsies, and worries inflicted by false positive results.
Kim et al Cancer screening: A modest proposal for prevention. Cleveland Clinic J. Medicine 86, (3), 2019. doi:10.3949/ccjm.86a.18092