A new report documents a disturbing rise in the number of cases of cancer related to HPV, a family of sexually transmitted viruses linked to tumors of the cervix, head and neck, and several organs.
The spike in HPV-related cancers defies the generally positive trends in cancer, whose incidence and mortality rates continue to fall slightly each year, according to the report, published online Monday in the Journal of the National Cancer Institute.
HPV, or human papillomavirus, is best known for causing cancer of the cervix and genital warts, both of which can now be prevented by vaccines. But HPV also causes cancers of the vagina, vulva, penis and anus, as well as oral cancers involving the back of the throat, tonsils and base of the tongue.
And while cervical cancer rates have fallen dramatically because of screening tests, rates of other HPV-related cancers are increasing, likely resulting from changes in sexual practices over the past 30 to 40 years.
"This is one of the epidemics of the 21st century," says Otis Brawley, chief medical officer at the American Cancer Society, a co-sponsor of the report. "This is a huge problem."
Trends in HPV-related cancers vary by race and sex. Among the biggest changes from 2000 to 2009:
- Oral cancer rates rose 4.9% in Native American men, 3.9% in white men, 1.7% in white women, 1% among Asian men, with smaller increases among Hispanic men and women.
- Anal cancer rates increased in every group. The largest increases were in black men, at 5.6%; white women, 3.7%; white men, at 2.6%; and Asian men, at 2.1%. Overall rates of anal cancers, which are more common among those with HIV and AIDS, doubled between 1975 and 2009.
- Vulvar cancers increased 1.4% among white women and 0.9% among black women.
- Penile cancers increased 0.5% among Asian men.
HPV is the most common sexually transmitted infection in the world, according to the National Cancer Institute, another co-sponsor of the report. Most sexually active people become infected at some point, although most clear the infection with no lingering effects.
More than 10% of men and 3.6% of women have a current oral HPV infection, according to a study published last year in the Journal of the American Medical Association.
The report should not be "cause for panic," says Ranit Mishori, associate professor of family medicine at Georgetown University School of Medicine, "because these cancers are still not very common."
About 12,200 women a year are diagnosed with cervical cancer, while 7,100 people develop HPV-related oral cancers, according to the Centers for Disease Control and Prevention, another sponsor of the report. If trends continue, oral cancers will overtake cervical cancers as the leading cause of HPV-related tumors by 2020.
Overall, oral cancers have been declining, as fewer Americans smoke or drink heavily, says Richard Schlegel, chairman of pathology at the Georgetown Lombardi Comprehensive Cancer Center.
The proportion of HPV-related oral tumors has increased, however, growing from 16% of all oral cancers in 1984 to 1989, to 72% of these tumors from 2000 to 2004, the report says.
The new HPV vaccines - recommended for both boys and girls at age 11 or 12 - have been shown to protect against cervical, vaginal and vulvar cancers, Mishori notes.
While doctors can find and remove cervical cancers and precancers through screening, there are no early detection methods for cancers of the throat, tonsils and base of the tongue, Brawley says. For many oral cancer patients - who tend to be in their 50s or early 60s - their first symptom is a swollen lymph node. Treatment typically involves radiation, sometimes preceded by chemotherapy.
Researchers haven't tested HPV vaccines on oral cancers, and aren't likely to, Brawley says. Researchers would have to follow study participants for 30 or 40 years to detect any difference in oral cancer rates. Scientists were able to detect a reduction in cervical precancers, however, after only six or seven years, he says.
Still, animal tests suggest that an HPV vaccine would work in oral cancer, Schlegel says. That's because both approved vaccines block HPV 16, a subtype of the virus that causes most of of these cancers.
"If we let it," Brawley says, "the HPV vaccine may prove to be a godsend for head and neck cancers in the United States."
Yet HPV vaccines so far have failed to reach their full potential, the report says. Fewer than half of American teen girls have gotten one or more dose, and only 32% have received all three recommended shots. In comparison, more than 70% of girls in Australia and the United Kingdom have completed all three shots.
According to the report, called the Annual Report to the Nation on the Status of Cancer, the girls most likely to die of cervical cancer are also among the least likely to get an HPV shot: those who are poor, uninsured or living in economically depressed areas of the South.
About half of the 4,000 American women who die of cervical cancer each year have never had a Pap test, which detects cancerous or precancerous cells on the cervix, Brawley says. Doctors can easily remove early cancers or precancers. Most of the other women who died from the disease hadn't had a cervical cancer screening for at least a decade.
The vaccines, which cost about $390 for three shots, have been marketed "to patients who can afford it, not those who need it," says Sheila Rothman, a professor at Columbia University's Mailman School of Public Health in New York. "The vaccine isn't really getting to the groups who need it."