Instances of HPV-caused throat cancer are on the rise and a lack of awareness means some cases are getting overlooked.

There are different anatomic parts of the throat where cancer occurs. In the U.S. and Canada, 80 to 90 percent of cancers found in an area known as the oropharynx are now caused by HPV — the human papilloma virus, Tucson head and neck cancer surgeon Dr. Steven J. Wang says. The oropharynx includes the back one-third of the tongue, the soft palate, the side and back walls of the throat, and the tonsils.

“It’s really a remarkable change from when I was in training in the late ’90s. It’s completely turned around in terms of the cause of this particular type of cancer,” Wang said in a recent interview.

“Among the public, even among the medical community, there is not a lot of awareness of this. For the vast majority of doctors this is something that wasn’t even on the horizon when they were in medical school doing their training. This is a relatively recent phenomenon.”

Wang is interim chair of the Department of Otolaryngology/Head and Neck Surgery at the University of Arizona College of Medicine in Tucson. He came to Tucson from the University of San Francisco in May and though he’s been in clinical practice here just a few weeks, he’s already seen six cases of HPV-caused throat cancer. Throat cancer is a lay term. The medical term oral cancer includes both oral cavity (mouth) and oropharynx cancers.

“Throat cancer certainly doesn’t have the same visibility as other cancers. But what people have in their mind, including in the medical community, is that throat cancer is predominantly caused by tobacco and alcohol,” Wang said.

“That remains a very important cause and I wouldn’t say that is no longer important. It still is. But what we are seeing increasingly is patients who are getting throat cancers who don’t have historic risks like smoking or alcohol. They are often younger.”

The age range for HPV-caused throat cancers is is typically late 40s to early 60s — about five to 10 years younger than the average tobacco-related throat cancer patient. Not all throat cancers are related to HPV, alcohol, or tobacco, he confirmed. Some patients have no known risk factors.

Usually when people think of HPV they think of cervical cancer. But within the next decade, oropharyngeal throat cancer is expected to become the leading HPV virus-caused cancer in the U.S., Wang said.

One of the reasons is that there is no easy, reliable screening test for throat cancer that’s analogous to the PAP smear test for cervical cancer, he said.

The Centers for Disease Control and Prevention says an estimated 3,100 new cases of HPV-associated oropharyngeal cancers are diagnosed in women and 12,638 are diagnosed in men each year in the U.S.

Here are five things to know about HPV-caused throat cancer:

The symptoms are easy to miss.

Since people who develop HPV-related throat cancer are often otherwise healthy, they could think a lump in their neck is a swollen lymph gland. Another symptom is a persistent sore throat, which could be mistaken for a lingering cold.

Tumors often begin as a small growth in the back of the throat, which can be easy to miss.

“Many doctors and patients have an incorrect stereotype of what the typical throat cancer patient is,” Wang said. “These are people who are healthy. They may have never had a health problem in their lives.”

With appropriate treatment, the prognosis is good.

HPV-caused cancers tend to have a high rate of metastasis. But Wang said the good news is that compared with non-HPV oral cancers, the ones caused by HPV have both a better prognosis and typically a better response to treatment. The cure rates, with appropriate treatment, can be in the 85 to 95 percent range.

Since oral cancer involves speaking and swallowing, early identification helps to minimize damage. Treatment can include surgery, radiation, chemotherapy and sometimes combinations of those. Even in advanced cases the prognosis is good, but earlier detection means less intense treatments.

Recent development of less radical and less invasive surgical techniques have improved outcomes that at one time could leave people with disfiguring scars and other impairments.

Wang uses a Da Vinci robot to pass through the patient’s mouth to cut out cancer, which allows him to more precisely avoid critical structures like the voice box and preserve as much of the tongue as possible.

Banner-University Medical Center Tucson has a head and neck tumor board that evaluates patients and tailor treatment options to their needs.

Transmission is primarily through oral sex.

The risk rises in proportion to the number of oral sex partners someone has had.

Still, most people exposed to HPV are unaffected by it.

For reasons that are still being studied, a small percentage of those exposed go on to develop persistent HPV infection. Not everyone with HPV infections goes on to develop cancer, but some of them will.

Men are four times more likely to be affected than women.

“You can certainly postulate or speculate, but we don’t know the answer,” Wang said. “Perhaps the virus more easily transmits going from a woman to a man than the other way around...But that is purely speculation.”

The HPV vaccine, recommended for 11 and 12 year olds is likely a preventive measure.

“All the studies that went into the development of these HPV vaccines were showing that it demonstrated efficacy against cervical cancer and other uro-genital cancers, such as anal cancers, for instance,” Wang said.

“We don’t actually have data that can demonstrate this vaccine, when administered to a person, prevents oral cancer. It probably does. ... There are some limited studies that suggest it does.”

But since HPV-caused cancers develop over a long period of time, the impact of the HPV vaccine to reduce the incidence of oropharynx cancer will be delayed, likely decades from now.

Contact health reporter Stephanie Innes at 573-4134 or email sinnes@tucson.com. On Twitter: @stephanieinnes