Happy Days star Erin Moran was being treated for throat cancer before she died at age 56, the actress’s friend and former co-star Anson Williams told People this week. Williams said that Moran was unable to speak in her final days; reports from local law enforcement also confirmed that she’d been relying on a feeding tube in her stomach and that she likely died from stage IV cancer.

Abie Mendelsohn, MD, assistant professor-in-residence at the David Geffen School of Medicine at UCLA and a member of UCLA's Jonsson Comprehensive Cancer Center, was not involved in Moran’s treatment, but he does see many patients each year with various types and stages of throat cancer. Here’s what he wants readers to know about this scary-sounding—but often treatable—condition.

Throat cancer can mean several things

It’s unclear what type of throat cancer Moran had, but the term is usually used to describe either cancer of the larynx (also known as the voicebox) or the pharynx (the upper portion of the throat, behind the mouth and nasal cavity). Cancers of the tongue or tonsils, similar to the type actor Michael Douglas had, are also sometimes referred to as throat cancer.

Cancerous tumors that form on the larynx itself usually cause a change in voice and, if they become large enough, can cause difficulty speaking. Tumors in other parts of the throat may not be as obvious, but nearly all throat cancers cause symptoms eventually. Other symptoms can include persistent sore throat, earaches, and pain when swallowing.

“Often the first sign is something in the lymph nodes,” says Dr. Mendelsohn. “I have guys come in and say that when they were shaving they noticed a new bump on their neck, which usually means the cancer has already advanced.”

It’s not just an old man’s disease

“We used to think that only really old men who smoked a lot of cigarettes would get throat cancer, says Dr. Mendelsohn. “And, historically, that was true—but it’s rapidly changing.” Now, Dr. Mendelsohn says many of the patients he sees for throat cancer are in their 50s, and some even younger.

According to the American Cancer Society, nearly 50,000 people will be diagnosed with oropharyngeal cancer (another name for head and neck cancer) this year, and 10,000 are expected to die from it. The average age of diagnosis is 62, but one-quarter of patients are younger than 55.

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It can be caused by the HPV virus

Doctors think the throat cancer increase in younger people is linked to the prevalence of human papillomavirus (HPV)—a common sexually transmitted infection that can also cause herpes, genital warts, and, in women, cervical cancer. HPV-related throat cancers are more common in men, but they also affect women.

Oral HPV, like genital HPV, is very common: It’s estimated that one in four Americans has HPV currently living in their mouth, says Dr. Mendelsohn. But only a few high-risk strains of the virus can cause cancer, he says, and only for a small percentage of people who have these strains.

Scientists don’t know for sure how people contract oral HPV, but some studies suggest oral sex and open-mouth kissing amy be to blame. And because the virus can lay dormant for decades, even people in long-term monogamous relationships can develop cancer from it—either from their current partner or a partner from long ago.

Luckily, says Dr. Mendelsohn, HPV-related throat cancers generally respond well to treatment. And even more fortunately, there’s now a safe and effective HPV vaccine available for children and young adults, which can greatly reduce their risk of getting these types of cancer in the future.

Smoking, alcohol use, and genetics are also risk factors

Exposure to cigarette and other types of smoke also put people at increased risk for throat cancer. In fact, throat cancers related to heavy smoking are often the most aggressive and hard to treat, says Dr. Mendelsohn.

Frequent alcohol use also raises the risk of throat and other types of cancer, says Dr. Mendelsohn, as does untreated gastroesophogeal reflux disorder (GERD). So does family history: “We know there is a genetic component as well,” he says.

It’s often treatable—even in stage IV

Despite the fact that throat cancer rates are up, Dr. Mendelsohn says the news isn’t all bad. “The success rates are through the roof in terms of cancer’s responsiveness to current treatment, as long as patients are diagnosed and treated in a reasonable timeframe,” he says.

That’s why he says it’s so important for people to see their doctors sooner, rather than later, if they have a suspicious symptom. “If we can identify cancer within about 6 to 8 weeks of when somebody first feels something, prognosis is usually excellent,” he says.

Still, it’s common for Dr. Mendelsohn to see patients who have ignored symptoms for longer than that. “I get people who have been on antibiotics for three or four months and aren’t getting better,” he says. “Any throat issue that doesn’t go away after two weeks really should be checked out.”

Treatment for throat cancer can involve radiation and chemotherapy, but surgical options—including minimally invasive procedures—have also improved greatly in recent years. Even cancers that have reached stage IV (the most advanced stage, which means tumors have spread to other parts of the throat, neck, or lymph nodes) can often be successfully treated.

“It really depends on the severity of the individual cancer,” says Dr. Mendelsohn. “Sometimes stage IV does mean there’s nothing more we can do, but other times it’s definitely not as bleak as it sounds.”

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Patients shouldn’t give up hope

Given the disease’s increased prevalence among younger people, Dr. Mendelsohn says it’s not a shock that Moran had throat cancer. It’s more surprising, he says, that the treatment was not successful.

“We hear about the people who lose the battle, but anyone who unfortunately does have throat cancer still has a lot to be optimistic about,” he says. Treatments today are effective and well tolerated, he says, and “we have a really have good chance of curing many of these patients.”