The United States is experiencing a “dramatic and concerning” rise in the rate of new anal cancer cases and deaths from the disease, particularly among young black men and elderly women, researchers reported Tuesday.

The incidence of squamous cell carcinoma of the anus — the most common type of anal cancer — rose 2.7 percent per year over a recent 15-year period, while anal cancer mortality rates increased 3.1 percent per year during that time.

At this rate, the disease can be considered as one of the fastest accelerating causes of cancer incidence and mortality in the U.S., said the study’s lead author Ashish Deshmukh, an assistant professor at the UTHealth School of Public Health in Houston.

“The rates are increasing very rapidly,” Deshmukh told the "Today" show. “It’s concerning. Traditionally, our perception of anal cancer has been that it’s one of the rarest forms of cancer and because of that, it’s neglected.”

Actress Farrah Fawcett, who died of the disease in 2009, was one of the first high-profile patients to talk about her diagnosis publicly.

Among some of the startling statistics: The risk of developing anal cancer was five times higher for black men born in the mid-1980s compared to those born in the mid-1940s. That may be because young black men are disproportionately affected by HIV, which raises the risk for developing the cancer, Deshmukh said.

The risk doubled among white men and white women born after 1960. The disease may surpass cervical cancer to become the leading human papillomavirus-linked cancer in elderly women, the study noted. One possible reason: Older people have weaker immune systems, impairing their ability to clear HPV from their bodies, and elderly women outnumber elderly men.

The proportion of cases diagnosed when the cancer had already spread to other parts of the body doubled, which suggests the rise in cases isn’t driven by more intense screening that would catch early-stage tumors, Deshmukh noted.

“It’s really hard to understand what might be causing the rise in incidence and mortality,” he added. Possible reasons include a shift in sexual behaviors in recent decades, including normalization of anal sex and more sexual partners, and the rise in obesity rates, which could be a factor, he said.

For the study, published in the Journal of the National Cancer Institute, researchers analyzed data in U.S. cancer registries from 2001 through 2015. They also looked at causes of death from a database compiled by the National Center for Health Statistics over that time.

They found 68,809 cases of anal cancer and 12,111 deaths from the disease.

The vast majority of these cases are associated with the human papillomavirus, but about three-quarters of American adults don't know HPV causes the disease, a recent study, also led by Deshmukh, found.

He called the findings “shocking.”

What is anal cancer?

It develops when malignant cells form in the tissues of the anus.

About 6,530 people are diagnosed with anal cancer each year, with 91 percent of the cases believed to be caused by HPV, according to the Centers for Disease Control and Prevention.

How to prevent HPV-related cancers

HPV is the most common sexually transmitted infection in the U.S. Most sexually active adults in their 20s have been exposed to it, but for most, the infections clear up without causing harm, NBC News medical contributor Dr. Natalie Azar said.

It’s important to remember the vast majority of people who have it don’t get anal cancer, the American Cancer Society said.

HPV also causes almost all cervical cancers and many cancers of the vagina, vulva and penis.

An HPV vaccine is available to protect against harmful strains of the virus and it’s the only vaccine that actually prevents cancer. The earlier you get it, the more effective it is, said Dr. Alanna Levine, a pediatrician and the spokeswoman for the American Academy of Pediatrics. She recommended it for both boys and girls. "It's made an incredible difference," she said.

What are the risk factors for anal cancer?

Besides being infected with HPV, the National Cancer Institute says they include:

Having many sexual partners

Having anal sex

Being over 50

Experiencing frequent anal redness, swelling and soreness

Having anal fistulas (abnormal openings)

Smoking

What are the symptoms?

They can be uncomfortable to talk about with a doctor, but early detection is key:

Bleeding from the anus or rectum, which is often the first sign of the disease

Pain or pressure in the area around the anus

Itching or discharge

A lump near the anus

A change in bowel movements, like narrowing of stools

How is the cancer diagnosed?

It’s often found when a doctor performs a digital rectal examination — inserting a gloved, lubricated finger into the lower part of the rectum to feel for lumps. That’s how actress Marcia Cross’ cancer was discovered during a routine medical appointment. She credits it for saving her life.

Thin, flexible instruments with lights and cameras can also help doctors take a closer look at any suspicious spots and a biopsy can determine if cancer is present.

Imaging scans are used to find if the cancer has spread to other parts of the body.

What is the treatment?

It depends where the tumor is located and whether it has metastasized.

Standard treatment includes radiation, chemotherapy and surgery to remove the tumor.

Doctors can also remove the anus, the rectum and part of the colon in a major operation called an abdominoperineal resection.

It’s used only if other treatments don’t work or if the cancer comes back after treatment, according to the American Cancer Society.

What is the outlook for patients?

As with all cancers, early detection is extremely important. More than 80 percent of patients whose anal cancer had not spread lived for at least five more years after diagnosis. That number dropped to 30 percent when the cancer had spread to the liver or lungs.