The "Courtesy of the Red, White and Blue" singer "passed peacefully last night on Feb. 5 surrounded by his family," a statement posted on X (formerly called Twitter) read. "He fought his fight with grace and courage."
While the statement didn't specify his cause of death, Keith was diagnosed with stomach cancer in 2022. He told E! News last year that his cancer journey was "a little bit of a roller coaster."
“It's always zero to 60 and 60 to zero, but I feel good today," he said at the time.
Keith first shared his diagnosis in a June 2022 Instagram post, noting that he had been diagnosed with stomach cancer the previous fall. "I’ve spent the last six months receiving chemo, radiation and surgery," he wrote. "So far, so good. I need time to breathe, recover and relax."
Keith's death raises a lot of questions about stomach cancer, including who it typically affects and how it's treated. Here's what you need to know.
What is stomach cancer?
Stomach cancer, also known as gastric cancer, is cancer that starts in the cells that line the stomach, according to the National Cancer Institute (NCI). There are several types of stomach cancer, but the most common is adenocarcinoma of the stomach, which starts in the mucus-producing cells in the innermost lining of the stomach, the NCI says.
"Cancer in the stomach can either grow as a tumor or can spread along the layers of the wall," Dr. Rutika Mehta, a medical oncologist with Moffitt Cancer Center, tells Yahoo Life.
"Stomach cancer most commonly occurs as a gradual change in the cells lining the stomach over time," Dr. Christopher Cann, assistant professor in the Department of Hematology/Oncology, Fox Chase Cancer Center, tells Yahoo Life. "Inflammation of these cells results in cellular damage that leads to alterations in cell function and mutations in the cell DNA. The cumulative damage to these cells can eventually develop into a cancer, which has a risk to cause a problem not only within the stomach itself, but also spread to other organs."
How common is stomach cancer?
An estimated 26,890 new cases of stomach cancer are expected to be diagnosed in the U.S. this year, according to the American Cancer Society (ACS). About 10,880 people are expected to die from stomach cancer in the U.S. this year, per the ACS.
Stomach cancer mostly affects older people, but aside from age, risk factors include being overweight or obese; eating a diet high in salted foods and grilled or processed meats with few or no fruits; smoking; consuming high amounts of alcohol and having a family history of stomach cancer.
"Men are slightly more at risk than women," Mehta says. "The average age of diagnosis is 68 years, but the rate of new diagnosis is on the rise for younger people."
The ACS also notes that, in the U.S., the disease is more common among Hispanic Americans, African Americans, Native Americans, Asian Americans and Pacific Islanders compared with non-Hispanic white people.
Stomach cancer symptoms
Stomach cancer usually doesn't have symptoms early on, or they're vague if a patient experiences them, the ACS says. However, if someone has symptoms, they may include:
Indigestion and stomach discomfort
A bloated feeling after eating
Loss of appetite
When stomach cancer spreads beyond the stomach to other parts of the body, the NCI says it can cause:
Unexplained weight loss
Build-up of fluid in the abdomen
"The symptoms can be very subtle, but they can also be more obvious — there really is a wide variety," Dr. Anton Bilchik, surgical oncologist, chief of medicine and director of the Gastrointestinal and Hepatobiliary Program at Providence Saint John's Cancer Institute in Santa Monica, Calif., tells Yahoo Life. "Anyone who has stomach discomfort that doesn't go away, unexplained weight loss or unexplained throwing up should see a doctor."
Stomach cancer treatment
Stomach cancer treatment usually depends on the patient and how advanced their cancer is, the ACS says. However, it is often treated with surgery, chemotherapy, targeted drug therapy, immunotherapy or radiation therapy, with the ACS noting that the best approaches use two or more types of treatment.
"Having the right diagnosis and staging is critical to deciding which treatment is the best," Mehta says. "I urge people diagnosed with stomach cancer to seek for a multidisciplinary consultation."
While survival rates depend a lot on where the cancer is located and how much it has spread, the five-year survival rate of patients with stomach cancer is 36%.
"For patients whose cancer has not spread, surgery is a chance for 'cure,'" Mehta says. But, she notes, there is a 40 to 50% risk that the cancer will come back, especially during the first two years after surgery.
"In more advanced cases, we are not yet at a point where we can offer patients a 'cure,'" she adds. However, there is treatment for advanced stomach cancer cases that can "prolong survival and give them a better quality of life."