Pancreatic Cancer: Why is 'Game Of Thrones' Actor Wilko Johnson's Condition So Deadly?

Wilko Johnson, the 65-year-old actor who played the part of Ilyn Payne in HBO's "Game of Thrones," has terminal pancreatic cancer and will not be receiving chemotherapy, according to news reports.

"He is currently in good spirits, is not yet suffering any physical effects and can expect to enjoy at least another few months of reasonable health and activity," a statement from Johnson's manager stated, as reported by The Guardian.

In 2012, 43,920 people are estimated to have developed pancreatic cancer and 37,390 people are estimated to have died from the disease, according to the National Cancer Institute.

Pancreatic cancer is notoriously deadly, with 75 percent of people dying within a year of being diagnosed, MyHealthNewsDaily reported. And within five years, 94 percent of people with the disease will die.

Survival rates are higher when the cancer is caught early, but even early-stage pancreatic cancer has a very low five-year survival rate. For the most common kind of pancreatic cancer tumors, called exocrine tumors, the survival rate is 14 percent for the earliest stage (stage 1A) -- it goes down to 7 percent for stage 2A, and 1 percent for stage 4, according to the American Cancer Society. News reports did not specify whether Johnson has the exocrine form of pancreatic cancer.

Pancreatic cancer is also not often caught early since symptoms usually don't appear until later on, MyHealthNewsdaily reported. And even when the symptoms do appear, they can be vague (like back pain, or experiencing indigestion).

The Mayo Clinic added that pancreatic cancer spreads very quickly, making it hard for surgery to be a treatment option. Surgery can only be used to treat pancreatic cancer if it has not spread outside of the organ, the Mayo Clinic noted. Other treatment options include chemotherapy, targeted drug therapy and radiation.