Jeopardy! host Alex Trebek says he has stage 4 pancreatic cancer. 

The 78-year-old made the announcement in a video message on Wednesday. 

"Now, normally, the prognosis for this is not very encouraging, but I'm going to fight this. And I'm going to keep working and with the love and support of my family and friends -- and with the help of your prayers also -- I plan to beat the low survival rate statistics for this disease," he said.

Trebek also joked: "Truth told, I have to because under the terms of my contract, I have to host 'Jeopardy' for three more years. So help me. Keep the faith, and we'll win. We'll get it done."

Trebek has hosted the game show since 1984.Â