Longtime Jeopardy! host Alex Trebek has been diagnosed with Stage 4 pancreatic cancer.

In a video posted to the game show’s YouTube page Wednesday, Trebek, 78, announced his diagnosis, saying he’s “keeping with my longtime policy of being open and transparent with our Jeopardy! fan base.”

“Now, normally the prognosis for this is not very encouraging,” Trebek said in the video, appearing in good spirits on the Jeopardy! stage. “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 your prayers, also, I plan to beat the low survival rate statistics for this disease. 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. Thank you."

Jeopardy! — which Trebek has hosted since 1984 — has a significant fan base in Philadelphia.

In February, the most recent ratings period, the quiz show averaged 447,000 viewers and pulled in a 7.8 market share for viewers 18 and over in the Philadelphia market, according to Nielsen. In comparison, The Big Bang Theory averaged 316,000 viewers in the market, with a 5.5 rating share.

In January 2018, Trebek took a brief medical leave from the quiz show to remove blood clots in his brain.

After returning to the Jeopardy! stage, the game-show host also appeared on the stage of the Hershey Lodge in August, moderating the only debate in the Pennsylvania gubernatorial race between Gov. Tom Wolf and Scott Wagner.

According to estimates from the American Cancer Society, pancreatic cancer will affect about 56,770 people in 2019. The disease accounts for about 3 percent of all cancers in the U.S. and about 7 percent of all cancer deaths, according to the organization.