WASHINGTON, D.C. — Former U.S. Senator Bob Dole announced Thursday that he has been diagnosed with stage 4 lung cancer.

The longtime GOP senator from Kansas made the announcement with a statement on Twitter.

“Recently, I was diagnosed with stage four lung cancer,” wrote the 97-year-old.

He said that his first cancer treatment will begin on Monday.

“While I certainly have some hurdles ahead, I also know that I join millions of Americans who face significant health challenges of their own,” wrote Dole.

Throughout his long political career, Dole served as a senator from 1969 to 1996. During that time, he was both the Senate majority leader and minority leader.

Dole was also the Republican presidential nominee in 1996, but he lost the election to Bill Clinton.