Billionaire philanthropist Warren Buffett has early-stage prostate cancer but says he remains in excellent condition and is giving no indication that he intends to retire, says the Associated Press.

The 81-year-old investor, one of the world’s richest individuals and most prominent donors and evangelists for philanthropy, revealed the diagnosis in a letter made public Tuesday.

The Giving Pledge co-founder will undergo two months of radiation treatment, and cancer experts said the early diagnosis means there is little chance the disease will be fatal. Mr. Buffett called his condition “not remotely life-threatening.”

“I feel great—as if I were in my normal excellent health,” he wrote. “And my energy level is 100 percent.”