Indianapolis TV reporter, Dave Calabro, discussed Andretti's battle in a video on the affiliate WTHR web site. The reporter said he'd spent two days with the driver, who raced in NASCAR's premier series from 1993-2010 and made five starts in the Indianapolis 500.
The second of his two Cup victories came in the No. 43 for Richard Petty at Martinsville Speedway.
Calabro said Andretti was undergoing chemotherapy and will have surgery in June.
A few of racing world's biggest names have already spoken out about the news.
One of THE nicest guys. Pulling for you John!!" wrote Dale Earnhardt Jr.
"Prayers r with U John @John_Andretti. U r 1 tough guy & I know you will beat this! Tweeters if you're 45 or older go get that colonoscopy!" Michael Andretti tweeted.
We're wishing the race car driver a quick recovery.
This article originally appeared on Womanista.com