The 68-year-old said he was in constant touch with the doctors for his pain but none of them discovered his cancer for almost nine months, reported Daily Mirror.
"I knew something was wrong. My tooth was really sore, and I thought I had an infection. I had two rounds of appointments with ear-nose-and-throat doctors and periodontists. They each gave me antibiotics. And then more antibiotics, but I still had pain," Douglas said.
After having more scans, the tumour was finally discovered on his tongue in 2010.
"And that was that. After complaining for nine months and them not finding anything, and then they told me I was stage four? That was a big day," he added.
The star said that the illness gave him a new rejuvenation and he now enjoys making movies more.
Douglas said that getting throat cancer may have been payback for his glittering career.