The actor, married to Catherine Zeta Jones, suffered from throat cancer in 2010.
"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," mirror.co.uk quoted Douglas.
The 58-year-old admits he was taken aback when news of cancer was revealed to him. "Two days later, after the biopsy, the doctor called and said I had to come in. He told me it was stage-four cancer. I said, ‘Stage four. Jesus'," he said.
"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.
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