Douglas, 68, who was diagnosed with cancer in August 2010, underwent treatment and is now two years clear of the disease, said he doesn't regret his heavy smoking and drinking in the past, London's The Guardian reported Sunday.
"Without wanting to get too specific, this particular cancer is caused by HPV (human papilloma virus), which actually comes about from cunnilingus," Douglas said.
"I did worry if the stress caused by my son's incarceration didn't help trigger it. But yeah, it's a sexually transmitted disease that causes cancer. And if you have it, cunnilingus is also the best cure for it," said Douglas, who is married to actress Catherine Zeta Jones.
In 2010, Douglas' son, Cameron, was sentenced to five years in prison for drug possession and dealing, and a year, his sentence was extended three years after he pleaded guilty to possessing drugs in prison, The Guardian said.
Douglas was diagnosed with stage-four cancer (stage five is death) after months of oral discomfort. Specialists missed a tumor in his mouth and instead prescribed antibiotics. Douglas eventually saw a friend's doctor in Montreal who used a tongue depressor to examine his mouth, The Guardian reported.
"I will always remember the look on his face. He said: 'We need a biopsy.' There was a walnut-size tumour at the base of my tongue that no other doctor had seen," Douglas said.