Alex Trebek baffled by 'mind-boggling' pancreatic cancer tumour shrink

The presenter says that some of his tumours have shrunk by more than 50 percent

'Jeopardy!' host Alex Trebek speaks as he is inducted into the National Association of Broadcasters Broadcasting Hall of Fame during the NAB Achievement in Broadcasting Dinner at the Encore Las Vegas on 9 April, 2018 in Las Vegas, Nevada. ((Photo by Ethan Miller/Getty Images))

Jeopardy host Alex Trebek has revealed he is shocked to have learned that some of his pancreatic cancer tumours have shrunk by up to 50 per cent.

Earlier this year, the 78-year-old announced he had been diagnosed with stage four pancreatic cancer in a clip posted on the show’s official Twitter account.

“Normally, the prognosis for this isn’t very encouraging but I’m going to fight this and keep working,” he told the show’s 200,000 social media followers.

However, according to the presenter’s doctors he is now “near remission” and is responding to chemotherapy treatment so well that some of his tumours have shrunk.

“It’s kind of mind-boggling,” he told People magazine.

Despite the male survival rate of pancreatic cancer estimated at 22 per cent for at least one year according to Cancer Research UK, Trebek said his doctors have never seen “this kind of positive result in their memory.

“Some of the tumours have already shrunk by more than 50 percent,” Trebek told the publication.

The presenter said that he will still have to go through several more rounds of chemotherapy in order to get into full remission but is happy at how much his health has improved.

Describing his emotions when he learned that some of his tumours had shrunk, the Canadian-American star said he cried “tears of joy, not tears of depression”.

Trebek credits the support of his fans around the world for his ongoing recovery.

“I’ve got a couple million people out there who have expressed their good thoughts, their positive energy directed towards me and their prayers,” he said.

“I told the doctors, this has to be more than just the chemo, and they agreed it could very well be an important part of this.”

He added: “I’ve got a lot of love out there headed in my direction and a lot of prayer, and I will never ever minimise the value of that.”

Host Alex Trebek poses on the set at Sony Pictures for the 28th Season Premiere of the television show 'Jeopardy' on 20 September 2011 in Culver City, California (Getty Images)

Earlier this month, the long-time television host opened up about how his cancer diagnosis often resulted in bouts of depression.

“My oncologist tells me I’m doing well even though I don’t always feel it,” Trebek told Good Morning America anchor Robin Roberts.

“I’ve had kidney stones, I’ve had ruptured discs, so I’m used to dealing with pain, but what I’m not used to dealing with is the surges that come on suddenly of deep, deep sadness — and it brings tears to my eyes.”

“Chemo takes it out of you,” he said. “I mean, I feel so weak all the time, and that’s not a good place to be.”

Pancreatic cancer occurs when abnormal cells grow and divide to form a tumour in the pancreas, a large gland located in the abdomen that aids in digestion, according to the NHS.

Causes of pancreatic cancer are not fully understand, however, there are certain known factors that increase the risk of developing the disease.

Age is the largest factor, as pancreatic cancer mainly affects people aged 50 to 80 and around half of all new cases are diagnosed in people aged 75 or over.