The British bassist underwent surgery for a mysterious ailment earlier this year (13), prompting the band to seek out a replacement for its upcoming tour while Bolder spent several months recuperating.
And now the rocker has revealed he has spent the past few weeks undergoing chemotherapy treatment after being diagnosed with the life-threatening disease.
He tells Classic Rock magazine, "I had pancreas cancer so I had to have that removed. Not the entire pancreas - but still, it was bad news. They've cut out the bad bit. I've had a bit of chemo, got to have that, which I'm doing now, in case there's anything hanging about. Once that's done, I should be back to doing what I do for a living."
And the 62 year old confesses he's been struggling with the side effects: "I need to get my concentration back, to be honest, because I get tired real quick at the moment.
"In a couple of months I should be back to normal and doing roadwork with Uriah Heep. Originally, I was told it would be nine months... They say it should be four months - as long as I take it steady."
The director thinks that the superhero style will go the "way of the Western".