The Harry Potter star was diagnosed with acute myeloid leukaemia in 1996 and underwent two courses of chemotherapy before he was eventually given the all-clear.
And he has now spoken out to publicly thank Professor Anthony Goldstone, insisting the doctor saved his life by preventing surgeons from carrying out a drastic bone-marrow transplant during his treatment.
Spall tells The Times, "He was having to play a bit of chess about what to do with me. What he didn't want to do was kill me by trying to cure me... I didn't have the transplant because I probably wouldn't have got through it. It was exactly the right decision. The man's a bl**dy genius."
And Spall was so delighted with the treatment he received during his cancer battle, he invited the medics who cared for him to a birthday party after he recovered.
He adds, "(It was) a wonderful, wonderful do. It was 50 per cent medics, 50 per cent actors. I was going round saying, 'This is Professor Goldstone. He saved my life.'"