My dad and 6 or 7 of his friends were persuaded by their wives to join a medical research thing about prostate cancer which they had seen advertised in their GP's surgery. All the men were late 60s / early 70s at the time. My dad was 70.
They were all investigated and four were found to have prostate cancer. None of them knew or had any symptoms.
The idea of the research was to randomly assign them to one of three groups - surgery, radiotherapy or leave alone and monitor. However, my dad's was found to be particularly fast growing, so he was taken out of the trial and given radiotherapy.
All four (weĺl, all 7 actually) are still alive, now in their later 80s. Two are still on the watching brief, and fully expect to die with - rather than from - prostate cancer. The other one had radiotherapy randomly assigned and, like my dad, remains cancer free now.
That massive trial has apparently been very informative - prostate cancer is a cancer they now know a lot about how to treat.
I do remember that heart-stopping, stomach-sinking moment when my dad told me he had cancer, OP, but you cross each bridge as you come to it, and there are lots of positive stories like my dad and his friends.