So as long as it hasn't started to metastasize, he should be fine.
Prostate cancer, as both Rudee and gym**rat have mentioned, is easily treatable and sometimes oncologists, even after diagnosing a patient with prostate cancer, will take a "wait and see" approach before considering surgery or chemo/radiation therapy.
They'll probably conduct PSA and DRE tests every 3-6 months and perform prostate biopsies every year to monitor the condition closely.
This is probably, as shitty as it sounds, the best type of cancer that you can get.
"1"