A prostate-specific antigen (PSA) test, which he had been taking regularly since 1992 -- the year he received his new heart -- indicated that he had the disease that can be deadly if not caught, and dealt with, quickly.
According to studies, more than 192,000 men will be diagnosed with prostate cancer this year, and more than 27,000 men will die from the disease. One new case occurs every 2.7 minutes, and a man dies from prostate cancer every 19 minutes.
It is estimated that there are more than 2 million American men living with prostate cancer.
Hamilton is one of them.
He is doing fine now, and his latest PSA count was 1.5, which is good.
Nine is not good, and that's the number that the test registered four years ago.
"I had no idea," Hamilton said. "I didn't have any symptoms that I can recall, but the doctor told me I had prostate cancer."
The Seattle Prostate Center, one of the most-renowned institutes in the world, provided the treatment for Hamilton.
"My doctor wanted me to do the seed implant, but my tumor was too large for that," he said. "They had a fairly new drug, a hormone pill that I took over a three-month period, and it reduced the size of the tumor almost half."
That allowed the seed implant treatment to work, and four years later, nearing his 70th birthday, Hamilton is on the job, filming Mariners players taking swings and throwing pitches.
"I only missed one day of work during the treatment," he said.
And he tells anyone that cares to listen that getting a PSA test could be the most important thing a man can do.
"From what I have heard and read, one in every six men will get it," he said. "And if you catch it soon enough, you can survive it. But you have to catch it early and that's why the PSA test is so important. I would highly recommend it to everyone."