What’s the chance that somebody who was exposed to radiation now has a subsequent cancer later on in their life? The chance of that is a statistical one, meaning there’s no large study out there where people are followed for hundreds of months.
Researchers have looked at young women who had breast cancer in the 1960s and had these large fields of radiation that were delivered back then – these are called mantel fields – and then they looked at them later on and said, “What was the chance of them developing breast cancer?” And there are large data bases where you can start measuring these.
In general the chance of a radiation induced secondary cancer is extraordinary low. And it usually takes 20 years, 15 years, maybe 10 years at the earliest to even see. For men with prostate cancer men, the rate of a radiation induced malignancy is very small.
Colorectal cancer is the number three cause of cancer in men. Bladder cancer is number four. Just because you have one cancer doesn’t mean you can’t have a subsequent cancer.
Good prostate cancer imaging often finds other malignancies. Oncologists see incidental secondary cancers all the time.
Radiation delivered to hundreds of millions of people will cause cancer in a very low number of people. So, with that said, when you have a child you try not to expose them to radiation. When you have any human being, you don’t expose them to even a drop of radiation if they don’t need it. Once someone has a diagnosis of cancer you’re trying to cure them of their disease, prevent metastatic disease, let them live the rest of their lives. For that individual, not exposing them to the necessary tests to accurately know where their tumor is much worse than the microscopic chance that you may induce a secondary malignancy 20 years later.
So really the issue at play, and we see really smart people who ask very thoughtful questions like this, is what’s dangerous to an individual versus what is dangerous to a population? Exposing a population, hundreds of millions of people, to radiation needlessly will cause cancer in a very small number of people. For people who already have that diagnosis to better assess what the cancer status is you have to expose them, but the exposure they’re getting is such a trivial thing it’s not something that doctors want to avoid.