Dr. Kerry Courneya

Yeah, and it varies dramatically by the types of cancer for sure.

So sometimes we see very small tumors might shed cancer cells.

So even though we find what we think is a small tumor, it may have already shed these cancer cells and they may have already spread.

Sometimes the tumor can be fairly large and not have disseminated any tumor cells yet.

And the real challenge there is these tumors can disseminate these tumor cells, and metastases may not happen right away.

Sometimes they sit dormant for years.

So this is where someone with breast cancer may go in.

We've got a primary tumor there.

We cut it out.

We don't know if any...

cells have disseminated.

But five years later, eight years later, 10 years later, we detect a brain metastasis or a lung metastasis.

So these cells can sit dormant for an extended period of time before they sort of start to regrow.

And so metastases can be a very, very long process or it can be a fairly short process.

Other cancers, these cells spread quickly and they grow quite rapidly at these other metastatic sites.

So that's the new area of hot research.

So in the past, we could essentially only detect these cancers based on imaging.

So these metastases would have to grow to a certain size, like one millimeter, two millimeters before they would show up on these scans.

So small numbers of cancer cells we couldn't detect.

And so you're waiting many, many years, you know, doing a follow-up scan five years later, and all of a sudden you see a spot on the lungs or a spot on the liver and say, okay, that could be cancer.