0:01

So, why prostate MRI as opposed to, say,

0:06

ultrasound or digital examination or serum PSA?

0:11

Well, first of all, serum PSA has a sensitivity

0:15

of 36 percent for diagnosing prostate cancer.

0:19

That, frankly, is not good enough.

0:22

Digital rectal examination is

0:24

somewhere far south of that.

0:27

And in terms of assessing tumors, we use

0:31

histologic rating called the Gleason score.

0:33

We'll talk about that at a separate time, but,

0:38

uh, a Gleason score of seven or over is considered

0:41

more aggressive; six or less, less aggressive,

0:44

and that'll be a story for another section.

0:47

Previously, we used transurethral rectal

0:50

ultrasound to biopsy and define aggressiveness

0:55

of the lesion with the histologic Gleason,

0:57

Gleason score, but those biopsies were not

1:00

directed to any one specific ominous locus.

1:05

They are somewhat random in

1:07

character until MRI came along.

1:10

So what are the indications for MRI?

1:12

Probably the most important indication is

1:15

surveillance in a low-risk Tier 1 individual.

1:20

So, what does a Tier 1 mean?

1:23

That is a separate vignette coming right up.

1:25

But we're going to have three

1:27

tiers of aggressiveness and risk.

1:30

There'll be Tier 1, Tier 2, and Tier 3.

1:34

Then we also can use MRI for staging.

1:39

And the staging will help us identify not only

1:43

how big the tumor is, but also its histologic

1:47

character, because there's a correlation between

1:50

the Gleason score and the appearance on MRI.

1:54

Now let's go back to surveillance for a minute.

1:57

Surveillance is used in

1:58

Tier 1 low-risk individuals.

2:01

So what does that give you?

2:04

Well, if you can survey the prostate gland

2:07

and assure that there's not an aggressive

2:10

lesion and use a conservative method for

2:13

following the gland, you avert the potential

2:15

complications of intervention on the prostate

2:19

gland with all the techniques that are

2:20

available out there, starting with surgery.

2:23

With surgery, the risk of having some

2:27

ejaculatory dysfunction is as high as 60%.

2:30

The risk of incontinence or

2:32

leaking is as high as 30%.

2:36

So if you don't need a procedure for an

2:38

aggressive lesion, you shouldn't have one.

2:40

And in the past, we have been operating

2:42

on cancers that are less aggressive.

2:46

So we've got surveillance, which can

2:48

prevent you from having a lesion.

2:50

An unnecessary procedure, probably

2:52

the most important indication of MRI

2:54

by far, and then second is staging.

2:58

And staging helps you not only decide the

3:01

character of the tumor but also what to do.

3:04

Because if the stage is later stage, that's

3:06

a different treatment than if it's early

3:09

stage, even if they are both aggressive.

3:13

So we've already talked about avoiding

3:15

unnecessary surgery; let's take the converse.

3:18

You've got somebody with a rising PSA, and we know

3:21

that the PSA goes up with age because the normal

3:24

gland gets bigger, more normal gland, more PSA.

3:28

So it may be a matter of how fast it rises.

3:32

But the converse that we're referring

3:34

to is, what if the PSA is rising and

3:37

there really is an aggressive cancer?

3:39

How good is MRI at picking

3:40

up Gleason 8s, 9s, and 10s?

3:43

Really, really good.

3:46

How good is it at picking up

3:48

Gleason 1s, 2s, 3s, 4s, 5s?

3:51

Not so good.

3:53

And that's a good thing.

3:55

Because we're not picking up, we're not

3:57

registering a lot of these smaller or

4:00

less aggressive cancers that should be.

4:03

Surveyed for conversion to more aggressive

4:06

character, which MRI does really, really well.

4:10

MRI is used for biopsy planning and overlay.

4:14

So instead of going into a gland, going through

4:17

the rectum from the back here, and just randomly

4:20

putting a needle in and saying, "Okay, I'll take 12

4:22

samples, one here, one here, one here," and so on.

4:26

With MRI, you have directed access to that nodule,

4:30

you overlay it on the ultrasound using it as a

4:34

map, and you can go directly to that locus and put

4:37

your needle right where you see the abnormality.

4:40

And the MR far more accurately shows you

4:44

these loci than ultrasound ever could.

4:48

So you have this very nice correlation

4:50

between MR, truce, and

4:52

where your needle should go.

4:55

On top of that, you can take three-dimensional

4:57

MRI, 3D MRI with thin sections, and you can

5:01

volumetrically take a nodule, and then on

5:04

a series of axial slices, you can simply

5:06

trace the outside of the nodule from one

5:09

slice to the next and get a volume of

5:12

tumor, and further assist the accuracy

5:16

of that transurethral biopsy

5:18

done under sonographic biopsy.

5:22

The other thing you can use MRI for is recurrence.

5:26

MR does pretty well in patients that

5:29

have had prior partial treatments,

5:33

including subtotal prostatectomies.

5:37

Prostatectomies, which is a more complete

5:39

treatment. But many of the other treatments that

5:42

include laser, heat ablation, extracorporation,

5:47

and other newer techniques that alter the

5:51

architecture of the prostate, but there

5:53

are, there are methods to assess tumor

5:56

recurrence that we'll discuss in a minute.

5:58

So we've got surveillance is probably the

6:02

most important aspect of MRI that's unique.

6:07

The second most important is directing

6:10

transurethral ultrasonographic biopsy.

6:13

Probably the third most important is staging.

6:17

And all of these combined will allow you

6:19

to avoid unnecessary surgery or intervene

6:22

if you need to intervene, if you've got

6:24

the MR correlate of a Gleason tumor,

6:26

eight, nine, or ten.

6:28

And we'll discuss what that correlate is.

6:31

We also said that we're going to survey

6:34

individuals that have Tier 1 disease

6:37

or lower-grade types of disease.

6:40

There'll be three tiers and we're going to

6:42

discuss those tiers in a separate section.