0:00

So in the second part of our first section, we're going

0:03

to be looking at the emergence of PSMA ligand PET scans

0:08

and how they have really changed the game in the assessment

0:11

of patients with prostate cancer.

0:14

And so PSMA stands for prostate specific membrane antigen,

0:17

and that's a transmembrane type two glycoprotein.

0:21

And this is physiologically expressed on the surface

0:24

of many cells all around the body.

0:25

And as we can see here with our normal, well,

0:28

this is a patient with disease,

0:29

but we can see normal uptake in multiple AL organs,

0:31

including saliva, glands, liver, spleen, bowel,

0:34

and excretion by the renal tract.

0:36

So it's not only seen in prostate cells,

0:38

it's not only seen in prostate cancer cells,

0:41

but where it becomes useful is

0:42

that it is upregulated in cells that have prostate cancer.

0:46

So those cells become more avid to the tracer

0:49

because of increased expression of PSMA antigen.

0:52

So the PSMA ligand RADIOPHARMACEUTICALS were developed

0:55

through the two thousands.

0:57

And I will pause here just to say

0:59

that PSMA ligand is really the name of

1:02

what the radiopharmaceutical that we're injecting is.

1:05

Um, it's a ligand that binds to the antigen,

1:07

which is present on the cell surface

1:09

for patients with prostate cancer.

1:10

And that's how we image it.

1:12

But you will notice that I will use the term

1:15

interchangeably, um,

1:16

and just assumed if I'm talking about PSMA

1:18

radiopharmaceutical, I'm talking about the PSMA ligand

1:22

and talking about the binding

1:23

and the uptake in the tissues in the body.

1:26

So with its development, it was fantastic

1:28

because all of a sudden we had a quite reasonably specific,

1:31

um, trace of the assessment

1:32

and treatment of prostate cancer.

1:34

And traditionally, FDG pet, which is our workhorse PET,

1:37

wasn't so good at imaging patients with prostate cancer

1:40

because of the way that the cells interacted with glucose.

1:43

Um, not all of them being particularly glucose avid

1:46

or hypermetabolic two radiopharmaceuticals have emerged, um,

1:50

although are quite a number on the market,

1:51

and that depends on variable practice.

1:54

But, um, in my experience, the ones

1:55

that I use in my practice are Gallium 68, PSMA 11,

1:59

which we'll shorten to gallium 68 PSMA

2:01

or just PSMA in the upcoming modules.

2:04

And this is one of the most widely used tracers worldwide,

2:07

um, but also one that will come across as well

2:08

as F 18 DCF pile, also called F 18 PSR.

2:13

And that uses the positron emitter of fluorine 18,

2:16

whereas Gallium 68 PSA, as the name suggests,

2:19

uses gallium 68 as the positron emitter

2:24

in terms of PS a's emergence into practice.

2:26

And there's been a lot of studies

2:27

that have demonstrated the utility

2:29

of these imaging investigations

2:31

for diff patients at different stages along

2:33

their prostate cancer journey.

2:35

So in one study, which was performed at, um,

2:37

in Sydney at actually at my hospital, it was found

2:39

that a 51% change in management was occurring in patients

2:43

referred for this PET scan, which is fantastic.

2:45

Um, and that change in management may relate

2:48

to surgical resection.

2:49

Radiotherapy be that external beam brachytherapy

2:52

or suitability for LUTETIUM 1 77 PSMA,

2:56

which is a theranostic agent where we

2:58

Swap out the Gallium 68

3:00

and put in the beta emitter LUTETIUM 1 77.

3:03

But we will come back to that in some upcoming modules

3:06

or systemic therapy,

3:07

and that includes androgen deprivation

3:09

therapy agents as well.

3:12

What the study did notice, however,

3:13

that the management change was more common in patients

3:17

with biochemical failure with a low PSA,

3:19

so low volume disease, and it's just starting to emerge.

3:22

So really low PSAs,

3:24

and that encountered a 62% change in management as opposed

3:28

to 51% in the overall cohort.

3:31

It noticed that there was less change for primary staging,

3:33

particularly with no change in prostatectomy rates.

3:35

However, when a management change was evoked,

3:39

it often was about, you know, treatment

3:41

of local regional disease, particularly whether

3:44

or not to give radio therapeutic pelvic nodes which were

3:47

involved, um, even though previously going undetected.

3:50

So there's also a role, um, for A-P-S-M-A pet, which is a,

3:53

it's a total body imaging modality.

3:55

So there is a role for detection

3:57

of clinically significant incidental findings.

3:59

And in this, this is a rotating MIP

4:01

or a MIP projection maximum intensity,

4:03

which we'll see in upcoming modules used quite a lot.

4:06

Um, but here with the purple arrow is the site

4:09

of primary disease in the prostate focal uptake.

4:12

But in this case, there was also another abnormality seen in

4:15

the thorax, which was found

4:17

to be an incidentally detected primary lung cancer.

4:20

Note that the lung cancer,

4:21

even though it isn't a prostate cancer metastasis

4:24

or anything to do with the prostate cancer,

4:25

still has a little bit of PSMA uptake.

4:27

And this is a pitfall that we will also revisit in upcoming

4:30

modules.