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Matthias Benz: Here we go. Good morning, everybody. Just following on Amir's talk. I have a relatively basic talk. Nothing to disclose. A pretty broad topic, this topic, but I just narrowed it down to two things.

I want to show a few false positive findings that also kind of follows what Amir says—that residency, radiology residency, and a good program that you're kind of attending is important. And then I also want to show the acquisition protocol that we're using at UCLA, where we do this a little differently maybe than other sites.

So we know that PSMA is not—or is also overexpressed in other cancers and the neovasculature of other cancers. And this blood kind of suggests that it's relatively low expressed in other cancers. But there's really a huge range of expression. And I just want to show a few examples of incidental findings that we relatively often detect in our daily routine.

And this, for example, is a patient with a huge mass in the right thyroid lobe, had very intense PSMA uptake. Just the location kind of tells us that this is very unlikely prostate cancer and, of course, this turned out to be papillary thyroid cancer. But the uptake is really, really intense in these cancers sometimes.

Same here, there's a huge mass. This is the pancreas that we're seeing here. There's a huge mass just anterior to the pancreas. There was a budding in the stomach, which is not shown here. Had moderate PSMA uptake. Maybe also the size and location didn't make it very likely that this will be prostate cancer. And this then also turned out to be a gastrointestinal stromal tumor.

This patient is interesting. Here, we see the right breast of a patient. There's a nodular lesion here in the right breast in this location. In this patient population, very often, we have gynecomastia, which most of the times is a little bit more diffuse, ill-defined. This was more nodular, asymmetric, had moderate PSMA uptake to it.

It was biopsied, resected, and then turned out to be, actually, breast cancer in a male patient. And maybe the first three are not huge diagnostic dilemmas because the location, maybe also the CT imaging appearance, didn't make it very likely to be metastatic disease from prostate cancer.

In the lung, it's a little different. This was a patient who came for staging of prostate cancer, had a remote history of renal cell cancer. We saw this right lower lobe lung lesion had very intense PSMA uptake to it, was biopsied, and then turned out to be a renal cell carcinoma metastasis.

So I think most of the time, depending on location of the lesion, CT imaging appearance, we're not really running into major diagnostic issues but, of course, if they're located in the lung or if they're retroperitoneal lymph node metastases, then sometimes, it can be a little tricky.

The classic things that we see pretty much in most patients are—maybe that's like these comma-shaped lesions here in the retroperitoneum. That's very close to the celiac trunk. And these typically have low or moderate PSMA uptake. And this is the classic imaging appearance of a ganglion, so kind of a nerve cell cluster located on both sides anterior to the spine.

We don't only have it here in the retroperitoneum, but we can also see it, for example, in the upper thoracic spine, level of T1 to T2. There, they are called the stellate ganglion. But then also anterior to the sacrum, that's where we also often see it. Those are the sacral ganglia.

These are benign things. They should be. They're nothing to worry about, but it's important to know about it, so they are not misclassified as malignant disease.

Also, the most common benign tumor of the liver is just shown here as this kind of hypervascular, hyperattenuating lesion. This is a hemangioma. Also, hemangiomas can show a broad range of PSMA uptake. This one was very, very intense.

Typically, if you see a hypervascular lesion in the liver, unlikely also to be prostate cancer metastases. These are more often hypovascular. Other hemangiomas are located, for example, in the spleen and the bone. In the spleen, they can also often be PSMA-avid. In the bone, they can be as reported, but that is not very often seen.

I think before we started imaging patients with PSMA, we didn't know how many benign lesions we all have. This is the classic example of an enchondroma. These are also often like rim sclerotic lesions, have a little bit of lucency to it, and also can express, most of the times, mild to moderate PSMA uptake.

But if you know about it, if you trained well, I think you can classify this lesion correctly. But then there are also other benign and malignant bone findings, often just degenerative changes or trauma that can have a little bit of PSMA uptake

And then also infectious inflammatory changes, just reactive lymph nodes, granulomatous disease in the mediastinum, but also post-radiation changes, for example, after radiation of an osseous lesion. All these pathologies or benign findings can have PSMA uptake to it.


All right, let's shift gears a little bit. I want to talk about the protocol that we're using at UCLA. And in the beginning, I think we saw a lot of patients coming for biochemical recurrence, and now, we see a lot of patients referred for primary staging. And I feel my reports or my impressions pretty much reach the same in 80% of patients.

First, I kind of describe the local finding. And then I don't really often see much in the pelvis, so I say there's no evidence of pelvic lymph node metastasis or just metastatic disease. But then also, what Amir was kind of pointing out, we have a great specificity, but then there's relatively low sensitivity for detection of prostate cancer, pelvic metastases, who come for primary staging.

To improve our reader confidence, maybe not sensitivity so much, maybe specificity a little bit, we use an additional protocol at UCLA. What everyone does is injecting the tracer, waiting 60 minutes, and then doing a whole-body PET scan. What we do is we send the patient afterwards to void, and then we put them back on the scanner and scan two bed positions over the pelvis.

And this, we use for troubleshooting, and I'll show a few examples of how this sometimes can be helpful. So this is a patient who came for primary staging. We see he has a small obturator node on the right side, and that is increasing on the late pelvic images.

Of course, I would have kind of called this before on the whole-body PET, but this is just to show that there is an increase in radiotracer uptake.

Already, after 20 to 30 minutes, often, we encounter not significant or sometimes significant, but often an increased PSMA uptake, and that, we often see in lymph nodes that are then really true positive prostate cancer metastases.

I think this is actually a more important scenario. So this is also a patient referred for primary staging. He had a small lymph node here in the left pelvis that has really just very faint PSMA uptake. And those are sometimes difficult to comment on. And you kind of want to call it positive, but you're a little uncertain about it.

And if we compare this to the late pelvic protocol or late pelvic images, we see that the PSMA uptake actually decreased or sometimes it's completely gone, and that, we often see in patients who have just a nonspecific uptake on the whole-body scan. So this turned out to be a true negative lymph node, for example.

Last scenario is a patient who came after HIFU therapy, so after local prostate therapy. This is a sagittal image. Here, we see the bladder. This is the prostate. Here's the rectum. And this is the sagittal fused PET-CT. And within that kind of hypoattenuating lesion that we see here in the posterior and peripheral gland, we have intense PSMA uptake.

Now, when we look at the late pelvic protocol, we see that there's some contrast media in the urinary bladder. But then also, in this hypoattenuating lesion—or this hypoattenuating lesion now fills actually with oral contrast. And that's not the tumor. That's just the defect from the HIFU.

And the PSMA uptake that we're seeing, in part, kind of also is within that HIFU defect, but then the actual recurrence is just below it. So the patient has recurrence, but it's below the actual HIFU defect.

So there's some recurrence or residual tumor. And with the late pelvic protocol, it's just easier to differentiate, again, between HIFU defect and actual tumor recurrence. Thank you very much.