PSMA-Ligand Uptake in Cervical, Coeliac and Sacral Ganglia as a Pitfall for Lymph Node Metastases in Prostate Cancer Imaging - Christoph Rischpler

( Length of Presentation 7 minutes)

Christoph Rischpler presents a study aimed at investigating the PSMA-ligand uptake in PET in cervical, coeliac and sacral ganglia as a pitfall for lymph node metastases in prostate cancer imaging.   This patient population consisted of 308 randomly selected patients who underwent Gallium 68 PSMA-PET between October 2012 and March 2014.  For image analysis, they determined the number of PSMA-PET positive cervical, coeliac and sacral ganglia as well as the SUVmax of the adjacent lymph node metastases.  

Christoph Rischpler, University Hospital Essen | UK Essen · Clinic for Nuclear Medicine


Read the Full Video Transcript:

Dr. Christopher Rischpler: Thanks for the kind introduction.

Dear ladies and gentlemen, the prostate-specific membrane antigen is highly expressed in prostate cancer cells. That's why PSMA-PET has evolved as a powerful tool for prostate cancer staging and re-staging. However, the PSMA expression is also high in non-prostatic malignant lesions, especially in the neovasculature. For example of renal carcinoma, bronchial carcinoma, or glioblastoma. The PSMA expression, however, can also be high in benign tissues, as you can see on the left side. For example, in the kidney or in the digestive system; and also in benign lesions, such as schwannomas, osteophytes, and thyroid adenomas.

There was a recent report that there's also high PSMA uptake in coeliac ganglia. In fact, in 90% of patients there was a PSMA-PET positive coeliac ganglia, in this paper here. The authors also demonstrated there's a high PSMA expression in the coeliac ganglia, as you can see here. Our group just recently reported that there's also a high PSMA expression in neurogenic tumors, such as the schwannoma.

The aim of this study was now to investigate the PSMA-ligand uptake in PET in cervical, coeliac, and sacral ganglia as a pitfall for lymph node metastases in prostate cancer imaging. The patient population consisted of 308 randomly selected patients who underwent Gallium 68 PSMA-PET between October 2012 and March 2014. Only patients with a diagnostic CT were included. The mean injected activity were around 150 MBq. PET/CT acquisition was started around 60 minutes after trace injection, and the scanning were performed on a Biograph mCT scanner.

For image analysis, we determined the number of PSMA-PET positive cervical, coeliac, and sacral ganglia. Also, we determined the SUVmax of the ganglia and the SUVmax of the adjacent lymph node metastases. Furthermore, the configuration of the ganglia and the adjacent lymph node metastases on CT were evaluated.

I will now show some examples. Here, you can see at the level of the thoracic inlet, this band-shaped structure here next to the vertebral body, which shows a pretty intense PSMA uptake. As you can also appreciate here on the overlaid images. This is one of those cervical ganglia.

Here, at the level of the kidneys, you can see these teardrop-shaped structures next to the ureter and here behind the inferior cava vein, which also shows an intense PSMA uptake, in which are these coeliac ganglia.
Last, also one example for the sacral ganglia. Those are here these band-shaped structures in front of the sacrum, which show a moderate to intense PSMA uptake, as you can also appreciate here on the overlaid images.

Here now, the results. In our 308 patients, we saw most of the PSMA-PET positive ganglia in the cervical region. In the coeliac region, we had about 90%, which is the same number as I showed in the paper before. In the sacral region, we only saw about 40% positive ganglia. The PSMA uptake was highest in the coeliac ganglia, followed by the cervical ganglia, and the lowest PSMA uptake was in the sacral ganglia; as measured by the SUVmax.

We also looked if there is a correlation between the PSMA uptake in the different ganglia, and we found that the SUVmax of the cervical ganglia correlated with the coeliac ganglia. As you can see, it's a weak but highly significant correlation. We found the same for the cervical ganglia versus the sacral ganglia. Also weak, but a significant correlation. Why is this important? This finding might help to differentiate between lymph node metastases and the ganglia. For example, if you look at a patient with a high uptake in the cervical ganglia and have a lymph node metastases next to the coeliac ganglia, then you can see it might even help to differentiate between a ganglia and a lymph node metastasis.

We then looked at the PSMA uptake in the ganglia compared to adjacent lymph node metastases. As you can see, the PSMA uptake was significantly higher in adjacent lymph node metastases in the cervical region, in the coeliac region, and also in the sacral region. I have one example here, at the bottom. Here again, this band-shaped structure next to the sacrum with a SUVmax of around 3. This was this sacral ganglia. About one to two centimeters below this, you can see this kind of nodular-shaped lesion here with an intense uptake. This is a lymph node metastasis.

As I said before, we also looked at the configuration of the ganglia. Here in the top row, you see the different shapes of the ganglia. We defined them as band-shaped, teardrop-shaped, or nodular shaped. Most of the ganglia were band-shaped, followed by teardrop-shaped, and only a few were nodular-shaped. In contrast to this, the adjacent lymph node metastases, most of them were nodular-shaped. A few were also teardrop-shaped. Almost none of them were band-shaped.

Here, you can see where these teardrop-shaped ganglia come from. The cervical ganglia, they show about 50%, the band-shaped ganglia and teardrop-shaped ganglia; almost no nodular shaped. Whereas in the coeliac and the sacral region, most of the ganglia were band-shaped, and less of them teardrop-shaped. Almost none of them were nodular-shaped.

In conclusion, I can say that the PSMA uptake along the sympathetic chain is an important pitfall in prostate cancer PSMA-PET imaging. The PSMA uptake is higher in coeliac ganglia compared to cervical and sacral ganglia; and the level of PSMA uptake seems to be patient-related. For differentiation between lymph node metastases and ganglia, both the intensity of the PSMA uptake, as well as the exact localization and configuration of the respective lesion should be taken into account.

Thanks for your attention.
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