Performance of 68Ga PSMA PET CT to Detect Prostate Cancer and Comparison with 18F Choline PET CT - Manuela Hoffmann

Radiolabeled prostate-specific membrane antigen (PSMA) has proven as a highly accurate method to detect recurrences and metastases of prostate cancer, but there are only sparse data about its diagnostic performance in primary prostate cancer.

Manuela Hoffman presents a retrospective study of the diagnostic performance of 68Ga-PSMA PET/CT to detect significant prostate cancer in comparison with 18F-Choline PET/CT.

Biography:

Manuela Hoffman, Bundeswehr Medical Service Headquarters Koblenz Germany, Department of Nuclear Medicine, Bundeswehrzentralkrankenhaus Koblenz Germany, Department of Nuclear Medicine, Johannes Gutenberg-University Mainz Germany

v2 Updated Aug 2019

Full transcript below with select scan images:

Contents

Introduction

We move on to the next speaker. Manuela Hoffmann will present on diagnostic performance of Gallium-PSMA PET/CT to detect significant prostate cancer in comparison with Choline PET/CT. And after the talk, I will hand over to my co-moderator, Michael, for questions and comments.

Dear Chairman, dear ladies and gentlemen, dear colleagues. I feel very honored to speak here today. My topic is a diagnostic performance of 68 Gallium-PSMA PET/CT to detect significant prostate cancer and the comparison with 18F-Choline PET/CT.

First, let us look at the topics. To start, I want to show you the objectives and methods of our study. Then, I'm going to talk about the results. We will finish with the conclusion.

Objectives & Methods of Study  

See here, the objectives. PSMA has been proven as a highly accurate method to detect recurrence and metastases of prostate cancer. But only sparse data is available about its performance in the diagnosis of clinically significant primary prostate cancer.

In this retrospective study, we included 61 consecutive patients from the Central Military Hospital Koblenz and four consecutive patients from the Practice of Radiology and Nuclear Medicine Cologne Triangle. All patients showed an increased PSA and were suspected for having prostate cancer.

  • PSMA PET/CT was performed in 25 patients
  • Choline PET/CT was performed in 40 patients.

All patients underwent a conventional prostate biopsy, which means a transrectal ultrasound-guided biopsy. The PET/CT results were compared with the histopathologic analysis of biopsies. The uptake of PSMA and Choline was quantified in terms of SUV. And correlations between PSA, SUV, Gleason score, and the detection of metastases were analyzed.

Results of Choline PET/CT  

First, let us look at the results of Choline PET/CT. The scans revealed suspect malignant lesions in 95%. The SUV means remained stable across all Gleason score categories. The four cases with Gleason score lower than six showed SUVs higher 2.5, taken 2.5 as cut off. There was one false positive and one false negative result. Bone or lymph node metastases were demonstrated in 10 patients.

Anterior Prostate

Choline PET CT Scan Image of Anterior Prostate

Let me show you an example of a Choline PET/CT scan with a hypermetabolic focus in the anterior prostate area.

PSMA PET/CT Results  

Now, this slide shows the results of the PSMA PET/CT. The scans revealed suspect malignant lesions in 84%. The SUVs tended to rise with increasing Gleason score category. All histopathologic high-grade cases with Gleason score higher or equal 7b showed SUVs higher 12. The two cases with Gleason score lower than six showed SUVs lower or equal 2.5, taken 2.5 as cut off. There were no false malignancies, but two false benign results. And bone or lymph node metastases were detected in eight patients.

Anterior Prostate

PSMA PET CT scan of Anterior Prostate

Now, this is an example of a PSMA PET/CT scan with a hypermetabolic focus in the anterior prostate area. Near the apex in the peripheral zone. There was a concordance in the multi-perimetric MRI, with a focus of high signal on diffusion weighted imaging and a focal area of reduced apparent diffusion coefficient.

Here's another example with PSMA positive. Focus in the left prostate lobe, which isn't easy to detect in MRI on T2W weighted imaging.

Here, we have another example with a positive PSMA uptake of the sclerotic bone metastases on the left side, which is also shown by MRI.

This image shows a scan of a prostate cancer patient with several bone metastases in the spinal column and in the pelvis, with positive PSMA uptake.

Characteristics of Patients  

Now, here in Table 1, you can see the characteristics of our patients.

This slide shows the relation between PSA and SUV of PSMA PET/CT and Choline PET/CT in patients without metastases. As you can see here from these two graphs, there was a tendency in the PSMA group that with increasing PSA, there was an increased SUV too, but there was no tendency in the Choline group. There was no statistically significant correlation in both groups, but we can show a correlation of 0.082 in the PSMA group, but only 0.875 in the Choline group.

Gleason Score of Two Groups

This slide shows the distribution of Gleason score in our two groups.

Here's one important point I'd like to mention. This slide shows the distribution between Gleason score and SUV in PSMA PET/CT and Choline PET/CT scans for prostate cancer. PSMA columns in blue, Choline columns in red. And as you can see here, the PSMA uptake is much higher than that in Choline and especially in the group of high-grade carcinoma with Gleason score higher or equal 7b. And we saw a statistically significant correlation of 0.005 for the PSMA group.

Conclusion  

Now, let me proceed with the conclusion.

Our results show that both methods are suitable for the detection of primary prostate cancer, but there are several advantages for PSMA PET/CT.

These are:

  • Excellent imaging quality
  • Higher specificity
  • Higher uptake than Choline in patients with Gleason score higher or equal 7b
  • Correlation of positive scans with Gleason score- which may allow differentiation between low and high-grade carcinoma.

See here, the acknowledgements.

The last picture shows you a little view of the so-called German corner in Koblenz, Germany, where the River Rhine and the River Moselle meet, and this is a very nice place I have the chance to work in. Thank you for your attention.

Questions & Answers

Thank you very much for this very nice presentation. Any questions from the audience?

Question:

Hi. If I got it right, you mentioned that the PSMA PET was false positive for two lesions. Can you comment on the false positive lesions? Or what kind of lesions these were?

Answer:

It was infection lesions.

Okay, okay. Thank you.

Question:

Do you think, from your results, that there is still a role for Choline? Complementary to PSMA? Or is PSMA superior to Choline and we no longer need Choline?

Answer:

Yes, of course, PSMA is superior in our mind.

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