PSMA-PET/CT: local recurrent or metastatic tumor?

PSMA-PET/CT: local recurrent or metastatic tumor?

The examination by means of PSMA PET/CT has a decisive influence on the further therapy planning. This was recently demonstrated by the so-called CHAPPP study1 (Changing care with PSMA-PET for prostate cancer), which was presented at this year's ASCO (American Society of Clinical Oncology) meeting. Thereafter, one quarter of patients with a diagnosed local recurrence experienced a change in the intended treatment after they were additionally screened in PSMA PET/CT. The reason for this was in most cases the presence of metastases, which remained undetected with conventional imaging.

If the PSA level rises again after prostate cancer therapy, this may be a sign that the tumouris growing again. If there is suspicion of recurrence of the cancer after surgery or radiation, it must be assessed whether it is a relapse in the area of the prostate (recurrence) or whether it is more likely to be caused by scattering (metastasis). This is the next step,"explains Dr. Pedram Derak-hshani, urologist at the West German Prostate Center (WPZ) in Cologne.

Higher hit rate through PSMA-PET/CT

In order to be able to make as precise a statement as possible, the WPZ urologists, in cooperation with the Clinic and Polyclinic for Nuclear Medicine at the University Hospital Cologne, use PSMA-PET imaging instead of the conventional examination in choline PET-CT. Just as with choline PET, PSMA (prostate specific membrane antigen) PET is injected with a radioactive substance that accumulates in the cells of the prostate carcinoma and the metastases and then becomes visible as a luminous dot. However, the hit rate of the PSMA-PET is considerably higher: The new substance even allows the detection of recurrence tumors with PSA values below 1.0. The sensitivity in very small bone metastases is also much better. 2/3 "This enables us to distinguish precisely whether a patient with a relapse of prostate cancer is again eligible for local treatment such as surgery or radiation, or whether systemic treatment such as chemotherapy or hormone treatment is appropriate," explains the urologist from Cologne.

Influence on therapy planning

An Australian study has now shown for the first time that this innovative technology has a significant influence on the way men are treated with a prostate relapse. In the so-called CHAPPP study (Changing care with PSMA-PET for prostate cancer), patients who were diagnosed with conventional imaging (CT, bone scintigraphy) with a local recurrence in the prostate tissue were examined again using PSMA imaging and the scans were then compared with each other. The results show that additional information with the PSMA radioactive marker has changed the choice of therapy for a quarter of men. In the majority of these patients (23 percent) metastases were detected by PSMA imaging that had previously remained unrecognized. Instead of a previously planned local treatment, they received systemic therapy. An additional lymph node infestation was diagnosed at 27 percent, which in some cases also changed the type of treatment.
With PSMA imaging, we will be able to detect local recurrences and metastases even earlier and treat them more effectively,"said Dr. Derakhshani. This in turn increases the chances of recovery and survival,"said the urologist.


The CHAPPP study: Changing care with PSMA-PET for Prostate cancer-A ret-rospective study of the role of PSMA imaging in altering treatment pathways, ASCO February 16,2017
Afshar-Oromieh A, Zechmann CM, et al.: Comparison of PET imaging with a (68)Ga-labelled PSMA ligand and (18)F-choline-based PET/CT for the diagnosis of recurrent prostate cancer. Eur J Nucl Med Mol Imaging. 2014 Jan; 41 (1): 11-20. doi: 10.1007/s00259-013-2525-5. Epub 2013 Sep 27.
Afshar-Oromieh A, Haberkorn U, et al: Comparison of PET/CT and PET/MRI hybrid systems using a 68Ga-labelled PSMA ligand for the diagnosis of recurrent prostate cancer: initial experience. Eur J Nucl Med Mol Imaging. 2014 May; 41 (5): 887-97. doi: 10.1007/s00259-013-2660-z. Epub 2013 Dec 19.

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