68Ga-PSMA-11 PET as a gate-keeper for the treatment of metastatic prostate cancer with radium-223: proof of concept

We retrospectively evaluated the utility of (68)Ga-PSMA-11 PET for planning (223)RaCl2 therapy of patients with metastatic prostate cancer and its impact on the therapeutic response as determined by PSA and ALP, as well as the correlation of PSA changes with the results of PSMA-PET, follow-up scans.

Sixty-three patients with a median age of 73 years who underwent a total of 307 cycles of therapy with (223)RaCl2 were analyzed. In thirty-one patients bone scans and radiological imaging was performed for pre therapeutic imaging (group 1). In 32 patients bone scans and PSMA-PET were performed before therapy (group 2). Patients with small lymph node metastases as well as local recurrence were not excluded from treatment consistent with current guidelines. PSA and ALP were measured prior to each treatment cycle and 4 weeks after the final cycle. Thirteen patients from group 2, who received a second PSMA-PET as a follow-up scan, were evaluated to determine the significance of PSA changes as a follow-up marker.

In group 1, four patients (12.9%) showed a PSA decline, of whom 2 patients and 1 patient showed a PSA decline > 30% and > 50%, respectively. In contrast, in group 2, 14 patients (43.8%) showed a PSA decline, of whom 10 and 8 patients showed a decline > 30% and > 50%; respectively (P = 0.007). Thirty-seven patients had a high ALP level (19 from group 1 and 18 from group 2). Twelve (63.2%) and 16 (88.9%) patients of group A and B, respectively, showed an ALP decline. This difference was not significant; however, 7 (36%) and 13 (72.2%) patients in group 1 and 2, respectively, showed an ALP decline > 30% (P = 0.04). Considering any ALP decline as a response, no patient with increasing ALP showed a PSA response (P = 0.036). There was a significant correlation between the PSA changes and the therapeutic response according to follow-up PSMA-PET.

Using PSMA-PET as the gatekeeper, radionuclide therapy with (223)Ra may be more effective and have more success regarding changes in the PSA. An increase in PSA during therapy cycles occurs due to disease progression.

Journal of nuclear medicine : official publication, Society of Nuclear Medicine. 2016 Sep 22 [Epub ahead of print]

Hojjat Ahmadzadehfar, Kambiz Azgomi, Stefan Hauser, Xiao Wei, Anna Yordanova, Florian Gaertner, Stefan Kürpig, Holger Strunk, Markus Essler

University Hospital Bonn-Department of Nuclear Medicine, Germany;, University Hospital Bonn - Department of Urology;, University Hospital Bonn - Department of Nuclear Medicine;, University Hospital Bonn - Department of Radiology.