Abstract
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Objectives A bone scintigraphy should precede radionuclide therapy with Ra-223 for the evaluation of eligible candidates for this therapy. The existence of any visceral metastasis is a contraindication for Ra-223 therapy. During the therapy cycles the majority of patients show a continuous PSA rise, which is interpreted sometimes as therapy-induced. In this study we evaluated retrospectively the utility of 68Ga-PSMA-PET as a gatekeeper for treatment planning with Ra-223.
Methods Fifty-three consecutive patients with bone metastatic prostate cancer who had been treated with at least three cycles of Ra-223 were included in this study. Twenty-nine patients were treated according to bone scintigraphy and radiological imaging (CT or MRI) (group A) and 24 patients were selected on the basis of a bone scintigraphy as well as PSMA-PET (group B). Those patients with small lymph node metastases as well as local recurrence were not excluded from treatment. PSA and alkaline phosphatase were measured prior to each cycle and at least 4 weeks after the last cycle.
Results Altogether 258 cycles were performed (median: 5). Mean PSA and alkaline phosphatase (ALP) values prior to the first cycle were 231 ng/ml (0.5-4410) and 173 U/l (2 -594). A PSA decline was observed in 13/53 patients (24.5 %). Four of 29 patients (14 %) in group A showed a PSA decline, while 9 of 24 patients (37.5%) in group B showed a PSA decline (p=0.04). Regarding an ALP decline there was no significant difference between both groups, which shows the general effect of radiation on metabolic active bone metastases, detected by bone scintigraphy.
Conclusions By using PSMA-PET as the gatekeeper Ra-223 therapy ‘may be more effective and have more success regarding changes in the PSA? A rising PSA during the therapy cycles is rather due to a disease progression.