Abstract
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Objectives Radioligand therapy (RLT) with 177Lu-PSMA-617 (Lu-PSMA) (prostate-specific membrane antigen) is a novel targeted therapy for metastatic prostate cancer. In this study we evaluated the effect of different pretherapeutic parameters on therapy response measured by PSA two months after RLT.
Methods RLT was performed in 40 hormone and/or chemorefractory patients with distant metastases and progressive disease (mean age: 71.4 y/o). 68Ga-PSMA PET/CT was performed in all patients one to two weeks prior to RLT. SUV max and mean were determined by region of interest. SUV values were recorded for up to five bone and lymph node lesions as well as for relevant normal organs such as liver and spleen as background for the calculation of lesion/background. CBC, renal and liver functions, different previous therapies, pain medication and SUVs were evaluated.
Results All patients were treated with a mean of 6 GBq. PSA was controlled two months after RLT. A proportion of 67.5% showed a PSA decline, with 45% and 35% showing a decline of more than 30% and 50%, respectively. In the univariate analysis, older age, a lower Gleason score, a lower number of platelets, lower CRP, no need for pain medication and lower LDH reflected a positive impact of better therapy response; however, multivariate analysis revealed that the most significant independent factors were the number of platelets and no need for pain medication. The response was independent of the amount of PSMA uptake, previous therapies with enzalutamide, abiretarone, Ra-223 and chemotherapy, and other measured factors.
Conclusions RLT with Lu-PSMA is an effective therapy in hormone-refractory patients. The metastases should be just PSMA-positive but the response is independent of the amount of PSMA expression. A better treatment response was observed in older patients with a lower Gleason score as well as in patients with platelets in the lower normal limit and without regular need for pain medication.