Treatment response and safety of ¹⁷⁷Lu-SPECT-specific membrane antigen-617 radioligand therapy in metastatic castration resistant prostate cancer: Uruguayan experience

The aim of this study was to evaluate treatment response and safety of radioligand therapy (RLT) with ¹⁷⁷Lu-PSMA-617 in metastatic castration-resistant prostate cancer patients (mCRPC). Between October/2017 and October/2020 seventeen patients (mean age 67.3 years, range 50-79 years; median PSA level 100 ng/ml, range 6-1000 ng/ml) with mCRPC underwent ⁶⁸Ga-PSMA-11 PET/CT and ¹⁷⁷Lu-PSMA therapy. We evaluated clinical response (by pain relief and use of analgesics), therapy response (by PSA and PSMA-PET-Progression-criteria), adverse events (CTCAE version 4.03) and dosimetry. All patients received 1 to 5 doses of ¹⁷⁷Lu-PSMA-617 (mean activity 7.1 GBq/cycle) every 6-8 weeks (1 cycle n=1, 2 cycles n=2, 3 cycles n=12, 4 cycles n=1 and 5 cycles n=1). Eleven patients (70.6%) completed three cycles of therapy. PSMA-avid metastatic lesions were seen in the following sites: bone (all patients), lymph nodes (n=11), liver (n=2), lung (n=2) and adrenal glands (n=1). Twelve patients (70, 6%) showed pain relief and reduction in the use of analgesics. Concerning PSA response five patients showed biochemical response, 3 patients stable disease and 7 patients progressive disease. 7/15 patients (46.6%) showed any PSA decline. We documented xerostomia (n=2), nausea (n=3), fatigue (n=5), thrombocytopenia (n=2) and pain relief (n=8). There was no hepatotoxicity and nephrotoxicity documented. The safety of ¹⁷⁷Lu-PSMA-617 for non target tissues was confirmed showing mean absorbed doses (Gy) below the recommended ones in critical organs. ⁶⁸Ga-PSMA-11 PET/CT images showed disease progression (n=9) and partial remission (n=5). During the observation period seven patients (41%) died. RLT is a safe and well tolerated therapeutic option for patients with mCRPC. (author)