¹⁷⁷Lu-EB-PSMA Radioligand Therapy with Escalating Doses in Patients with Metastatic Castration-Resistant Prostate Cancer.

Abstract

This study was designed to assess the safety and therapeutic response to ¹⁷⁷Lu-labeled Evans blue-modified prostate-specific membrane antigen (PSMA) 617 (EB-PSMA-617) treatment with escalating doses in patients with metastatic castration-resistant prostate cancer. <b>Methods:</b> With institutional review board approval and informed consent, patients were randomly divided into 3 groups: group A (<i>n</i> = 10) was treated with a 1.18 ± 0.09 GBq dose of ¹⁷⁷Lu-EB-PSMA. Group B (<i>n</i> = 10) was treated with a 2.12 ± 0.19 GBq dose of ¹⁷⁷Lu-EB-PSMA. Group C (<i>n</i> = 8) was treated with a 3.52 ± 0.58 GBq dose of ¹⁷⁷Lu-EB-PSMA. Eligible patients received up to 3 cycles of ¹⁷⁷Lu-EB-PSMA therapy, at 8-wk intervals. <b>Results:</b> Because of disease progression or bone marrow suppression, 4 of 10, 5 of 10, and 5 of 8 patients completed 3 cycles of therapy as planned in groups A, B, and C, respectively. The prostate-specific antigen response was correlated with treatment dose, and the prostate-specific antigen disease control rates were higher in groups B (70%) and C (75%) than in group A (10%) (<i>P =</i> 0.007), but no correlation between groups B and C was found. ⁶⁸Ga-PSMA PET/CT showed a response in all treatment groups; however, there was no significant difference among the 3 groups. A hematologic toxicity study found that platelets decreased more in groups B and C than in group A and that grade 4 thrombocytopenia occurred in 2 (25.0%) patients in group C. No serious nephritic or hepatic side effects were observed. <b>Conclusion:</b> This study demonstrated that a 2.12-GBq dose of ¹⁷⁷Lu-EB-PSMA seems to be safe and adequate in tumor treatment. Further investigations with an increased number of patients are warranted.