ASCO GU 2018: Lu-177-labeled PSMA-I&T Radioligand Therapy for mCRPC

San Francisco, CA (UroToday.com) The authors of this study aimed to report their clinical experience with 177Lutetium-labeled prostate-specific membrane antigen-ligand (177Lu-PSMA-I&T) for systemic radioligand therapy in 100 consecutive patients with metastatic castration-resistant prostate cancer (mCRPC).

Methods:
All patients were treated under a review board-approved compassionate use protocol. Eligibility criteria for 177Lu-PSMA-I&T therapy included previous treatment with abiraterone or enzalutamide, previous taxane-based chemotherapy, or unsuitability for taxanes, as well as a positive 68Ga-PSMA tracer uptake of metastases in a prior PET-scan. Intravenous treatment with 177Lu-PSMA-I&T was given on a 6- to 8-weekly basis, with an activity of 7.4GBq up to 6 cycles in patients without clinical or radiographic progression. The study endpoints included PSA decline, PSA progression-free survival (PSA-PFS), clinical progression-free survival (cPFS), overall survival (OS), and toxicity.

Results:
The median age was 72 years (range 46-85) and median PSA level was 164 ng/ml (range 0-6178). Bone, lymph node and visceral metastases were present in 94%, 85% and 33% of patients, respectively. The median number of previous treatment regimens for mCRPC was 3 (range 1-6) and 84% of patients were pretreated with chemotherapy. At the time of evaluation, 286 cycles with 177Lu-PSMA-I&T had already been applied (median 2 cycles per patient, range 1-6), while treatment was still ongoing in 27% of patients. Overall, 4 and 6 cycles were applied in 33 and 15 patients, respectively. A PSA decline ≥30%, ≥50% and ≥90% was achieved in 40%, 32% and 9% of patients, respectively. Median PSA-PFS was 3.4 months (95%CI 2.7-4.0), median cPFS was 4.1 months (95%CI 2.5-5.7) and median OS was 12.2 months (95%CI 8.8-15.7). Treatment-associated adverse hematologic grade 3/4 toxicities included anemia in 7%, thrombocytopenia in 5%, and neutropenia in 4% of patients. Grade 3/4-non-hematologic toxicities were not observed. The main non-hematologic grade 1/2 toxicities included dry mouth in 18%, fatigue in 16% and loss of appetite in 9/% of patients.

Conclusions:
The authors concluded that radioligand therapy with 177Lu-PSMA I&T appears to be safe and beneficial in late-stage mCRPC patients.

Presented by: Matthias Michael Heck

Written by: Hanan Goldberg, MD, Urologic Oncology Fellow (SUO), University of Toronto, Princess Margaret Cancer Centre, Twitter:@GoldbergHanan at the 2018 American Society of Clinical Oncology Genitourinary (ASCO GU) Cancers Symposium, February 8-10, 2018 - San Francisco, CA
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