ESMO 2017: Lutetium-177 PSMA (LuPSMA) Theranostics Phase II trial: Efficacy, safety and QoL in patients with castrate-resistant prostate cancer treated with LuPSMA

Madrid, Spain ( Dr. Hofman and colleagues from Melbourne, Australia presented results from their phase II Lutetium-177 PSMA (177Lu-PSMA) trial for the treatment of metastatic castrate-resistant prostate cancer (mCRPC) at today’s prostate cancer session at ESMO 2017 in Madrid, Spain. Ultimately, progressive mCRPC is lethal providing an opportunity for new therapeutics to attempt to improve survival in this palliative disease state. 177Lu-PSMA, a radiolabelled small molecule, is one such option. 177-Lu-PSMA binds with high affinity to the prostate specific membrane antigen (PSMA) enabling beta particle therapy targeted to mCRPC. The objective of this study was to assess efficacy and safety of 177-Lu-PSMA treatment for patients with mCRPC who have failed standard therapies.

This was a phase II prospective trial, enrolling 30 patients with PSMA-avid mCRPC who had failed standard therapies. Patients received up to four cycles of 177Lu-PSMA every 6 weeks. The primary endpoints were PSA and imaging response (based on PCWG2) and toxicity (based on CTCAE v4). Secondary endpoints included quality of life (EORTC QLQ-C30/BM22, BPI), dosimetry, progression free survival (PFS) and overall (OS). All 30 patients were enrolled between October 2015 and December 2016, with a median age 69 of years, ECOG of 1, and PSA doubling time of 2.2 months. Prior treatment included chemotherapy (87%; 47% of which was cabazitaxel) and abiraterone/enzalutamide (83%). The mean dose of 177Lu-PSMA was 7.5 GBq (range 4.4 – 8.7 GBq), adjusted according to tumor burden, renal function and weight. At the interim analysis, 17 patients (57%) achieved PSA decline >50%, including 11 patients (37%) with decline >80%. Among 17 patients with soft tissue disease, objective response (RECIST partial response or complete response) occurred in 12 patients (71%). Most common adverse events were grade 1 xerostomia (63%) and nausea (50%). Grade 3 or higher hematoxicity occurred in 5 patients (17%). Following the first cycle of 177Lu-PSMA, global health score improved significantly (≥10 points) in 37% of patients, while in those with bone pain, mean severity score improved significantly (≥ 10 points) in 43% of patients.

In conclusion, this phase II trial demonstrates that 177Lu-PSMA treatment for patients with mCRPC who have failed standard therapy provides encouraging response rates with acceptable toxicity, in addition to improved QoL and pain reduction. Based on this trial, we eagerly await the results of larger studies with long-term follow-up.

Speaker: Michael S. Hofman, Peter MacCallum Cancer Centre, Melbourne, Australia

Co-Authors: S. Sandhu (Melbourne, Australia) P. Eu (Melbourne, Australia) J. Price (Melbourne, Australia) T. Akhurst (Melbourne, Australia) A. Iravani (Melbourne, Australia) G. Kong (Melbourne, Australia) A. Ravi-Kumar (Melbourne, Australia) S. Williams (Melbourne, Australia) S. Thang (Melbourne, Australia) D. Murphy (Melbourne, Australia) M. Scalzo (Melbourne, Australia) R. J. Hicks (Melbourne, Australia) J. Violet (Melbourne, Australia)

Written By: Zachary Klaassen, MD, Urologic Oncology Fellow, University of Toronto, Princess Margaret Cancer Centre, Twitter: @zklaassen_md
at the European Society for Medical Oncology Annual Congress - September 8 - 12, 2017 - Madrid, Spain
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