Study of the dosimetry, safety, and potential benefit of 177Lu-PSMA-617 radionuclide therapy prior to radical prostatectomy in men with high-risk localized prostate cancer (LuTectomy study).

TPS264 Background: High-risk localised prostate cancer (HRCaP) is treated by radical prostatectomy (RP) or radiotherapy. Despite curative intent, a significant number of men will progress with metastatic disease or local recurrence. Lutetium-177 radiolabelled to the small molecule PSMA-617 targeting prostate-specific membrane antigen (Lu-PSMA) has proven efficacious in men with metastatic castration-resistant prostate cancer who have progressed after standard-of-care. The LuTectomy trial evaluates whether administration of Lu-PSMA before radical prostatectomy in men with HRCaP will deliver high doses of radiation to the prostate and involved lymph nodes. It also aims to assess the feasibility, safety profile and oncological efficacy of Lu-PSMA. Methods: Lutectomy is an open-label, phase I/II non-randomised clinical trial. 20 men with HRCaP defined by European Association of Urology who are scheduled for RP and pelvic lymph node dissection (PLND) will be recruited. All men will have high PSMA-avidity with a standardised uptake value (SUVmax) of ≥ 20 on 68 Ga-PSMA PET/CT. The initial 10 participants will receive one cycle of 5GBq Lu-PSMA intravenously and the latter 10 men will receive two cycles of 5GBq Lu-PSMA per cycle six weeks apart. RP with PLND will be performed six weeks later. Participants will be followed up for three years. The primary outcome is to determine the radiation absorbed dose in the prostate and involved lymph nodes. Three-time point quantitative single-photon emission computed tomography (SPECT/CT) will be used to estimate radiation dosimetry using a voxelated technique incorporating partial volume correction. Marrow absorbed dose will also be evaluated using serial blood measures to model pharmacokinetic clearance with a multi-phase exponential model. Translational research samples will include the original biopsy, prostatectomy specimen and plasma/whole blood samples. Secondary objectives include evaluation of the PSMA PET/CT imaging response (defined by SUVmax decline >30%), PSA response, pathological response following Lu-PSMA, adverse effects of Lu-PSMA, surgical safety, and health-related quality of life. Post estimates for time-to-event endpoints will be estimated using the Kaplan-Meier method. The first patient was recruited in July 2020 and recruitment is expected to take up to two years. ClinicalTrials.gov Identifier: NCT04430192. Funding: Movember and Medical Research Future Fund (MRFF), Endocyte Inc., a Novartis Company, E.J. Whitten Foundation. Clinical trial information: NCT04430192.