ENZA-p trial protocol: a randomized phase II trial using prostate-specific membrane antigen as a therapeutic target and prognostic indicator in men with metastatic castration-resistant prostate cancer treated with enzalutamide (ANZUP 1901).

OBJECTIVES: To determine the activity and safety of lutetium-177 (177 Lu)-prostate-specific membrane antigen (PSMA)-617 in men with metastatic castration-resistant prostate cancer (mCRPC) commencing enzalutamide, who are at high risk of early progression, and to identify potential prognostic and predictive biomarkers from imaging, blood and tissue. PARTICIPANTS AND METHODS: ENZA-p (ANZUP 1901) is an open-label, randomized, two-arm, multicentre, phase 2 trial. Participants are randomly assigned (1:1) to treatment with enzalutamide 160 mg daily alone or enzalutamide plus 177 Lu-PSMA-617 7.5 GBq on Days 15 and 57. Two additional 177 Lu-PSMA-617 doses are allowed, informed by Day-92 Gallium-68 (68 Ga)-PSMA positron emission tomography (PET; up to four doses in total). The primary endpoint is prostate-specific antigen (PSA) progression-free survival (PFS). Other major endpoints include radiological PFS, PSA response rate, overall survival, health-related quality of life, adverse events and cost-effectiveness. Key eligibility criteria include: biochemical and/or clinical progression; 68 Ga-PSMA PET-avid disease; no prior androgen signalling inhibitor, excepting abiraterone; no prior chemotherapy for mCRPC; and ≥2 high-risk features for early enzalutamide failure. Assessments are 4 weekly during study treatment, then 6 weekly until radiographic progression. Response Evaluation Criteria in Solid Tumours (RECIST) are used to assess imaging conducted every 12 weeks, 68 Ga-PSMA PET at baseline, Days 15 and 92, and at progression, and 18 F-fluorine deoxyglucose (18 F-FDG) PET at baseline and progression. Translational samples include blood (and optional biopsies) at baseline, Day 92, and first progression. Correlative studies include identification of prognostic and predictive biomarkers from 68 Ga-PSMA and 18 F-FDG PET/CT, circulating tumour cells and circulating tumour DNA. The trial will enrol 160 participants, providing 80% power with a two-sided type-1 error rate of 5% to detect a hazard ratio of 0.625 assuming a median PSA-PFS of 5 months with enzalutamide alone. RESULTS AND CONCLUSION: The combination of 177 Lu-PSMA-617 and enzalutamide may be synergistic. ENZA-p will determine the safety and efficacy of the combination in addition to developing predictive and prognostic biomarkers to better guide treatment decisions.

68 Ga-somatostatin analogue PET-CT: Analysis of costs and benefits in a public hospital setting.

INTRODUCTION: Between 2009 and 2012, 68 Ga-somatostatin analogue PET-CT progressively replaced 111 In-octreotide scintigraphy for imaging neuroendocrine tumours in WA public hospitals due to published literature demonstrating improved diagnostic accuracy and increased availability. Despite significantly improved sensitivity and specificity, 68 Ga-somatostatin analogue PET is currently unfunded in Australia. This study sought to undertake cost analysis of the two modalities in a public hospital setting and to compare them with regard to patient factors such as imaging time and radiation dose. METHODS: This analysis was based on retrospective clinical data from 95 111 In-octreotide scintigraphies performed in 2007 and 2008 at Sir Charles Gairdner (SCGH) and Royal Perth (RPH) hospitals and 219 68 Ga-somatostatin analogue PET-CT studies performed in 2013 at SCGH. Whole body effective radiation dose was derived from the radiopharmaceutical and low-dose CT scan. The cost analysis included radiopharmaceutical and imaging costs. RESULTS: The median imaging time for an 111 In-octreotide scintigraphy was 152 min at SCGH, 100 min at RPH and 20 min for a 68 Ga-somatostatin analogue PET-CT scan. The mean effective radiation dose for 111 In-octreotide scintigraphy was 18.1 mSv at SCGH and 13.8 mSv at RPH. The effective dose for 68 Ga-somatostatin analogue PET-CT was 8.7-10.8 mSv. The average cost of 68 Ga-somatostatin analogue PET-CT was four times less than 111 In-octreotide scintigraphy. CONCLUSION: 68 Ga-somatostatin analogue PET-CT is not only more accurate than 111 In-octreotide scintigraphy, this study has also shown that it is significantly less expensive, delivers a lower radiation dose to patients and requires less imaging time for patients and staff. 68 Ga-somatostatin PET-CT provides an important combination of both reduced cost and improved clinical care for patients.