Detecting Metastases by PyL PET/CT in Subjects Starting Enzalutamide for Untreated Castration Resistant Prostate Cancer.

Prostate cancer (PCa) is the most common solid organ cancer in North American men and is initially androgen sensitive. Therefore, castration and/or androgen receptor blockade remains the central palliative treatment once PCa has metastasized or failed to locoregional therapies. Because androgen deprivation therapy is not curative, all patients will eventually progress to the metastatic castration-resistant prostate cancer state. About 5% of prostate cancers will be metastatic by conventional imaging techniques at diagnosis while most patients achieving CRPC state will first be localized and then progress to metastatic state later in the disease course. Therefore, a significant proportion of patients will progress through an intermediary state of disease defined as the non-metastatic CRPC state (M0CRPC). Over the last year and a half, M0CRPC treatment landscape has completely changed with demonstrating the benefits of second-generation antiandrogens (darolutamide, enzalutamide and apalutamide) to prevent progression of M0CRPC patients. Enzalutamide have then been approved by the Federal Drug Administration and Health Canada for the treatment of M0CRPC.

On the other hand, conventional imaging techniques based on bone turnover (bone scan (BS)) or anatomical features (magnetic resonance imaging (MRI) or computed tomography (CT)) have important limitations and poor accuracy. Bone scans (BS) is the commonest imaging technique used to detect bone metastases in the clinics. BS does not image directly cancer cells, but the effect of cancer on the bone. Other pathologies such as fractures, degenerative arthritis and other benign bone lesions can also cause focal uptake on BS and lead to false-positive results. Another drawback of BS is its poor sensitivity to image small metastases confined to bone marrow. These limitations stress the importance to improve PCa imaging by using new imaging modalities.

Because novel agents targeting the androgen synthesis and receptor axis (e.g. enzalutamide), bone metastasis (radium-223) and microtubules assembly (docetaxel, cabazitaxel) have been shown to increase metastatic CRPC patients overall survival, a burning question is to determine if the non-metastatic CRPC status is real. There is growing evidence that newer imaging techniques using positron emission tomography can improve metastasis detection accuracy and may refine PCa patient prognostic stratification and treatment eligibility.

Inclusion criteria

• Histologically confirmed adenocarcinoma of the prostate per original diagnosis, with undergoing androgen deprivation therapy such as prior bilateral orchiectomy or surgical castration or LHRH-agonists/LHRH-antagonists.
• Suspected recurrence of prostate cancer based on rising PSA under androgen deprivation therapy. Recurrent castration resistant prostate cancer patients are defined by a rising PSA >1 ng/mL under ADT or surgical castration and with testosterone castration levels < 1.7 nM (PCWG3 criteria).
• Negative, equivocal findings or oligometastatic disease (< 5) for prostate cancer on conventional imaging bone scan AND 2) abdomen-pelvis CT/MRI and chest CT or FDG-PET/CT or 18F-NaF PET/CT performed as standard of care workup within 90 days of signing the ICF.
• The subject is candidate for second line androgen axis targeted inhibitors such as enzalutamide and planned to receive it.
• Life expectancy ≥6 months as determined by the investigator
• Able and willing to provide signed informed consent and comply with protocol requirement
• PSA doubling time less or equal to 10 months
• Eastern Cooperative Oncology Group (ECOG) performance status of 0 or 1 at screening.
• Able to swallow the study drug and comply with study requirements.

Exclusion criteria

• Subjects administered any high energy (>300 KeV) gamma-emitting radioisotope within 5 physical half-lives prior to study drug injection.
• Receipt of investigational drug therapy for prostate cancer within 60 days of Day 1.
• Known or suspected brain metastasis or active leptomeningeal disease.
• Prior cytotoxic chemotherapy, aminoglutethimide, ketoconazole, abiraterone acetate, or enzalutamide for prostate cancer.
• History of seizure or any condition that may predispose to seizure (e.g., prior cortical stroke or significant brain trauma). History of loss of consciousness (unless of cardiac origin) or transient ischemic attack within 12 months before enrollment.
• Major surgery within 4 weeks before randomization date.
• Absolute neutrophil count < 1000/μL, platelet count < 100,000/μL, or hemoglobin < 10 g/dL (6.2 mmol/L) at screening.
• Total bilirubin ≥ 1.5-times the upper limit of normal or alanine aminotransferase (ALT) or aspartate aminotransferase (AST) ≥ 2.5-times the upper limit of normal at screening.
• Creatinine > 2 mg/dL (177 μmol/L) at screening.
• Albumin < 3.0 g/dL (30 g/L) at screening.
• Clinically significant cardiovascular disease
• Gastrointestinal disorder affecting absorption.
• Ongoing drug or alcohol abuse as per investigator judgment.
• Subject has received any investigational radioactive agent within 28 days or 5 half-lives, whichever is longer, prior to screening.
• Subjects with any medical condition or other circumstances that, in the opinion of the investigator, compromise obtaining reliable data, achieving study objectives, or completing the study.
• Contraindication to enzalutamide
• Treatment with specific (5-α reductase inhibitors, estrogens, cyproterone actetate, biologic agents with antitumor activity, systemic glucocorticoids, androgens, ...) within 4 weeks of day 1 and during the study treatment period