18F-fluciclovine PET in Metastatic Castration Resistant Prostate Cancer Treated With Life Prolonging Therapies

Prostate cancer is a hormonally-driven disease and androgens are key in the growth of both normal prostate and prostate cancer cells. Once mCRPC is evident, most patients receive a second-generation hormonal therapy to further suppress the synthesis or androgens (abiraterone) and to block androgen receptor (AR) activation, nuclear translocation and DNA binding (enzalutamide).

Conventional imaging of prostate cancer has limitations in staging, restaging after biochemical relapse, and response assessment. Functional imaging with positron emission tomography (PET) can target various aspects of tumor biology and is clearly superior in the detection of extra-prostatic disease. 18F-fluciclovine is a synthetic amino acid transported across mammalian cell membranes by amino acid transporters that are upregulated in prostate cancer cells.

18F-fluciclovine is approved for PET imaging to identify sites of prostate cancer recurrence in men with rising prostate specific antigen (PSA) following prior definitive treatment. This study describes the changes in 18F-fluciclovine PET scan and compare these results with PSA and conventional computerized tomography (CT) and bone scans, in mCRPC patients treated with abiraterone acetate-prednisone, enzalutamide or docetaxel.

Inclusion criteria

• Eastern Cooperative Oncology Group (ECOG) Performance status 0-2;
• Age ≥ 18 years;
• Histologically confirmed adenocarcinoma of the prostate;
• Ongoing use of luteinizing hormone-releasing hormone (LHRH) required in the absence of surgical castration and castrate concentration of testosterone (< 50 ng/dL);
• Detectable PSA of at least 2 ng/dL;
• Metastatic disease documented by CT or bone scan within 42 days of cycle 1 day 1;
• Life expectancy of ≥ 6 months;
• Must have disease progression despite a castrate concentration of testosterone of < 50 ng/dL based on:

A. PSA progression defined as increase in PSA of at least 2 ng/dL and 25% from nadir values of prior therapy, determined by 2 separate measurement taken at least 1 week apart;

And/or

B. Radiographic disease progression based on response evaluation criteria in solid tumors (RECIST) 1.1 for soft tissue disease and/or prostate cancer working group 3 (PCWG3) for bone only disease;

• No prior life-prolonging therapies for mCRPC are allowed, except Sipuleucel-T;
• The use of docetaxel in the metastatic hormone-sensitive prostate cancer (mHSPC) setting is allowed;
• Low dose prednisone (10 mg or less) or equivalent is allowed;
• Acceptable liver function (within 28 days from enrollment) defined as:

A. Bilirubin < 2.5 times upper limit of normal (ULN), except for patients with known Gilbert disease (in such cases bilirubin < 5 times ULN);

B. AST (SGOT) and ALT (SGPT) < 3 times ULN

• Acceptable renal function (within 28 days from enrollment):

A. Serum creatinine ≤ 2.0 x ULN or creatinine clearance ≥ 30 mL/min

• Acceptable hematologic status (within 28 days from enrollment):

A. Absolute neutrophil count (ANC) ≥ 1000 cell/mm3 (100 x 109/L)

B. Platelet count ≥ 100,000 platelet/mm3 (100 x 109/L)

C. Hemoglobin ≥ 9 g/dL

• At least 2 weeks since prior radiation before starting study treatment (cycle 1 day 1);
• Able to understand and willing to sign a written informed consent document;
• Patients who have partners of childbearing potential must be willing to use a method of birth control with adequate barrier protection as determined to be acceptable by the principal investigator and sponsor during the study and for 1 week after last dose of abiraterone acetate.

Exclusion criteria

• Pathological findings consistent with small cell carcinoma of the prostate;
• Prior treatment with docetaxel for metastatic castration-resistant prostate cancer (CRPC);
• Patient with normal 18F-flucicolovine PET/CT scans at baseline;
• Know allergies, hypersensitivity, or intolerance to abiraterone, prednisone, 18F-fluciclovine or their excipients;
• Any chronic medical condition requiring ≥ 10 mg daily of systemic prednisone (or equivalent);
• Major surgery (e.g., required general anesthesia) within 2 weeks before screening;
• Uncontrolled active infection (including hepatitis B or C or AIDS). Patients with hepatitis B/C who have disease under control and no significant liver function impairment, and undetectable viral load will be allowed to participate. Similarly, patients with known HIV and ≥ 400 CD4 + T cells are allowed to participate;
• Evidence of other metastatic malignancies within the last year;
• Evidence of serious and/or unstable pre-existing medical, psychiatric or other condition (including laboratory abnormalities) that could interfere with patient safety or provision of informed consent to participate in this study.