F-18-Fluciclovine¹⁸F-fluciclovine

Quick Answer

F-18-fluciclovine (Axumin, anti-3-FACBC) is a synthetic leucine analog taken up by upregulated amino-acid transporters (ASCT2, LAT1) in prostate cancer. It was FDA-approved and widely used to localize biochemically recurrent prostate cancer, but it has been largely superseded by PSMA-PET, which detects more disease — especially at low PSA. Its residual advantage is low early urinary excretion, aiding prostate-bed assessment. The interpretive caveat: uptake is not cancer-specific (inflammation, benign prostatic tissue), and reading uses early dynamic timing before blood-pool clearance.

Mechanism

Fluciclovine is transported into cells by the sodium-dependent ASCT2 and sodium-independent LAT1 amino-acid transporters, both upregulated in prostate and other cancers to feed proliferation. Unlike a metabolic substrate, it is not significantly incorporated into protein and is not metabolized — uptake reflects transporter activity and washes out over time, which is why early imaging (shortly after injection) gives the best lesion-to-background.

Biodistribution

Intense physiologic uptake in the pancreas and liver, moderate in marrow and salivary glands, and minimal urinary excretion early — the feature that aids prostate-bed evaluation before bladder activity accumulates. Blood-pool activity is prominent early and clears over the acquisition.

Physics

Clinical Indications

• Biochemically recurrent prostate cancer — localizing disease to direct salvage therapy, where PSMA-PET is unavailable.
• Prostate-bed assessment — low early bladder activity is advantageous vs renally-excreted agents.

Preparation & Protocol

• Fast ~4 h; avoid significant exercise before imaging (muscle amino-acid uptake).
• Image early — begin acquisition from the pelvis shortly after injection (~3–5 min) to catch lesions before blood-pool clearance and before bladder fills.
• Typical activity ~370 MBq (10 mCi).

Interpretation Highlights

• Compare lesion uptake to marrow and blood pool references (not liver, which is intensely physiologic).
• Prostate bed and pelvic nodes are the highest-value territories, exploiting low bladder activity.
• Detection, like all recurrence agents, rises with PSA but is lower than PSMA-PET at matched PSA — the reason for the field's shift.

Reporting Checklist

• State agent, PSA, uptake/timing, and that early pelvic imaging was performed.
• Report prostate-bed, nodal, and osseous findings; use marrow/blood-pool reference.
• Note the non-specificity caveat (inflammation, benign prostatic tissue).

Common Pitfalls

• Benign/inflammatory uptake (prostatitis, benign prostatic tissue, reactive nodes) → false positives.
• Delayed imaging losing lesion conspicuity (tracer washes out; bladder fills).
• Using fluciclovine where PSMA-PET (higher yield) is available.

Board Pearls

F-18-fluciclovine is a synthetic amino-acid (leucine) analog transported by ASCT2/LAT1, used for biochemically recurrent prostate cancer but now largely superseded by PSMA-PET, which detects more disease — especially at low PSA. Its residual advantage is low early urinary excretion, aiding prostate-bed assessment where bladder activity would obscure a renally-excreted agent.

Image early — fluciclovine uptake is transient and washes out while the bladder fills, so pelvic acquisition begins shortly after injection. Uptake is not cancer-specific (prostatitis, benign prostatic tissue, reactive nodes), so read pattern and correlate clinically.

Reference uptake to marrow/blood pool, not liver (intensely physiologic). Fluciclovine's mechanism (proliferation-driven transporter upregulation) is shared by other amino-acid tracers; in prostate cancer specifically, PSMA's target-density advantage and higher low-PSA detection have made it the preferred recurrence agent where available.

Related Pages

• Disease: Prostate cancer, PSMA biochemical recurrence; contrast tracer: PSMA PET agents.

Figure / Diagram Suggestions

• An ASCT2/LAT1 transporter uptake cartoon (early uptake → washout timeline).
• A prostate-bed low-bladder-activity advantage illustration (fluciclovine vs renally-excreted agent).

Self-Check