A pilot study of [18F]F-fluciclovine positron emission tomography/computed tomography for staging muscle invasive bladder cancer preceding radical cystectomy

Abstract

Aim

To assess the ability of [¹⁸F]F-fluciclovine-PET/CT to stage muscle invasive bladder cancer (MIBC) before radical cystectomy.

Methods

This single-site prospective pilot study enrolled patients with MIBC and T2-T4, N0 disease on CT/MRI slated to undergo radical cystectomy (RC). Dynamic and static [¹⁸F]F-fluciclovine-PET/CT images were acquired. Clinical readers assessed for confirmation of the primary bladder lesion on imaging and the presence of pelvic nodal metastases. Findings were compared to pathology at RC. Kinetic parameters from dynamic PET/CT were compared across bladder lesions of different clinical stages.

Results

The study enrolled sixteen patients (median age: 73 years, range: 57–88 years, 11 males, 5 females), twelve receiving neoadjuvant chemotherapy before RC. There was high specificity amongst all three readers for detecting lymph node metastases (overall specificity: 0.91, 95%CI: 0.81–1.00) with good overall agreement rate with pathology (0.67, 95%CI: 0.44–0.83). The overall PPV for all readers for identifying node-positive disease was 0.4 (95%CI: 0–1.00), and the overall sensitivity was 0.13 (95%CI: 0–0.44). The overall PPV for detecting the primary tumor was 0.69 (95%CI: 0.47–0.88), and the sensitivity was 0.89 (95%CI: 0.78–1.00), with NPV and specificity being 0.70 (95%CI: 0.33, 1.00) and 0.39 (95%CI: 0.33, 0.50), respectively. Compartmental analysis of the primary bladder tumor revealed that k₁ and v_b parameters significantly differentiated between low (pT0-pT1) and high (pT2-pT4) risk disease (p < 0.05). Immunohistochemical assessment showed no significant correlation of tumor [¹⁸F]F-fluciclovine uptake nor kinetic parameter with amino acid transporter expression.

Conclusions

[¹⁸F]F-fluciclovine demonstrates good specificity and agreement rate for MIBC staging, with sensitivity like CT/MRI. Kinetic parameters such as k₁ was able to delineate higher-stage ( ≥ = pT2) primary lesions. Heterogeneous amino acid transporter expression can be seen across lesions. Further studies are warranted to understand [¹⁸F]F-fluciclovine PET/CT use in the context of other imaging modalities in this disease.

Clinical trial registration

NCT04018053 Registered 2/26/2020.