To evaluate whether extracellular volume (ECV) fraction derived from contrast-enhanced computed tomography (CT) is associated with recurrence risk in patients with treatment-naïve high-risk non-muscle-invasive bladder cancer (HR-NMIBC) receiving intravesical gemcitabine/docetaxel (Gem/Doce) therapy.
This retrospective cohort study, conducted at a tertiary referral centre, included 103 patients with HR-NMIBC treated with intravesical Gem/Doce between 2012 and 2024. All patients underwent pre-resection contrast-enhanced CT with an equilibrium phase (~3 min post-injection). Tumour ECV fraction (%) was calculated using the formula: ECV = (ΔHUtumour/ΔHUaorta) × (1 - haematocrit) × 100, where Δ Hounsfield units (HU) represents the change in attenuation between non-contrast and equilibrium phases. Regions of interest were manually placed in the tumour and abdominal aorta, and haematocrit values obtained within ±10 days were used. Associations between clinical variables, ECV, and recurrence were evaluated using Cox proportional hazards models, with discrimination assessed by Uno's C-statistic.
The median (interquartile range) follow-up was 17 (10-25) months. High-grade recurrence-free survival (HG-RFS) was 76% at 12 months and 69% at 24 months. CT-derived ECV was the only variable significantly associated with HG-RFS (hazard ratio 1.05, 95% confidence interval 1.03-1.08), demonstrating strong discrimination (C-statistic, 0.81; P < 0.01). A 15% threshold offered the best sensitivity-specificity trade-off (~70% each) for predicting HG-RFS at 12 and 24 months. Patients with ECV ≤15% had markedly better HG-RFS than those with ECV >15% at 24 months (88% vs 41%).
The CT-derived ECV is a practical, first-of-its-kind imaging biomarker associated with recurrence risk and useful for risk stratification in patients with HR-NMIBC treated with intravesical Gem/Doce, a regimen increasingly used in the setting of global Bacillus Calmette-Guérin shortages and intolerance. ECV can be rapidly quantified from routine contrast-enhanced CT using standard picture archiving and communication system (PACS) tools, without additional imaging or proprietary software, making it a feasible metric for integration into risk-adapted management pending large-scale validation with extended follow-up.
BJU international. 2026 May 28 [Epub ahead of print]
Mohamad Abou Chakra, Issa Alsamarah, Helen Y Hougen, Yousef Zakharia, James A Brown, Amanda A Myers, Kathryn A Marchetti, Grant M Henning, Sarah L Mott, Igor Duquesne, Bogdan Adrian Buhas, Michael A O'Donnell
Department of Urology, University of Iowa Health Care, Iowa City, IA, USA., Department of Radiology, University of Iowa Health Care, Iowa City, IA, USA., Division of Hematology and Oncology, Department of Medicine, Mayo Clinic, Phoenix, AZ, USA., Holden Comprehensive Cancer Center, University of Iowa, Iowa City, IA, USA., Department of Urology, Hôpitaux Universitaires Henri Mondor, Assistance Publique - Hôpitaux de Paris, Université Paris-Est Créteil, Créteil, Paris, France., Department of Urology, Groupe Hospitalier Diaconesses Croix Saint-Simon, Paris, France.