Adding 18F-fluorodeoxyglucose positron-emission tomography-computed tomography (18F-FDG-PET/CT) to standard workup can result in re-staging and changes in treatment for patients with high-risk or very high-risk nonmuscle invasive bladder cancer (NMIBC) considered for radical cystectomy, according to investigators.
The study is the first to evaluate the clinical value of 18F-FDG-PET/CT for pretreatment staging of high-risk NMIBC.
Laura S. Mertens, MD, PhD, of Netherlands Cancer Institute in Amsterdam, and colleagues retrospectively reviewed medical records from 92 patients at their institution who underwent pretreatment 18F-FDG-PET/CT in addition to contrast-enhanced CT of the chest and abdomen/pelvis from 2011-2021. In 14 patients (15%), 18F-FDG-PET/CT additionally detected 12 suspicious lymph nodes and 4 distant metastases, the investigators reported in Clinical Genitourinary Cancer. Re-staging occurred in 11 patients (12%) based on the findings. Treatment was changed for 9 patients (10%). Specifically, clinicians advised neoadjuvant or induction chemotherapy rather than upfront radical cystectomy for 4 patients, and neoadjuvant or induction chemotherapy rather than intravesical instillations for 2 patients. They recommended palliative care instead of radical cystectomy to 2 patients with cN3M1b found on 18F-FDG-PET/CT. Upfront radical cystectomy instead of systemic treatment was offered to 1 patient who was downstaged.
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Standard histopathology, cytology, and imaging identified 25 patients (27%) with metastases, the investigators reported. The sensitivity, specificity and accuracy of 18F-FDG-PET/CT was 36%, 93% and 77% respectively, compared with 12%, 97%, and 74% for contrast-enhanced CT only, using this reference standard. The area under the receiver operating characteristic curve was significantly higher for 18F-FDG-PET/CT than for contrast-enhanced CT: 0.64 vs 0.55.
Diagnostic CT is limited in its ability to detect metastases in normal or minimally enlarged lymph nodes, requires good renal function, and is associated with high radiation dose, according to Dr Mertens’ team.
“The addition of FDG-PET/CT to CE-CT imaging changed the treatment in 10% of patients and proved to be a valuable diagnostic tool in a selected subgroup of NMIBC patients scheduled for [radical cystectomy],” the investigators wrote. They noted, however, that 18F-FDG-PET/CT may result in false-positive findings, and patients must endure urinary excretion of FDG. Micro-metastases were still missed in approximately two-thirds of patients.
The potential benefits of additional 18F-FDG-PET/CT imaging before radical cystectomy needs to be weighed against its disadvantages for each patient.
Reference
van Ginkel N, van Gennep EJ, Oosterbaan L, et al. Added clinical value of 18F-FDG-PET/CT to stage patients with high-risk non-muscle invasive bladder cancer before radical cystectomy. Clin Genitourin Cancer. Published online Feb 22, 2023. doi:10.1016/j.clgc.2023.02.004
