Fluorodeoxyglucose (FDG)-positron emission tomography (PET)/computed tomography (CT) had high sensitivity in the detection of recurrent cutaneous squamous cell carcinoma (cSCC), according to study data published in the Journal of the American Academy of Dermatology.

Investigators retrospectively reviewed 115 FDG-PET/CT scans from 100 consecutive patients who had been treated for cSCC between 2002 and 2016. PET/CT scans were reviewed by two independent physicians. Sites of abnormal uptake were identified and correlated with histopathology, if available, or with clinical/imaging follow-up data. Comparison with available CT/magnetic resonance (MR) data was also performed. Sensitivity, positive predictive value, and accuracy of FDG-PET/CT were calculated, with pathology as the reference standard. Changes in patient management plans after PET scan were also noted. Cox proportional hazards models were used to assess the prognostic value of FDG-PET/CT.

Of 115 analyzed FDG-PET/CT scans, 96 (84%) were positive for recurrence. Distant metastatic disease involving one or more sites was seen in 25 (26%) of the 96 recurrence-positive scans. PET/CT detected unsuspected disease sites in 39 of 115 scans (34%): locoregional disease (n=14), distant metastases (n=11), locoregional disease with distant metastases (n=8), additional local cutaneous disease (n=5), and second malignancy (n=1). The sensitivity, positive predictive value, and accuracy of FDG-PET/CT scan were 99%, 94%, and 94%, respectively. When compared with 78 CT/MR scans, PET/CT scans detected 37 additional abnormalities, most commonly skin/subcutaneous lesions and nodes. PET/CT scan resulted in management change in 28% patients; 12 patients underwent intermodality management change and 16 underwent intramodality changes or addition of modality.

In multivariate analyses, the number of FDG-positive lesions (hazard ratio [HR], 1.58 for a 5-lesion increase; 95% CI, 1.00-2.49; P =.05) and the presence of lung metastasis (HR, 4.34; 95% CI, 1.54-12.30; P =.006) were significantly associated with risk for death. Risk for disease progression also correlated with FDG-PET/CT parameters, including the number of FDG-positive lesions and the presence of lung and bone metastasis.

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These data suggest that FDG-PET/CT has high sensitivity for the detection of recurrent disease in patients with cSCC. Additionally, several FDG-PET/CT parameters had utility as prognostic tools. As a retrospective study with risk for selection bias, however, results must be extrapolated with care.

“FDG-PET/CT adds incremental value to anatomic imaging by detecting unsuspected disease sites and is advantageous for physicians in selecting the optimum treatment strategy for patient management,” investigators wrote.

Disclosure: Neeta Pandit-Taskar, MD, and Christopher A. Barker, MD, declared affiliations with the pharmaceutical industry. Please see the original reference for a full list of authors’ disclosures.

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Reference

Mahajan S, Barker CA, Mauguen A, Singh B, Pandit-Taskar N. Restaging FDG-PET/CT scan in recurrent cutaneous SCC: diagnostic performance and prognostic significance [published online September 25, 2019]. J Am Acad Dermatol. doi:10.1016/j.jaad.2019.09.035