18-FDG PET/CT assessment of basal cell carcinoma with vismodegib

Abstract

The use of 18-fluorodeoxyglucose (FDG) positron emission tomography with computed tomography (PET/CT) in subjects with advanced basal cell carcinoma (BCC) has not been fully explored due to the rarity of disease presentation. This study evaluated PET/CTs from subjects with advanced BCC participating in a phase I dose-escalation clinical trial of vismodegib. Fourteen subjects with BCC were imaged with 18-FDG PET/CT for lesion identification and response categorizing (European Organisation for Research and Treatment for Cancer [EORTC] and PET response criteria in solid tumors [PERCIST] 1.0). Several parameters including metabolic activity of target lesions, site of disease presentation and spread, treatment response, and prognostic significance of metabolic activity following therapy were evaluated. All subjects exhibited at least one hypermetabolic lesion. Most subjects had only four organ systems involved at study enrollment: skin-muscle (93%), lung (57%), lymph nodes (29%), and bone (21%). SUVmax measured across all lesions decreased (median 33%, SD ± 45%) following therapy with metabolic activity normalizing or disappearing in 42% of lesions. No significant difference was observed between EORTC and PERCIST 1.0. Subjects that demonstrated at least a 33% reduction in SUVmax from baseline had a significantly longer progression-free survival (PFS) (median 17 months, 95% confidence interval [CI] ±4 months vs. 9 months, 95% CI ±5 months, P = 0.038) and overall survival (OS) (median 24 months, 95% CI ±4 months vs. 17 months, 95% CI ±13 months, P = 0.019). BCC lesions are hypermetabolic on 18-FDG PET/CT. A decrease in SUVmax was associated with improved PFS and OS. These results further support the incorporation of 18-FDG PET/CT scans in advanced BCC management.

Trial registration: ClinicalTrials.gov NCT00607724.

Keywords: Basal cell carcinoma; PET/CT; imaging; vismodegib.

Figure 1

Representative images from 18-FDG PET/CT scans. Panels A–D represent baseline and follow-up 18F-FDG PET/CT scans in two separate subjects with soft tissue, bone, and muscle involvement (panels A and B; SUVmax 5.6 vs. 2.8 baseline vs. follow-up, respectively) and lung involvement (panels C and D; SUVmax 12.6 vs. 0.2 at baseline vs. follow-up, respectively). Panels E–H are sample images demonstrating typical locations of BCC metastasis on 18-FDG PET/CT in the skull base (E), lymph nodes (F), lungs, bone, and pleural space (G and H). Panels I–J show the value of baseline axial 18-FDG PET/CT image and three-dimensional CT volume rendering depicting the extent of superficial and deep tissue lesion involvement of a hypermetabolic lesion (SUVmax 21.1; panels I and K) of the inferior left orbit, left cheek, nasal tissues, and maxillary tissue. After therapy, the axial 18-FDG PET/CT fusion image and three-dimensional CT volume rendering exhibited significant reduction in metabolic activity (SUVmax <2.0) and soft-tissue healing (panels J and L).

Figure 2

Progression-free survival (P = 0.038) (A) and overall survival (P = 0.019) (B); Kaplan–Meier (censored) curves demonstrating significant differences in days between subjects with at least 33% reduction (solid line) in SUVmax compared to those exhibiting less than 33% reduction in SUVmax (broken line).