Late Pseudoprogression in glioblastoma: diagnostic value of dynamic O-(2-[18F]fluoroethyl)-L-tyrosine PET

Purpose: Pseudoprogression (PsP) is characterized by therapy-associated but not tumor growth-associated increases of contrast-enhancing glioblastoma lesions on MRI. Although typically occurring during the first 3 months after radiochemotherapy (RCX), PsP may occur later in the course of the disease and may then be particularly difficult to distinguish from true tumor progression. We explored PET using O-(2-[18F]fluoroethyl)-L-tyrosine (18F-FET-PET) to approach the diagnostic dilemma. Experimental Design: Twenty-six patients with glioblastoma that presented with increasing contrast-enhancing lesions later than 3 months after completion of RCX underwent 18F-FET-PET. Maximum and mean tumor/brain ratios (TBRmax, TBRmean) of 18F-FET uptake as well as time-to peak (TTP) and patterns of the time-activity curves were determined. The final diagnosis of true progression vs. latePsP was based on follow-up MRI using RANO criteria. Results: LatePsP occurred in seven patients with a median time from RCX completion of 24 weeks while the remaining patients showed true tumor progression. TBRmax and TBRmean were significantly higher in patients with true progression than in patients with latePsP (TBRmax 2.4±0.1 vs. 1.5±0.2, p=0.003; TBRmean 2.1±0.1 vs. 1.5±0.2, p=0.012) while TTP was significantly shorter (mean TTP 25±2 vs. 40±2 min, p<0.001). ROC analysis yielded an optimal cut-off of 1.9 for TBRmax to differentiate between true progression and latePsP (sensitivity 84%, specificity 86%, accuracy 85%, p=0.015). Conclusions: O-(2-[18F]fluoroethyl)-L-tyrosine PET provides valuable information in assessing the elusive phenomenon of late pseudoprogression.

from Cancer via ola Kala on Inoreader http://ift.tt/2299Oro
via IFTTT