Published in:
01-04-2016 | Original Article
[18F]FPRGD2 PET/CT imaging of integrin αvβ3 levels in patients with locally advanced rectal carcinoma
Published in: European Journal of Nuclear Medicine and Molecular Imaging | Issue 4/2016
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Purpose
Our primary objective was to determine if [18F]FPRGD2 PET/CT performed at baseline and/or after chemoradiotherapy (CRT) could predict tumour regression grade (TRG) in locally advanced rectal cancer (LARC). Secondary objectives were to compare baseline [18F]FPRGD2 and [18F]FDG uptake, to evaluate the correlation between posttreatment [18F]FPRGD2 uptake and tumour microvessel density (MVD) and to determine if [18F]FPRGD2 and FDG PET/CT could predict disease-free survival.
Methods
Baseline [18F]FPRGD2 and FDG PET/CT were performed in 32 consecutive patients (23 men, 9 women; mean age 63 ± 8 years) with LARC before starting any therapy. A posttreatment [18F]FPRGD2 PET/CT scan was performed in 24 patients after the end of CRT (median interval 7 weeks, range 3 – 15 weeks) and before surgery (median interval 4 days, range 1 – 15 days).
Results
All LARC showed uptake of both [18F]FPRGD2 (SUVmax 5.4 ± 1.5, range 2.7 – 9) and FDG (SUVmax 16.5 ± 8, range 7.1 – 36.5). There was a moderate positive correlation between [18F]FPRGD2 and FDG SUVmax (Pearson’s r = 0.49, p = 0.0026). There was a moderate negative correlation between baseline [18F]FPRGD2 SUVmax and the TRG (Spearman’s r = −0.37, p = 0.037), and a [18F]FPRGD2 SUVmax of >5.6 identified all patients with a complete response (TRG 0; AUC 0.84, 95 % CI 0.68 - 1, p = 0.029). In the 24 patients who underwent a posttreatment [18F]FPRGD2 PET/CT scan the response index, calculated as [(SUVmax1 − SUVmax2)/SUVmax1] × 100 %, was not associated with TRG. Post-treatment [18F]FPRGD2 uptake was not correlated with tumour MVD. Neither [18F]FPRGD2 nor FDG uptake predicted disease-free survival.
Conclusion
Baseline [18F]FPRGD2 uptake was correlated with the pathological response in patients with LARC treated with CRT. However, the specificity was too low to consider its clinical routine use.