Aida Karoliina Kiviniemi MD, Presenter: Nothing to Disclose

Maria Gardberg MD, Abstract Co-Author: Nothing to Disclose

Marko Pesola, Abstract Co-Author: Nothing to Disclose

Janek Frantzen MD, PhD, Abstract Co-Author: Nothing to Disclose

Riitta K. Parkkola MD, PhD, Abstract Co-Author: Nothing to Disclose

Ville Vuorinen MD, PhD, Abstract Co-Author: Nothing to Disclose

Tuula Tolvanen, Abstract Co-Author: Nothing to Disclose

Jarkko Johansson, Abstract Co-Author: Nothing to Disclose

Jukka Kemppainen, Abstract Co-Author: Nothing to Disclose

Anne Roivainen, Abstract Co-Author: Nothing to Disclose

Heikki Ralph Minn MD, PhD, Abstract Co-Author: Support, Bayer AG

Somatostatin receptor type 2 (sstr2) targeted radionuclide therapy is a potential new therapeutic strategy in high-grade glioma (HGG). The purpose of this study was to detect sstr2 expression in HGG with [68Ga]DOTATOC or [68Ga]DOTANOC PET/CT and to investigate the effect of blood-brain barrier (BBB) integrity on tumor tracer uptake with T1-weighted gadolinium enhancement on MRI (T1gad).

27 patients with primary or recurrent HGG underwent dynamic [68Ga]DOTATOC or [68Ga]DOTANOC PET/CT prior to surgery. Maximum standardized uptake values (SUVmax) were calculated and Logan plot was applied to measure receptor binding potential (BP). PET data was correlated to tumor sstr2 immunohistochemistry. Tumor volume concordance between PET (40% SUVmax threshold) and T1gad was assessed by Dice similarity coefficient (DC). Finally, sstr2 expression was correlated to molecular biomarkers with a prognostic value such as mutated IDH1.

Tumor SUVmax significantly correlated with T1gad volume (r=0.90, p<0.001) and tumor grade (r=0.63, p<0.001). DC for PET and T1gad tumor volume concordance, however, was only 0.41±0.19 with PET/T1gad volume proportion being 1.05±0.87. No tracer uptake was detected in eight anaplastic gliomas with intact BBB. Tumor SUVmax values at 30-60 min after tracer injection (range 0.46−5.68) correlated to receptor BP (r=0.91, p=0.000). However, no correlation was found between SUVmax and sstr2 immunostaining among tumors showing tracer uptake. Positive sstr2 immunostaining corresponded to mutated IDH1 (r=0.52, p<0.001) and oligodendroglial differentiation (r=0.67, p<0.001).

[68Ga]DOTATOC and [68Ga]DOTANOC uptake and binding to sstr2 in HGG is highly dependant on BBB disruption evaluated by T1gad on MRI. However, tracer uptake cannot be predicted by sstr2 immunohistochemistry which together with relatively low tumor SUVmax suggests limited feasibility of HGG to sstr2 targeted radionuclide therapy.

Sstr2 expression in HGG corresponds to biomarkers associated with favorable prognosis. However, sstr2 expression in HGG cannot be predicted by [68Ga]DOTATOC or [68Ga]DOTANOC PET/CT.

Kiviniemi, A, Gardberg, M, Pesola, M, Frantzen, J, Parkkola, R, Vuorinen, V, Tolvanen, T, Johansson, J, Kemppainen, J, Roivainen, A, Minn, H, Imaging Somatostatin Receptor Subtype 2 in High-Grade Glioma with [68Ga]DOTATOC and [68Ga]DOTANOC PET/CT.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14018146.html