Predictive Value of Asphericity in Pretherapeutic [111In]DTPA-Octreotide SPECT/CT for Response to Peptide Receptor Radionuclide Therapy with [177Lu]DOTATATE.

Abstract

The purpose of this study was to assess the value of the spatial heterogeneity of somatostatin receptor (SSR) volume, quantified as asphericity (ASP), and to predict response to peptide receptor radionuclide therapy (PRRT) in patients with metastatic gastroenteropancreatic neuroendocrine neoplasms (GEP-NEN). From June 2011 to May 2013, patients suffering from GEP-NEN who underwent pretherapeutic [111In-DTPA0]octreotide scintigraphy (Octreoscan®) prior to [177Lu-DOTA0-Tyr3]octreotate ([177Lu]DOTATATE)-PRRT were enrolled in this retrospective evaluation. SSR expression in 20 NEN patients was qualitatively and quantitatively assessed using the Krenning score, the metastasis to liver uptake ratio (M/L ratio), and ASP at baseline. Response to PRRT was evaluated based on lesions, which were classified as responding lesions (RL) and non-responding lesions (NRL) after 4- and 12-month follow-ups. The values of the Krenning score, M/L ratio, and ASP for response prediction were compared by using the Mann-Whitney U test, Kruskal-Wallis test, and receiver operating characteristic (ROC) curves. Seventy-seven metastases (liver, n=40; lymph node, n=24; bone, n=11; pancreas, n=2) showed SSR expression. A higher ASP level was significantly associated with poorer response at both time points. ROC analyses revealed the highest area under the curve (AUC) for discrimination between RL and NRL for ASP after 4months (AUC 0.97; p=0.019) and after 12months (AUC 0.96; p<0.001), followed by the Krenning score (AUC 0.74; p=0.082 and AUC 0.85; p<0.001, respectively) and M/L ratio (AUC 0.77; p=0.107 and AUC 0.82; p<0.001). The optimal cutoff value for ASP was 5.12% (sensitivity, 90%; specificity, 93%). Asphericity of SSR-expressing lesions in pretherapeutic single-photon emission computed tomography with integrated computed tomography (SPECT/CT) is a promising parameter for predicting response to PRRT in gastroenteropancreatic neuroendocrine neoplasms.