Predictive and Prognostic Role of Pre-Therapy and Interim 68Ga-DOTATOC PET/CT Parameters in Metastatic Advanced Neuroendocrine Tumor Patients Treated with PRRT

Abstract

Peptide receptor radionuclide therapy (PRRT) is an effective therapeutic option in patients with metastatic neuroendocrine tumor (NET). However, PRRT fails in about 15–30% of cases. Identification of biomarkers predicting the response to PRRT is essential for treatment tailoring. We aimed to evaluate the predictive and prognostic role of semiquantitative and volumetric parameters obtained from the 68Ga-DOTATOC PET/CT before therapy (bPET) and after two cycles of PRRT (iPET). A total of 46 patients were included in this retrospective analysis. The primary tumor was 78% gastroenteropancreatic (GEP), 13% broncho-pulmonary and 9% of unknown origin. 35 patients (76.1%) with stable disease or partial response after PRRT were classified as responders and 11 (23.9%) as non-responders. Logistic regression analysis identified that baseline total volume (bTV) was associated with therapy outcome (OR 1.17; 95%CI 1.02–1.32; p = 0.02). No significant association with PRRT response was observed for other variables. High bTV was confirmed as the only variable independently associated with OS (HR 12.76, 95%CI 1.53–107, p = 0.01). In conclusion, high bTV is a negative predictor for PRRT response and is associated with worse OS rates. Early iPET during PRRT apparently does not provide information useful to change the management of NET patients.

Relevance of Volumetric Parameters Applied to [68Ga]Ga-DOTATOC PET/CT in NET Patients Treated with PRRT

“…This finding highlights that [ 68 Ga]Ga-DOTATOC PET/CT could also be important in the assessment of response to PRRT, which is actually performed only with RECIST 1.1 criteria on ceCT. Moreover, our study strengthens the results of Durmo and colleagues [26], highlighting the importance of a volumetric evaluation of the disease burden in patients treated with PRRT, both at baseline and at follow-up [ 68 Ga]Ga-DOTATOC PET/CT.…”

“…Ezzidin et al [38] already reported a correlation between baseline liver tumor burden ≥25% on radiological imaging and OS after PRRT. Furthermore, Durmo et al [26] recently discriminated PRRT-responders from nonresponders according to baseline SRETV (which they called bTV), similarly to the work previously published by Pauwels et al [25]. To the best of our knowledge, this is the first work reporting that post-SRETV_WB and post-SRETV_L on [ 68 Ga]Ga-DOTATOC PET/CT both correlated with early clinical response.…”

“…In this context, a few studies have explored the possible application of semiquantitative parameters extracted from [ 68 Ga]Ga-DOTA-SSTR PET/CT in patients treated with PRRT [25][26][27][28]. In particular, volumetric parameters are widely used for interpreting [ 18 F]F-FDG PET/CT imaging in several types of malignancies [29,30].…”

Somatostatin Receptor Targeted PET-Imaging for Diagnosis, Radiotherapy Planning and Theranostics of Meningiomas: A Systematic Review of the Literature

“…However, several approaches (i.e., CT-based, SUV-based, etc.) have been proposed for segmentation [ 51 , 52 ]; in particular, a threshold above 41% of SUVmax has been utilized for volume segmentation in neuroendocrine tumors [ 53 ]. In this regard, Kowalski and collaborators [ 33 ] applied a threshold of 2.3 SUVmax for contouring meningiomas’ lesions.…”

Endocrine and Neuroendocrine Tumors: A Special Issue

“…Although peptide receptor radionuclide therapy (PRRT) is an effective therapeutic option in patients with metastatic NET, this treatment modality is inefficacious in about 15–30% of cases. The paper by Durmo et al [ 6 ] was designed to retrospectively identify biomarkers able to predict responses to PRRT in metastatic NET patients with different primary malignancies. The results found that a high baseline tumor volume was the only parameter negatively associated with the disease response to PRRT and patient survival.…”