Quantitative PET Parameters for Outcome Prediction of Peptide Receptor Radionuclide Therapy in Patients with Gastroenteropancreatic Neuroendocrine Tumors (GEP-NETs)

 

• Areas of Interest:

  • PRRT

  • Theragnostics

Background: Peptide receptor radionuclide therapy (PRRT) is an effective systemic treatment for advanced Gastroenteropancreatic neuroendocrine tumors (GEP-NETs); however, there is an unmet need for predictive biomarkers. We aimed to evaluate the role of a series of quantitative PET parameters as imaging biomarkers predictive of response to PRRT.

Methods: We performed a prospective study in progressive, unresectable GEP-NETs patients treated with ¹⁷⁷Lu-PRRT. ⁶⁸Ga-DOTATATE PET/CT and diagnostic CT/MRI were scheduled at baseline, 1 to 3 weeks before each treatment cycle and 3 months after the last one. Maximum five target lesions (TL) per patient (RECIST 1.1 measurable) were selected on baseline images. Lesions were delineated on all PET images to calculate: SUVmax/peak, tumor receptor expression (TRE = SUVmean × volume), tumor-to-Spleen (T/S)/tumor-to-blood (T/B) ratios, and their relative changes. The longest axial diameter was documented on all CTs/MRIs to assess morphological response as per RECIST 1.1. All parameters were correlated to progression-free survival (PFS) to assess their predictive value.

Results: Median PFS for the whole cohort (n = 37) was 28.1 months. Evaluated PET parameters decreased significantly after the first cycle (p < 0.0001), with mean TRE decrease greater than 10% discriminating two groups with distinct PFS (32.2 vs. 22.8 months, p = 0,0095). Mean percentage change of TL diameter was not predictive of improved PFS (p = 0,208). There was no correlation between the percentage change in TL diameter on anatomical imaging and the percentage change in SUVmax/peak, T/S, and T/B after first and last PRRT.

Conclusion: Early decrease of mean TRE of greater than 10% was the only parameter associated with improved PFS. No correlation was found between ⁶⁸Ga-DOTATATE PET parameters and morphological response to PRRT.

Publication History

Article published online:
10 May 2022

© 2022. World Association of Radiopharmaceutical and Molecular Therapy (WARMTH). This is an open access article published by Thieme under the terms of the Creative Commons Attribution-NonDerivative-NonCommercial License, permitting copying and reproduction so long as the original work is given appropriate credit. Contents may not be used for commercial purposes, or adapted, remixed, transformed or built upon. (https://creativecommons.org/licenses/by-nc-nd/4.0/)

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