Comparison of RECIST 1.1, mRECIST and PERCIST for assessment of peptide receptor radionuclide therapy treatment response in metastatic neuroendocrine tumors.

Purpose: To compare RECIST 1.1, modified RECIST (mRECIST) and PERCIST for assessment of Peptide Receptor Radionuclide Therapy (PRRT) treatment response in metastatic neuroendocrine tumors.

Materials: In this IRB-approved, HIPAA compliant retrospective study, patients treated with PRRT between July 2019 and Dec 2022 were identified. Inclusion criteria were presence of at least one pre-and one post-treatment imaging (CT, MRI, Ga 68 or Cu64 DOTATATE PET/CT) within one year of the start and end of PRRT respectively. The imaging was reviewed independently by two radiologists using RECIST 1.1, modified RECIST (mRECIST) and PERCIST criteria. Response of first post treatment scan and presence of disease progression during follow-up were recorded along with the date of best response and disease progression. Statistical analysis was performed to determine inter-reader agreement and agreement between the various response criteria using kappa statistics.

Results: Best response by RECIST 1.1 was recorded in 26 patients (PR-7, SD- 13, PD- 6), by mRECIST in 22 patients (PR-7, SD- 10, PD- 5), by PERCIST in 14 patients (PR-4, SD- 3, PD- 7). Inter-reader agreement was highest for PERCIST (weighted kappa 0.921, standard error 0.078 95% CI 0.769 to 1.000) followed by RECIST 1.1 (weighted kappa 0.897, standard error 0.071 95% CI 0.758 to 1.000) and mRECIST (weighted kappa 0.883, standard error 0.079 95% CI 0.727 to 1.000).