J Nucl Med. 2008; 49 (Supplement 1):143P
Oncology-Basic Science: Therapy, Metrics & InterventionImaging for Assesment of Response or Therapy Planning |
Monitoring response to peptide receptor radionuclide therapy (PRRT) in patients with metastasized neuroendocrine tumors (NET): Quantitative intra-individual comparison between Ga-68-DOTA-NOC, F-18-FDG-PET/CT, and CT alone
Sowon Oh1,
Vikas Prasad2,
Dong Soo Lee1 and
Richard Baum2
1 Department of Nuclear Medicine, Seoul Nat'l Univ. Hospital, Seoul, South Korea;
2 Department of Nuclear Medicine/Center for PET/CT, Zentralklinik Bad Berka, Bad Berka, Germany
571
Objectives: Response to PRRT was monitored using Ga-68-DOTA-NOC-somatostatin-receptor-PET/CT (SSR-PET, "molecular response") in comparison to F-18-FDG-PET/CT (FDG, "metabolic response") and contrast-enhanced CT alone (ceCT, "morphologic response").
Methods: In 25 patients (57.5±13.4 years) with metastasized NETs, 138 discrete lesions were analyzed by SSR-PET, FDG and ceCT alone, pre and post treatment (up to 3 cycles). RECIST criteria for ceCT, and modified EORTC criteria for SSR-PET and FDG were applied to assess the response. Maximum standardized uptake values (SUVmax) were measured, and a Response Index (RI= 100 x [(post-PRRT SUVmax)-(pre-PRRT SUVmax)] / pre-PRRT SUVmax) was calculated for each lesion. ROC was calculated for SSR-SUVmax of metastatic liver lesions. SD, PR, and PD were determined for response assessment and correlated with clinical/biochemical improvement.
Results: No significant correlation was found amongst the three different modalities. Molecular response were seen in 13 patients (PR 60%, SD 24%, PD 16%), and metabolic responses in 6 patients (PR 36%, SD 55%, PD 9%), respectively, whereas ceCT alone showed either SD (64%) or PD or PR (16% each). The cut-off value of SSR-SUVmax >2.5 predicted molecular response of metastatic liver lesions to PRRT with a sensitivity of 88.9% and a specificity of 71.4%.
Conclusions: Ga-68-DOTA-NOC-SMS-receptor-PET/CT is superior to ceCT alone for the early assessment of response to PRRT in metastatic NET ("molecular response precedes morphology").
