Quantification of Intratherapeutic SPECT/CT for Lutetium-177-DOTATOC PRRT in Neuroendocrine Tumors
Introduction: In PRRT for NET, feasibility of lesion uptake quantification in Lu-177-DOTATOC SPECT/CT for therapy monitoring remains unclear.
Aim(s): To evaluate association of lesion SUV, estimated lesion dose and response.
Materials and methods: Retrospective analysis in 10 NET patients undergoing first 2 PRRT cycles (activity: 7.0 [5.5-7.1] GBq). Max/peak/mean counts and metabolic tumor volume (MTV) of primary tumor (n=1) or metastases (liver: 16, extrahepatic: 9) were measured on Lu-177 SPECT/CT 24h p.i. at both cycles. SUV (max/peak/mean) were calculated based on volume sensitivity for a homogenous cylindrical phantom. Relative change of metabolic tumor load (product MTV*SUV) between 1st and 2nd cycle was correlated for each lesion to its relative change in maximum diameter (CT/MRI) and the estimated lesion dose (Gy). Response in patient-based analysis was defined by change in summed MTV*SUV for all target lesions between PRRT cycles following RECIST (PD: >+20%; PR: >-30%; SD: others).
Conference: 17th Annual ENETSConcerence (2020)
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