Abstract
1535
Introduction: Radionuclide imaging of neuroendocrine tumors (NET) relies on detection of somatostatin receptors expressed by these tumors. When evaluating activity, Krenning score system has been established in the past for the single photon emitter In-111 Octreotide. Availability of Ga-68 DOTATATE PET/CT (Ga68) has allowed better visualization of these tumors and semiquantitation of receptors with SUVmax (SUV). A number of clinical trials on therapeutic agents for patients with NET continue to utilize certain Krenning score (#II) for patient inclusion into the study. We sought to compare the performance of Krenning score system versus SUV in evaluation of NET lesions.
Methods: A consecutive series of 26 patients (nineteen females and seven males) at a median age of 56 years (IQR: 42-62) underwent Ga68 for evaluating known or suspected neuroendocrine tumors (NET). The primary site of malignancy included pancreas (ten patients, 38%), bowel (eight patients, 31%), lung (one patient) and unknown (seven patients, 27%). SUVs and Krenning scores were used to evaluate all lesions. For Krenning scoring, lesions were visually compared to liver activity. Lesions with very mild activity were scored Krenning I, those with uptake nearly equal to the liver were scored as Krenning score II, greater than the liver and less than the spleen as III, and greater than the spleen as IV (1). The continuous variables expressed as medians with interquartile ranges and categorical variables as proportions. Continuous variables among Krenning groups were compared using the non-parametric Kruskal-Wallis test.
Results: Of the 26 patients, 19 patients (73%) had metastases while seven (27%) did not. Among the 19 patients, there were 26 sites (39%) stratified as Krenning class VI, 24 (36%) as III, 10 (15%) as II, and seven (10%) as I. Metastases sites had median SUVmax of 22.6 (IQR: 18-39) for Krenning VI, 10.7 (IQR: 8-15) for Krenning III, four (IQR: 3-7) for Krenning II, and 2.8 (IQR: 2-5) for Krenning I. Using Kruskal-Wallis test, there were significant differences between the SUVmax medians for the metastases sites with 23 (IQR: 18-39) for IV, 11 (IQR: 3-7) for III, and four (IQR: 3-7) I and II classes (p<0.001).
Conclusions: In this patient population,Krenning scores and measured SUV provided useful tool in our evaluation of NET. There was a trend of greater SUV values with higher Krenning scores. Additional research with larger cohort of patients is required to further define utility of Krenning criteria now that SUV measurement can easily be obtained with Ga-68. Reference:(1) Semin Nucl Med. 2002 Apr;32(2):84-91. Somatostatin receptor imaging. Kwekkeboom DJ1, Krenning EP.
