Brain-Specific Quantification of Somatostatin Receptor Expression: SUVmax and SUVRsss as Quantitative Correlates of the Krenning Score in Meningioma.

Abstract

Somatostatin receptor type 2 is highly expressed in meningiomas and can be quantified using [⁶⁸Ga]Ga-DOTATATE PET. The Krenning score, originally developed for [¹¹¹In]In-octreotide scintigraphy, remains the standard visual grading system for somatostatin receptor expression and is widely used to guide eligibility for peptide receptor radionuclide therapy. However, visual grading may not optimally translate to intracranial disease. This study evaluated the relationship between brain-specific quantitative PET parameters-SUV_max and SUV ratio normalized to the superior sagittal sinus (SUVR_sss)-and the Krenning score in meningioma. Methods: This single-institution retrospective study included 44 patients (70 meningiomas) who underwent clinical vertex-to-thigh [⁶⁸Ga]Ga-DOTATATE PET/CT. Quantitative parameters (SUV_max, SUVR_sss, lesion size) were extracted from coregistered PET and MR images. Spearman rank correlation analysis was performed to assess associations between imaging variables and Krenning score. Differences in quantitative PET parameters across Krenning categories were evaluated using Kruskal-Wallis test and Holm-Bonferroni-corrected Mann-Whitney U test. Receiver-operating-characteristic curve analysis using the Youden J index identified optimal cutoffs for clinically relevant thresholds (Krenning score of <3 vs. ≥3 and 3 vs. 4). Results: SUVR_sss and SUV_max were strongly correlated with the Krenning score (SUVR_sss: Spearman ρ = 0.70; 95% CI, 0.55-0.82; SUV_max: Spearman ρ = 0.77; 95% CI, 0.64-0.85; P < 0.0001). PET parameters differed significantly across Krenning categories (all P < 0.001). SUVR_sss optimal thresholds were 9.00 (area under the curve [AUC], 0.86; 95% CI, 0.74-0.96) for Krenning scores of 2 versus 3 and 29.84 (AUC, 0.98; 95% CI, 0.93-1.00) for Krenning scores of 3 versus 4. SUV_max optimal thresholds were 7.20 (AUC, 0.92; 95% CI, 0.84-0.99) and 30.70 (AUC, 0.98; 95% CI, 0.95-1.00), respectively. Conclusion: SUVR_sss and SUV_max are complementary quantitative correlates of Krenning scores 2-4 in [⁶⁸Ga]Ga-DOTATATE PET-visible, MRI-measurable meningiomas. Brain-only PET evaluation may provide an alternative to liver- and spleen-based visual grading and reduce the need for whole-body imaging in selected settings. Receiver-operating-characteristic curve-derived SUV thresholds correspond to Krenning scores used for eligibility for treatment with peptide receptor radionuclide therapy, supporting further evaluation of quantitative PET parameters for theranostic decision-making for patients with meningioma.