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Table 1 Dual tracer molecular imaging grading scales of neuroendocrine tumours

From: Molecular imaging phenotyping for selecting and monitoring radioligand therapy of neuroendocrine neoplasms

Study Reference for positive lesion Group SSTR PET 18F-FDG PET Suitability for PRRT
Chan et al. [29] (NETPET)  > Background
(Modified Krenning score 2–4)
P0 Negative Negative Not suitable
P1 Positive Negative Probably suitable
P2 Positive Positive (avidity on 18F-FDG < SSTR) Probably suitable
P3 Positive Positive (avidity on 18F-FDG = SSTR) Probably suitable
P4 Positive Positive (avidity on 18F-FDG > SSTR) Probably suitable if P4aa; Maybe suitable with additional therapy required if P4b
P5 Negative Positive No
Karfis et al. [30]  > Background
(Modified Krenning score 2–4)
C1 Positive (all lesions) Negative (all lesions) Probably suitable
C2 Positive (all lesions) Positive (≥ 1 lesion) Probably suitable
C3 Negative (≥ 1 lesion) b Positive (≥ 1 lesion) Not suitable
Zidan et al. [14]  > Liver
(Modified Krenning score 3–4)
1 Negative (all lesions) Negative (all lesions Not suitable
2 Positive (all lesions) Negative (all lesions) Suitable
3 Positive (all lesions) Positive (≥ 1 lesion) Suitable
4 Negative (≥ 1 lesion)b Positive (≥ 1 lesion) Not suitable
  1. aa – 1–2 lesions; b – 3 or more lesions showing the grade-specific pattern of avidity
  2. b At least one of the.18F-FDG avid lesions is SSTR PET negative