Table 12.
Summary of SSTR-RADS version 1.0 system for the interpretation of SSTR-PET imaging and RLT eligibility.
| SSTR-RADS | ||||
|---|---|---|---|---|
| Category | Findings | Uptake Level |
Action | RLT |
| SSTR-RADS 1 (benign) |
Benign lesion confirmed by biopsy or with a pathognomonic appearance on anatomic imaging | |||
| SSTR-RADS 1A | Benign lesion, characterized by biopsy or by anatomic imaging and without any abnormal uptake | 1 | Not to be considered | |
| SSTR-RADS 1B | Benign lesion, characterized by biopsy or by anatomic imaging but with increased (focal) uptake | 2–3 | Not to be considered | |
| SSTR-RADS 2 (likely benign) |
Soft-tissue site atypical of metastatic NET or equivocal uptake in bone lesion atypical for NET | 1 | Not to be considered | |
| SSTR-RADS 3 | Further work-up might be required | |||
| SSTR-RADS 3A | Suggestive but not definitive for NET. Equivocal uptake in soft-tissue sites typical for NET metastases (e.g., regional lymph nodes). |
1–2 | Biopsy or initial fu imaging (SSTR-PET or whole-body MRI after 3 months), also depending on Ki-67/Grading. | Not to be considered |
| SSTR-RADS 3B | Suggestive but not definitive for NET. Uptake in bone lesions not atypical for NET. |
1–2 | Initial fu imaging (SSTR-PET or whole-body MRI after 3 months) might confirm diagnosis, also depending on Ki-67/Grading. | Single lesions: locoregional procedure. Increased number of lesions: RLT |
| SSTR-RADS 3C | Intense uptake in a site highly atypical for NET. Suggestive of an SSTR-expressing, non-NET benign tumor or malignant process. | 3 | Tissue confirmation of tumor histology should be considered. | Not to be considered |
| SSTR-RADS 3D | High likelihood of malignant NET lesion, but negative on an SSTR-PET scan (de-differentiated NET or another type of malignancy). | n/a | [18F]FDG PET should be considered. Tissue confirmation of tumor histology should be considered. |
Not to be considered |
| SSTR-RADS 4 NET highly likely |
Intense uptake in common site typical for NET lesion, but without confirmatory findings on anatomic imaging. | 3 | Further confirmation by biopsy might be not necessary. | To be considered |
| SSTR-RADS 5 NET almost certainly present |
Intense uptake in site typical for NET with corresponding findings on conventional imaging. | 3 | Further confirmation by biopsy might be not necessary. | Definitely to be considered. |
Adapted from Werner et al. [17] Abbreviations: SSTR, somatostatin receptors; RADS, Reporting and Data Systems; RLT, radioligand therapy; NET, neuroendocrine tumor; fu, follow-up; PET, positron emission tomography; MRI, magnetic resonance imaging; FDG, fluorodeoxyglucose.