Comparison of 111In-DOTA-DPhe1-Tyr3-octreotide and 111In-DOTA-lanreotide scintigraphy and dosimetry in patients with neuroendocrine tumours

Purpose Somatostatin receptor scintigraphy with ¹¹¹In-DOTA-DPhe¹-Tyr³-octreotide (¹¹¹In-DOTA-TOC) and ¹¹¹In-DOTA-lanreotide (¹¹¹In-DOTA-LAN) has been used for staging of neuroendocrine tumours (NETs). However, the comparative diagnostic value of these radioligands on a lesion basis has not yet been established. The aim of this study was to compare the diagnostic capacity of ¹¹¹In-DOTA-TOC and ¹¹¹In-DOTA-LAN scintigraphy in patients with NETs, evaluating whether significant differences exist in lesion imaging with these radioligands. Furthermore, dosimetric data were compared. Methods Forty-five patients with NETs were investigated with ¹¹¹In-DOTA-TOC and ¹¹¹In-DOTA-LAN scintigraphy. Scintigraphic results were compared with those of conventional imaging and/or surgery in each patient, and also ¹⁸F-fluorodeoxyglucose positron emission tomography (FDG-PET) in 20 patients. Results ¹¹¹In-DOTA-TOC and ¹¹¹In-DOTA-LAN scintigraphy were true positive in 42/45 (93%) and 39/45 (87%) patients, and imaged 74/91 (81%) and 73/91 (80%) tumour lesions, respectively. ¹¹¹In-DOTA-TOC and ¹¹¹In-DOTA-LAN detected liver metastases in 21 and 14 patients, mediastinal metastases in seven and 11 patients, and bone metastases in two and seven patients, respectively. These radioligands revealed lesions not seen by conventional imaging in seven and eight patients, respectively, or by ¹⁸F-FDG-PET in eight and seven patients, respectively. The estimated tumour absorbed doses for ⁹⁰Y-DOTA-TOC were higher than those for ⁹⁰Y-DOTA-LAN in 14 patients, whereas the opposite was true in 12 patients. Conclusion Both ¹¹¹In-DOTA-TOC and ¹¹¹In-DOTA-LAN are suitable for imaging tumour lesions in patients with NETs and can detect lesions that may not be seen by conventional imaging and ¹⁸F-FDG-PET. Compared with ¹¹¹In-DOTA-LAN, ¹¹¹In-DOTA-TOC has a superior diagnostic capacity for liver metastases, but a lower diagnostic capacity for metastatic lesions in mediastinum and bone.