The effect of long-acting somatostatin analogues on the uptake of [ 177 Lu]Lu-HA-DOTATATE

Purpose According to IAEA/EANM/SNMMI guidelines, long-acting somatostatin analogues (LA-SSAs) should be discontinued 4–6 weeks prior to peptide receptor radionuclide therapy (PRRT) to prevent somatostatin receptor saturation. The aim of this study was to determine the effect of continued use of long-acting SSAs during PRRT on the uptake of [ 177 Lu]Lu-HA-DOTATATE on SPECT/CT. Methods Consecutive patients with neuroendocrine tumours who were treated with PRRT receiving 7.4 GBq of [ 177 Lu]Lu-HA-DOTATATE were included. Patients were divided into 3 groups: (1) control (LA-SSA stopped > 6 weeks prior to PRRT), or continued treatment with (2) long-acting octreotide < 6 weeks prior to PRRT, or (3) long-acting lanreotide < 6 weeks prior to PRRT. The uptake of [ 177 Lu]Lu-HA-DOTATATE was quantified in healthy tissues (spleen, liver, kidneys, bone marrow) and tumour lesions on SPECT/CT performed 24 h after PRRT. A Mann–Whitney U test was used to determine differences in uptake between the long-acting octreotide and long-acting lanreotide groups compared to the control group. Results Forty-two patients with 135 cycles of PRRT were included: 28 with lanreotide, 50 with octreotide, and 57 cycles without LA-SSAs. Uptake of [ 177 Lu]Lu-HA-DOTATATE was significantly decreased in liver parenchyma in patients with lanreotide ( p < 0.001) and in the spleen in patients with either octreotide or lanreotide (both p < 0.001). No differences were observed for uptake in kidneys, bone marrow, and blood pool. Uptake of [ 177 Lu]Lu-HA-DOTATATE in tumours was the same in patients with lanreotide compared to the control ( p = 0.862) and in patients with octreotide compared to the control ( p = 0.201), independent of tumour location. Conclusion Long-acting octreotide and lanreotide do not interfere with the uptake of [ 177 Lu]Lu-HA-DOTATATE in tumour lesions 24 h post-injection. Uptake in healthy liver parenchyma significantly decreases after lanreotide administration prior to PRRT, while uptake in healthy spleen tissue significantly decreases with both octreotide and lanreotide administration.