Relationships between uptake of [68Ga]Ga-DOTA-TATE and absorbed dose in [177Lu]Lu-DOTA-TATE therapy

Background Somatostatin receptor 68 Ga PET imaging is standard for evaluation of a patient’s suitability for 177 Lu peptide receptor radionuclide therapy of neuroendocrine tumours (NETs). The 68 Ga PET serves to ensure sufficient somatostatin receptor expression, commonly evaluated qualitatively. Th...

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Published in:	EJNMMI research 2022-12, Vol.12 (1), p.75-15, Article 75
Main Authors:	Stenvall, Anna, Gustafsson, Johan, Larsson, Erik, Roth, Daniel, Sundlöv, Anna, Jönsson, Lena, Hindorf, Cecilia, Ohlsson, Tomas, Sjögreen Gleisner, Katarina
Format:	Article
Language:	eng
Subjects:	Cardiac Imaging Clinical Medicine Correlation coefficients Dosimetry DOTA-TATE Ga PET Gallium isotopes Imaging Klinisk medicin Lu SPECT Lutetium isotopes Mathematical analysis Medical and Health Sciences Medical imaging Medicin och hälsovetenskap Medicine Medicine & Public Health Neuroendocrine tumours Nuclear Medicine Oncology Original Research Orthopedics Peptide receptor radionuclide therapy Positron emission Radiation therapy Radioisotopes Radiologi och bildbehandling Radiology Radiology, Nuclear Medicine and Medical Imaging Radionuclide therapy Receptors Somatostatin receptor imaging Spleen Tumors
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Summary:	Background Somatostatin receptor 68 Ga PET imaging is standard for evaluation of a patient’s suitability for 177 Lu peptide receptor radionuclide therapy of neuroendocrine tumours (NETs). The 68 Ga PET serves to ensure sufficient somatostatin receptor expression, commonly evaluated qualitatively. The aim of this study is to investigate the quantitative relationships between uptake in 68 Ga PET and absorbed doses in 177 Lu therapy. Method Eighteen patients underwent [ 68 Ga]Ga-DOTA-TATE PET imaging within 20 weeks prior to their first cycle of [ 177 Lu]Lu-DOTA-TATE. Absorbed doses for therapy were estimated for tumours, kidney, spleen, and normal liver parenchyma using a hybrid SPECT/CT–planar method. Gallium-68 activity concentrations were retrieved from PET images and also used to calculate SUVs and normalized SUVs, using blood and tissue for normalization. The 68 Ga activity concentrations per injected activity, SUVs, and normalized SUVs were compared with 177 Lu activity concentrations 1 d post-injection and 177 Lu absorbed doses. For tumours, for which there was a variable number per patient, both inter- and intra-patient correlations were analysed. Furthermore, the prediction of 177 Lu tumour absorbed doses based on a combination of tumour-specific 68 Ga activity concentrations and group-based estimates of the effective half-lives for grade 1 and 2 NETs was explored. Results For normal organs, only spleen showed a significant correlation between the 68 Ga activity concentration and 177 Lu absorbed dose ( r = 0.6). For tumours, significant, but moderate, correlations were obtained, with respect to both inter-patient ( r = 0.7) and intra-patient ( r = 0.45) analyses. The correlations to absorbed doses did not improve when using 68 Ga SUVs or normalized SUVs. The relationship between activity uptakes for 68 Ga PET and 177 Lu SPECT was stronger, with correlation coefficients r = 0.8 for both inter- and intra-patient analyses. The 177 Lu absorbed dose to tumour could be predicted from the 68 Ga activity concentrations with a 95% coverage interval of − 65% to 248%. Conclusions On a group level, a high uptake of [ 68 Ga]Ga-DOTA-TATE is associated with high absorbed doses at 177 Lu-DOTA-TATE therapy, but the relationship has a limited potential with respect to individual absorbed dose planning. Using SUV or SUV normalized to reference tissues do not improve correlations compared with using activity concentration per injected activity.
ISSN:	2191-219X 2191-219X