Use of 68Ga-DOTA-TATE PET/CT for predicting the dose of 177Lu-DOTA-TATE therapy in patients with neuroendocrine tumors (NETs)

96 Objectives Radiopeptide therapy with 177-Labeled DOTA-TATE is increasingly used for therapy of NETs. However, quantitative criteria for selection of patients for this new form of therapy are lacking. Therefore, the aim of the present study was to evaluate whether the tumor radiation dose by treatment with 177Lu-DOTA-TATE can be predicted by quantitative PET imaging with 68Ga-DOTA-TATE, which is frequently performed for staging of NETs. Methods Tumor uptake of 68Ga-DOTA-TATE was quantified by maximum standardized uptake values (SUVs) measured 60 min after injection of 150-250 MBq 68Ga-DOTA-TATE. Following treatment with 3.0-7.7 GBq 177-Lu DOTA-TATE patients underwent 3 SPECT/CT (Philips Brightview XCT) studies of the tumor regions at 15 h, 40 h and 64 h p.i. The counts per voxel in the attenuation corrected SPECT images were calibrated to Bq/ml by measurements with a body phantom. Time activity curves and beta radiation dose estimates were calculated on a voxel basis (Philips STRATOS). Time activity curves were extrapolated by assuming that after the last SPECT/CT study the intratumoral radioactivity decreases by physical decay. Results A total of 15 lesions were analyzed in 6 patients (2 f, 4 m). The maximum SUV of the lesions ranged from 5 to 189 g/ml and the mean SUV from 4 to 155 g/ml. The corresponding mean and maximum tumor doses by 177Lu-DOTA-TATE therapy were 0.45-12.4 Gy/GBq and 0.51-24.1 Gy/GBq, respectively. There was a significant (p Conclusions Tumor uptake of pretherapeutic 68Ga-DOTA-TATE can be used to estimate the tumor radiation dose by 177Lu-DOTA-TATE. This information may be helpful in selecting patients for radiopeptide therapy