Predicting [177Lu]Lu-DOTA-TATE dosimetry by using pre-therapy [68Ga]Ga-DOTA-TATE PET/CT and biomarkers in patient with neuroendocrine tumors.

Background: Lutetium-177 DOTA-TATE peptide receptor radionuclide therapy (PRRT) is an established and effective treatment modality for patients with metastatic neuroendocrine tumors (NETs).

Purpose: This study aims to predict patient-absorbed doses from [177Lu]Lu-DOTA-TATE PRRT in the liver, kidney and lesion by utilizing patient-specific absorbed doses from pre-therapeutic [68Ga]Ga-DOTA-TATE PET/CT.

Methods: Before the treatment of cycle 1, 11 patients with NETs underwent PET/CT scans at 0.5, 1.0, 2.0 and 4.0 h after the injection of [68Ga]Ga-DOTA-TATE. Patients then received [177Lu]Lu-DOTA-TATE PRRT and underwent SPECT/CT scans at 4, 24, 96, and 168 h post-administration. The segmentations and dosimetry were performed by using a professional software. The linear regression model used the absorbed doses from [68Ga]Ga-DOTA-TATE alone as the predictor variable. The multiple linear regression model used the absorbed doses from [68Ga]Ga-DOTA-TATE and the relevant clinical biomarkers as the predictor variables.

Results: The mean absorbed doses from [177Lu]Lu-DOTA-TATE PRRT in kidney and liver were 4.1 and 2.1 Gy, respectively. In comparison, the mean absorbed doses from [68Ga]Ga-DOTA-TATE were significantly lower: 18.0 mGy and 11.0 mGy, respectively. For lesions, the maximum absorbed dose from [68Ga]Ga-DOTA-TATE ranged from 24.1 to 170.4 mGy, while the maximum absorbed dose from [177Lu]Lu-DOTA-TATE PRRT was significantly higher, ranging from 9.6 to 77.9 Gy. The linear regression model yielded moderate R-squared values of 0.50, 0.59, and 0.36 for kidney, liver and lesion, respectively. The performance of multiple linear regression model was better, with R-squared values increasing to 0.81, 0.77, and 0.84.

Conclusion: Absorbed doses from [177Lu]Lu-DOTA-TATE PRRT can be accurately predicted. Moreover, our models are formalized into simple equations.