Correlations between [68Ga]Ga-DOTA-TOC Uptake and Absorbed Dose from [177Lu]Lu-DOTA-TATE

Ragnar Bruvoll; Johan Blakkisrud; Lars Tore Mikalsen; James Connelly; Caroline Stokke

doi:10.3390/cancers15041134

Correlations between [⁶⁸Ga]Ga-DOTA-TOC Uptake and Absorbed Dose from [¹⁷⁷Lu]Lu-DOTA-TATE

Cancers (Basel). 2023 Feb 10;15(4):1134. doi: 10.3390/cancers15041134.

Authors

Ragnar Bruvoll^{1

2}, Johan Blakkisrud¹, Lars Tore Mikalsen^{1

3}, James Connelly¹, Caroline Stokke^{1

2}

Affiliations

¹ Division of Radiology and Nuclear Medicine, Oslo University Hospital, 0424 Oslo, Norway.
² Department of Physics, University of Oslo, 0315 Oslo, Norway.
³ Department of Life Sciences and Health, Oslo Metropolitan University, 0130 Oslo, Norway.

Abstract

Purpose: The aim of this paper was to investigate correlations between pre- therapeutic [⁶⁸Ga]Ga-DOTA-TOC uptake and absorbed dose to tumours from therapy with [¹⁷⁷Lu]Lu-DOTA-TATE.

Methods: This retrospective study included 301 tumours from 54 GEP-NET patients. The tumours were segmented on pre-therapeutic [⁶⁸Ga]Ga-DOTA-TOC PET/CT, and post-therapy [¹⁷⁷Lu]Lu-DOTA-TATE SPECT/CT images, using a fixed 40% threshold. The SPECT/CT images were used for absorbed dose calculations by assuming a linear build-up from time zero to day one, and mono-exponential wash-out after that. Both SUV_mean and SUV_max were measured from the PET images. A linear absorbed-dose prediction model was formed with SUV_mean as the independent variable, and the accuracy was tested with a split 70-30 training-test set.

Results: Mean SUV_mean and SUV_max from [⁶⁸Ga]Ga-DOTA-TOC PET was 24.0 (3.6-84.4) and 41.0 (6.7-146.5), and the mean absorbed dose from [¹⁷⁷Lu]Lu-DOTA-TATE was 26.9 Gy (2.4-101.9). A linear relationship between SUV_mean and [¹⁷⁷Lu]Lu-DOTA-TATE activity concentration at 24 h post injection was found (R² = 0.44, p < 0.05). In the prediction model, a root mean squared error and a mean absolute error of 1.77 and 1.33 Gy/GBq, respectively, were found for the test set.

Conclusions: There was a high inter- and intra-patient variability in tumour measurements, both for [⁶⁸Ga]Ga-DOTA-TOC SUVs and absorbed doses from [¹⁷⁷Lu]Lu-DOTA-TATE. Depending on the required accuracy, [⁶⁸Ga]Ga-DOTA-TOC PET imaging may estimate the [¹⁷⁷Lu]Lu-DOTA-TATE uptake. However, there could be a high variance between predicted and actual absorbed doses.

Keywords: PET/CT; SPECT/CT; [177Lu]Lu-DOTA-TATE; [68Ga]Ga-DOTA-TOC; dosimetry; peptide receptor radionuclide therapy; prediction model.

Grants and funding

This research received no external funding.