Effect of previous 177Lu-DOTATATE treatment on 90Y-microsphere treatment response in neuroendocrine tumor patients with liver metastasis.

OBJECTIVE

This study evaluates the impact of prior PRRT with Lu-177 DOTATATE on the response to TARE in NET patients with liver metastases.

METHODS

Twenty-one patients who underwent TARE after PRRT between 2015 and 2022 were retrospectively analyzed. Tumor-specific cumulative Lu-177 DOTATATE counts were calculated from SPECT/CT images. Treatment planning was conducted with a standard target dose of 150 Gy to the tumoral tissue. Treatment response was assessed using changes in SUVmax, SUVmean, and somatostatin receptor-expressing tumor volume (SRE-TV) values derived from Ga-68 DOTATATE PET/CT before and 2-4 months after TARE. Lesion size was evaluated using RECIST v1.1 criteria. Dosimetry calculations were performed on Tc-99 m MAA SPECT/CT and Y-90 microsphere PET/MRI using Simplicit90Y™. Statistical analyses included Spearman correlation and Kruskal-Wallis tests.

RESULTS

The median age of patients was 56 years (range 36-78 years). PRRT involved a mean cumulative Lu-177 DOTATATE dose of 43.5 ± 13.4 GBq (1175 ± 362 mCi). Post-TARE reductions in SUVmax (38.49 ± 20.46 to 19.94 ± 10.43 g/mL), SUVmean (9.51 ± 5.60 to 5.39 ± 3.64 g/mL), and SRE-TV (217.43 ± 155.87 to 175.62 ± 147.77 cm3) were observed. No significant correlation was found between cumulative Lu-177 DOTATATE counts and changes in SUV parameters, SRE-TV values, or lesion size after TARE. Similarly, no correlation was detected between tumor-to-normal liver activity ratios, calculated using either the partition model or voxel-based dosimetry and cumulative Lu-177 DOTATATE counts.

CONCLUSION

Prior PRRT does not significantly affect TARE response in NET patients with liver metastases. Radioembolization planning should prioritize factors like tumor, target, or healthy liver doses over previous PRRT.