Comparative dosimetry between 99mTc-MAA SPECT/CT and 90Y PET/CT in primary and metastatic liver tumors

Introduction The aim of this study is to determine whether Tc-99m-MAA SPECT/CT-based dosimetry could predict the actual absorbed dose in hepatocellular carcinoma (HCC) or liver metastases, treated by glass or resin microspheres. Material and methods Fifty-seven patients who underwent selective internal radiation therapy (SIRT) were retrospectively included in the study, for a total of 59 treatments. Nineteen HCC were treated by resin microspheres (HCC-SIR), 20 HCC with glass microspheres (HCC-Thera), and 20 liver metastases with resin microspheres (Metastases-SIR). The mean absorbed doses in tumoral liver (Dm) and non-tumoral liver (DmNTL) were determined on the Tc-99m-MAA SPECT/CT and the Y-90 PET/CT, and compared with each other. Results DmNTL was < 50 Gy in the 3 groups, with a strong correlation in all population, albeit slightly lower in Metastases-SIR than HCC-SIR and HCC-Thera (CCC 0.8, 0.94 and 0.96, respectively). In tumoral liver, Dm was higher in HCC than metastases (159 +/- 117 Gy versus 63 +/- 31 Gy). Tc-99m-MAA SPECT/CT proved to be a better indicator of Dm in HCC compared with metastases, with similar Tc-99m-MAA-Y-90 concordance in resin and glass microspheres (CCC HCC-SIR 0.82, CCC HCC-Thera 0.82, and CCC Metastases-SIR 0.52). Conclusion Tc-99m-MAA SPECT/CT is a reasonably reliable tool for predicting the dose to the non-tumoral liver in both HCC and metastases, regardless of the type of microspheres. It is also fairly reliable for predicting the tumor dose in HCC, again regardless of the type of spheres, although individual variations are observed.