Semi-Quantitative Analysis of Post-Transarterial Radioembolization 90Y Microsphere Positron Emission Tomography Combined with Computed Tomography (PET/CT) Images in Advanced Liver Malignancy: Comparison With 99mTc Macroaggregated Albumin (MAA) Single Photon Emission Computed Tomography (SPECT)

Objectives

The purpose of this study is to evaluate the correlation between pretreatment planning technetium-99m (^99mTc) macroaggregated albumin (MAA) SPECT images and posttreatment transarterial radioembolization (TARE) yttirum-90 (⁹⁰Y) PET/CT images by comparing the ratios of tumor-to-normal liver counts.

Methods

Fifty-two patients with advanced hepatic malignancy who underwent ⁹⁰Y microsphere radioembolization from January 2010 to December 2012 were retrospectively reviewed. Patients had undergone ^99mTc MAA intraarterial injection SPECT for a pretreatment evaluation of microsphere distribution and therapy planning. After the administration of ⁹⁰Y microspheres, the patients underwent posttreatment ⁹⁰Y PET/CT within 24 h. For semiquantitative analysis, the tumor-to-normal uptake ratios in ⁹⁰Y PET/CT (TNR-yp) and ^99mTc MAA SPECT (TNR-ms) as well as the tumor volumes measured in angiographic CT were obtained and analyzed. The relationship of TNR-yp and TNR-ms was evaluated by Spearman''s rank correlation and Wilcoxon''s matched pairs test.

Results

In a total of 79 lesions of 52 patients, the distribution of microspheres was well demonstrated in both the SPECT and PET/CT images. A good correlation was observed of between TNR-ms and TNR-yp (rho value = 0.648, p < 0.001). The TNR-yp (median 2.78, interquartile range 2.43) tend to show significantly higher values than TNR-ms (median 2.49, interquartile range of 1.55) (p = 0.012). The TNR-yp showed weak correlation with tumor volume (rho = 0.230, p = 0.041).

Conclusions

The ^99mTc MAA SPECT showed a good correlation with ⁹⁰Y PET/CT in TNR values, suggesting that ^99mTc MAA can be used as an adequate pretreatment evaluation method. However, the ^99mTc MAA SPECT image consistently shows lower TNR values compared to ⁹⁰Y PET/CT, which means the possibility of underestimation of tumorous uptake in the partition dosimetry model using ^99mTc MAA SPECT. Considering that ^99mTc MAA is the only clinically available surrogate marker for distribution of microsphere, we recommend measurement of tumorous uptake using ⁹⁰Y PET/CT should be included routinely in the posttherapeutic evaluation.