Estimation of Post-therapeutic Liver Reserve Capacity Using 99mTc-GSA Scintigraphy Prior to Carbon-ion Radiotherapy for Liver Tumors

Abstract

Background: There is currently no established imaging method for assessing liver reserve capacity prior to carbon-ion radiotherapy (CIRT) for liver tumors. In order to perform safe CIRT, it is essential to estimate the post-therapeutic residual reserve capacity of the liver. Purpose: To evaluate the ability of pre-treatment 99m Tc-GSA scintigraphy to accurately estimate the residual liver reserve capacity in patients treated with CIRT for liver tumors. Materials and Methods: This retrospective study evaluated 50 patients who were performed CIRT for liver tumors between December 2018 and September 2020 and underwent 99m Tc-GSA scintigraphy before and 3 months after CIRT, Gd-EOB-DTPA-enhanced MRI within 1 month before CIRT were evaluated. The maximal removal rate of 99m Tc-GSA (GSA-Rmax) was analyzed for the evaluation of pre-treatment liver reserve capacity. Then, the GSA-Rmax of the estimated residual liver (GSA-RL) was calculated using liver SPECT images fused with the Gd-EOB-DTPA-enhanced MRI. GSA-RL before CIRT and GSA-Rmax at 3 months after CIRT were compared using non-parametric Wilcoxon signed-rank test and linear regression analysis. Results: Overall, 50 patients were included (mean age ± standard deviation, 73 years ± 11; range, 29–89 years, 35 men). The median GSA-RL was 0.393 [range, 0.057–0.729] mg/min, the median GSA-Rmax after CIRT was 0.369 [range, 0.037–0.780] mg/min ( P = .40). The linear regression equation representing the relationship between the GSA-RL and GSA-Rmax after CIRT was y = 0.05 + 0.84x (R 2 = 0.67, P < .0001). There was a positive correlation between the estimated and actual post-treatment values for all patients, as well as in the group with impaired liver reserve capacity (y = - 0.02 + 1.09x (R 2 = 0.62, P = .0005)). Conclusions: 99m Tc-GSA scintigraphy has potential clinical utility for estimating the residual liver reserve capacity in patients undergoing carbon-ion radiotherapy for liver tumors. Clinical Trial registration: UMIN000038328, https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000043545