High-Dose Radioembolization with Resin Microspheres Limited by Lung Shunt for Localized Hepatocellular Carcinoma: Virtual Tumor Absorbed Dose as a Predictor of Complete Response.

[PURPOSE] To identify the optimal tumor absorbed dose (TAD) thresholds predictive of radiological complete response (CR) in patients with localized hepatocellular carcinoma (HCC) undergoing resin-based yttrium-90 (Y) transarterial radioembolization (TARE).

[MATERIALS AND METHODS] This retrospective single-center study included 160 patients with HCC treated with resin-based Y TARE; 4 dosimetric metrics-mean absorbed dose (mAD), pretreatment TAD (pre-TAD), posttreatment TAD (post-TAD), and virtual TAD (vTAD)-were analyzed. Pre-TAD and post-TAD were retrospectively measured using single photon emission computed tomography (SPECT)/computed tomography (CT) and positron emission tomography (PET)/CT images, respectively. The vTAD was calculated assuming that Y microspheres were distributed exclusively within the tumor. Tumor response was assessed using modified Response Evaluation Criteria for Solid Tumors. Cutoff thresholds for predicting CR were determined using maximally selected rank statistics.

[RESULTS] Mean tumor size was 8.6 cm (median size, 7.9 cm; interquartile range [IQR], 5.6-10.2 cm), and 68 patients (42.5%) had single nodular tumor. Median mAD, pre-TAD, post-TAD, and vTAD were 178 Gy (IQR, 124-228 Gy), 375 Gy (IQR, 219-514 Gy), 427 Gy (IQR, 283-605 Gy), and 728 Gy (IQR, 417-1,105 Gy), respectively. CR was achieved in 37.5% (60 of 160) of patients. Multivariate analysis identified vTAD >597 Gy as the independent predictor of CR (P = .004).

[CONCLUSIONS] A vTAD ≥600 Gy represents a practical and reliable threshold for predicting CR in resin-based TARE. Given its ease of calculation and independence from registration artifacts, vTAD may serve as a valuable dosimetric tool in both clinical practice and treatment planning.