Maximum tumor-absorbed dose measured by voxel-based multicompartmental dosimetry as a response predictor in yttrium-90 radiation segmentectomy for hepatocellular carcinoma

Objective Advances in hepatic radioembolization are based on a selective approach with radical intent and the use of multicompartment dosimetric analysis. The objective of this study is to assess the utility of voxel-based dosimetry in the quantification of actual absorbed doses in radiation segmentectomy procedures and to establish cutoff values predictive of response. Methods Ambispective study in hepatocarcinoma patients treated with radiation segmentectomy. Calculated dosimetric parameters were mean tumor-absorbed dose, maximum tumor AD, minimal tumor AD in 30, 50, and 70% of tumor volume and mean AD in non-tumor liver. The actual absorbed dose (aAD) was calculated on the Y-90-PET/CT image using 3D voxel-based dosimetry software. To assess radiological response, localized mRECIST criteria were used. The objective response rate (ORR) was defined as CR or PR. Results Twenty-four HCC patients, BCLC 0 (5), A (17) and B (2) were included. The mean yttrium-90 administered activity was 1.38 GBq in a mean angiosome volume of 206.9 cc and tumor volume 56.01 cc. The mean theoretical AD was 306.3 Gy and aAD 352 Gy. A very low concordance was observed between both parameters (rho_c 0.027). ORR at 3 and 6 m was 84.21% and 92.31%, respectively. Statistically significant relationship was observed between the maximum tumor-absorbed dose and complete radiological response at 3 m (p 0.022). Conclusion A segmental approach with radical intention leads to response rates greater than 90%, being the tumor maximum absorbed dose the dosimetric parameter that best predicts radiological response in voxel-based dosimetry.