A sequential radiation-sorafenib regimen is most efficacious against HCC <i>in vivo</i>.

<p>A HepG2 hind-flank xenograft model was utilized to measure the efficacy of (A) 5 different treatment arms: control (sham injection of vehicle control on days 1–5), sorafenib alone (SOR; injection of 6 mg/mL sorafenib on days 1–5), radiation alone (RT; irradiation at a dose of 3 Gy on days 1–3), concurrent radiation-sorafenib (CONC; sorafenib injection on days 1–5 and irradiation at a dose of 3 Gy on days 2–4), and sequential radiation-sorafenib (SEQ; irradiation at a dose of 3 Gy on days 1–3 and sorafenib injection on days 4–8). The number of tumors per arm was: <i>n</i> = 13 for control, <i>n</i> = 12 for SOR, <i>n</i> = 15 for RT, <i>n</i> = 17 for CONC, and <i>n</i> = 19 for SEQ. Data for each arm are plotted as (B) tumor volume ratio over time (<i>left</i>) and as Kaplan-Meier curves with attainment of quadruple the pre-treatment tumor volume as the event of interest (<i>right</i>). Using two methods of statistical analysis (Mann-Whitney U-test for <i>left</i> and log-rank test for <i>right</i>), SEQ was shown to achieve a significantly longer time to quadruple the pre-treatment tumor volume than any of the other treatment arms. The CONC and RT arms were not significantly different from one another. (C–F) Immunofluorescence staining from xenografts harvested from all treatment arms show significantly more downregulation of vascularity (CD31) (C – <i>left column</i>, D) and decreased mitotic index (Ki-67) (C – <i>right column</i>, E) in arms that received sorafenib treatment, with the most pronounced reductions occurring in the SEQ arm. Immunohistochemical staining for γ-H2AX (C – <i>middle column</i>, F), however, revealed a significantly greater percent of nuclei with high or moderate numbers of foci, as well as a lower percent of nuclei with no foci, for the SEQ and RT arms compared to the CONC arm, similar to our <i>in vitro</i> results above. Column graphs summarizing the data for CD31, γ-H2AX, and Ki-67 are shown in D-F. Asterisks represent significant differences between columns ascertained by Student's <i>t-</i>test (CD31) or by Fisher's exact test (γ-H2AX and Ki-67) as indicated by the accompanying brackets.