Yttrium-90 Radioembolization and Tumor Hypoxia: Gas-challenge BOLD Imaging in the VX2 Rabbit Model of Hepatocellular Carcinoma.

Rationale and objectivesTo use a rapid gas-challenge blood oxygen-level dependent magnetic resonance imaging exam to evaluate changes in tumor hypoxia after 90Y radioembolization (Y90) in the VX2 rabbit model.Materials and methodsWhite New Zealand rabbits (n = 11) provided a Y90 group (n = 6 rabbits) and untreated control group (n = 5 rabbits). R2* maps were generated with gas-challenges (O2/room air) at baseline, 1 week, and 2 weeks post-Y90. Laboratory toxicity was evaluated at baseline, 24 hours, 72 hours, 1 hours, and 2 weeks. Histology was used to evaluate tumor necrosis on hematoxylin and eosin and immunofluorescence imaging was used to assess microvessel density (CD31) and proliferative index (Ki67).ResultsAt baseline, median tumor volumes and time to imaging were similar between groups (p = 1.000 and p = 0.4512, respectively). The median administered dose was 50.4 Gy (95% confidence interval:44.8-55.9). At week 2, mean tumor volumes were 5769.8 versus 643.7 mm3 for control versus Y90 rabbits, respectively (p = 0.0246). At two weeks, ΔR2* increased for control tumors to 12.37 ± 12.36sec-1 and decreased to 4.48 ± 9.00sec-1 after Y90. The Pearson correlation coefficient for ΔR2* at baseline and percent increase in tumor size by two weeks was 0.798 for the Y90 group (p = 0.002). There was no difference in mean microvessel density for control versus Y90 treated tumors (p = 0.6682). The mean proliferative index was reduced in Y90 treated tumors at 30.5% versus 47.5% for controls (p = 0.0071).ConclusionThe baseline ΔR2* of tumors prior to Y90 may be a predictive imaging biomarker of tumor response and treatment of these tumors with Y90 may influence tumor oxygenation over time

Unexpected diversity in socially synchronized rhythms of shorebirds

The behavioural rhythms of organisms are thought to be under strong selection, influenced by the rhythmicity of the environment. Such behavioural rhythms are well studied in isolated individuals under laboratory conditions, but free-living individuals have to temporally synchronize their activities with those of others, including potential mates, competitors, prey and predators. Individuals can temporally segregate their daily activities (for example, prey avoiding predators, subordinates avoiding dominants) or synchronize their activities (for example, group foraging, communal defence, pairs reproducing or caring for offspring). The behavioural rhythms that emerge from such social synchronization and the underlying evolutionary and ecological drivers that shape them remain poorly understood. Here we investigate these rhythms in the context of biparental care, a particularly sensitive phase of social synchronization where pair members potentially compromise their individual rhythms. Using data from 729 nests of 91 populations of 32 biparentally incubating shorebird species, where parents synchronize to achieve continuous coverage of developing eggs, we report remarkable within-and between-species diversity in incubation rhythms. Between species, the median length of one parent's incubation bout varied from 1-19 h, whereas period length-the time in which a parent's probability to incubate cycles once between its highest and lowest value-varied from 6-43 h. The length of incubation bouts was unrelated to variables reflecting energetic demands, but species relying on crypsis (the ability to avoid detection by other animals) had longer incubation bouts than those that are readily visible or who actively protect their nest against predators. Rhythms entrainable to the 24-h light-dark cycle were less prevalent at high latitudes and absent in 18 species. Our results indicate that even under similar environmental conditions and despite 24-h environmental cues, social synchronization can generate far more diverse behavioural rhythms than expected from studies of individuals in captivity. The risk of predation, not the risk of starvation, may be a key factor underlying the diversity in these rhythms.</p

Unexpected diversity in socially synchronized rhythms of shorebirds

The behavioural rhythms of organisms are thought to be under strong selection, influenced by the rhythmicity of the environment1, 2, 3, 4. Such behavioural rhythms are well studied in isolated individuals under laboratory conditions1, 5, but free-living individuals have to temporally synchronize their activities with those of others, including potential mates, competitors, prey and predators6, 7, 8, 9, 10. Individuals can temporally segregate their daily activities (for example, prey avoiding predators, subordinates avoiding dominants) or synchronize their activities (for example, group foraging, communal defence, pairs reproducing or caring for offspring)6, 7, 8, 9, 11. The behavioural rhythms that emerge from such social synchronization and the underlying evolutionary and ecological drivers that shape them remain poorly understood5, 6, 7, 9. Here we investigate these rhythms in the context of biparental care, a particularly sensitive phase of social synchronization12 where pair members potentially compromise their individual rhythms. Using data from 729 nests of 91 populations of 32 biparentally incubating shorebird species, where parents synchronize to achieve continuous coverage of developing eggs, we report remarkable within- and between-species diversity in incubation rhythms. Between species, the median length of one parent’s incubation bout varied from 1–19 h, whereas period length—the time in which a parent’s probability to incubate cycles once between its highest and lowest value—varied from 6–43 h. The length of incubation bouts was unrelated to variables reflecting energetic demands, but species relying on crypsis (the ability to avoid detection by other animals) had longer incubation bouts than those that are readily visible or who actively protect their nest against predators. Rhythms entrainable to the 24-h light–dark cycle were less prevalent at high latitudes and absent in 18 species. Our results indicate that even under similar environmental conditions and despite 24-h environmental cues, social synchronization can generate far more diverse behavioural rhythms than expected from studies of individuals in captivity5, 6, 7, 9. The risk of predation, not the risk of starvation, may be a key factor underlying the diversity in these rhythms

Radioembolization for the treatment of unresectable hepatocellular carcinoma: A clinical review

Hepatocellular carcinoma (HCC) is the sixth most common cancer in the world. The majority of patients with HCC present with unresectable disease. These patients have historically had limited treatment options secondary to HCC demonstrating chemoresistance to the currently available systemic therapies. Additionally, normal liver parenchyma has shown intolerance to tumoricidal radiation doses, limiting the use of external beam radiation. Because of these limitations, novel percutaneous liver-directed therapies have emerged. The targeted infusion of radioactive microspheres (radioembolization) represents one such therapy. Radioembolization is a minimally invasive transcatheter therapy through which radioactive microspheres are infused into the hepatic arteries that supply tumor. Once infused, these microspheres traverse the hepatic vascular plexus and selectively implant within the tumor arterioles. Embedded within the arterioles, the 90Y impregnated microspheres emit high energy and low penetrating radiation doses selectively to the tumor. Radioembolization has recently shown promise for the treatment of patients with unresectable HCC. The objective of this review article is to highlight two currently available radioembolic devices (90Y, 188Rh) and provide the reader with a recent review of the literature

Yttrium-90 Portal Vein Radioembolization in Sprague-Dawley Rats: Dose-Dependent Imaging and Pathological Changes in Normal Liver.

PurposePortal vein embolization (PVE) is an established neoadjuvant method to induce future liver remnant hypertrophy prior to surgical resection of hepatic tumors. The purpose of our study was to examine the feasibility of PVE with glass 90Y microspheres (Y90 PVE) in Sprague-Dawley rats. We tested the hypothesis that increased doses of Y90 PVE would increase target lobe fibrosis and atrophy.MethodsTwenty-two rats were assigned to four groups for Y90 PVE to the right median lobe: very high- (273.8&nbsp;MBq; n = 2), high- (99.9&nbsp;MBq; n = 10), medium- (48.1&nbsp;MBq; n = 5), and low-dose (14.8&nbsp;MBq; n = 5). An untreated control group included seven rats. 90Y PET/CT of 90Y distributions confirmed lobar targeting. MRI volumes were measured at baseline, 2-, 4-, 8- and 12-weeks. Explanted hepatic lobes were weighed, sectioned, and stained for H&amp;E and immunohistochemistry. Digitized slides allowed quantitative measurements of fibrosis (20 foci/slide).ResultsEx vivo measurements confirmed 91-97% activity was localized to the target lobe (n = 4). The percent growth of the target lobe relative to baseline was -&nbsp;5.0% (95% CI -&nbsp;17.0-6.9%) for high-, medium dose rats compared to + 18.6% (95% CI + 7.6-29.7%) in the low-dose group at 12-weeks (p = 0.0043). Radiation fibrosis increased in a dose-dependent fashion. Fibrotic area/microsphere was 22,893.5, 14,946.2 ± 2253.3, 15,304.5 ± 4716.6, and 5268.8 ± 2297.2&nbsp;μm2 for very high- (n = 1), high- (n = 4), medium- (n = 3), and low-dose groups (n = 5), respectively.ConclusionY90 PVE was feasible in the rat model, resulted in target lobe atrophy, and dose-dependent increases in hepatic fibrosis at 12&nbsp;weeks. The onset of imaging-based volumetric changes was 8-12&nbsp;weeks

Feasibility of Combination Intra-arterial Yttrium-90 and Irinotecan Microspheres in the VX2 Rabbit Model.

PurposeTo evaluate the combination of 90Y radioembolization (Y90) and drug-eluting bead irinotecan (DEBIRI) microspheres in the VX2 rabbit model.Materials and methodsAn initial dose finding study was performed in 6 White New Zealand rabbits to identify a therapeutic but subcurative dose of Y90. In total, 29 rabbits were used in four groups: Y90 treatment (n = 8), DEBIRI treatment (n = 6), Y90 + DEBIRI treatment (n = 7), and an untreated control group (n = 8). Hepatic toxicity was evaluated at baseline, 24&nbsp;h, 72&nbsp;h, 1&nbsp;week, and 2&nbsp;weeks. MRI tumor volume (TV) and enhancing tumor volume were assessed baseline and 2&nbsp;weeks. Tumor area and necrosis were evaluated on H&amp;E for pathology.ResultsInfused activities of 84.0-94.4&nbsp;MBq (corresponding to 55.1-72.7&nbsp;Gy) were selected based on the initial dose finding study. Infusion of DEBIRI after Y90 was technically feasible in all cases (7/7). Overall, 21/29 animals survived to 2&nbsp;weeks, and the remaining animals had extrahepatic disease on necropsy. Liver transaminases were elevated with Y90, DEBIRI, and Y90 + DEBIRI compared to control at 24&nbsp;h, 72&nbsp;h, and 1&nbsp;week post-treatment and returned to baseline by 2&nbsp;weeks. By TV, Y90 + DEBIRI was the only treatment to show statistically significant reduction at 2&nbsp;weeks compared to the control group (p = 0.012). The change in tumor volume (week 2-baseline) for both Y90 + DEBIRI versus control (p = 0.002) and Y90 versus control (p = 0.014) was significantly decreased. There were no statistically significant differences among groups on pathology.ConclusionIntra-arterial Y90 + DEBIRI was safe and demonstrated enhanced antitumor activity in rabbit VX2 tumors. This combined approach warrants further investigation