Enhanced tumor growth after portal vein embolization in a rabbit tumor model. J Surg Res. 2013;180:89-96. [PMID: 23149224 DOI: 10.1016/j.jss.2012.10.032]

Rabbit VX2 Liver Tumor Model: A Review of Clinical, Biology, Histology, and Tumor Microenvironment Characteristics

The rabbit VX2 is a large animal model of cancer used for decades by interventional radiologists to demonstrate the efficacy of various locoregional treatments against liver tumors. What do we know about this tumor in the new era of targeted therapy and immune-oncology? The present paper describes the current knowledge on the clinics, biology, histopathology, and tumor microenvironment of VX2 based on a literature review of 741 publications in the liver and in other organs. It reveals the resemblance with human cancer (anatomy, vascularity, angiogenic profile, drug sensitivity, immune microenvironment), the differences (etiology, growth rate, histology), and the questions still poorly explored (serum and tissue biomarkers, genomic alterations, immune checkpoint inhibitors efficacy).

Current strategies to induce liver remnant hypertrophy before major liver resection

Hepatic resection is the gold standard for patients affected by primary or metastatic liver tumors but is hampered by the risk of post-hepatectomy liver failure. Despite recent improvements, liver surgery still requires excellent clinical judgement in selecting patients for surgery and, above all, efficient pre-operative strategies to provide adequate future liver remnant. The aim of this article is to review the literature on the rational, the preliminary assessment, the advantages as well as the limits of each existing technique for preparing the liver for major hepatectomy.

Monitoring the therapeutic efficacy of CA4P in the rabbit VX2 liver tumor using dynamic contrast-enhanced MRI

PURPOSE

The present work aims to evaluate whether dynamic contrast-enhanced magnetic resonance Imaging (DCE-MRI) can monitor non-invasively the blocking effect on microvessels of the Combretastatin-A4-phosphate (CA4P) and assess the therapeutic efficacy.

METHODS

Forty rabbits were implanted the VX2 tumors specimens. Two weeks later, serial MRI (T1 weighted image, T2 weighted image and DCE) were performed at 0 h, 4 h, 24 h, 3 d and 7 d after CA4P (10 mg/kg) or saline treatment. The parameters of DCE (Ktrans, Kep, Ve and iAUC60) of enhancement tumor portions were measured. Then all the tumor samples were stained to count microvessel density (MVD). At last, two-way repeated measures ANOVA was used to analyze the difference between and within groups. The correlation between the Ktrans, Kep, Ve, iAUC60 and MVD was analyzed by using the Pearson correlation analysis and Spearman's rank correlation.

RESULTS

The Ktrans and iAUC60 in the CA4P group were lower than the values of the control group at 4 h after treatment, which have significant differences (D-value: -0.133 min-1, 95%CI: -0.169~-0.097 min-1，F = 59.109, p < 0.001 for Ktrans; D-value: -10.533 mmol/sec, 95%CI: -17.147~-3.919 mmol/sec，F = 11.110, and p = 0.003 for iAUC60). In the CA4P group, the Ktrans and iAUC60 reached the minimum values at 4 h. There were significant differences between 4 h and other different time points of the Ktrans and iAUC60 in the treatment group (all p < 0.01). The parameters Ktrans (r = 0.532, P = 0.016 and r = 0.681, P = 0.001, respectively) and iAUC60 (r = 0.580, P = 0.007 and r = 0.568, P = 0.009, respectively) of 7 days showed correlation with MVD in both groups, while Kep and Ve did not show correlation with MVD (P > 0.05).

CONCLUSION

The blocking effect of microvessels after CA4P treatment can be evaluated by DCE-MRI, and the parameters of quantitative Ktrans and semi- quantitative iAUC60 can assess the change of the tumor angiogenesis noninvasively.

Oncological benefits of portal vein embolization for patients with hepatocellular carcinoma

Portal vein embolization (PVE) for hepatocellular carcinoma (HCC) was first introduced in 1986 and has been continuously developed throughout the years. Basically, PVE has been applied to expand the indication of liver resection for HCC patients of insufficient future liver remnant. Importantly, PVE can result in tumor progression in both embolized and non-embolized livers; however, long-term survival after liver resection following PVE is at least not inferior compared with liver resection alone despite the smaller future liver remnant volume. Five-year disease-free survival and 5-year overall survival were 17% to 49% and 12% to 53% in non-PVE patients, and 21% to 78% and 44% to 72% in PVE patients, respectively. At present, it has proven that PVE has multiple oncological advantages for both surgical and nonsurgical treatments. PVE can also enhance the anticancer effects of transarterial chemoembolization and can avoid intraportal tumor cell dissemination. Additional interventional transarterial chemoembolization and hepatic vein embolization as well as surgical two-stage hepatectomy and associated liver partition and portal vein ligation for staged hepatectomy can enhance the oncological benefit of PVE monotherapy. Taken together, PVE is an important treatment which we recommend for listing in the guidelines for HCC treatment strategies.

The use of neoadjuvant lobar radioembolization prior to major hepatic resection for malignancy results in a low rate of post hepatectomy liver failure

Background

Neoadjuvant yttrium-90 transarterial radioembolization (TARE) is increasingly being used as a strategy to facilitate resection of otherwise unresectable tumors due to its ability to generate both tumor response and remnant liver hypertrophy. Perioperative outcomes after the use of neoadjuvant lobar TARE remain underinvestigated.

Methods

A single center retrospective review of patients who underwent lobar TARE prior to major hepatectomy for primary or metastatic liver cancer between 2007 and 2018 was conducted. Baseline demographics, radioembolization parameters, pre- and post-radioembolization volumetrics, intra-operative surgical data, adverse events, and post-operative outcomes were analyzed.

Results

Twenty-six patients underwent major hepatectomy after neoadjuvant lobar TARE. The mean age was 58.3 years (17-88 years). 62% of patients (n=16) had primary liver malignancies while the remainder had metastatic disease. Liver resection included right hepatectomy or trisegmentectomy, left or extended left hepatectomy, and sectorectomy/segmentectomy in 77% (n=20), 8% (n=2), and 15% (n=4) of patients, respectively. The mean length of stay was 8.3 days (range, 3-33 days) and there were no grade IV morbidities or 90-day mortalities. The incidence of post hepatectomy liver failure (PHLF) was 3.8% (n=1). The median time to progression after resection was 4.5 months (range, 3.3-10 months). Twenty-three percent (n=6) of patients had no recurrence. The median survival was 28.9 months (range, 16.9-46.8 months) from major hepatectomy and 37.6 months (range, 25.2-53.1 months) from TARE.

Conclusions

Major hepatectomy after neoadjuvant lobar radioembolization is safe with a low incidence of PHLF.

Induction of Contralateral Hepatic Hypertrophy by Unilobar Yttrium-90 Transarterial Radioembolization versus Portal Vein Embolization: An Animal Study

PURPOSE

To compare hepatic hypertrophy in the contralateral lobe achieved by unilobar transarterial radioembolization (TARE) versus portal vein embolization (PVE) in a swine model.

METHODS

After an escalation study to determine the optimum dose to achieve hypertrophy after unilobar TARE in 4 animals, 16 pigs were treated by TARE (yttrium-90 resin microspheres) or PVE (lipiodol/n-butyl cyanoacrylate). Liver volume was calculated based on CT before treatment and during 6 months of follow-up. Independent t-test (P < .05) was used to compare hypertrophy. The relationship between hypertrophy after TARE and absorbed dose was calculated using the Pearson correlation.

RESULTS

At 2 and 4 weeks after treatment, a significantly higher degree of future liver remnant hypertrophy was observed in the PVE group versus the TARE group, with a median volume gain of 31% (interquartile range [IQR]: 16%-66%) for PVE versus 23% (IQR: 6%-36%) for TARE after 2 weeks and 51% (IQR: 47%-69%) for PVE versus 29% (IQR: 20%-50%) for TARE after 4 weeks. After 3 and 6 months, hypertrophy converged without a statistically significant difference, with a volume gain of 103% (IQR: 86%-119%) for PVE versus 82% (IQR: 70%-96%) for TARE after 3 months and 115% (IQR: 70%-46%) for PVE versus 86% (IQR: 58%-111%) for TARE after 6 months. A strong correlation was observed between radiation dose (median 162 Gy, IQR: 139-175) and hypertrophy.

CONCLUSIONS

PVE resulted in rapid hypertrophy within 1 month of the procedure, followed by a plateau, whereas TARE resulted in comparable hypertrophy by 3-6 months. TARE-induced hypertrophy correlated with radiation absorbed dose.

Major hepatectomy decreased tumor growth in an experimental model of bilobar liver metastasis

BACKGROUND/PURPOSE

Two-stage hepatectomy (TSH), is associated with a risk of drop-out due to tumoral progression following portal vein occlusion (PVO). We explored the impact of majorhepatectomy on tumor growth by objective radiological measures comparing to PVO and minor hepatectomy, using a model of bilobar colorectal liver metastasis (CLM).

METHODS

CLM were induced in 48 BDIX rats by injection of DHDK12-cells. 7 days after cells injection, animals were distributed into 4 groups of equal number (n = 12): portal vein ligation (PVL), sham laparotomy (sham), minor (30%Phx) and major (70%Phx) hepatectomy. MR imaging was used for in vivo analysis of tumor implantation, growth and volumes.

RESULTS

At POD10, tumour volumes were homogeneously distributed among the 4 groups. Lower TV were significantly observed after 70%Phx comparing to PVL at POD17 (0.63 ± 0.14cm3 vs 0.9 ± 0.16cm3, p = 0.008) and to the 3 others groups at POD24: 1.78 ± 0.38cm3 vs 3.2 ± 0.62cm3 (PVL, p = 0.019), 2.41 ± 0.74cm3 (Sham, p = 0.024) and 2.32 ± 0.59cm3 (30%PHx, p = 0.019).

CONCLUSION

We confirmed in a reproducible model that contrary to PVO, a major hepatectomy decreases the growth of CLM in the remnant liver. This result leads to questioning the usual TSH and justifies exploring alternative strategies. The "major hepatectomy first-approach" should be an option to be evaluated.

Colorectal cancer liver metastases within the central and peripheral segments: Parenchymal sparing surgery adaptation

Background

The debate over the surgical strategy optimization in colorectal cancer patients with liver metastases (mCRC) has been ongoing in the last 20 years. However, parenchyma sparing surgery (PPS) in cases of hard to reach liver cites (HTRLC) remain to be controversial.

Methods

A prospective analysis of 185 mCRC patients performed who were devided in two groups depending by predominant liver cite localization. Peripherally localized metastases (PLM) (n = 107) (S2, S3, S6, S7, Spiegel lobe and subcapsular area 1-2 cm below the liver surface). Group 2 included those with metastases localized in HTRLC (n = 78) - metastatic lesions of the "right venous core", portal and caval hilum, paracaval part of S1, "deep" parenchyma cites of S5, S8 and S4.

Results

In 26 (33,3%) and 32 (29,9%) patients of HTRLC and PLM, respectively, performed one liver re-resection (0,62). In HTRLC group 2 and more re-resection were performed in 7 (8,9%) cases while in PLM in 11 (10,3%), p = 0,76. Postoperative major morbidity was 24,4%, 21,8% (p = 0,15) and mortality 8,9%, 4,6% for HTRLC and PLM groups, respectively. R1v principles were implemented in 24 (30,7%) cases with centrally located metastases and in only 6 cases (5.6%) with peripheral localized metastases (p = 0,001). Cumulative 3-year disease-free survival (DSF) for PLM and HTRLC groups was 63% and 41% (p = 0,008). DFS for R1v (n = 24) and R0 (54) cochorts in HTRLC group was 33% and 43%, respeсtively (p = 0,44).

Conclusions

Principles of the PPS tactic provides an adequate removal of metastatic lesions in hard to reach liver cites allowing to maintain organ functions and increases the feasibility of the repeated liver resections in case of the initial disease progression.

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

PURPOSE

Portal 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.

METHODS

Twenty-two rats were assigned to four groups for Y90 PVE to the right median lobe: very high- (273.8 MBq; n = 2), high- (99.9 MBq; n = 10), medium- (48.1 MBq; n = 5), and low-dose (14.8 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&E and immunohistochemistry. Digitized slides allowed quantitative measurements of fibrosis (20 foci/slide).

RESULTS

Ex 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 - 5.0% (95% CI - 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 μm² for very high- (n = 1), high- (n = 4), medium- (n = 3), and low-dose groups (n = 5), respectively.

CONCLUSION

Y90 PVE was feasible in the rat model, resulted in target lobe atrophy, and dose-dependent increases in hepatic fibrosis at 12 weeks. The onset of imaging-based volumetric changes was 8-12 weeks.

Expression of MMP-2 in residual VX2 liver tumor after transcatheter arterial embolization combined with portal venous embolization in an animal model

Objective

This study aimed to analyze the effects of transcatheter arterial embolization (TAE) combined with portal venous embolization (PVE) on the expression of MMP-2 in residual VX2 liver tumor tissues, liver function and non-embolic lobe regeneration.

Methods

A total of 72 rabbits were randomly divided into Sham, TAE, PVE and TAE ​+ ​PVE groups (n ​= ​18/group). The tissue samples from each group were taken at 6 ​h, 3 days and 7 days after interventional operation, respectively. MMP-2 expression was detected by immunohistochemistry, Real-time PCR, and Western-blotting. The main indicators (such as AST, ATL, and TBIL) of liver function and the volume of non-embolized hepatic lobes were measured in each group after operation. One-way ANOVA and Kruskal-wallis method were used for statistical analysis.

Results

The expression of MMP-2 mRNA and protein remained the highest in the Sham group, and the expression of MMP-2 mRNA and protein in TAE, PVE and TAE ​+ ​PVE groups were successively increased, and the expression of MMP-2 in TAE ​+ ​PVE group was always significantly higher than TAE group. The AST and ALT levels in each group on day 7 after operation showed a significant declination, and all groups have recovered to the preoperative baseline level and TBIL has a slight fluctuation in each group after operation with no statistical difference. On day 7 after operation, the increasing volume of non-embolized liver lobes in TAE ​+ ​PVE group showed a more significant effect than those in PVE group, but there was no statistical significance (37.62 ​± ​1.54 ​ml VS 36.18 ​± ​1.15 ​ml, P ​= ​0.881), and its volume was significantly higher than those in the sham group (27.03 ​± ​1.11 ​ml).

Conclusion

TAE ​+ ​PVE is considered to be an efficient and safe approach for treating rabbit VX2 liver transplantation tumor, but the expression of MMP-2 increased fastest after TAE ​+ ​PVE, which might promote tumor cell invasion and metastasis.

Correlation Between Sarcopenia and Growth Rate of the Future Liver Remnant After Portal Vein Embolization in Patients with Colorectal Liver Metastases

PURPOSE

To investigate whether sarcopenia and myosteatosis correlate with the degree of hypertrophy (DH) and kinetic growth rate (KiGR) of the future liver remnant (FLR) in patients with colorectal liver metastases undergoing portal vein embolization (PVE) in preparation for right hepatectomy.

MATERIALS AND METHODS

Forty-two patients were included. Total liver volume and FLR volume were measured before and 2-4 weeks after PVE. KiGR of the FLR was calculated. Sarcopenia was assessed using the total psoas muscle volume (PMV), the psoas muscle cross-sectional area (PMCS) and the total skeletal muscle index (L3SMI) at the level of 3rd lumbar vertebra. Degree of myosteatosis was assessed by mean muscle attenuation at L3 (L3MA). Correlations between muscle indices and DH and KiGR were assessed using simple linear regression analyses.

RESULTS

Mean DH was 8.9 ± 5.7%, and mean KiGR was 3.6 ± 2.3. Mean PMV was 55.56 ± 14.19 cm3/m3, mean PMCS was 8.76 ± 2.3 cm2/m2, mean L3SMI was 45.6 ± 9.89 cm2/m2, and mean L3MA was 27.9 ± 18.6 HU. There was a strong positive correlation between PMV and DH (R = 0.503, p = 0.001) and PMV and KiGR (R = 0.545, p < 0.001). Furthermore, there was a moderate correlation between PMCS and KiGR (R = 0.389, p = 0.014). L3SMI and L3MA were neither associated with DH (p = 0.390 and p = 0.768, respectively) nor with KiGR (p = 0.188 and p = 0.929, respectively).

CONCLUSION

We identified a positive correlation between PMV and PMCS, as markers for sarcopenia, and the KiGR of the FLR after PVE. PMV and PMCS might therefore aid to identify patients who are poor candidates for FLR augmentation using PVE alone.

Comparison of functional and volumetric increase of the future remnant liver and postoperative outcomes after portal vein embolization and complete or partial associating liver partition and portal vein ligation for staged hepatectomy (ALPPS)

Background

Portal vein embolization (PVE) is performed to induce hypertrophy of an insufficient future remnant liver (FRL) before major liver resection. Associating liver partition and portal vein ligation for staged hepatectomy (ALPPS) aims to offer a more rapid and increased hypertrophy response. The first stage can be performed with complete or partial (laparoscopic) transection of the liver parenchyma. This study aimed to investigate the increase in FRL volume and function, as well as postoperative outcomes after PVE or complete- or partial-ALPPS1.

Methods

Patients with insufficient FRL undergoing either PVE or ALPPS underwent CT-volumetry and functional assessment using ^99mTc-mebrofenin hepatobiliary scintigraphy (HBS). Severe complications and 90-day mortality were evaluated after liver resection.

Results

Seventy-two patients were included; 51 underwent PVE, 12 complete-ALPPS1 and 9 partial-ALPPS1 of which 7 laparoscopic. The median increase in FRL function was 1.5-, 1.7- and 1.3-fold higher, respectively, than the increase in volume; (P<0.01, P<0.01 and P=0.44). The target hypertrophy response did not differ between the groups, but was reached earlier in both ALPPS1 groups (8 and 10 days) compared to the PVE group (23 days). Of the resected patients, 18%, 30% and 17% had severe postoperative complications and the 90-day mortality was 2%, 25% and 0%, respectively.

Conclusions

Increase of FRL function exceeded increase of volume after both PVE and ALPPS1. The target hypertrophy response was reached earlier in ALPPS. Complete and partial-ALPPS1 showed comparable functional and volumetric hypertrophy responses. A (laparoscopic) partial-ALPPS1 is preferred considering lower morbidity and mortality rates after resection.

Detection of Hyperacute Reactions of Desacetylvinblastine Monohydrazide in a Xenograft Model Using Intravoxel Incoherent Motion DWI and R2* Mapping

OBJECTIVE

This study aimed to investigate the feasibility of intravoxel incoherent motion (IVIM) DWI and R2* (transverse relaxation rate) mapping to monitor the hyperacute therapeutic efficacy of desacetylvinblastine monohydrazide (DAVLBH) on an experimental hepatocellular carcinoma mouse model within 24 hours.

MATERIALS AND METHODS

Forty-four mice were implanted with hepatocellular carcinoma and divided into three random groups. A treatment group and a control group underwent IVIM-DWI and R2* mapping examinations before and after a single injection of DAVLBH or saline at 1, 2, 4, and 24 hours. The pathology group was set for pathologic analysis, including H and E staining and CD31 and hypoxia-inducible factor (HIF)-1α immunohistochemical staining.

RESULTS

DAVLBH caused hyperacute disruptions on the tumor capillaries in the treatment group. Water molecule diffusion (D), microcirculation perfusion (D*), and perfusion fraction (f) decreased initially but then gradually recovered to the baseline level by 24 hours after the first injection of DAVLBH. In contrast, R2* increased dramatically at 1 hour and then gradually decreased from 1 hour to 24 hours after treatment. D*, f, and D showed similar trends and were positively correlated with CD31 expression (r = 0.868, 0.721, and 0.730, respectively), but were negatively correlated with HIF-1α expression (r = -0.784, -0.737, and -0.673, respectively). R2* showed a negative correlation with CD31 expression (r = -0.823) and a positive correlation with HIF-1α expression (r = 0.791).

CONCLUSION

Both IVIM-DWI and R2* mapping can adequately detect the vascular-disrupting effect of DAVLBH as early as 1 hour after injection in a mouse xenograft model. Moreover, D* and R2* are the two most sensitive hemodynamic parameters and can monitor the hyperacute changes associated with DAVLBH treatment in vivo.

Progression of Colorectal Liver Metastases from the End of Chemotherapy to Resection: A New Contraindication to Surgery?

BACKGROUND

Not all patients with resectable colorectal liver metastases (CLM) benefit from liver resection (LR); only patients with disease progression during chemotherapy are excluded from surgery.

OBJECTIVE

This study was performed to determine whether tumor behavior (stable disease/progression) from the end of chemotherapy to LR impacts prognosis.

METHODS

Patients undergoing LR after tumor response or stabilization during chemotherapy were considered. Overall, 128 patients who underwent examination by two imaging modalities (computed tomography/magnetic resonance imaging) after chemotherapy with a > 3-week interval between the two imaging modalities were analyzed. Any variation in CLM size was registered. Tumor progression was defined according to the response evaluation criteria in solid tumors (RECIST) criteria.

RESULTS

Among 128 patients with stable disease or partial response to preoperative chemotherapy, 32 (25%) developed disease progression in the chemotherapy to LR interval, with a disease progression rate of 17% when this interval was < 8 weeks. Survival was lower among patients with progression than those with stable disease [3-year overall survival (OS) 23.0 vs. 52.4%, and recurrence-free survival (RFS) 6.3% vs. 21.6%; p < 0.001]. Survival was extremely poor in patients with early progression (< 8 weeks) (0.0% 2-year OS, 12.5% 6-month RFS). Disease progression in the chemotherapy to LR interval was an independent negative prognostic factor for OS and RFS [hazard ratio 3.144 and 2.350, respectively; p < 0.001].

CONCLUSIONS

Early disease progression in the chemotherapy to LR interval occurred in approximately 15% of patients and was associated with extremely poor survival. Even if these data require validation, the risk for early disease progression after chemotherapy should be considered, and, if progression is evident, the indication for surgery should be cautiously evaluated.

Remnant Liver Tumor Growth Activity During Treatment Associating Liver Partition and Portal Vein Occlusion for Staged Hepatectomy (ALPPS)

BACKGROUND

We compared tumor growth activity during treatment associating liver partition and portal vein occlusion for staged hepatectomy (ALPPS) with that in classical 2-stage hepatectomy.

METHODS

Short-term outcomes, serial changes in volume of the future liver remnant (FLR), and tumor growth activity during the treatment period were compared between 12 patients treated with ALPPS and 20 patients treated with 2-stage hepatectomy for colorectal liver metastases. This study was registered in UMIN Clinical Trials Registry (registration number, UMIN000018622).

RESULTS

The FLR hypertrophy ratio at 1 week after the first operation was greater in the ALPPS group (1.43 ± 0.24) than the 2-stage group (1.21 ± 0.28, P = 0.043). The mean kinetic growth rate (mKGR) of tumors in the ALPPS group (0.548 ± 7.29 mL/day) did not differ significantly from that in the 2-stage group (-3.53 ± 7.02 mL/day) in the first week after the initial procedure (P = 0.210). However, mKGR between 1 and 3 weeks after the first procedure (1.29 ± 2.34 mL/day) was significantly greater than that in first week after the procedure in the 2-stage group (P = 0.034).

CONCLUSIONS

ALPPS induces a rapid FLR volume increase while avoiding remnant tumor progression.

Surgery-induced tumor growth in (metastatic) colorectal cancer

Metastatic colorectal cancer (mCRC) is a devastating disease causing 700.000 deaths annually worldwide. Metastases most frequently develop in the liver. Partial hepatectomy has dramatically improved clinical outcome and is the only curative treatment option for eligible patients with mCRC. Pre-clinical studies have shown that surgical procedures can have tumor-promoting local 'side-effects' such as hypoxia and inflammation, thereby altering the behaviour of residual tumor cells. In addition, systemically released factors following (colon or liver) surgery can act as a wakeup-call for dormant tumor cells in distant organs and/or help establish a pre-metastatic niche. Tumor handling during resection may also increase the number of circulating tumor cells. Despite the overwhelming amount of pre-clinical data demonstrating the pro-tumorigenic side effects of surgery, clinical evidence is scarce. Indications for hepatic surgery are rapidly increasing due to a rise in the incidence of mCRC and a trend towards more aggressive surgical treatment. Therefore, it is increasingly important to understand the principles of surgery-induced tumor growth, in order to devise perioperative or adjuvant strategies to further enhance long-term tumor control. In the current study we review the evidence for surgery-stimulated tumor growth and suggest strategies to assess the clinical relevance of such findings.

Ablative Liver Partition and Portal Vein Embolization: Proof-of-Concept Testing in a Rabbit Model

PURPOSE

To test the hypothesis that a modified approach to portal vein embolization (PVE)-termed ablative liver partition (ALP) and PVE (ALP-PVE)-is feasible and results in greater future liver remnant (FLR) growth compared with PVE alone in a rabbit model.

MATERIALS AND METHODS

Eighteen rabbits (median weight, 2.7 kg) underwent PVE (n = 9) or ALP-PVE (n = 9). PVE to cranial liver lobes was performed with 100-300-μm microspheres and metallic coils; the caudal lobe was spared as the FLR. In the ALP-PVE cohort, a liver partition between cranial and caudal lobes was created by using microwave ablation (40 W, 1 min). Animals were euthanized and livers were harvested on postprocedure day 7. Caudal and cranial liver lobes were weighed after 4 weeks of oven drying. Ki-67 immunohistochemistry was used to quantify liver mitotic index. ALP-PVE feasibility was determined based on procedure technical success. Standardized FLR (sFLR; ie, FLR divided by whole liver weight) and mitotic index were compared between PVE and ALP-PVE groups by two-tailed independent-samples Mann-Whitney U test.

RESULTS

One PVE-group rabbit died during anesthesia induction and was excluded from technical success calculation. Eight of 8 (100%) and 8 of 9 rabbits (89%) underwent technically successful PVE and ALP-PVE, respectively. There was no difference in sex or weight distribution between groups. sFLR (0.32 vs 0.29; P = .022) and mitotic index (17.5% vs 6.2%; P = .051) were higher in ALP-PVE vs PVE caudal lobes when the first "learning-curve" case from each group was excluded.

CONCLUSIONS

ALP-PVE is feasible and may stimulate greater FLR growth compared with PVE in a rabbit model.

ALPPS (associating liver partition and portal vein ligation for staged hepatectomy) does not affect proliferation, apoptosis, or angiogenesis as compared to standard liver resection for colorectal liver metastases

Background

ALPPS (associating liver partition and portal vein ligation for staged hepatectomy) is a novel two-stage strategy to induce rapid hypertrophy of the future liver remnant (FLR) when patients are in danger of postoperative liver failure due to insufficient FLR. However, the effects of ALPPS on colorectal liver metastases (CRLM) are not clear so far. The aim of our study was to determine whether ALPPS induces proliferation, apoptosis, or vascularization compared to standard (one-stage) liver resection.

Methods

Six patients who underwent ALPPS were matched with 12 patients undergoing standard liver resection regarding characteristics of the metastases (size, number), time of appearance (syn-/metachronous), preoperative chemotherapy, primary tumor (localization, TNM stage, grading), and patient variables (gender, age). The largest resected metastasis was used for the analyses. Tissue was stained for tumor cell proliferation (Ki67), apoptosis (TUNEL, caspase-3), vascularization (CD31), and pericytes (αSMA).

Results

Vascularization (CD31; p = 0.149), proliferation (Mib-1; p = 0.244), and αSMA expression (p = 0.205) did not significantly differ between the two groups, although a trend towards less proliferation and αSMA expression was observed in patients undergoing ALPPS. Concerning apoptosis, caspase-3 staining showed significantly fewer apoptotic cells upon ALPPS (p < 0.0001), but this was not confirmed by TUNEL staining (p = 0.7344).

Conclusions

ALPPS does not induce proliferation, apoptosis, or vascularization of CRLM when compared to standard liver resection.

Yttrium-90 Radioembolization of Hepatocellular Carcinoma-Performance, Technical Advances, and Future Concepts

Hepatocellular carcinoma (HCC) is a lethal tumor, claiming over half a million lives per year. Treatment of HCC is commonly performed without curative intent, and palliative options dominate, including catheter-based therapies, namely, transarterial chemoembolization and yttrium-90 ((90)Y) radioembolization. This review will showcase the performance of (90)Y radioembolization for the treatment of HCC, focusing on recent seminal data and technical advances. In particular, novel radioembolization treatment concepts are discussed and compared with conventional HCC therapy.

Combining dynamic contrast enhanced magnetic resonance imaging and microvessel density to assess the angiogenesis after PEI in a rabbit VX2 liver tumor model

OBJECTIVES

To evaluate the correlation between parameters of dynamic contrast enhanced magnetic resonance imaging (DCE-MRI) and microvessel density (MVD) measurements in rabbit VX2 liver tumor models after percutaneous ethanol injection (PEI) and to observe influence of PEI on angiogenesis in a rabbit VX2 liver tumor model with dynamic contrast enhanced magnetic resonance imaging (DCE-MRI).

MATERIALS AND METHODS

Forty five New Zealand white rabbits were used in this study. VX2 tumor tissue blocks were implanted in the left lobe of liver by percutaneous puncture under CT guidance. 2 weeks later, all rabbits underwent conventional MRI (T1WI, T2WI) to determine the successful models. Then those successful implanted VX2 liver tumor models in the study were randomly divided into the control group and the experimental group, the former did not have processing, and the latter underwent PEI under CT guidance. MRI (T1WI, T2WI and DCE-MRI) was performed 1 week later again, the parameters of DCE-MRI (Ktrans, Kep, Ve and iAUC60) of viable tumor portions were observed. Then all the liver samples were processed for hematoxylin and eosin (H&E) staining and immunohistochemical staining for CD31 to determine MVD. At last, data (including DCE-MRI perfusion parameters and MVD) were compared between experimental and control groups, correlation of DCE-MRI perfusion parameters and MVD was evaluated.

RESULTS

Twenty six VX2 liver tumor models underwent all examinations (thirteen models for each group) 1 week later after PEI. For the experimental group, the parameters Ktrans (r=0.6382, P=0.0189) and iAUC60 (r=0.6591, P=0.0143) in viable tumor portions were positively moderately correlated with MVD, whereas the parameters Kep (r=0.4656, P=0.1088) and Ve (r=0.2918, P=0.3333) were not correlated with MVD. For the control group, the parameters Ktrans (r=0.6385, P=0.0188) and iAUC60 (r=0.6391, P=0.0187) in viable tumor portions were also positively moderately correlated with MVD, while the parameters Kep (r=0.5518, P=0.0506) and Ve (r=-0.0824, P=0.789) were not correlated with MVD. Ktrans, Kep, Ve, iAUC60 and MVD of residual viable tumors in the experimental group 1 week later after PEI were similar to the viable tumors of the control group (P>0.05).

CONCLUSIONS

DCE-MRI could be used to evaluate the efficiency of VX2 liver tumor after PEI. The quantitative parameter Ktrans and semi-quantitative parameter iAUC60 of DCE-MRI are correlated with MVD, which can assess tumor angiogenesis noninvasively of VX2 liver tumor model, and ethanol has no significant impact on angiogenesis of viable tumor 1week later after PEI.

Portal vein embolization effect on colorectal cancer liver metastasis progression: Lessons learned

Colorectal liver metastasis (CRLM) is the major cause of death in patients diagnosed with colorectal cancer. The gold standard treatment of CRLM is surgical resection. Yet, in the past, more than half of these patients were deemed unresectable due to the inadequate future liver remnant (FLR). The introduction of efficient portal vein embolization (PVE) preoperatively allowed more resections of metastasis in CRLM patients by stimulating adequate liver hypertrophy. However, several experimental and clinical studies reported tumor progression after PVE which critically influences the subsequent management of these patients. The underlying pathophysiological mechanism of tumor progression post-PVE is still not fully understood. In spite of the adverse effects of PVE, it remains a potentially curative procedure in patients who would remain otherwise unresectable because of the insufficient FLR. Currently, the challenge is to halt tumor proliferation following PVE in patients who require this technique. This could potentially be achieved by either attempting to suppress the underlying oncologic stimulus or by inhibiting tumor growth once observed after PVE, without jeopardizing liver regeneration. More research is still required to better identify patients at risk of experiencing tumor growth post-PVE.

Effect of liver regeneration on malignant hepatic tumors

Liver regeneration after major surgery may activate occult micrometastases and facilitate tumor growth, leading to liver tumor recurrence. Molecular changes during liver regeneration can provide a microenvironment that stimulates intrahepatic tumor propagation through alterations in cellular signaling pathways, where activation and proliferation of mature hepatocytes, hepatic progenitor cells, non-parenchymal liver cells might favor both liver regeneration and tumor growth. This review highlights recent advances of tumor growth and development in the regenerating liver, possible mechanisms and clinical implications.

A review of animal models for portal vein embolization

BACKGROUND

Portal vein embolization (PVE) is a preoperative intervention to increase the future remnant liver (FRL) through regeneration of the non-embolized liver lobes. This review assesses all the relevant animal models of PVE available, to guide researchers who intend to study PVE.

MATERIALS AND METHODS

We performed a systematic literature search in Medline and Pubmed, from 1993-June 2013, using search headings "PVE" and "portal vein ligation". Articles were included when meeting the selection criteria: experimental animal study on PVE or portal vein ligation and experiments described in 5 animals or more.

RESULTS

Sixty-one articles were selected, describing six different animal models. Most articles reported experiments with rats, rabbits, and pigs. In rats, the increase in wet-weight ratio of the non-occluded liver or total liver weight is greatest in the first 7 d with values ranging from 75%-80.5% on day 7. The volume increase of FRL in the rabbit model is greatest in the first 7 d with values ranging from 33.6%-80% on day 7. In pigs, the largest gain in volume of the FRL was seen in the first 2 wk.

CONCLUSIONS

The choice of the model depends on the specific aim of the study. Evaluating the increase in liver volume and liver function after PVE, larger animals as the pig, rabbit, or the dog is useful because of the possibility to apply computed tomography volumetry. To evaluate mechanisms of regeneration after PVE, the rat model is useful, because of the variety of antibodies commercially available.

Intravoxel incoherent motion diffusion-weighted MR imaging for monitoring the therapeutic efficacy of the vascular disrupting agent CKD-516 in rabbit VX2 liver tumors

PURPOSE

To evaluate the diagnostic value of intravoxel incoherent motion (IVIM) diffusion-weighted (DW) magnetic resonance (MR) imaging in the quantitative assessment of the therapeutic efficacy of a vascular disrupting agent (VDA) (CKD-516) in rabbit VX2 liver tumors.

MATERIALS AND METHODS

The institutional animal care and use committee approved this study. In 21 VX2 liver tumor-bearing rabbits, IVIM DW imaging examinations were serially performed with a 3.0-T imaging unit by using 12 b values from 0 to 800 sec/mm(2). The apparent diffusion coefficient (ADC), true diffusion coefficient (D), pseudodiffusion coefficient (D*), perfusion fraction (f), and blood flow-related parameter (fD*) of tumors at different time points (baseline, 4 hours, 24 hours, 3 days, and 7 days after CKD-516 administration) were compared within the treated group (n = 15) by using the Friedman test as well as between the control (n = 6) and treated groups by using the Mann-Whitney test. Correlation between the change in tumor size and IVIM DW imaging parameters was analyzed by using the Spearman rank test.

RESULTS

In the treated group, D* and f significantly decreased at 4 hours and then recovered to baseline at 24 hours, while D significantly increased at 24 hours (P < .005). All IVIM-derived parameters showed no significant differences between the control and treated groups at 3- and at 7-day follow-up. The greater decrease observed in f and fD* at 4 hours correlated with the smaller increase in tumor size during the 7 days of follow-up (ρ = 0.53 and 0.65, respectively; P < .05 for both).

CONCLUSION

The therapeutic effect induced by a VDA could be effectively evaluated by using IVIM DW imaging, and f and fD* may be early predictive indicators of tumor response.

Radiation lobectomy: time-dependent analysis of future liver remnant volume in unresectable liver cancer as a bridge to resection

BACKGROUND & AIMS

Portal vein embolization (PVE) is a standard technique for patients not amenable to liver resection due to small future liver remnant ratio (FLR). Radiation lobectomy (RL) with (90)Y-loaded microspheres (Y90) is hypothesized to induce comparable volumetric changes in liver lobes, while potentially controlling the liver tumor and limiting tumor progression in the untreated lobe. We aimed at testing this concept by performing a comprehensive time-dependent analysis of liver volumes following radioembolization.

METHODS

83 patients with right unilobar disease with hepatocellular carcinoma (HCC; N=67), cholangiocarcinoma (CC; N=8) or colorectal cancer (CRC; N=8) were treated by Y90 RL. The total liver volume, lobar (parenchymal) and tumor volumes, FLR and percentage of FLR hypertrophy from baseline (%FLR hypertrophy) were assessed on pre- and post-Y90 CT/MRI scans in a dynamic fashion.

RESULTS

Right lobe atrophy (p=0.003), left lobe hypertrophy (p<0.001), and FLR hypertrophy (p<0.001) were observed 1 month after Y90 and this was consistent at all follow-up time points. Median %FLR hypertrophy reached 45% (5-186) after 9 months (p<0.001). The median maximal %FLR hypertrophy was 26% (-14 → 86). Portal vein thrombosis was correlated to %FLR hypertrophy (p=0.02). Median Child-Pugh score worsening (6 → 7) was seen at 1 to 3 months (p=0.03) and 3 to 6 months (p=0.05) after treatment. Five patients underwent successful right lobectomy (HCC N=3, CRC N=1, CC N=1) and 6 HCCs were transplanted.

CONCLUSIONS

Radiation lobectomy by Y90 is a safe and effective technique to hypertrophy the FLR. Volumetric changes are comparable (albeit slightly slower) to PVE while the right lobe tumor is treated synchronously. This novel technique is of particular interest in the bridge-to-resection setting.

Multispectral Imaging

The field of anatomic pathology has changed significantly over the last decades and, as a result of the technological developments in molecular pathology and genetics, has had increasing pressures put on it to become quantitative and to provide more information about protein expression on a cellular level in tissue sections. Multispectral imaging (MSI) has a long history as an advanced imaging modality and has been used for over a decade now in pathology to improve quantitative accuracy, enable the analysis of multicolor immunohistochemistry, and drastically reduce the impact of contrast-robbing tissue autofluorescence common in formalin-fixed, paraffin-embedded tissues. When combined with advanced software for the automated segmentation of different tissue morphologies (eg, tumor vs stroma) and cellular and subcellular segmentation, MSI can enable the per-cell quantitation of many markers simultaneously. This article covers the role that MSI has played in anatomic pathology in the analysis of formalin-fixed, paraffin-embedded tissue sections, discusses the technological aspects of why MSI has been adopted, and provides a review of the literature of the application of MSI in anatomic pathology.