Animal Models for Associating Liver Partition and Portal Vein Ligation for Staged Hepatectomy (ALPPS): Achievements and Future Perspectives

Background: Since 2012, Associated Liver Partition and Portal vein ligation for Staged hepatectomy (ALPPS) has been standing in the limelight of modern liver surgery and numerous questions have been raised regarding this novel approach. On the one hand, ALPPS has proved to be a valuable method in the treatment of hepatic tumors, while on the other hand, there are many controversies, such as high mortality and morbidity rates. Further surgical research is essential for a better understanding of underlying mechanisms and for enhancing patient safety. Summary: Until recently, only 8 animal models have been created with the purpose to mimic ALPPS-induced liver regeneration. From these 7 are rodent (6 rat and 1 mouse) models, while only 1 is a large animal model, which uses pigs. In case of rodent models, portal flow deprivation of 75-90% is achieved via portal vein ligation leaving only the right (20-25%) or left median (10-15%) lobes portally perfused, while liver splitting in general is carried out positioned according to the falciform ligament. As for the swine model, the left lateral and medial lobes (70-75% of total liver volume) are portally ligated, and the right lateral lobe (accounting for 20-24% of the parenchyma) is partially resected in order to reach critical liver volume. Each model is capable of reproducing the accelerated liver regeneration seen in human cases. However, all species have significantly different liver anatomy compared with the human anatomic situation, making clinical translation somewhat difficult. Key Messages: Unfortunately, there are no perfect animal models available for ALPPS research. Small animal models are inexpensive and well suited for basic research, but may only provide limited translational potential to humans. Clinically large animal models may provide more relevant data, but currently no suitable one exists.

Timing of two-stage liver resection during chemotherapy for otherwise unresectable colorectal metastases

BACKGROUND

Tumor downsizing by effective chemotherapy while increasing remnant liver volume by two-stage hepatectomy can expand eligibility for resection of otherwise unresectable liver metastases. However, optimal timing of two-stage hepatectomy with respect to chemotherapy is undetermined.

METHODS

We retrospectively analyzed the effect of timing of two-stage hepatectomy and chemotherapy using data from 95 patients whose colorectal liver metastases initially were considered unresectable.

RESULTS

In 21 of 22 (95 %) patients whose first liver resection preceded chemotherapy (Hx-CTx group) and in 39 of 73 (53 %) patients whose chemotherapy preceded surgery (CTx-Hx group), macroscopic complete resection ultimately was achieved (P < 0.01). Overall and disease-free survivals were comparable between groups. However, overall survival of patients not achieving complete resection in the CTx-Hx group was significantly poorer than that for patients achieving complete resection (P < 0.01). When the 21 patients with complete resection in the Hx-CTx group were compared to the 39 patients with complete resection in the CTx-Hx group, no difference in overall or disease-free survival was observed (P = 0.12 and P = 0.24, respectively), although poor response to chemotherapy was more frequent in the Hx-CTx group.

CONCLUSIONS

Optimal timing of hepatectomy and chemotherapy is difficult to specify, but performing the initial resection in a two-stage hepatectomy before chemotherapy may increase likelihood of macroscopic complete resection, even in patients with a poor response to chemotherapy or with limited courses of chemotherapy.

Enhanced tumor growth after portal vein embolization in a rabbit tumor model

BACKGROUND

Preoperative portal vein embolization (PVE) is used to increase future remnant liver volume through induction of hepatocellular regeneration. This event, however, potentially enhances tumor growth. The aim of our study was to assess tumor growth and liver regeneration after PVE in a rabbit hepatic tumor model. The VX2 carcinoma is derived from a virus-induced papilloma tumor in rabbits. The tumor grows rapidly, and its blood supply is similar to that of human hepatocellular carcinoma.

MATERIALS AND METHODS

Two weeks after subcapsular implantation of a VX2 carcinoma in the cranial liver lobe, New Zealand White rabbits were allocated to a control or PVE group (n = 5 per group). In the PVE group, the portal vein branch to the cranial liver lobes (80%) was embolized using particles and coils, leaving the caudal liver lobe (20%) free. In the tumor control group, the liver was mobilized. Computed tomography volumetry was performed on days 3, 7, 10, and 14. Tumor growth rate (TGR), hepatocellular proliferation rate, and liver damage parameters were assessed before PVE and on days 1, 3, 7, 10, and 14.

RESULTS

Portography confirmed complete occlusion of the portal vein branch to the cranial liver lobes in all PVE rabbits. The hypertrophy response and proliferation rate in the nonembolized liver lobes were significantly higher in the PVE group, which was confirmed by liver-to-body weight index assessment. TGR was increased in both groups, with a significantly larger increase in the PVE group over time (day 14: mean, 34.4 ± 4.3 mL/d versus control: mean, 24.1 ± 7.2 mL/d; P < 0.05).

CONCLUSIONS

TGR was significantly increased after PVE in the rabbit tumor model. This finding supports the notion that PVE potentially enhances tumor growth, along with the regeneration of the nonembolized liver lobe.

Liver hypertrophy and accelerated growth of implanted tumors in nonembolized liver of rabbit after left portal vein embolization

BACKGROUND

Portal vein embolization (PVE) has become a standard preoperative procedure to promote hypertrophy of the future remnant liver to reduce postoperative liver failure. Whether PVE accelerates tumor growth is still controversial. We developed a left PVE procedure and investigated its effect on liver hypertrophy and tumor growth in a rabbit liver tumor model.

MATERIALS AND METHODS

VX2 tumors were implanted in both the external left and right middle lobe (the bilateral group) or in the external left lobe only (the unilateral group) of rabbit liver. Both groups were further divided into a PVE or a sham/control group. Tumor volume and tumor growth rate as volume relative increase were determined by ultrasound. Liver volume-to-body weight index, an index for liver volume, was compared. Serum HGF was measured by ELISA.

RESULTS

In the bilateral PVE group, tumor volume and relative increase value in the nonembolized lobe were significantly (71% and 65%, respectively) greater than those in the control group at 5 d post-PVE. In the unilateral PVE group, liver volume-to-body weight index of the nonembolized lobes was significantly increased by 17%. Increase of serum HGF level after PVE was correlated well with both tumor growth and liver hypertrophy.

CONCLUSIONS

Left PVE promoted both the growth of implanted tumors and liver hypertrophy in the nonembolized liver, in which serum HGF might play an important role.

Impact of biomarkers expression before and after portal vein embolization on recurrence after two-stage hepatectomy for colorectal liver metastases

BACKGROUND

The adverse oncological effect of portal vein embolization (PVE) in patients with colorectal liver metastases (CLM) remains controversial. This study was designed to evaluate the effect of PVE on change of tumor characteristics using tumor specimens obtained from sequential hepatectomy before and after PVE.

METHODS

Between December 1996 and April 2009, among 55 patients who achieved two-stage hepatectomy (TSH) combined with PVE, 39 had available cancer tissue blocks from both the first- and second-stage hepatectomy and constituted the study population. The immunohistochemistry of Ki67 and Bcl-2 before and after PVE was performed. Biomarker expressions and clinicopathological variables were assessed and their impact on recurrence was analyzed.

RESULTS

Whereas tumor volume and carcinoembryonic serum level significantly increased after PVE, the expression of Ki67 and Bcl-2 remained similar before and after PVE. The Bcl-2 ratio (expressed as Bcl-2 after PVE over Bcl-2 before PVE) was an independent prognostic factor for recurrence-free survival (P=0.030). Patients with Bcl-2 ratio ≤ 1 had a significantly longer median recurrence-free survival compared with those with Bcl-2 ratio >1 receiving or not receiving adjuvant chemotherapy (24.8 months versus 8.9 or 5.8 months, respectively).

CONCLUSION

Bcl-2 ratio may predict early recurrence and identify patients who do not require postoperative chemotherapy in patients undergoing TSH with PVE for CLM.

Sinusoidal obstruction syndrome compromises liver regeneration in patients undergoing two-stage hepatectomy with portal vein embolization

PURPOSE

Several factors have been reported to affect liver regeneration after portal vein embolization (PVE); however, the effect of sinusoidal obstruction syndrome (SOS) has not been evaluated. Therefore, we assessed the effect of SOS on liver regeneration after PVE in patients with multiple bilobar colorectal liver metastases scheduled to undergo two-stage hepatectomy (TSH) combined with PVE.

METHODS

The subjects of this study were 78 patients prospectively scheduled to undergo TSH between December 1996 and August 2009. Archived formalin-fixed, paraffin-embedded nontumoral tissue samples were collected from the 1st- and 2nd-stage hepatectomies in 42 and 45 patients, respectively, and SOS and steatohepatitis were diagnosed pathologically. We analyzed the clinicopathological variables affecting liver regeneration after PVE.

RESULTS

Sinusoidal obstruction syndrome was diagnosed in 11 (26.2%) and 20 patients (44.4%) at the time of the 1st- and 2nd-stage hepatectomy, respectively. Patients with SOS at the 1st-stage hepatectomy had a significantly lower hypertrophy ratio of the future remnant liver (FRL) after PVE than patients without SOS (16.8 ± 24.0 vs 55.6 ± 32.5; P < 0.001). Multivariate logistic regression analysis revealed that SOS was an independent factor predicting lower FRL hypertrophy after PVE (Δ% FRL <20: hazard ratio 31.7, 95% confidence interval 2.84-355.12; P = 0.005). The incidence of postoperative transient liver failure after the 2nd-stage hepatectomy in patients presenting with SOS was higher than that in those without SOS, but the difference did not reach significance (25.0% vs 4.0%; P = 0.052). Steatohepatitis was confirmed at the 1st- and 2nd-stage hepatectomy in 6 (14.3%) and 3 (6.7%) patients, respectively.

CONCLUSION

Sinusoidal obstruction syndrome inhibits FRL hypertrophy after PVE and induces postoperative liver failure. Therefore, an alternative strategy is needed to perform TSH safely in the presence of SOS.

Induction of tumor growth after preoperative portal vein embolization: is it a real problem?

Although preoperative portal vein embolization (PVE) is an effective means to increase future remnant liver (FRL) volume, little has been published on possible adverse effects. This review discusses the clinical and experimental evidence regarding the effect of PVE on tumor growth in both embolized and nonembolized liver lobes, as well as potential strategies to control tumor progression after PVE. A literature review was performed using MEDLINE with keywords related to experimental and clinical studies concerning PVE, portal vein ligation (PVL), and tumor growth. Cross-references and references from reviews were also checked. Clinical and experimental data suggest that tumor progression can occur after preoperative PVE in embolized and nonembolized liver segments. Clinical evidence indicating possible tumor progression in patients with colorectal metastases or with primary liver tumors is based on studies with small sample size. Although multiple studies demonstrated tumor progression, evidence concerning a direct increase in tumor growth rate as a result of PVE is circumstantial. Three possible mechanisms influencing tumor growth after PVE can be recognized, namely changes in cytokines or growth factors, alteration in hepatic blood supply and an enhanced cellular host response promoting local tumor growth after PVE. Post-PVE chemotherapy and sequential transcatheter arterial chemoembolization (TACE) before PVE have been proposed to reduce tumor mass after PVE. We conclude that tumor progression can occur after PVE in patients with colorectal metastases as well as in patients with primary liver tumors. However, further research is needed in order to rate this risk of tumor progression after PVE.

Portal vein embolization in preparation for major hepatic resection: evolution of a new standard of care

Portal vein (PV) embolization (PVE) is gaining acceptance in the preoperative management of patients selected for major hepatic resection. PVE redirects portal blood flow to the intended liver remnant to induce hypertrophy of the nondiseased portion of the liver and thereby reduce complications and shorten hospital stays after resection. This article reviews the rationale and existing literature on PVE, including the mechanisms of liver regeneration, the pathophysiology of PVE, the imaging techniques used to measure liver volumes and estimate functional hepatic reserve, and the technical aspects of PVE, including approaches and embolic agents used. In addition, the indications and contraindications for performing PVE in patients with and without chronic liver disease and the multidisciplinary approach required for the treatment of these complex cases are emphasized.

Non-resection approaches for colorectal liver metastases

The field of in situ destruction of liver tumors has expanded rapidly with various institutions' results suggesting that these methods represent viable palliative options, primarily because of the low associated morbidity and mortality. Despite this enthusiasm, clinical trials are needed to determine the true nature and degree of palliation. Treating a systemic disease such as colorectal liver metastases with local therapy strategies alone is of dubious value. In fact, it has been shown by most reports that the limiting factor inpatient outcome is disease progression rather than technical failure. For optimal results, physicians performing in situ ablation of liver lesions should be familiar with tumor biology and the natural history of the malignancy, and possess expertise in proper integration of other therapeutic modalities (eg, systemic chemotherapy and hepatic artery chemotherapy). Patients with liver metastases from colorectal carcinoma should therefore be evaluated for curability by a surgical oncologist within the context of a multidisciplinary team, as surgical resection remains the best treatment to achieve long-term survival. Such an assessment offers the patient the opportunity of a tailored therapy that may consist of hepatic resection, intravenous or regional chemotherapy, and local ablative therapy. Furthermore, results of RF ablation should be reported in terms of well-established oncological outcomes (eg, overall survival, disease-free survival, progression-free survival) that are more meaningful to the patient, rather than lesion-oriented outcomes. Because most of the ablative techniques have not yet been validated, it is imperative that well-designed clinical trials are conducted under the auspices of national cooperative groups. To consider them standard independent therapies otherwise would be premature.