Determinants of long-term outcome in patients undergoing simultaneous resection of synchronous colorectal liver metastases

BRAF mutations and survival with surgery for colorectal liver metastases: A systematic review and meta-analysis

INTRODUCTION

Mutations in the BRAF gene (BRAFmut) are associated with an unfavorable prognosis in patients with metastatic colorectal cancer (CRC). The aim of this meta-analysis was to evaluate the prognosis of colorectal cancer (CRC) patients with liver metastases and the potential benefits of liver resection in patients with BRAFmut CRC.

MATERIAL AND METHODS

A systematic search of PubMed, Cochrane Central Controlled Trials, and Embase databases was conducted on May 31, 2023. The inclusion criteria were as follows:1) reporting of outcomes in patients with BRAFmut CRC who underwent surgery for liver metastases and/or comparison of outcomes between those who underwent and those who did not undergo resection; 2) reporting of survival information as hazard ratios (HR); and 3) publication in English.

RESULTS

34 studies were included. Median follow up was 48 months for prognostic BRAF status meta-analysis. BRAFmut status showed a significantly increased risk of mortality (hazard ratio [HR] = 2.56, 95% confidence interval [CI] 2.04-3.22; P < 0.01) and relapse (HR = 1.97, 95% CI 1.44-2.71; P < 0.01). Resection of liver metastases was associated with a survival benefit (median follow up 46 months). The HR for survival was 0.44 (95% confidence interval [CI] 0.33-0.59; P < 0.01) in favor of surgery.

CONCLUSIONS

and Relevance: Our analysis indeed confirms that BRAF mutation is associated with poor survival outcomes after liver resection of CRC metastases. However, upon quantitatively assessing the survival benefit of surgical intervention in patients with BRAF-mutated CRC liver metastases, we identified a significant 56% reduction in the risk of death.

Colorectal Cancer Liver Metastases: Genomics and Biomarkers with Focus on Local Therapies

Molecular cancer biomarkers help personalize treatment, predict oncologic outcomes, and identify patients who can benefit from specific targeted therapies. Colorectal cancer (CRC) is the third-most common cancer, with the liver being the most frequent visceral metastatic site. KRAS, NRAS, BRAF V600E Mutations, DNA Mismatch Repair Deficiency/Microsatellite Instability Status, HER2 Amplification, and NTRK Fusions are NCCN approved and actionable molecular biomarkers for colorectal cancer. Additional biomarkers are also described and can be helpful in different image-guided hepatic directed therapies specifically for CRLM. For example, tumors maintaining the Ki-67 proliferation marker after thermal ablation was shown to be particularly resilient to ablation. Ablation margin was also shown to be an important factor in predicting local recurrence, with a ≥10 mm minimal ablation margin being required to attain local tumor control, especially for patients with mutant KRAS CRLM.

Stage IV colon cancer patients without DENND2D expression benefit more from neoadjuvant chemotherapy

According to the EPOC study, chemotherapy could improve 5-year disease-free survival of stage IV colon cancer patients by 8.1%. However, more molecular biomarkers are required to identify patients who need neoadjuvant chemotherapy. DENND2D expression was evaluated by immunohistochemistry in 181 stage IV colon cancer patients. The prognosis was better for patients with DENND2D expression than patients without DENND2D expression (5-year overall survival [OS]: 42% vs. 12%, p = 0.038; 5-year disease-free survival: 20% vs. 10%, p = 0.001). Subgroup analysis of the DENND2D-negative group showed that patients treated with neoadjuvant chemotherapy achieved longer OS than patients without neoadjuvant chemotherapy (RR = 0.179; 95% CI = 0.054-0.598; p = 0.003). DENND2D suppressed CRC proliferation in vitro and in vivo. Downregulation of DENND2D also promoted metastasis to distant organs in vivo. Mechanistically, DENND2D suppressed the MAPK pathway in CRC. Colon cancer patients who were DENND2D negative always showed a worse prognosis and were more likely to benefit from neoadjuvant chemotherapy. DENND2D may be a new prognostic factor and a predictor of the need for neoadjuvant chemotherapy in stage IV colon cancer.

Patient stratification in hepatocellular carcinoma: impact on choice of therapy

INTRODUCTION

HCC comprises around 60 to 80% of all primary liver cancers and exhibits wide geographical variability. Appropriate treatment allocation needs to include both patient and tumor characteristics.

AREAS COVERED

Current HCC classification systems to guide therapy are either liver function-centric and evaluate physiologic liver function to guide therapy or prognostic stratification classification systems broadly based on tumor morphologic parameters, patient performance status, and liver reserve assessment. This review focuses on different classification systems for HCC, their strengths, and weaknesses as well as the use of artificial intelligence in improving prognostication in HCC.

EXPERT OPINION

Future HCC classification systems will need to incorporate clinic-pathologic data from a multitude of sources and emerging therapies to develop patient-specific treatment plans targeting a patient's unique tumor profile.

Limited Prognostic Value of KRAS in Patients Undergoing Hepatectomy for Colorectal Liver Metastases

BACKGROUND

RAS mutation status is considered a powerful prognostic factor in patients undergoing hepatectomy for colorectal liver metastases (CLM). However, whether its prognostic power is robust regardless of administration of preoperative chemotherapy or tumor burden remains unclear.

METHODS

Consecutive patients who underwent initial hepatectomy for CLM from April 2010 through March 2017 in two hospitals were included. The prognostic value of KRAS was compared based on whether patients received preoperative chemotherapy and their tumor burden score (TBS).

RESULTS

We included 409 patients (median follow-up 38 months). In the preoperative chemotherapy group, patients with mutant KRAS (mt-KRAS) CLM had poorer overall survival (OS) than those with wild KRAS (wt-KRAS; 5-year OS: 37.7% vs 53.8%, p = 0.024), although their OS was not different from patients undergoing upfront surgery. Similarly, patients with mt-KRAS had poorer OS than those with wt-KRAS in TBS of 3-9 (5-year OS: 33.1% vs 63.2%, p = 0.001), although their OS was not different from patients with TBS < 3 or ≥ 9. In multivariate analysis, mt-KRAS was an independent prognostic factor of OS among patients receiving preoperative chemotherapy (hazard ratio [HR] 1.61, 95% confidence interval [CI]: 1.034-2.491; p = 0.035) and patients with TBS of 3-9 (HR 1.836, 95% CI 1.176-2.866; p = 0.008). However, it was not a prognostic factor in patients who underwent upfront surgery or with TBS > 3 or ≥ 9.

CONCLUSIONS

In patients undergoing hepatectomy for CLM, the prognostic value of KRAS depends on their history of preoperative chemotherapy or tumor burden.

Mutant KRAS as a prognostic biomarker after hepatectomy for rectal cancer metastases: Does the primary disease site matter?

BACKGROUND

The prognostic implication of mutant KRAS (mKRAS) among patients with primary disease in the rectum remains unknown.

METHODS

From 2000 to 2018, patients undergoing hepatectomy for colorectal liver metastases at 10 collaborating international institutions with documented KRAS status were surveyed.

RESULTS

A total of 834 (65.8%) patients with primary colon cancer and 434 (34.2%) patients with primary rectal cancer were included. In patients with primary colon cancer, mKRAS served as a reliable prognostic biomarker of poor overall survival (OS) (hazard ratio [HR]: 1.58, 95% CI 1.28-1.95) in the multivariable analysis. Although a trend towards significance was noted, mKRAS was not found to be an independent predictor of OS in patients with primary rectal tumors (HR 1.34, 95% CI 0.98-1.80). For colon cancer, the specific codon impacted in mKRAS appears to reflect underlying disease biology and oncologic outcomes, with codon 13 being associated with particularly poor OS in patients with left-sided tumors (codon 12, HR 1.56, 95% CI 1.22-1.99; codon 13, HR 2.10 95% CI 1.43-3.08;). Stratifying the rectal patient population by codon mutation did not confer prognostic significance following hepatectomy.

CONCLUSIONS

While the left-sided colonic disease is frequently grouped with rectal disease, our analysis suggests that there exist fundamental biologic differences that drive disparate outcomes. Although there was a trend toward significance of KRAS mutations for patients with primary rectal cancers, it failed to achieve statistical significance.

Reevaluating the prognostic role of BRAF mutation in colorectal cancer liver metastases

INTRODUCTION

Mutations in the BRAF proto-oncogene have been shown to predict poor patient survival following curative-intent liver surgery for metastatic colorectal cancer. The aim of the present systematic review and meta-analysis is to evaluate the effect of mutated BRAF status (mutBRAF) on the overall (OS) and disease-free survival (DFS) in these patients.

METHODS

A comprehensive literature search was performed for studies reporting outcomes of patients undergoing curative-intent surgery stratified by BRAF mutation status. Subgroup analysis was performed to evaluate whether inclusion of KRAS mutation status significantly influenced the results.

RESULTS

Six studies incorporating 1857 patients with known BRAF status were identified. Pooled results revealed significantly worse OS (Hazard Ratio 2.8, 95% C.I. 2.09 to 3.77) and DFS (Hazard Ratio 2.29, 95% C.I. 2.09 to 3.77) in mutBRAF patients. Subgroup analysis revealed no statistically significant impact of including KRAS status testing on the obtained results.

CONCLUSIONS

Patients with metastatic colorectal cancer carrying BRAF mutations have significantly worse oncologic outcomes following surgery and more aggressive disease phenotype overall.

Genetic mutations associated with sensitivity to neoadjuvant chemotherapy in metastatic colon cancer: A case report and review of literature

BACKGROUND

Colorectal liver metastases (CLM) occur in 15%-30% of patients with colorectal cancer (CRC). Advancements in next generation sequencing (NGS) can provide more precise prognoses for cancer patients and help guide clinical treatment. However, the genetic variants that predict high sensitivity to neoadjuvant chemotherapy remain unclear, especially in patients with CLM. The aim of this study was to identify the relevant genetic variants in a single CLM patient and to summarize the current evidence on mutations and single nucleotide polymorphisms (SNPs) that objectively predict sensitivity to neoadjuvant chemotherapy.

CASE SUMMARY

A 76-year-old male patient, who was diagnosed as stage IV colon cancer with liver metastases, was found to have APC/TP53/KRAS mutations. He showed a good therapeutic response to 12 courses of oxaliplatin regimens combined with Bevacizumab. Genetic analysis of the patient identified 5 genes with 7 detected SNPs that may be related to a better response to chemotherapy drugs. In addition, a critical literature review was performed based on a standardized appraisal form after selecting the articles. Ultimately, 21 eligible studies were appraised to assess the association between gene mutations and good prognosis. Mutations in KRAS, TP53, SMAD4, and APC were identified as being associated with a poor response to chemotherapy drugs, whereas mutations of CREBBP and POLD1 were associated with longer overall survival.

CONCLUSION

NGS can identify precise predictors of response to neoadjuvant chemotherapy, leading to improved outcomes for CRC patients.

Therapeutic implications of B-RAF mutations in colorectal cancer

Colorectal cancers (CRC) with B-RAF mutation carry a particularly poor prognosis. In this context, the value of first-line intensified chemotherapy associated with an anti-VEGF (Vascular endothelial growth factor) to treat metastatic CRC has recently been called into question. In patients with mutated B-RAF, the efficacy of first-line anti-EGFR (Epidermal Growth Factor Receptor) associated with chemotherapy for treatment of metastatic CRC is uncertain while that of anti-VEGF has been shown to be effective. The therapeutic pathways involving inhibition of B-RAF activity, although ineffective as monotherapy, have received marketing authorization when used in association with anti-EGFR for second-line treatment of metastatic CRC. Immunotherapy has provided very encouraging results in a recent phase III study in patients with microsatellite instability, irrespective of their B-RAF status. Finally, new therapies, targeting other RAF proteins and other specific receptors are currently under development. Surgery for liver metastases in patients with the B-RAF mutation should be considered whenever possible, after a complete search for peritoneal carcinomatosis and distant metastases, similarly to workup for patients without the B-RAF mutation.

[BRAF V600E-mutant colorectal cancers: Where are we?]

The BRAF^V600E mutation, observed in 8 % of colorectal cancers (CRC), introduces a particular phenotype and a poor prognosis at the localized or metastatic stage. BRAF mutant CRCs are more often localized in the right colon, poorly differentiated and mucinous. They affect an older population (more often female) and are associated with a more frequent metastatic lymph node and peritoneal evolution. The BRAF^V600E mutation is associated with a sporadic microsatellite instability (MSI) status in 20 to 40% of cases. In localized colon cancer, it does not imply any modification of the adjuvant treatment. In metastatic CRC, the first action must be the systematic search for an MSI phenotype, given its frequent association with the presence of a BRAF mutation, in order to propose immunotherapy that has been demonstrated to be very effective in MSI metastatic CRC. In non-MSI CRC, a first-line trichimiotherapy associated with bevacizumab is an option to be favored in patients in good general condition but the association with an anti-EGFR can be discussed, especially when the objective is tumor response. At the same time, surgical resection must be systematically discussed in the case of resectable hepatic metastases since the presence of a BRAF^V600E mutation is not a risk factor for recurrence and that prolonged survival may be observed after surgery. In the second or third line, the triplet encorafenib, binimetinib and cetuximab, as well as the doublet encorafenib and cetuximab are superior to the association of irinotecan plus cetuximab in terms of response and survival (phase III study BEACON) and represent a new therapeutic standard. Their use on the front line is under study.

Health-Related Quality of Life as a Prognostic Factor in Patients After Resection of Hepatic Malignancies

BACKGROUND

Numerous studies have argued health-related quality of life (HRQoL) measures to be prognostic of survival in patients with chronic disease processes including cancer; however, only a few small studies have evaluated HRQoL changes in the setting of oncologic resections. The objectives of the present study were to investigate factors predicting HRQoL, the change in HRQoL over time, and HRQoL prognostic value in patients undergoing surgical resection of hepatic malignancies.

METHODS

We administered the Functional Assessment of Cancer Therapy-Hepatobiliary, Center for Epidemiologic Studies-Depression, Functional Assessment of Cancer Therapy-Fatigue, and Brief Pain Inventory to 128 patients with primary and metastatic hepatic malignancies enrolled between January 2008 to November 2011 and November 2013 to June 2015. Quality of life was obtained at the baseline, 4, 8, and 12 mo, using HRQoL questionnaires.

RESULTS

The mean age of all patients included was 61 y, 42.6% had hepatocellular carcinoma, and 50.7% had metastatic colorectal carcinoma. HRQoL decreased from baseline at the 4-mo follow-up but stabilized to preoperative values at 8 and 12 mo. Depressive symptoms (P < 0.001), pain (P = 0.032), and fatigue (P < 0.001) were associated with HRQoL before surgery. Variables associated with HRQoL at 8 mo included extrahepatic recurrence (P = 0.002), depressive symptoms (P < 0.001), pain (P < 0.001), fatigue (P < 0.001), tumor macrovascular (P = 0.011), and microvascular invasion (P = 0.003). Using Cox regression and adjusting for demographics and disease-specific factors, preoperative HRQoL was significantly associated with overall survival.

CONCLUSIONS

HRQoL is independently associated with survival in patients with liver malignancies undergoing surgical resection. Major curative liver surgery can be performed with short-term worsening of HRQoL but long-term improvement and stabilization in overall quality of life for patients with cancer.

Gene mutation and surgical technique: Suggestion or more?

Advancements in chemotherapy and molecular targeted therapy have improved long-term outcomes for patients with resectable colorectal liver metastases (CLM). RAS mutation status was an original focus as a molecular biomarker as it predicted treatments response to anti-epidermal growth factor receptor agents. More recently, studies have incorporated somatic mutation data in analyses pertaining to surgical outcomes and prognosis. This evidenced-based review covers the implications of somatic mutations in patients undergoing resection of CLM.

Liver resection is justified for patients with bilateral multiple colorectal liver metastases: A propensity-score-matched analysis

BACKGROUND

Increasingly, patients with multiple colorectal liver metastases (CLM) are surgically treated. Some studies have shown that patients with bilobar and unilobar multiple CLM have similar outcomes, but other have shown that patients with bilobar CLM have worse outcomes after resection. We aimed to compare clinical outcomes of surgical treatment of bilobar and unilobar CLM using propensity score matching.

METHODS

The single-institution study included patients who underwent hepatectomy for ≥3 histologically confirmed CLM during 1998-2014. Clinicopathologic characteristics and long-term outcomes were compared between patients with bilobar and unilobar CLM in a propensity-score-adjusted cohort.

RESULTS

A total of 473 patients met the inclusion criteria, 271 (57%) with bilobar and 202 (43%) with unilobar CLM. In the propensity-score-matched population (bilobar, 170; unilobar, 170), no differences were observed according to the distribution of CLM except for a greater frequency of concomitant ablation, and R1 resection in the bilobar group. There was no difference between the bilobar and unilobar groups in 5-year overall survival rates (46% and 49%, respectively; P = 0.740) or 3-year recurrence-free survival rates (21% and 24%, respectively; P = 0.674).

CONCLUSIONS

Tumor distribution may not affect the curability of surgery for multiple CLM. Liver resection would be justified for selected patients with bilobar CLM.

Tumor Deposits in Colorectal Cancer: Improving the Value of Modern Staging-A Systematic Review and Meta-Analysis

Purpose Colorectal cancer (CRC) treatment is largely determined by tumor stage. Despite improvements made in the treatment of various types of metastatic disease, staging has not been refined. The role of tumor deposits (TDs) in staging remains debated. We have assessed the relation of TDs with metastatic pattern to evaluate whether TDs might add significant new information to staging. Methods We performed a systematic literature search that was focused on the role of TDs in CRC. Studies with neoadjuvant-treated patients were excluded. Data on stage, histologic factors, and outcome were extracted. Data from four large cohorts were analyzed for the relevance of the presence of TDs, lymph node metastases (LNMs), and extramural vascular invasion (EMVI) on the pattern of metastases and outcomes. Results Of 10,106 included patients with CRC, 22% presented with TDs. TDs are invariably associated with poor outcome. Presence of TDs was associated with presence of LNMs and EMVI. In a pairwise comparison, effects of TD were stronger than those of both LNMs and EMVI. In the logistic regression model, TDs in combination with LNMs is the strongest predictor for liver (odds ratio [OR], 5.5), lung (OR, 4.3) and peritoneal metastases (OR, 7.0). Presence of EMVI adds information for liver and lung metastases, but not for peritoneal metastases. Conclusion We have shown that TDs are not equal to LNMs or EMVI with respect to biology and outcome. We lose valuable prognostic information by allocating TDs into nodal category N1c and only considering TDs in the absence of LNMs. Therefore, we propose that the number of TDs should be added to the number of LNMs to derive a final N stage.

Comparative diagnostic accuracy of hepatocyte-specific gadoxetic acid (Gd-EOB-DTPA) enhanced MR imaging and contrast enhanced CT for the detection of liver metastases: a systematic review and meta-analysis

PURPOSE

This systematic review evaluated the diagnostic accuracy and impact on patient management of hepatocyte-specific gadoxetic acid enhanced magnetic resonance imaging (GA-MRI) compared to contrast enhanced computed tomography (CE-CT) in patients with liver metastases.

METHOD

Four biomedical databases (PubMed, EMBASE, Cochrane Library, York CRD) were searched from January 1991 to February 2016. Studies investigating the accuracy or management impact of GA-MRI compared to CE-CT in patients with known or suspected liver metastases were included. Bias was evaluated using QUADAS-II. Univariate meta-analysis of sensitivity ratios (RR) were conducted in the absence of heterogeneity, calculated using I ² , Tau values (τ) and prediction intervals.

RESULTS

Nine diagnostic accuracy studies (537 patients with 1216 lesions) and four change in management studies (488 patients with 281 lesions) were included. Per-lesion sensitivity and specificity estimates for GA-MRI ranged from 86.9-100.0 % and 80.2-98.0 %, respectively, compared to 51.8-84.6 % and 77.2-98.0 % for CE-CT. Meta-analysis found GA-MRI to be significantly more sensitive than CE-CT (RR = 1.29, 95 % CI = 1.18-1.40, P < 0.001), with equivalent specificity (RR = 0.97, 95 % CI 0.910-1.042, P = 0.44). The largest difference was observed for lesions smaller than 10 mm for which GA-MRI was significantly more sensitive (RR = 2.21, 95 % CI = 1.47-3.32, P < 0.001) but less specific (RR = 0.92, 95 % CI 0.87-0.98, P = 0.008). GA-MRI affected clinical management in 26 of 155 patients (16.8 %) who had a prior CE-CT; however, no studies investigated the consequences of using GA-MRI instead of CE-CT.

CONCLUSION

GA-MRI is significantly more sensitive than CE-CT for detecting liver metastases, which leads to a modest impact on patient management in the context of an equivocal CE-CT result.

mRNA expression profiles of colorectal liver metastases as a novel biomarker for early recurrence after partial hepatectomy

BACKGROUND

Identification of specific risk groups for recurrence after surgery for isolated colorectal liver metastases (CRLM) remains challenging due to the heterogeneity of the disease. Classical clinicopathologic parameters have limited prognostic value. The aim of this study was to identify a gene expression signature measured in CRLM discriminating early from late recurrence after partial hepatectomy.

METHODS

CRLM from two patient groups were collected: I) with recurrent disease ≤12 months after surgery (N = 33), and II) without recurrences and disease free for ≥36 months (N = 30). The patients were clinically homogeneous; all had a low clinical risk score (0-2) and did not receive (neo-) adjuvant chemotherapy. Total RNA was hybridised to Illumina arrays, and processed for analysis. A leave-one-out cross validation (LOOCV) analysis was performed to identify a prognostic gene expression signature.

RESULTS

LOOCV yielded an 11-gene profile with prognostic value in relation to recurrent disease ≤12 months after partial hepatectomy. This signature had a sensitivity of 81.8%, with a specificity of 66.7% for predicting recurrences (≤12 months) versus no recurrences for at least 36 months after surgery (X² P < 0.0001).

CONCLUSION

The current study yielded an 11-gene signature at mRNA level in CRLM discriminating early from late or no relapse after partial hepatectomy.

Laparoscopic simultaneous resection of colorectal primary tumor and liver metastases: a propensity score matching analysis

BACKGROUND

Preliminary series have shown the feasibility of combined laparoscopic resection of colorectal cancer (CRC) and synchronous colorectal liver metastases (SCRLM). The aim of this study was to compare the short- and long-term outcomes for matched patients undergoing combined resections.

METHODS

An international multicenter database of 142 patients that underwent combined laparoscopic resection of CRC and SCRLM between 1997 and 2013 was compared to a database of 241 patients treated by open during the same period. Comparison of short- and long-term outcomes was performed after propensity score adjustment.

RESULTS

After matching, 89 patients were compared in each group including mostly ASA I-II patients, presenting with mean number of 1.5 CRLM, with a mean diameter of 30 mm, and resectable by a wedge resection or a left lateral sectionectomy. A rectal resection was required in 46 and 43 % of laparoscopic and open procedures, respectively (p = 0.65). There was no difference in global operative time, blood loss and transfusion rates between the two groups. A conversion was required in 7 % of the laparoscopic procedures. Morbidity rates were similar in the two groups (p = 1.0). The 3-year overall survival in the laparoscopy and open groups were 78 and 65 %, respectively (p = 0.17).

CONCLUSIONS

In patients without severe comorbidities presenting with one, small (≤3 cm), CRLM resectable by a wedge resection or a left lateral sectionectomy, combined laparoscopic resection of CRC and SCRLM allowed similar short- and long-term outcomes compared with the open approach.

Laparoscopic simultaneous resection of colorectal primary tumor and liver metastases: a propensity score matching analysis

BACKGROUND

Preliminary series have shown the feasibility of combined laparoscopic resection of colorectal cancer (CRC) and synchronous colorectal liver metastases (SCRLM). The aim of this study was to compare the short- and long-term outcomes for matched patients undergoing combined resections.

METHODS

An international multicenter database of 142 patients that underwent combined laparoscopic resection of CRC and SCRLM between 1997 and 2013 was compared to a database of 241 patients treated by open during the same period. Comparison of short- and long-term outcomes was performed after propensity score adjustment.

RESULTS

After matching, 89 patients were compared in each group including mostly ASA I-II patients, presenting with mean number of 1.5 CRLM, with a mean diameter of 30 mm, and resectable by a wedge resection or a left lateral sectionectomy. A rectal resection was required in 46 and 43 % of laparoscopic and open procedures, respectively (p = 0.65). There was no difference in global operative time, blood loss and transfusion rates between the two groups. A conversion was required in 7 % of the laparoscopic procedures. Morbidity rates were similar in the two groups (p = 1.0). The 3-year overall survival in the laparoscopy and open groups were 78 and 65 %, respectively (p = 0.17).

CONCLUSIONS

In patients without severe comorbidities presenting with one, small (≤3 cm), CRLM resectable by a wedge resection or a left lateral sectionectomy, combined laparoscopic resection of CRC and SCRLM allowed similar short- and long-term outcomes compared with the open approach.