Microsatellite Instability as a Prognostic Factor in Resected Colorectal Cancer Liver Metastases

Prognostic Significance of the Histopathological Growth Pattern and Tumor-Infiltrating Lymphocytes in Stratifying Survival After Hepatectomy for Colorectal Liver Metastases

BACKGROUND

A histopathological growth pattern (HGP) occurs at the interface between tumor cells and the surrounding liver parenchyma. Desmoplastic HGP (dHGP) is associated with a favorable prognosis and shows denser infiltration of lymphocytes than other HGPs. Tumor-infiltrating lymphocytes (TILs) exert antitumor immunity, nonetheless, their prognostic significance in patients with dHGP is unknown. This study aimed to identify the prognostic significance of HGP and TILs in colorectal liver metastasis (CRLM).

METHODS

The study analyzed 140 patients who underwent hepatectomy for CRLM. Depending on the type of HGP and TIL, the patients were categorized into four groups (dHGP/high TIL, dHGP/low TIL, non-dHGP/high TIL, and non-dHGP/low TIL) for a comparison of their recurrence-free survival (RFS) and overall survival (OS). Uni- and multivariate analyses were performed using a Cox proportional hazards model.

RESULTS

The RFS and OS curves differed significantly between the groups. The multivariate analysis showed that a combination of HGP and TIL could stratify the recurrence and survival outcomes.

CONCLUSION

This study indicated that a combination of HGP and TIL can stratify the risk of survival after hepatectomy in patients with CRLM.

Histomorphological and molecular genetic characterization of different intratumoral regions and matched metastatic lymph nodes of colorectal cancer with heterogenous mismatch repair protein expression

PURPOSE

To better understand the clinicopathological characteristics and molecular alterations in different intratumoral components of colorectal cancer (CRC) with heterogeneity of mismatch repair (MMR) protein expression and microsatellite instability (MSI) status.

METHODS

The histopathological features, MSI status, and other molecular alterations were analyzed in separately microdissected intratumoral regions and matched metastatic lymph nodes in four cases with intratumoral heterogenous MMR expression screened from 500 CRC patients, using PCR-based MSI testing, MLH1 promoter methylation, and targeted next-generation sequencing (NGS).

RESULTS

High microsatellite instability (MSI-H) was identified in MLH1/PMS2-deficient regions in Cases 1 to 3 and in MSH2/MSH6-deficient regions in Case 4, while microsatellite stability (MSS) was detected in all the intratumoral regions and metastatic lymph nodes with proficient MMR expression (pMMR). Intratumoral heterogeneity of MLH1 promoter methylation and/or other common driving gene mutations of CRC, such as KRAS and PIK3CA mutations, was identified in all four CRCs. Further, three cases (75%) showed heterogeneous histomorphological features in intratumoral components and metastatic lymph nodes (Cases 1, 2, and 4), and the corresponding metastatic lymph nodes showed moderate differentiation with MSS/pMMR (Cases 2 and 3).

CONCLUSIONS

Intratumoral heterogeneous MSI status is highly correlated with intratumoral histomorphological heterogeneity, which is also an important clue for the intratumoral heterogeneity of drive gene mutations in CRC. Thus, it is essential to detect MMR protein expression and other gene mutations in metastases before treatment, especially for CRCs with intratumoral heterogenous MMR protein expression or heterogenous histomorphological features.

Microsatellite and RAS/RAF Mutational Status as Prognostic Factors in Colorectal Peritoneal Metastases Treated with Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemotherapy (HIPEC)

BACKGROUND

Cytoreductive surgery (CRS) with hyperthermic intraperitoneal chemotherapy (HIPEC) leads to prolonged survival for selected patients with colorectal (CRC) peritoneal metastases (PM). This study aimed to analyze the prognostic role of micro-satellite (MS) status and RAS/RAF mutations for patients treated with CRS.

METHODS

Data were collected from 13 Italian centers with PM expertise within a collaborative group of the Italian Society of Surgical Oncology. Clinical and pathologic variables and KRAS/NRAS/BRAF mutational and MS status were correlated with overall survival (OS) and disease-free survival (DFS).

RESULTS

The study enrolled 437 patients treated with CRS-HIPEC. The median OS was 42.3 months [95% confidence interval (CI), 33.4-51.2 months], and the median DFS was 13.6 months (95% CI, 12.3-14.9 months). The local (peritoneal) DFS was 20.5 months (95% CI, 16.4-24.6 months). In addition to the known clinical factors, KRAS mutations (p = 0.005), BRAF mutations (p = 0.01), and MS status (p = 0.04) were related to survival. The KRAS- and BRAF-mutated patients had a shorter survival than the wild-type (WT) patients (5-year OS, 29.4% and 26.8% vs 51.5%, respectively). The patients with micro-satellite instability (MSI) had a longer survival than the patients with micro-satellite stability (MSS) (5-year OS, 58.3% vs 36.7%). The MSI/WT patients had the best prognosis. The MSS/WT and MSI/mutated patients had similar survivals, whereas the MSS/mutated patients showed the worst prognosis (5-year OS, 70.6%, 48.1%, 23.4%; p = 0.0001). In the multivariable analysis, OS was related to the Peritoneal Cancer Index [hazard ratio (HR), 1.05 per point], completeness of cytoreduction (CC) score (HR, 2.8), N status (HR, 1.6), signet-ring (HR, 2.4), MSI/WT (HR, 0.5), and MSS/WT-MSI/mutation (HR, 0.4). Similar results were obtained for DFS.

CONCLUSION

For patients affected by CRC-PM who are eligible for CRS, clinical and pathologic criteria need to be integrated with molecular features (KRAS/BRAF mutation). Micro-satellite status should be strongly considered because MSI confers a survival advantage over MSS, even for mutated patients.

Determination of therapeutic agents efficiencies of microsatellite instability high colon cancer cells in post-metastatic liver biochip modeling

Two distinct genetic mutational pathways characterized by either chromosomal instability or high-frequency microsatellite instability (MSI-H) are recognized in the pathogenesis of colorectal cancer (CRC). Recently, it has been shown that patients with primary CRC that displays MSI-H have a significant, stage-independent, multivariate survival advantage. Biological properties of CMS1 (MSI-H type) can affect therapeutic efficiencies of agents used in the treatment of CRC, and therefore become a new predictive factor of the treatment. But, the predictive impact of MSI-H status for adjuvant chemotherapy remains controversial. This study will assess whether there is any unnecessary or inappropriate use of treatment agents recommended for adjuvant therapy of stage 2 and 3 of disease and for palliative or curative treatment of liver metastatic disease in microsatellite instability high group, a molecular subtype of colon cancer. Within this scope, the efficiencies of fluorouracil- and oxaliplatin-based chemotherapeutic agents will be shown on stage 3 microsatellite instability high colon tumor cell lines first, and then a microfluidic model will be created, imitating the metastasis of colon cancer to the liver. In the microfluidic chip model, we will create in liver tissue, where the metastasis of microsatellite instability high colon cancer will be simulated; the effectiveness of chemotherapeutic agents, immunotherapy agents, and targeted agents on tumor cells as well as drug response will be assessed according to cell viability through released biomarkers from the cells. The proposed hypothesis study includes the modeling and treatment of patient-derived post-metastatic liver cancer in microfluidics which has priority at the global and our region and consequently develop personal medication.

Evaluating Mismatch Repair/Microsatellite Instability Status Using Cytology Effusion Specimens to Determine Eligibility for Immunotherapy

CONTEXT.—

The approval of pembrolizumab for treatment of patients with microsatellite instability-high (MSI-H) or mismatch repair-deficient (dMMR) advanced cancers has led to increased requests for MSI and/or MMR immunoperoxidase (IPOX) testing. Diagnoses for patients with advanced-stage cancer are frequently made from cytology specimens.

OBJECTIVE.—

To investigate the feasibility of using cell block (CB) preparations of effusions for MMR IPOX evaluation.

DESIGN.—

Surgical pathology cases of colorectal and endometrial carcinomas with known MMR/MSI status and matched effusions with available CBs were identified. Cell block sections were evaluated for adequacy and stained with MMR IPOX (MSH2, MSH6, MLH1, and PMS2). The CBs were reviewed, the number of tumor cells quantified, and MMR IPOX was interpreted as retained, lost, suboptimal, or noncontributory.

RESULTS.—

We identified 748 cases with MMR/MSI testing on surgical specimens having matched effusions. Of these, 131 cases (17.5%) had an available CB and 53 were deemed adequate for MMR IPOX staining. MMR IPOX results between effusion CBs and surgical pathology specimens were concordant in 45 of 53 (85%), inconclusive in 6 of 53 (11%), and discordant in 2 of 53 (4%) cases.

CONCLUSIONS.—

There was high concordance of MMR IPOX testing between cytologic and surgical specimens, with no false-positive and 2 false-negative CB results. Limited tumor cells, staining in cells indefinite as tumor, tumor staining heterogeneity, and lack of internal control staining were problematic in some cases. Our findings indicate that cytologic effusion specimens may be suitable substrates for MMR IPOX biomarker testing; however, inconclusive cases need to be interpreted with caution.

Mismatch repair status between primary colorectal tumor and metastatic tumor, a retrospective consistent study

Objectives Mismatch repair (MMR) and Microsatellite instability (MSI) are critical when considering immunotherapy and chemotherapeutic drugs an option for patients with colorectal cancer (CRC). We investigated the consistence of MMR status as well as MSI between primary CRC and metastatic tumor to see if the expression of four MMR proteins and the status of MSI are congruent in primary tumor and metastatic tumor. With the results of the study and future more relevant studies, the sites of MMR testing may be more precise for individualized treatment.

Study design Patients with clear diagnosis of sporadic CRC and distal organ metastasis were identified from a prospectively established database. The status of MMR and MSI was evaluated by immunohistochemistry (IHC) and Polymerase Chain Reaction (PCR) respectively of synchronously obtained tissue samples.

Results Forty patients with complete clinical date were enrolled. For primary tumor, 36/40 samples were tested as MMR-proficient (pMMR) and 4 were MMR-deficient (dMMR). For metastatic samples, 30 samples were tested as pMMR while 10 samples were dMMR. Six out of forty patients were tested as inconsistent status of MMR and MSI. After statistical analysis, the expression status of MMR was not statistically significant between primary and metastatic tumors (P=0.1405, larger than 0.05).

Conclusion Based on our samples, the status of MMR between primary CRC and metastatic tumor was consistent, thus test of MMR status can be performed at both sites. However, due to the limited samples enrolled in our study, the results should be interpreted carefully.

Enrichment of the tumour immune microenvironment in patients with desmoplastic colorectal liver metastasis

BACKGROUND

Patients with resected colorectal liver metastasis (CRLM) who display only the desmoplastic histopathological growth pattern (dHGP) exhibit superior survival compared to patients with any non-desmoplastic growth (non-dHGP). The aim of this study was to compare the tumour microenvironment between dHGP and non-dHGP.

METHODS

The tumour microenvironment was investigated in three cohorts of chemo-naive patients surgically treated for CRLM. In cohort A semi-quantitative immunohistochemistry was performed, in cohort B intratumoural and peritumoural T cells were counted using immunohistochemistry and digital image analysis, and in cohort C the relative proportions of individual T cell subsets were determined by flow cytometry.

RESULTS

One hundred and seventeen, 34, and 79 patients were included in cohorts A, B, and C, with dHGP being observed in 27%, 29%, and 15% of patients, respectively. Cohorts A and B independently demonstrated peritumoural and intratumoural enrichment of cytotoxic CD8+ T cells in dHGP, as well as a higher CD8+/CD4+ ratio (cohort A). Flow cytometric analysis of fresh tumour tissues in cohort C confirmed these results; dHGP was associated with higher CD8+ and lower CD4+ T cell subsets, resulting in a higher CD8+/CD4+ ratio.

CONCLUSION

The tumour microenvironment of patients with dHGP is characterised by an increased and distinctly cytotoxic immune infiltrate, providing a potential explanation for their superior survival.

Current and Future Horizons of Patient-Derived Xenograft Models in Colorectal Cancer Translational Research

Our poor understanding of the intricate biology of cancer and the limited availability of preclinical models that faithfully recapitulate the complexity of tumors are primary contributors to the high failure rate of novel therapeutics in oncology clinical studies. To address this need, patient-derived xenograft (PDX) platforms have been widely deployed and have reached a point of development where we can critically review their utility to model and interrogate relevant clinical scenarios, including tumor heterogeneity and clonal evolution, contributions of the tumor microenvironment, identification of novel drugs and biomarkers, and mechanisms of drug resistance. Colorectal cancer (CRC) constitutes a unique case to illustrate clinical perspectives revealed by PDX studies, as they overcome limitations intrinsic to conventional ex vivo models. Furthermore, the success of molecularly annotated "Avatar" models for co-clinical trials in other diseases suggests that this approach may provide an additional opportunity to improve clinical decisions, including opportunities for precision targeted therapeutics, for patients with CRC in real time. Although critical weaknesses have been identified with regard to the ability of PDX models to predict clinical outcomes, for now, they are certainly the model of choice for preclinical studies in CRC. Ongoing multi-institutional efforts to develop and share large-scale, well-annotated PDX resources aim to maximize their translational potential. This review comprehensively surveys the current status of PDX models in translational CRC research and discusses the opportunities and considerations for future PDX development.

Deleterious Effect of RAS and Evolutionary High-risk TP53 Double Mutation in Colorectal Liver Metastases

OBJECTIVE

To assess the impact of somatic gene mutations on survival among patients undergoing resection of colorectal liver metastases (CLM).

BACKGROUND

Patients undergoing CLM resection have heterogeneous outcomes, and accurate risk stratification is necessary to optimize patient selection for surgery.

METHODS

Next-generation sequencing of 50 cancer-related genes was performed from primary tumors and/or liver metastases in 401 patients undergoing CLM resection. Missense TP53 mutations were classified by the evolutionary action score (EAp53)-a novel approach that dichotomizes mutations as low or high risk.

RESULTS

The most frequent somatic gene mutations were TP53 (65.6%), followed by KRAS (48.1%) and APC (47.4%). Double mutation in RAS/TP53, identified in 31.4% of patients, was correlated with primary tumor location in the right colon (P = 0.006). On multivariable analysis, RAS/TP53 double mutation was an independent predictor of shorter overall survival (hazard ratio 2.62, 95% confidence interval 1.41-4.87, P = 0.002). In patients with co-mutated RAS, EAp53 high-risk mutations were associated with shorter 5-year overall survival of 12.2%, compared with 55.7% for TP53 wild type (P < 0.001). The negative prognostic effects of RAS and TP53 mutations were limited to tumors harboring mutations in both genes.

CONCLUSIONS

Concomitant RAS and TP53 mutations are associated with decreased survival after CLM resection. A high EAp53 predicts a subset of patients with worse prognosis. These preliminary analyses suggest that surgical resection of liver metastases should be carefully considered in this subset of patients.

The survival outcome of patients with metastatic colorectal cancer based on the site of metastases and the impact of molecular markers and site of primary cancer on metastatic pattern

BACKGROUND

Pattern of spread in patients with metastatic colorectal cancer (mCRC) is variable and may reflect different biology in subsets of patients. This is a retrospective study to explore the outcome of patients with mCRC based on their site of metastasis at diagnosis and to explore the association between tumor characteristics [KRAS/RAS, BRAF, mismatch repair (MMR) status, site of primary] and the site of metastasis.

METHODS

Patients from two Australian databases were divided into six groups based on site of metastasis at time of diagnosis of metastatic disease; lung-only, liver-only, lymph node-only or any patients with brain, bone or peritoneal metastases. Primary endpoint was overall survival (OS) of each cohort compared with the rest of the population. A Mantel-Haenszel chi-squared test used to explore the association between site of metastasis and selected tumor characteristics.

RESULTS

Five thousand nine hundred and sixty-seven patients were included. In a univariate analysis, median OS was significantly higher when metastases were limited to lung or liver and shorter for those with brain, bone or peritoneal metastases (p < .001) in both datasets. BRAF mutation was strongly associated with peritoneal metastases (relative risk = 1.8, p < .001) with lower incidence of lung (RR = 0.3, p = .004) and liver (RR = 0.7, p = .005) limited metastases. Lung-only metastases were more frequent with KRAS/RAS mutation (RR = 1.4, p = .007). Left colon tumors were associated with bone (RR = 1.6, p < .001) and lung-only metastases (RR = 2.3, p = .001) while peritoneal spread was less frequent compared with right colon tumors (RR = 0.6, p < .001). Rectal cancer was associated with brain, bone and lung metastases (RR = 1.7; p = .002, 1.7; p < .001, 2.0; p < .001). Liver-only metastases were less frequent in deficient MMR tumors (RR = 0.7, p = .01).

CONCLUSION

Survival duration with mCRC is related to the site of metastases with lung limited disease showing a more favorable survival outcome compared to other single metastatic site disease. The BRAF mutation and primary rectal cancer were associated with poor prognostic metastatic sites.

Copy number load predicts outcome of metastatic colorectal cancer patients receiving bevacizumab combination therapy

Increased copy number alterations (CNAs) indicative of chromosomal instability (CIN) have been associated with poor cancer outcome. Here, we study CNAs as potential biomarkers of bevacizumab (BVZ) response in metastatic colorectal cancer (mCRC). We cluster 409 mCRCs in three subclusters characterized by different degrees of CIN. Tumors belonging to intermediate-to-high instability clusters have improved outcome following chemotherapy plus BVZ versus chemotherapy alone. In contrast, low instability tumors, which amongst others consist of POLE-mutated and microsatellite-instable tumors, derive no further benefit from BVZ. This is confirmed in 81 mCRC tumors from the phase 2 MoMa study involving BVZ. CNA clusters overlap with CRC consensus molecular subtypes (CMS); CMS2/4 xenografts correspond to intermediate-to-high instability clusters and respond to FOLFOX chemotherapy plus mouse avastin (B20), while CMS1/3 xenografts match with low instability clusters and fail to respond. Overall, we identify copy number load as a novel potential predictive biomarker of BVZ combination therapy.

Increased copy number alterations, indicative of chromosomal instability, is associated with poor cancer outcome. Here, metastatic colorectal cancer patients displaying intermediate-high CIN associate with improved outcome following chemotherapy and bevacizumab treatment, suggesting CIN as a predictive biomarker.

Emerging paradigms in the treatment of liver metastases in colorectal cancer

Efforts to combat colorectal cancer have benefited from improved screening and surveillance, which facilitates early detection. The survival rate associated with diagnosis at stage I is approximately 90%. However, progress in improving survival in metastatic colorectal cancer (mCRC) has been minimal. This review focuses on mCRC with special emphasis on the molecular aspects of liver metastases, which is one of the most frequently involved organ site. Better molecular evidence is required to guide the decisions for surgical and other interventions used in the clinical management of mCRC. Results from different treatment modalities have exposed significant gaps in the existing paradigms of the mCRC management. Indeed there is a critical need to better understand molecular events and pathways that lead to colorectal cancer liver metastasis. Such a focused approach may help identify biomarkers and drug targets that can be useful in the clinical applications. With this focus, we provide an account of the molecular pathways involved in the spread of CRC to the liver. Specifically, the molecular changes at the DNA and RNA levels that are associated with liver metastases are discussed. Similarly, we describe relevant microRNAs that are identified as regulators of gene expression and can also serve as biomarkers. Conventionally applied biomarkers are not yet specific and sensitive enough to be relied in routine clinical decision making. Hence search for novel biomarkers is critically needed especially if these can be utilized using liquid biopsies. This review provides a comprehensive analysis of current molecular evidence along with potential future directions that could reshape the diagnostic and management paradigms and thus mitigate the devastating impact of colorectal cancer metastasis to the liver.

Outcomes of Chemotherapy for Microsatellite Instable-High Metastatic Colorectal Cancers

PURPOSE

Microsatellite instable-high (MSI-H) colorectal cancers (CRCs) are known to carry better survival in the local disease stage even without treatment. The influence of types of treatment on survival of MSI-H metastatic CRCs (mCRCs) is still unclear and is evaluated in this study.

MATERIALS AND METHODS

Patients with MSI-H mCRC treated with first-line chemotherapy, with or without bevacizumab, identified in the Israeli population-based Molecular Epidemiology of Colorectal Cancer (MECC) study, were diagnosed between 1998 and 2013 and followed up until May 2017; MSI status was determined by comparing 10 markers in tumor and normal tissue. Dates of metastases and death and treatment details were extracted from oncology records.

RESULTS

Among 590 patients treated for mCRC, 106 (18%) had MSI-H tumors. Patients with MSI-H had a median overall survival (OS, from start of first-line treatment) of 1.6 years. The presence of a somatic B-Raf proto-oncogene (BRAF) mutation was a significant adverse prognostic factor in the MSI-H group (hazard ratio [HR], 1.8; 95% CI, 1.1 to 3.0; P = .026). MSI-H tumors without BRAF mutation (n = 87) had similar OS benefit from fluorouracil (FU) only as from any combination protocols (HR, 0.93; P = .78), whereas microsatellite-stable (MSS) tumors without BRAF mutation (n = 456) showed improved OS over FU-only regimens when combination chemotherapy with or without bevacizumab was used (HR, 0.58; P < .01; P value for interaction = .07). Patients with MSI-H/BRAF wild type (WT) had survival advantage over patients with MSS disease (adjusted HR, 0.58; 95% CI, 0.35 to 0.98) when treated with FU-only protocols.

CONCLUSION

Clinical outcomes differ substantially between patients with MSS/BRAF-WT mCRC and MSI-H/BRAF-WT mCRC, with measurable differences between chemotherapy regimens. MSI-H mCRCs are a clinically distinct subset of colorectal cancers. Their current poor outcome suggests that new clinical trials are needed to identify therapeutic options, potentially taking advantage of the new developments in the field of immunotherapy.

Colorectal Liver Metastases: Does the Future of Precision Medicine Lie in Genetic Testing?

Colorectal liver metastases (CRLM) present an important clinical challenge in both surgical and medical oncology. Despite improvements in management, survival among patients undergoing resection of CRLM is still very variable and there is a paucity of clinical trial data and reliable biomarkers that could guide prognostic forecasts, treatment selection, and follow-up. Fortunately, recent advances in molecular biology and tumor sequencing have identified a number of critical genetic loci and proliferation markers that may hold the key to understanding the biologic behavior of CRLM; specifically, mutations of KRAS, BRAF, TP53, PIK3CA, APC, expression of Ki-67, and the presence of microsatellite instability appear to have a decisive impact on prognosis and response to treatment in patients with CRLM. While the applicability of genetic biomarkers in everyday clinical practice remains conditional on the development of inexpensive bedside sequencing, targeted therapies, and the conduct of appropriate clinical trials, the promise of personalized treatment may be closer to realization than ever before.

Biomarkers in colorectal liver metastases

BACKGROUND

Despite a 5-year overall survival rate of 58 per cent after liver resection for colorectal liver metastases (CLMs), more than half of patients develop recurrence, highlighting the need for accurate risk stratification and prognostication. Traditional prognostic factors have been superseded by newer outcome predictors, including those defined by the molecular origin of the primary tumour.

METHODS

This review synthesized findings in the literature using the PubMed database of articles in the English language published between 1998 and 2017 on prognostic and predictive biomarkers in patients undergoing resection of CLMs.

RESULTS

Responses to preoperative chemotherapy define prognosis in patients undergoing CLM resection. There are differences by embryological origin too. Somatic mutations in the proto-oncogenes KRAS and NRAS are associated with positive surgical margins and tumour regrowth after ablation. Other mutations (such as BRAF) and co-occurring mutations in RAS/TP53 and APC/PIK3CA have emerged as important biomarkers that determine an individual patient's tumour biology and may be used to predict outcome after CLM resection.

CONCLUSION

Knowledge of somatic mutations can guide the use of preoperative therapy, extent of surgical margin and selection for ablation alone.

Selective analysis of cancer-cell intrinsic transcriptional traits defines novel clinically relevant subtypes of colorectal cancer

Stromal content heavily impacts the transcriptional classification of colorectal cancer (CRC), with clinical and biological implications. Lineage-dependent stromal transcriptional components could therefore dominate over more subtle expression traits inherent to cancer cells. Since in patient-derived xenografts (PDXs) stromal cells of the human tumour are substituted by murine counterparts, here we deploy human-specific expression profiling of CRC PDXs to assess cancer-cell intrinsic transcriptional features. Through this approach, we identify five CRC intrinsic subtypes (CRIS) endowed with distinctive molecular, functional and phenotypic peculiarities: (i) CRIS-A: mucinous, glycolytic, enriched for microsatellite instability or KRAS mutations; (ii) CRIS-B: TGF-β pathway activity, epithelial–mesenchymal transition, poor prognosis; (iii) CRIS-C: elevated EGFR signalling, sensitivity to EGFR inhibitors; (iv) CRIS-D: WNT activation, IGF2 gene overexpression and amplification; and (v) CRIS-E: Paneth cell-like phenotype, TP53 mutations. CRIS subtypes successfully categorize independent sets of primary and metastatic CRCs, with limited overlap on existing transcriptional classes and unprecedented predictive and prognostic performances.

Stromal cells contribute to the gene expression profiles based on which colorectal cancer (CRC) molecular subtypes are classified. Here, patient-derived xenografts enable the authors to obtain cancer cell-specific transcriptomes by excluding transcripts from murine stromal cells, based on which they define CRC intrinsic subtypes (CRIS) and evaluate their prognostic and predictive potential.

Tumor-Associated Macrophage Infiltration in Colorectal Cancer Liver Metastases is Associated With Better Outcome

BACKGROUND

Tumor-associated macrophages (TAMs) support growth in most human cancers, with the notable exception of colorectal adenocarcinoma, in which TAM infiltration of primary tumors is correlated with a better outcome. The importance of TAMs in colorectal liver metastases (CLM) is unknown.

METHODS

Using a tissue microarray of CLM resected at their institution from 1998 to 2000, the authors quantified immune marker expression by immunohistochemistry (IHC) using Metamorph Image Analysis software. Findings showed that CD68, CD3, CD4, CD8, FoxP3, and MHC-I were correlated with overall survival (OS) and disease-free survival (DFS).

RESULTS

Tumor cores from 158 patients were analyzed. The median follow-up period was 117 months for survivors (n = 39). The univariate analysis showed a significant positive association between DFS and CD4⁺ (p = 0.025) and CD68⁺ (p = 0.007). The findings showed a significant positive correlation of OS with CD4⁺ (p = 0.042), whereas the correlation with CD68⁺ was not significant (p = 0.17). Cutoffs were determined to dichotimize each marker for the highest log-rank statistic. Patients with CD4^high had a median OS of 115 months and DFS of 41 months (p = 0.007 compared with 40 and 16 months, respectively, for patients with CD4^low (p = 0.022). Patients with CD68^high had a median OS of 50 months and a median DFS of 25 months (p = 0.67) compared with 43 and 15 months (p = 0.028). In the multivariate analysis of factors affecting DFS, high CD68 was associated with longer DFS (hazard ratio [HR], 0.63, 95% confidence interval [CI], 0.43-0.94; p = 0.02), independently of clinicopathologic variables and CD4.

CONCLUSIONS

High TAM infiltration in resected CLM is associated with better outcome, independently of known clinicopathologic and immune predictors. This suggests that TAM depletion, which is being tested clinically in other cancers, may be detrimental in CLM.

Comparison of the Mismatch Repair System between Primary and Metastatic Colorectal Cancers Using Immunohistochemistry

Background

Colorectal cancer (CRC) is one of the most common malignancies worldwide. Approximately 10%–15% of the CRC cases have defective DNA mismatch repair (MMR) genes. Although the high level of microsatellite instability status is a predictor of favorable outcome in primary CRC, little is known about its frequency and importance in secondary CRC. Immunohistochemical staining (IHC) for MMR proteins (e.g., MLH1, MSH2, MSH6, and PMS2) has emerged as a useful technique to complement polymerase chain reaction (PCR) analyses.

Methods

In this study, comparison between the MMR system of primary CRCs and paired liver and lung metastatic lesions was done using IHC and the correlation with clinical outcomes was also examined.

Results

Based on IHC, 7/61 primary tumors (11.4%) showed deficient MMR systems, while 13/61 secondary tumors (21.3%) showed deficiencies. In total, 44 cases showed proficient expression in both the primary and metastatic lesions. Three cases showed deficiencies in both the primary and paired metastatic lesions. In 10 cases, proficient expression was found only in the primary lesions, and not in the corresponding metastatic lesions. In four cases, proficient expression was detected in the secondary tumor, but not in the primary tumor.

Conclusions

Although each IHC result and the likely defective genes were not exactly matched between the primary and the metastatic tumors, identical results for primary and metastatic lesions were obtained in 77% of the cases (47/61). These data are in agreement with the previous microsatellite detection studies that used PCR and IHC.

Prognostic Implication of KRAS Status after Hepatectomy for Colorectal Liver Metastases Varies According to Primary Colorectal Tumor Location

BACKGROUND

Right-sided and left-sided colorectal cancer (CRC) is known to differ in their molecular carcinogenic pathways. We sought to investigate the variable prognostic implication of KRAS mutation after hepatectomy for colorectal liver metastases (CRLM) according to the site of primary CRC.

METHODS

A total of 426 patients who underwent a curative-intent hepatic resection and whose KRAS status was available were identified. Clinicopathologic characteristics and long-term outcomes were stratified by KRAS status (wild type vs. mutant type) and primary tumor location (right-sided vs. left-sided). Cecum, right and transverse colon were defined as right-sided, whereas left colon and rectum were defined as left-sided.

RESULTS

Among patients with a right-sided CRC, 5-year recurrence-free survival (RFS) and overall survival (OS) were not correlated with KRAS status (wild type: 30.8 and 47.2 % vs. mutant type: 38.5 and 49.1 %, respectively) (both P > 0.05). Specifically, mutant-type KRAS was not associated with either RFS or OS on multivariable analysis (hazard ratio [HR] 1.51, 95 % confidence interval [CI] 0.73-3.14, P = 0.23 and HR 1.03, 95 % CI 0.51-2.08, P = 0.95, respectively). In contrast, among patients who underwent resection of CRLM from a left-sided primary CRC, 5-year RFS and OS were worse among patients with mutant-type KRAS (wild type: 23.7 and 57.2 % vs. mutant type: 19.6 and 38.2 %, respectively) (both P < 0.05). On multivariable analysis, mutant-type KRAS remained independently associated with worse RFS and OS among patients with a left-sided primary CRC (HR 1.57, 95 % CI 1.01-2.44, P = 0.04 and HR 1.81, 95 % CI 1.11-2.96, P = 0.02, respectively).

CONCLUSIONS

KRAS status has a variable prognostic impact after hepatic resection for CRLM depending on the site of the primary CRC. Future studies examining the impact of KRAS status on prognosis after hepatectomy should take into account the primary CRC tumor site.

Glucose Transporter 1 (SLC2A1) and Vascular Endothelial Growth Factor A (VEGFA) Predict Survival After Resection of Colorectal Cancer Liver Metastasis

OBJECTIVE

To investigate the individual and combined prognostic value of HIF1α, SLC2A1, and vascular endothelial growth factor A (VEGFA) in a multi-institutional cohort of patients with resected colorectal cancer liver metastasis (CRCLM).

BACKGROUND

In the majority of patients with CRCLM, resection seems not to be curative, despite its curative intent. Overexpression of hypoxia-inducible factor 1α (HIF1α), glucose transporter 1 (SLC2A1; also known as GLUT1), and VEGFA has been associated with tumor progression and poor prognosis of patients with colorectal cancer (CRC).

METHODS

Tissue microarrays were generated using CRCLM and patient-matched primary CRC from patients who underwent CRCLM resection between 1990 and 2010. Prognostic value of HIF1α, SLC2A1, and VEGFA was determined by immunohistochemistry. A 500-fold cross-validated hazard rate ratio (HRRav) for overall survival was calculated.

RESULTS

HIF1α, SLC2A1, and VEGFA expression could be evaluated in 328, 350, and 335 patients, respectively. High SLC2A1 expression was associated with good prognosis (HRRav, 0.67; P (HRR >1)  < 0.01) and high VEGFA expression to poor prognosis (HRRav, 1.84; P (HRR < 1)  = 0.02), also after multivariate analysis including established clinicopathological prognostic variables (HRRav, 0.67; P (HRR > 1)  < 0.01 and HRRav, 1.50; P (HRR < 1)  = 0.02, respectively). SLC2A1 showed prognostic value particularly in patients treated with systemic therapy (P < 0.01), whereas the prognostic value of VEGFA expression was mainly observed in patients not treated with systemic therapy (P < 0.01). Prognosis was especially poor in patients with both low SLC2A1 and high VEGFA expression (P < 0.01). HIF1α expression was not associated with survival.

CONCLUSIONS

SLC2A1 and VEGFA expression are prognostic molecular biomarkers for patients with CRCLM with added value to established clinicopathological variables.

Central, But Not Peripheral, Circulating Tumor Cells are Prognostic in Patients Undergoing Resection of Colorectal Cancer Liver Metastases

BACKGROUND

Colorectal cancer liver metastases (CRLMs) are potentially curable with resection, but most patients recur and succumb to their disease. Clinical covariates do not account for all outcomes. Circulating tumor cells (CTCs) are prognostic in the primary and metastatic settings of breast, prostate and colorectal cancer (CRC), and evolving evidence supports their role in CRLMs. Our objective was to determine whether CTCs in peripheral (PV) and hepatic venous (HV) compartments are associated with disease-free survival (DFS) and overall survival (OS) post-CRLM resection.

METHODS

CTCs were measured by CellSearch assay from intraoperative HV and PV samples from 63 patients who underwent CRLM resection from June 2007 to August 2012 at a single center. DFS and OS were primary endpoints.

RESULTS

HV CTCs > 3 were associated with shorter DFS and OS, but not PV CTCs, although no significant difference was found between CTC measurements in the two compartments. By univariate analysis, CRC stage and site, CRLM recurrence, and hepatic capsule invasion were also associated with OS, but only HV CTCs and CRC site were significant by multivariate Cox. Only HV CTCs were associated with DFS by multivariate analysis. Cases with elevated HV CTCs had hepatic vein invasion and lymph node metastases, and were younger with larger tumors.

CONCLUSIONS

Elevated HV CTCs are prognostic for DFS and OS following CRLM resection. Clinicopathologic features associated with HV CTCs are identifiable preoperatively and should be considered in CRLM surgical decision making. We found no evidence that PV CTCs are prognostic in this setting.

Molecular markers for colon diagnosis, prognosis and targeted therapy

Colorectal adenocarcinoma (CRC), the second leading cancer-related death in the United States, remains a global public health issue. Sporadic CRC is considered the result of sequential mucosal changes from normal colonic mucosa to adenocarcinoma. Efforts in understanding the molecular pathways leading to CRC tumorigenesis may lead to identifying novel, individually tailored therapeutic targets for patients. In this review, we focus on well-published prognostic and predictive markers in CRC and examine their role in clinical practice.

Epidermal growth factor receptor (EGFR) and prostaglandin-endoperoxide synthase 2 (PTGS2) are prognostic biomarkers for patients with resected colorectal cancer liver metastases

Background:

Resection of colorectal cancer liver metastasis (CRCLM) with curative intent has long-term benefit in ∼40% of cases. Prognostic biomarkers are needed to improve clinical management and reduce futile surgeries. Expression of epidermal growth factor receptor (EGFR) and prostaglandin-endoperoxide synthase 2 (PTGS2; also known as cyclooxygenase-2) has been associated with carcinogenesis and survival. We investigated the prognostic value of EGFR and PTGS2 expression in patients with resected CRCLM.

Methods:

Formalin-fixed paraffin-embedded CRCLM tissue and corresponding primary tumour specimens from a multi-institutional cohort of patients who underwent liver resection between 1990 and 2010 were incorporated into tissue microarrays (TMAs). TMAs were stained for EGFR and PTGS2 by immunohistochemistry. The hazard rate ratio (HRR) for the association between expression in CRCLM and overall survival was calculated using a 500-fold cross-validation procedure.

Results:

EGFR and PTGS2 expression could be evaluated in 323 and 351 patients, respectively. EGFR expression in CRCLM was associated with poor prognosis (HRR 1.54; P<0.01) with a cross-validated HRR of 1.47 (P=0.03). PTGS2 expression was also associated with poor prognosis (HRR 1.60; P<0.01) with a cross-validated HRR of 1.63 (P<0.01). Expression of EGFR and PTGS2 remained prognostic after multivariate analysis with standard clinicopathological variables (cross-validated HRR 1.51; P=0.02 and cross-validated HRR 1.59; P=0.01, respectively). Stratification for the commonly applied systemic therapy regimens demonstrated prognostic value for EGFR and PTGS2 only in the subgroup of patients who were not treated with systemic therapy (HRR 1.78; P<0.01 and HRR 1.64; P=0.04, respectively), with worst prognosis when both EGFR and PTGS2 were highly expressed (HRR 3.08; P<0.01). Expression of PTGS2 in CRCLM was correlated to expression in patient-matched primary tumours (P=0.02, 69.2% concordance).

Conclusions:

EGFR and PTGS2 expressions are prognostic molecular biomarkers with added value to standard clinicopathological variables for patients with resectable CRCLM.

Prognostic implication of mucinous histology in resected colorectal cancer liver metastases

BACKGROUND

Colorectal mucinous adenocarcinoma (MAC) is a subtype of colorectal adenocarcinoma with prominent mucin production associated with proximal location of tumor, advanced stage at diagnosis, microsatellite instability, and BRAF mutation. The prognostic implication of MAC in colorectal cancer liver metastases (CRCLM) is unknown. The purpose of our study was to determine the frequency and elucidate the prognostic implication of mucinous histology in CRCLM.

METHODS

The medical records of 118 patients who underwent CRCLM resection between 2000 and 2010 were reviewed. Clinicopathologic variables and outcome parameters were examined. Resected specimens were submitted to routine histologic evaluation. Patients were grouped according to the metastasis mucinous content: >50%, MAC; <50%, adenocarcinoma with intermediated mucinous component (AIM); and without any mucinous component, non-MAC (NMA).

RESULTS

Mean follow-up after resection was 37 months. Tumor recurrence was observed in 75% of patients. Overall survival and disease-free survival rates after hepatectomy were 61%, 56%, and 26%, 24% at 3 and 5 years, respectively. Tumors with mucinous component (AIM and MAC) were related to proximal location of the primary tumor and were more frequently observed in females. Multivariate analysis revealed that MAC was an independent negative prognostic factor (hazard ratio, 3.13; 95% CI, 1.30-6.68; P = .011) compared with non-MAC (NMA and AIM).

CONCLUSION

MAC has an adverse prognostic impact compared with NMA, which may influence therapeutic strategy raising an important subject for discussion and future investigation.

Adjuvant therapy in patients with stage II and III colon cancer under 70 years of age

SUMMARY Colorectal cancer is a common malignancy and its prognosis has improved over recent decades due to sustained efforts of the scientific community. This review focuses on adjuvant therapy across the lifespan of patients under 70 years of age. Here, we discuss the standard management of patients with stage III colon cancer, consisting of fluoropyrimidines and oxaliplatin combination for 6 months. The specific issues faced by patients with stage II colon cancer, including adjuvant chemotherapy in high-risk patients, are discussed. Finally, we describe the distinctive characteristics of patients with colon cancer under 40 years of age and the prospects of adjuvant chemotherapy in patients with colon cancer.

[Prognostic marker profiles for risk of distant metastases in colorectal cancer]

In colorectal cancer (CRC) prognostic markers correlating with distant metastasis are of high clinical value. In recent years it could be demonstrated that sporadic CRC with microsatellite instability (MSI) exhibits a very low risk for distant spread. Within this group the medullary subtype represents a morphological prototype. In the new WHO classification other morphological variants, such as mucinous, signet ring cell, serrated, cribriform comedo type and solid-undifferentiated forms are graded according to their microsatellite status. The clinical value of BRAF mutations is also dependent on the microsatellite status. Recent data have shown an ambivalent prognostic impact of BRAF mutations. A BRAF mutation in combination with MSI is associated with a good prognosis, whereas a BRAF mutation in the background of microsatellite stability (MSS) indicates a very poor outcome. Based on the concept of migrating stem cells, combined high scores of CD133 and nuclear β-catenin expression can be additionally used as markers for a high risk of distant metastasis. Hence, an immunohistochemical algorithm can be defined by the combination of three markers (hMLH1, CD133 and β-catenin) which allows CRC with either a very high or a very low risk of distant spread to be identified.

A molecularly annotated platform of patient-derived xenografts ("xenopatients") identifies HER2 as an effective therapeutic target in cetuximab-resistant colorectal cancer

Only a fraction of patients with metastatic colorectal cancer receive clinical benefit from therapy with anti-epidermal growth factor receptor (EGFR) antibodies, which calls for the identification of novel biomarkers for better personalized medicine. We produced large xenograft cohorts from 85 patient-derived, genetically characterized metastatic colorectal cancer samples ("xenopatients") to discover novel determinants of therapeutic response and new oncoprotein targets. Serially passaged tumors retained the morphologic and genomic features of their original counterparts. A validation trial confirmed the robustness of this approach: xenopatients responded to the anti-EGFR antibody cetuximab with rates and extents analogous to those observed in the clinic and could be prospectively stratified as responders or nonresponders on the basis of several predictive biomarkers. Genotype-response correlations indicated HER2 amplification specifically in a subset of cetuximab-resistant, KRAS/NRAS/BRAF/PIK3CA wild-type cases. Importantly, HER2 amplification was also enriched in clinically nonresponsive KRAS wild-type patients. A proof-of-concept, multiarm study in HER2-amplified xenopatients revealed that the combined inhibition of HER2 and EGFR induced overt, long-lasting tumor regression. Our results suggest promising therapeutic opportunities in cetuximab-resistant patients with metastatic colorectal cancer, whose medical treatment in the chemorefractory setting remains an unmet clinical need.

SIGNIFICANCE

Direct transfer xenografts of tumor surgical specimens conserve the interindividual diversity and the genetic heterogeneity typical of the tumors of origin, combining the flexibility of preclinical analysis with the informative value of population-based studies. Our suite of patient-derived xenografts from metastatic colorectal carcinomas reliably mimicked disease response in humans, prospectively recapitulated biomarker-based case stratification, and identified HER2 as a predictor of resistance to anti-epidermal growth factor receptor antibodies and of response to combination therapies against HER2 and epidermal growth factor receptor in this tumor setting.

Prognostic and predictive impact of DNA mismatch repair in the management of colorectal cancer

Colorectal cancers develop via two major pathways that include chromosomal instability and microsatellite instability. Microsatellite instability occurs due to deficient DNA mismatch repair (MMR), which can be caused by epigenetic silencing of the MLH1 MMR gene in sporadic colorectal cancers or germline mutations in MMR genes that result in Lynch syndrome. While the molecular origin of deficient MMR differs, sporadic and Lynch syndrome tumors share similar pathological features and have a more favorable stage-adjusted prognosis compared with MMR-proficient cases. While controversy remains, there is evidence to suggest that deficient MMR may predict a lack of benefit from 5-fluorouracil-based adjuvant chemotherapy. The focus of this article is on the MMR phenotype and its prognostic and predictive implications for the management of patients with colorectal cancer.

Association between deficient mismatch repair system and efficacy to irinotecan-containing chemotherapy in metastatic colon cancer

The present study investigated the association between deficient mismatch repair (dMMR) and efficacy outcomes of irinotecan-based first-line chemotherapy in patients with metastatic colorectal cancer (mCRC). Among 297 patients with sporadic mCRC receiving an irinotecan-containing regimen as first-line chemotherapy, 197 with available paraffin-embedded tissues were included in the current analysis. Tumors displaying loss of MMR protein (MLH1 or MSH2) and/or a microsatellite instability-high (MSI-H) genotype by PCR were classified as dMMR. Deficient mismatch repair was found in 23 evaluable tumors, among which eight displayed negativity for MLH1 expression, 11 for MSH2 expression, and four for both. The overall response rate was 47.2% (46.0% in proficient MMR (pMMR) and 56.5% in dMMR), with no significant difference between the two groups (P = 0.569). Median progression-free survival was 8.85 months in patients with dMMR tumors and 6.82 months in patients with pMMR tumors, but this difference did not reach statistical significance (P = 0.089). Median overall survival was not different between the two groups (P = 0.413). Efficacy outcomes of first-line irinotecan-based chemotherapy did not differ significantly between mCRC patients with pMMR and those with dMMR. Our data collectively indicate that MMR status is not effective as a single predictive marker for response to irinotecan-based chemotherapy in mCRC patients.

Tumor heterogeneity in neoplasms of breast, colon, and skin

BACKGROUND

Different cell subpopulations in a single tumor may show diverse capacities for growth, differentiation, metastasis formation, and sensitivity to treatments. Thus, heterogeneity is an important feature of tumors. However, due to limitations in experimental and analytical techniques, tumor heterogeneity has rarely been studied in detail.

PRESENTATION OF THE HYPOTHESIS

Different tumor types have different heterogeneity patterns, thus heterogeneity could be a characteristic feature of a particular tumor type.

TESTING THE HYPOTHESIS

We applied our previously published mathematical heterogeneity model to decipher tumor heterogeneity through the analysis of genetic copy number aberrations revealed by array CGH data for tumors of three different tissues: breast, colon, and skin. The model estimates the number of subpopulations present in each tumor. The analysis confirms that different tumor types have different heterogeneity patterns. Computationally derived genomic copy number profiles from each subpopulation have also been analyzed and discussed with reference to the multiple hypothetical relationships between subpopulations in origin-related samples.

IMPLICATIONS OF THE HYPOTHESIS

Our observations imply that tumor heterogeneity could be seen as an independent parameter for determining the characteristics of tumors. In the context of more comprehensive usage of array CGH or genome sequencing in a clinical setting our study provides a new way to realize the full potential of tumor genetic analysis.

A review of the most promising biomarkers in colorectal cancer: one step closer to targeted therapy

Rapidly growing insights into the molecular biology of colorectal cancer (CRC) and recent developments in gene sequencing and molecular diagnostics have led to high expectations for the identification of molecular markers to be used in optimized and tailored treatment regimens. However, many of the published data on molecular biomarkers are contradictory in their findings and the current reality is that no molecular marker, other than the KRAS gene in the case of epidermal growth factor receptor (EGFR)- targeted therapy for metastatic disease, has made it into clinical practice. Many markers investigated suffer from technical shortcomings, resulting from lack of quantitative techniques to capture the impact of the molecular alteration. This understanding has recently led to the more comprehensive approaches of global gene expression profiling or genome-wide analysis to determine prognostic and predictive signatures in tumors. In this review, an update of the most recent data on promising biological prognostic and/or predictive markers, including microsatellite instability, epidermal growth factor receptor, KRAS, BRAF, CpG island methylator phenotype, cytotoxic T lymphocytes, forkhead box P3-positive T cells, receptor for hyaluronic acid-mediated motility, phosphatase and tensin homolog, and T-cell originated protein kinase, in patients with CRC is provided.

Genetic and molecular diversity of colon cancer hepatic metastases

BACKGROUND

Colon cancer arises through distinct molecular pathways resulting in diverse tumor populations demonstrated by differences in microsatellite instability (MSI), CpG island methylator phenotype (CIMP), and mutations in oncogenes KRAS and BRAF. Although these molecular differences are well-described for primary neoplasms, the molecular nature of hepatic metastases is not well-characterized. This study seeks to describe molecular characteristics of colon cancer hepatic metastases in terms of oncogenic pathway.

METHODS

Tumor DNA was isolated from fresh frozen hepatic metastases from colon cancer and analyzed for MSI by polymerase chain reaction (PCR)-based microsatellite analysis and for CIMP using MethyLight quantitative PCR. KRAS and BRAF oncogenes were analyzed for DNA mutations. Metastases were classified by their molecular and genetic features. Unfortunately, tissue from the primary neoplasms from these patients were not available

RESULTS

Thirty patients with liver metastases from colon cancer were studied. Molecular analysis revealed 10% (3/30) were MSI-H, 10% (3/30) were CIMP positive, 33% (10/30) had KRAS mutations, and none had BRAF mutations. Literature describing primary colon cancers reports an incidence of approximately 20% MSI-H, 20% CIMP-positive, 35% KRAS mutants, and 17% BRAF mutants.

CONCLUSION

Hepatic metastases from colon cancer, like primary colon adenocarcinomas, show genetic and molecular diversity. Furthermore, hepatic metastases may have a different incidence of MSI and methylation compared with primary neoplasms. These differences could impact treatment decisions.

Clinical implications of microsatellite instability in sporadic colon cancers

PURPOSE OF REVIEW

To review data demonstrating the prognostic and predictive impact of microsatellite instability (MSI) in human colon carcinomas.

RECENT FINDINGS

MSI is a molecular marker of defective DNA mismatch repair that is detected in approximately 15% of sporadic colon cancers. Most, but not all retrospective studies, have shown that colon cancers with MSI have better stage-adjusted survival rates compared with non-MSI tumors. Furthermore, analyses of colon cancers from participants in randomized adjuvant therapy trials have suggested that MSI tumors do not benefit from treatment with 5-fluorouracil. Recent studies, including a pooled analysis, validate prior data demonstrating the prognostic and predictive impact of MSI status in colon cancer.

SUMMARY

MSI is a molecular marker that can provide valuable prognostic and predictive information in colon cancer patients. In the appropriate clinical setting, MSI data can be used in clinical decision-making. Specifically, the favorable outcome of stage II colon cancers with MSI indicates that such patients should not receive adjuvant chemotherapy. Although data for stage III colon cancers with MSI suggest a lack of benefit from 5-fluorouracil alone, the benefit of the current standard treatment, 5-fluorouracil, leucovorin, and oxaliplatin, in this subgroup remains unknown and awaits further study.

Deficient mismatch repair system in patients with sporadic advanced colorectal cancer

A deficient mismatch repair system (dMMR) is present in 10–20% of patients with sporadic colorectal cancer (CRC) and is associated with a favourable prognosis in early stage disease. Data on patients with advanced disease are scarce. Our aim was to investigate the incidence and outcome of sporadic dMMR in advanced CRC. Data were collected from a phase III study in 820 advanced CRC patients. Expression of mismatch repair proteins was examined by immunohistochemistry. In addition microsatellite instability analysis was performed and the methylation status of the MLH1 promoter was assessed. We then correlated MMR status to clinical outcome. Deficient mismatch repair was found in only 18 (3.5%) out of 515 evaluable patients, of which 13 were caused by hypermethylation of the MLH1 promoter. The median overall survival in proficient MMR (pMMR), dMMR caused by hypermethylation of the MLH1 promoter and total dMMR was 17.9 months (95% confidence interval 16.2–18.8), 7.4 months (95% CI 3.7–16.9) and 10.2 months (95% CI 5.9–19.8), respectively. The disease control rate in pMMR and dMMR patients was 83% (95% CI 79–86%) and 56% (30–80%), respectively. We conclude that dMMR is rare in patients with sporadic advanced CRC. This supports the hypothesis that dMMR tumours have a reduced metastatic potential, as is observed in dMMR patients with early stage disease. The low incidence of dMMR does not allow drawing meaningful conclusions about the outcome of treatment in these patients.

Wild-type BRAF is required for response to panitumumab or cetuximab in metastatic colorectal cancer

PURPOSE Cetuximab or panitumumab are effective in 10% to 20% unselected metastatic colorectal cancer (CRC) patients. KRAS mutations account for approximately 30% to 40% patients who are not responsive. The serine-threonine kinase BRAF is the principal effector of KRAS. We hypothesized that, in KRAS wild-type patients, BRAF mutations could have a predictive/prognostic value. PATIENTS AND METHODS We retrospectively analyzed objective tumor responses, time to progression, overall survival (OS), and the mutational status of KRAS and BRAF in 113 tumors from cetuximab- or panitumumab-treated metastatic CRC patients. The effect of the BRAF V600E mutation on cetuximab or panitumumab response was also assessed using cellular models of CRC. Results KRAS mutations were present in 30% of the patients and were associated with resistance to cetuximab or panitumumab (P = .011). The BRAF V600E mutation was detected in 11 of 79 patients who had wild-type KRAS. None of the BRAF-mutated patients responded to treatment, whereas none of the responders carried BRAF mutations (P = .029). BRAF-mutated patients had significantly shorter progression-free survival (P = .011) and OS (P < .0001) than wild-type patients. In CRC cells, the introduction of BRAF V600E allele impaired the therapeutic effect of cetuximab or panitumumab. Treatment with the BRAF inhibitor sorafenib restored sensitivity to panitumumab or cetuximab of CRC cells carrying the V600E allele. CONCLUSION BRAF wild-type is required for response to panitumumab or cetuximab and could be used to select patients who are eligible for the treatment. Double-hit therapies aimed at simultaneous inhibition of epidermal growth factor receptor and BRAF warrant exploration in CRC patients carrying the V600E oncogenic mutation.

Neoadjuvant chemotherapy for patients with liver metastases from colorectal cancer

Colorectal cancer is the second most common type of cancer in industrialized countries. Despite improved resection procedures and optimized adjuvant chemotherapy, local or distant recurrences occur in 22-25% of patients with stage II/III colon cancer. Approximately 30% of patients have advanced disease at presentation. The liver is the most common site of colorectal metastases and, interestingly, 20-30% of patients with colorectal cancer have liver-only metastases. The combined modality of chemotherapy and surgery increases overall survival and the chance of cure for metastatic patients, even if there is no agreement in terms of the best schedule and how long the treatment must last. In this paper, we review the role and the rationale of neoadjuvant chemotherapy within a multimodal approach, and discuss remaining questions and future directions.

Molecular prognostic markers in resectable colorectal liver metastases: A systematic review

BACKGROUND

Determination of prognosis in patients with resectable colorectal liver metastases (CLM) is desirable in order to improve case selection for surgery and tailor adjuvant treatment according to individual recurrence risk. Conventional clinicopathological factors lack the sensitivity to accurately achieve this goal. Consideration of tumour biology and the identification of molecular prognostic markers may allow more accurate risk stratification.

METHOD

This systematic review examines evidence from published manuscripts looking at molecular markers in resectable colorectal liver metastases and their correlation with disease recurrence and survival following hepatectomy.

RESULTS

Studies have yielded promising results in the search for prognostic molecular markers of CLM. Molecular biomarkers from varied aspects of tumour biology have been examined and a number of these, including proliferation indices, telomerase, thymidylate synthase, microvessel density and thrombospondin-1 appear to have prognostic utility in this context. Validation of other markers, notably p53, has been limited by a failure of methodologies to account for their biological complexity.

CONCLUSIONS

A biomarker-based approach may yield significant benefits through informed treatment of resectable metastatic colorectal malignancy. Standardised retrospective analyses are necessary to confirm preliminary findings and identify existing and novel markers for inclusion into prospective studies. Assessment and verification of multiple molecular markers in this manner may allow molecular profiling of metastases and tailoring of therapy according to the biological aggressiveness of individual tumours. The advent of genomic- and proteomic-based technologies will allow the simultaneous analysis of multiple molecular markers and the derivation of disease profiles associated with disease recurrence and poor survival.

Microsatellite instability in colorectal cancer

BACKGROUND

Microsatellite instability (MSI) causes hereditary non-polyposis colorectal cancer (HNPCC), and occurs in about 15 per cent of sporadic colorectal cancers. Although the basic mechanisms are not clear, there is increased understanding of the clinicopathological consequences of MSI.

METHODS

Medline was searched for articles with a combination of keywords relating to MSI in colorectal cancer, focusing on molecular mechanisms, clinicopathological implications, and prognostic and predictive value. Emphasis was placed on articles from the past 5 years.

RESULTS

The genetic mechanisms differ in hereditary (germline mutation) and sporadic (epigenetic silencing) colorectal cancer. The MSI pathway frequently has altered transforming growth factor beta receptor II and BAX genes, often beta-catenin, and occasionally p16INK4A and PTEN. Changes in K-ras, adenomatous polyposis coli and p53 are rare. Polymerase chain reaction testing for MSI is superior to immunohistochemistry, but complicated by the number and types of nucleotide markers. The Bethesda panel guides HNPCC testing, but guidelines are lacking for general screening. The presence and role of low-frequency MSI remains controversial. Tumours with MSI tend to occur in the proximal colon and be large, but they have a good prognosis. Their reduced response to adjuvant chemotherapy requires confirmation.

CONCLUSION

Research on colorectal cancer needs to be stratified according to microsatellite status in order further to explore the molecular mechanisms and clinicopathological consequences of MSI.