Microsatellite instability accounts for tumor site-related differences in clinicopathologic variables and prognosis in human colon cancers

Right-sided versus left-sided colorectal cancer in elderly patients: a sub-analysis of a large multicenter case-control study in Japan

PURPOSE

This study investigated the impact of sidedness of colorectal cancer (CRC) in elderly patients on the prognosis.

METHODS

In a sub-analysis of a multicenter case-control study of CRC patients who underwent surgery at ≥ 80 years old conducted in Japan between 2003 and 2007, both short- and long-term outcomes were compared between right-sided colon cancers (RCCs) and left-sided colorectal cancers (LCCs). RCCs were defined as those located from the cecum to the transverse colon.

RESULTS

Among the 1680 patients who underwent curative surgery, 812 and 868 had RCCs and LCCs, respectively. RCCs were more frequent than LCCs in those who were female, had renal comorbidities, and had a history of abdominal surgery. Regarding tumor characteristics, RCCs were larger, invaded more deeply, and were diagnosed as either mucinous or signet ring-cell carcinoma more frequently than LCCs. Regarding the prognosis, patients with RCCs had a significantly longer cancer-specific survival (CS-S) and cancer-specific relapse-free survival (CS-RFS) than those with LCCs. Furthermore, sidedness was determined to be an independent prognostic factor for CS-S and CS-RFS.

CONCLUSION

RCCs, which accounted for half of the cases in patients ≥ 80 years old, showed better long-term outcomes than LCCs.

Deep learning to assess microsatellite instability directly from histopathological whole slide images in endometrial cancer

Molecular classification, particularly microsatellite instability-high (MSI-H), has gained attention for immunotherapy in endometrial cancer (EC). MSI-H is associated with DNA mismatch repair defects and is a crucial treatment predictor. The NCCN guidelines recommend pembrolizumab and nivolumab for advanced or recurrent MSI-H/mismatch repair deficient (dMMR) EC. However, evaluating MSI in all cases is impractical due to time and cost constraints. To overcome this challenge, we present an effective and efficient deep learning-based model designed to accurately and rapidly assess MSI status of EC using H&E-stained whole slide images. Our framework was evaluated on a comprehensive dataset of gigapixel histopathology images of 529 patients from the Cancer Genome Atlas (TCGA). The experimental results have shown that the proposed method achieved excellent performances in assessing MSI status, obtaining remarkably high results with 96%, 94%, 93% and 100% for endometrioid carcinoma G1G2, respectively, and 87%, 84%, 81% and 94% for endometrioid carcinoma G3, in terms of F-measure, accuracy, precision and sensitivity, respectively. Furthermore, the proposed deep learning framework outperforms four state-of-the-art benchmarked methods by a significant margin (p < 0.001) in terms of accuracy, precision, sensitivity and F-measure, respectively. Additionally, a run time analysis demonstrates that the proposed method achieves excellent quantitative results with high efficiency in AI inference time (1.03 seconds per slide), making the proposed framework viable for practical clinical usage. These results highlight the efficacy and efficiency of the proposed model to assess MSI status of EC directly from histopathological slides.

Gastrointestinal Malignancy: Genetic Implications to Clinical Applications

Advances in molecular genetics have revolutionized our understanding of the pathogenesis, progression, and therapeutic options for treating gastrointestinal (GI) cancers. This chapter provides a comprehensive overview of the molecular landscape of GI cancers, focusing on key genetic alterations implicated in tumorigenesis across various anatomical sites including GIST, colon and rectum, and pancreas. Emphasis is placed on critical oncogenic pathways, such as mutations in tumor suppressor genes, oncogenes, chromosomal instability, microsatellite instability, and epigenetic modifications. The role of molecular biomarkers in predicting prognosis, guiding treatment decisions, and monitoring therapeutic response is discussed, highlighting the integration of genomic profiling into clinical practice. Finally, we address the evolving landscape of precision oncology in GI cancers, considering targeted therapies and immunotherapies.

Conditional Overall Survival After Diagnosis of Non-Metastatic Colon Cancer: Impact of Laterality, MSI, and KRAS Status

BACKGROUND

The prognostic relevance of laterality, microsatellite instability (MSI), and KRAS status in colon cancer has been established. However, their effect on conditional overall survival (COS) remains unknown.

METHODS

COS is the probability of surviving additional years after a time from diagnosis. The National Cancer Database (2010-2017) was queried for adults with non-metastatic colon cancer and known mutation status undergoing curative resection. COS was investigated at 2 years.

RESULTS

Of 4838 patients, 3716 survived at least 2 years: 15% had stage I, 38% stage II, and 46% stage III disease. Fifty-nine percent had a right-sided tumor, 16% were MSI-high, and 37% were mutated KRAS (mKRAS). The proportion of patients alive at 2 years was higher for stage I compared with stage II and III (65 vs. 61 vs. 54%). The 5-year overall survival for stage I-III was 80, 76, and 67% for the initial cohort, and 90, 88, and 86% for those alive at 2 years. After adjustment, higher pathologic T and N stage, tumor deposits, and no chemotherapy were associated with worse COS (p < 0.01). While laterality and MSI status were not associated with COS, mKRAS was independently associated with decreased COS (HR 1.35, 95% CI 1.12-1.62).

CONCLUSION

Patients with mKRAS had worse COS, suggesting that these mutations confer an aggressive biologic behavior, with patients remaining at higher risk of death 2 years after diagnosis. Routine evaluation of KRAS status should be considered in patients with non-metastatic disease for prognostication and to identify those who might benefit from modified surveillance protocols.

Biomarkers for chemotherapy and drug resistance in the mismatch repair pathway

Drugs targeting DNA repair have developed rapidly in cancer therapy, and numerous inhibitors have already been utilized in preclinical and clinical stages. To optimize the selection of patients for treatment, it is essential to discover biomarkers to anticipate chemotherapy response. The DNA mismatch repair (MMR) pathway is closely correlated with cancer susceptibility and plays an important role in the occurrence and development of cancers. Here, we give a concise introduction of the MMR genes and focus on the potential biomarkers of chemotherapeutic response and resistance. It has been clarified that the status of MMR may affect the outcome of chemotherapy. However, the specific underlying mechanisms as well as contradictory results continue to raise considerable controversy and concern. In this review, we summarize the current literature to provide a general overview.

Mutations in Classical Signaling Pathways and Their Functional Impact in Microsatellite Instability High Colorectal Cancer

Aims: Colorectal carcinomas with microsatellite instability high (MSI-H) are a distinctive group among colorectal cancers (CRCs). This study investigated the mutations of genes in the common signaling pathways and their potential clinical implications in MSI-H CRC. Materials and Methods: Twenty-five MSI-H tumors were selected from 384 primary CRCs, and the related clinical and pathological information were also collected from medical records. A commercial kit was used to detect the mutational status of crucial oncogenes within these tumors using next generation sequencing (NGS). Fluorescence in situ hybridization and immunohistochemistry were used to validate the NGS findings. Result: In the present study, MSI-H cases accounted for 6.51% of primary CRCs, with special clinicopathological features. NGS showed that the average number of mutations per tumor in the target genes evaluated was 3.36 and ranged from 1 to 9. In total, there were 17 cases (68%) with mutations in the RAS-RAF pathway and 18 cases (72%) with mutations in the PI3K pathway among the MSI-H CRCs. The remaining two cases included an EMAP Like 4-ALK Receptor Tyrosine Kinase (EML4-ALK) fusion and one with a Erb-B2 Receptor Tyrosine Kinase 2 (ERBB2) missense mutation. Conclusion: This study found multiple variants within different signaling pathways that were mutually present in MSI-H CRCs, suggesting that such a heterogeneous group of tumors requires complex treatment responses. Thus, additional clinical molecular testing is recommended for such patients, such as NGS, to inform the appropriate treatment strategies.

Development and validation of a new stage-specific nomogram model for predicting cancer-specific survival in patients in different stages of colon cancer: A SEER population-based study and external validation

Background

The effects of laterality of the primary tumor on survival in patients in different stages of colon cancer are contradictory. We still lack a strictly evaluated and validated survival prediction tool, considering the different roles of tumor laterality in different stages.

Methods

A total of 101,277 and 809 colon cancer cases were reviewed using the Surveillance, Epidemiology, and End Results database and the First Affiliated Hospital of Xi 'an Jiaotong University database, respectively. We established training sets, internal validation sets and external validation sets. We developed and evaluated stage-specific prediction models and unified prediction models to predict cancer-specific survival and compared the prediction abilities of these models.

Results

Compared with right-sided colon cancers, the risk of cancer-specific death of left-sided colon cancer patients was significantly higher in stage I/II but was markedly lower in stage III patients. We established stage-specific prediction models for stage I/II and stage III separately and established a unified prediction model for all stages. By evaluating and validating the validation sets, we reported high prediction ability and generalizability of the models. Furthermore, the stage-specific prediction models had better predictive power and efficiency than the unified model.

Conclusions

Right-sided colon cancer patients have better cancer-specific survival than left-sided colon cancer patients in stage I/II and worse cancer-specific survival in stage III. Using stage-specific prediction models can further improve the prediction of cancer-specific survival in colon cancer patients and guide clinical decisions.

Mesothelioma Mouse Models with Mixed Genomic States of Chromosome and Microsatellite Instability

Malignant mesothelioma (MMe) is a rare malignancy originating from the linings of the pleural, peritoneal and pericardial cavities. The best-defined risk factor is exposure to carcinogenic mineral fibers (e.g., asbestos). Genomic studies have revealed that the most frequent genetic lesions in human MMe are mutations in tumor suppressor genes. Several genetically engineered mouse models have been generated by introducing the same genetic lesions found in human MMe. However, most of these models require specialized breeding facilities and long-term exposure of mice to asbestos for MMe development. Thus, an alternative model with high tumor penetrance without asbestos is urgently needed. We characterized an orthotopic model using MMe cells derived from Cdkn2a+/-;Nf2+/- mice chronically injected with asbestos. These MMe cells were tumorigenic upon intraperitoneal injection. Moreover, MMe cells showed mixed chromosome and microsatellite instability, supporting the notion that genomic instability is relevant in MMe pathogenesis. In addition, microsatellite markers were detectable in the plasma of tumor-bearing mice, indicating a potential use for early cancer detection and monitoring the effects of interventions. This orthotopic model with rapid development of MMe without asbestos exposure represents genomic instability and specific molecular targets for therapeutic or preventive interventions to enable preclinical proof of concept for the intervention in an immunocompetent setting.

Colorectal cancer with microsatellite instability: Right-sided location and signet ring cell histology are associated with nodal metastases, and extranodal extension influences disease-free survival

Colorectal cancer (CRC) with microsatellite instability (MSI) accounts for 15-18 % of all CRCs and represents the category with the best prognosis. This study aimed at determining any possible clinical/pathological features associated with a higher risk of nodal metastasization in MSI-CRC, and at defining any possible prognostic moderators in this setting. All surgically resected CRCs of the last 20 years (mono-institutional series) with a PCR-based diagnosis of MSI, with and without nodal metastasis, have been retrieved for histological review, which was performed following WHO guidelines. Furthermore, the most important prognostic moderators have been investigated with a survival analysis. The study of 33 cases of MSI-CRCs with nodal metastasis highlighted a high fidelity of histology maintenance between primary tumors and matched nodal metastases. At survival analysis, the strongest prognostic variable in MSI-CRCs with nodal metastasis was the extranodal extension (multivariate analysis, HR: 14.4, 95 %CI: 1.46-140.9, p = 0.022). Furthermore, through a comparison between nodal positive (33 cases) and nodal negative (71 cases) MSI-CRCs, right-sided location (p < 0.0001), pT4 stage (p = 0.0004) and signet-ring histology (p = 0.0089) emerged as parameters more commonly associated with nodal metastasization. These findings shed new light on the biology of MSI-CRC and can be of help for the prognostic stratification of MSI-CRC patients.

Genome profiling of mismatch repair genes in eight types of tumors

Mismatch repair (MMR) plays an important role in the occurrence and development of tumors. At present, it is widely believed that MMR is a protective mechanism of tumors that plays a critical role in the progresses of cancer. In this study, 34 genes related to MMR selected from Gene Ontology (GO) database were scored by single sample Gene sets enrichment analysis (ssGSEA), and eight cancers were screened from 23 TCGA solid cancers to investigate the clinical significance of MMR score. MMR had different effects on the prognosis of the eight tumors, with a protective effect in three cancers and functioning as a risk factor in the remaining five cancers. We used unsupervised clustering to divide the patients into four clusters. We found that the immune and metabolic status of the four clusters were extremely different, among which cluster1 had the lowest tumor purity and the most complex microenvironment; this may explain its poor prognosis and immunotherapy effect. In summary, MMR scores can improve the predictive ability and provide effective guidance for immunotherapy in individual type of tumors.

Effect of sidedness on survival among patients with early-stage colon cancer: a SEER-based propensity score matching analysis

BACKGROUND

Most previous studies compared survival between left-sided and right-sided colon cancer without adjustment for clinicopathological parameters. We investigated the effect of sidedness on survival among patients with early-stage colon cancer, using a propensity score matching method.

METHODS

The 18 registry custom data within the SEER database were used to identify patients who were diagnosed with colon cancer between 2010 and 2014. A propensity score matching analysis was performed using the nearest neighbor method. Survival was estimated using the Kaplan-Meier method. A Cox proportional hazards model was applied to determine the prognostic factors.

RESULTS

In the unmatched cohort, 25,094 (35.72%) patients were diagnosed with left-sided colon cancer and 45,156 (64.28%) with right-sided colon cancer. After propensity score matching, each cohort included 5118 patients, and the clinicopathological characteristics were well balanced. In the unmatched cohort, left-sided colon cancer had superior all-cause (χ²=315, P<0.01) and cancer-specific (χ²=43, P<0.01) survival than right-sided tumors. However, in the matched cohort, no difference was observed for all-cause (χ²=0.7, P=0.4) and cancer-specific (χ²=0, P=0.96) survival between left and right colon cancer. The Cox model did not indicate sidedness as a prognostic factor. In the subgroup analysis, stage II right-sided colon cancer had a better survival outcome, while stage III left-sided tumors had a better survival outcome.

CONCLUSIONS

After adjusting for clinicopathological characteristics in this study, sidedness showed no impact on survival in early-stage colon cancer. However, sidedness was associated with prognostic differences in stages II and III early-stage colon cancer.

Recent developments in targeting genes and pathways by RNAi-based approaches in colorectal cancer

A wide spectrum of genetic and epigenetic variations together with environmental factors has made colorectal cancer (CRC), which involves the colon and rectum, a challenging and heterogeneous cancer. CRC cannot be effectively overcomed by common conventional therapies including surgery, chemotherapy, targeted therapy, and hormone replacement which highlights the need for a rational design of novel anticancer therapy. Accumulating evidence indicates that RNA interference (RNAi) could be an important avenue to generate great therapeutic efficacy for CRC by targeting genes that are responsible for the viability, cell cycle, proliferation, apoptosis, differentiation, metastasis, and invasion of CRC cells. In this review, we underline the documented benefits of small interfering RNAs and short hairpin RNAs to target genes and signaling pathways related to CRC tumorigenesis. We address the synergistic effects of RNAi-mediated gene knockdown and inhibitors/chemotherapy agents to increase the sensitivity of CRC cells to common therapies. Finally, this review points new delivery systems/materials for improving the cellular uptake efficiency and reducing off-target effects of RNAi.

Universal Screening of Gastrointestinal Malignancies for Mismatch Repair Deficiency at Stanford

Background

In light of recent Food and Drug Administration (FDA) approval of immune checkpoint inhibitors for mismatch repair deficient (dMMR) malignancies, identifying patients with dMMR malignancies has become increasingly important. Although screening for dMMR in colorectal cancer (CRC) is recommended, it is less common for extracolonic gastrointestinal (GI) malignancies. At Stanford Comprehensive Cancer Institute (SCCI), all GI malignancies have been screened for dMMR via immunohistochemistry since January 2016.

Methods

In this study, we conducted a retrospective review of all patients with GI malignancies screened for dMMR between January 2016 and December 2017. Tumor sequencing was performed on cases negative for germline pathogenic variants where tumor material was available.

Results

A total of 1425 consecutive GI malignancies were screened for dMMR at SCCI during the study period, and 1374 were included for analysis. dMMR was detected in 7.2% of all GI malignancies. We detected the highest prevalence of dMMR in gastric (15 of 150, 10.0%) followed by colorectal (63 of 694, 9.1%), pancreatic (13 of 244, 5.3%), and gastroesophageal malignancy (6 of 132, 4.5%) patients. Lynch syndrome was the most common etiology for dMMR in colorectal cancer (41.5%), double somatic (confirmed or possible) pathogenic variants the most common etiology in pancreatic cancer (44.4%), and somatic MLH1 hypermethylation the most common etiology in gastric (73.3%) and gastroesophageal cancer (83.3%).

Conclusions

Given the relatively high incidence of dMMR in GI malignancies, we recommend screening all GI malignancies. Our results suggest that although a rare occurrence, double somatic pathogenic variants may be a biologically significant pathway causing dMMR in pancreatic cancer.

[Best supportive care in a young patient with locally advanced MSI-high colon cancer?]

Molecular diagnostics are increasingly important to guide treatment decisions in oncologic patients. For instance, the presence of high-grade microsatellite-instability (MSI-high) is considered to be one of the major positive predictors of therapy response to immune-checkpoint inhibitors in patients with solid tumors. Based on impressive results from several immune-oncology trials, the American Food and Drug Administration (FDA) granted approval to immunotherapy in any previously treated, MSI-high solid cancer in 2017. Here, we report the clinical case of a young patient with MSI-high colorectal cancer. The case illustrates, that insurance companies in Germany are still reluctant to cover the cost of immunotherapy in this specific patient subgroup, which, in our opinion, results in an ethically problematic therapeutic dilemma.

Instability of Non-Standard Microsatellites in Relation to Prognosis in Metastatic Colorectal Cancer Patients

Very few data are reported in the literature on the association between elevated microsatellite alterations at selected tetranucleotide repeats (EMAST) and prognosis in advanced colorectal cancer. Moreover, there is no information available in relation to the response to antiangiogenic treatment. We analyzed EMAST and vascular endothelial growth factor-B (VEGF-B) microsatellite status, together with standard microsatellite instability (MSI), in relation to prognosis in 141 patients with metastatic colorectal cancer (mCRC) treated with chemotherapy (CT) alone (n = 51) or chemotherapy with bevacizumab (B) (CT + B; n = 90). High MSI (MSI-H) was detected in 3% of patients and was associated with progression-free survival (PFS; p = 0.005) and overall survival (OS; p < 0.0001). A total of 8% of cases showed EMAST instability, which was associated with worse PFS (p = 0.0006) and OS (p < 0.0001) in patients treated with CT + B. A total of 24.2% of patients showed VEGF-B instability associated with poorer outcome in (p = 0.005) in the CT arm. In conclusion, our analysis indicated that EMAST instability is associated with worse prognosis, particularly evident in patients receiving CT + B.

Gene mutation profiling in Chinese colorectal cancer patients and its association with clinicopathological characteristics and prognosis

Background

Gene mutations may play an important role in the development, response to treatment and prognosis of colorectal cancer (CRC). This retrospective study aimed to investigate the mutation profiling of Chinese patients with CRC, and its correlation with clinicopathological features and prognosis.

Methods

This study included 1190 Chinese CRC patients who were diagnosed between May 1998 and December 2018 and received clinical genetic testing. The OncoCarta Panel was used to test a total of 238 possible mutations in 19 common oncogenes.

Results

Five hundred and eighty‐two (48.9%) cases were detected with gene mutations. Of the 582 cases, there were 111 cases (19.7%) with two concurrent mutations, and six cases (1.0%) with three concurrent mutations. KRAS was the most common gene mutation that occurred in all cases (429, 36.1%), followed by PIK3CA (121, 10.2%), NRAS (47, 3.9%), BRAF (35, 2.9%), HRAS (11, 0.9%) and epidermal growth factor receptor (EGFR) (11, 0.9%). AKT1, KIT, FGFR1, FGFR3, FLT3, CDK, ERBB2, ABL1, MET, RET and PDGFRA mutations were also detected in several cases. When it came to prognosis, we found that KRAS/NRAS/PIK3CA/BRAF mutation was not associated with prognosis. But BRAF mutation was associated with poor prognosis in patients who accepted anti‐EGFR therapy.

Conclusions

The molecular testing offered the clinical data and mutation profile of Chinese CRC patients. The information of these mutated genes may help to find out the correlation between mutated genes and the development or prognosis of CRC.

Primary tumour location affects survival after resection of colorectal liver metastases: A two-institutional cohort study with international validation, systematic meta-analysis and a clinical risk score

BACKGROUND

Colorectal cancer (CRC) represents a major cause for cancer death and every third patient develops liver metastases (CRLM). Several factors including number and size of metastases and primary tumour lymph-node status have been linked to survival. The primary tumour location along the colo-rectum continuum (sidedness) was analysed in first-line chemotherapy trials, where right-sided CRCs showed decreased survival. This association has not yet been clearly established in patients undergoing resection for CRLM.

METHODS

Clinicopathological differences in CRLM resections according to sidedness in two Austrian centres (2003-2016) are described and survival is compared through Kaplan-Meier and multivariable analysis. A risk-score is presented with time-dependent receiver operating curve analysis and international validation in two major hepatobiliary centres. Furthermore, a systematic meta-analysis of studies on primary tumour location and survival after CRLM resection was performed.

RESULTS

259 patients underwent hepatectomy. Right-sided CRC patients (n = 59) more often had positive primary tumour lymph-nodes (76.3%/61.3%;p = 0.043) and RAS-mutations (60%/34.9%;p = 0.036). The median overall and disease-free survival was 33.5 and 9.1 months in right-sided versus 55.5 (p = 0.051) and 12.1 months (p = 0.078) in left-sided patients. In multivariable analysis nodal-status (HR 1.52), right-sidedness (HR 1.53), extrahepatic disease (HR 1.71) and bilobar hepatic involvement (HR 1.41) were significantly associated with overall survival. Sidedness was not independently associated with disease-free survival (HR 1.33; p = 0.099). A clinical risk score including right-sidedness, nodal-positivity and extrahepatic involvement significantly predicted overall (p = 0.005) and disease-free survival (p = 0.027), which was confirmed by international validation in 527 patients (p = 0.001 and p = 0.011). Meta-analysis including 10 studies (n = 4312) showed a significant association of right-sidedness with overall survival after resection (HR 1.55;p<0.001). There was no significant association with disease-free survival (HR 1.22;p = 0.077), except when rectal-cancers were excluded (HR 1.39;p = 0.006).

CONCLUSIONS

Patients with liver metastases from right-sided CRC experience worse survival after hepatic resection. Sidedness is a simple yet effective factor to predict outcome.

Mismatch repair deficiency/microsatellite instability-high as a predictor for anti-PD-1/PD-L1 immunotherapy efficacy

Immunotherapies have led to substantial changes in cancer treatment and have been a persistently popular topic in cancer research because they tremendously improve the efficacy of treatment and survival of individuals with various cancer types. However, only a small proportion of patients are sensitive to immunotherapy, and specific biomarkers are urgently needed to separate responders from nonresponders. Mismatch repair pathways play a vital role in identifying and repairing mismatched bases during DNA replication and genetic recombination in normal and cancer cells. Defects in DNA mismatch repair proteins and subsequent microsatellite instability-high lead to the accumulation of mutation loads in cancer-related genes and the generation of neoantigens, which stimulate the anti-tumor immune response of the host. Mismatch repair deficiency/microsatellite instability-high represents a good prognosis in early colorectal cancer settings without adjuvant treatment and a poor prognosis in patients with metastasis. Several clinical trials have demonstrated that mismatch repair deficiency or microsatellite instability-high is significantly associated with long-term immunotherapy-related responses and better prognosis in colorectal and noncolorectal malignancies treated with immune checkpoint inhibitors. To date, the anti-programmed cell death-1 inhibitor pembrolizumab has been approved for mismatch repair deficiency/microsatellite instability-high refractory or metastatic solid tumors, and nivolumab has been approved for colorectal cancer patients with mismatch repair deficiency/microsatellite instability-high. This is the first time in the history of cancer therapy that the same biomarker has been used to guide immune therapy regardless of tumor type. This review summarizes the features of mismatch repair deficiency/microsatellite instability-high, its relationship with programmed death-ligand 1/programmed cell death-1, and the recent advances in predicting immunotherapy efficacy.

Prognostic Value of Mismatch Repair Genes for Patients With Colorectal Cancer: Meta-Analysis

DNA mismatch repair was proposed to play a pivotal role in the development and prognosis of colorectal cancer. However, the prognostic value of mismatch repair on colorectal cancer is still unknown. The PubMed, EMBASE, and Cochrane Central Register of Controlled Trials databases were searched. The articles about mismatch repair (including hMLH1, hMSH2, hMSH3, hMSH6, hPMSH1, and hPMSH2) deficiency for the prognosis of patients with colorectal cancer were included in the study. The hazard ratio and its 95% confidence interval were used to measure the impact of mismatch repair deficiency on survival time. Twenty-one articles were included. The combined hazard ratio for mismatch repair deficiency on overall survival was 0.59 (95% confidence interval: 0.50-0.69) and that on disease-free survival was 0.57 (95% confidence interval: 0.43-0.75). In subgroup analysis, there were a significant association between overall survival and mismatch repair deficiency in Asian studies (hazard ratio: 0.67; 95% confidence interval: 0.50-0.91) and Western studies (hazard ratio: 0.56; 95% confidence interval: 0.46-0.67). For disease-free survival, the hazard ratios in Asian studies and Western studies were 0.55 (95% confidence interval: 0.38-0.81) and 0.62 (95% confidence interval: 0.50-0.78), respectively. Our meta-analysis indicated that mismatch repair could be used to evaluate the prognosis of patients with colorectal cancer.

Colorectal Cancer: Why Does Side Matter?

Colorectal cancer (CRC) is a heterogeneous disease, and the search for clinical and molecular prognostic and predictive factors is thus necessary to better tailor each individual patient's management. Primary tumor location (PTL) seems to act as a master prognostic factor pooling different clinical, pathological, and molecular poor prognostic factors. In fact, right-sided (RS) CRC patients are more frequently female and elderly with microsatellite unstable, BRAF mutated, CpG island methylator phenotype (CIMP)-high, poorly differentiated tumors, compared to left-sided (LS) CRC patients. PTL does not seem to clearly influence disease-free survival (DFS) in localised colon cancer even though the opposite prognostic value of RS tumors on DFS depending on RAS/BRAF mutational status has been recently suggested in these patients. In metastatic CRC (mCRC), the poor prognosis associated with RS tumors is confirmed in the most recent publications in the era of double and triple chemotherapeutic regimens and targeted agents. Concerning the predictive value of PTL, in patients with RAS wild-type mCRC in the first-line setting, anti-epidermal growth factor receptor (EGFR) therapy combined with chemotherapy appears to be more effective than bevacizumab in LS CRC, while patients with RS CRC benefit less from anti-EGFR therapy, and intensive chemotherapy plus bevacizumab may be more appropriate but EGFR antibodies remain an option if objective response is needed. Due to the limitation of the current data (unplanned and retrospective analyses), these conclusions must be interpreted with caution. Clinical trials in RS CRC may be of interest to clarify what is the best treatment strategy in these patients.

Survival benefit of lymph node dissection in surgery for colon cancer in elderly patients: A multicenter propensity score-matched study in Japan

INTRODUCTION

In surgery for elderly patients with colorectal cancer, it is unclear whether radical lymph node (LN) dissection safely offers a survival benefit. The aim of the study was to evaluate the impact of the LN yield in elderly patients undergoing surgery for colorectal cancer.

METHODS

The subjects were selected from a surgical database of 2065 patients aged ≥80 years old who underwent surgery for colorectal cancer at 41 hospitals in Japan between 2003 and 2007. The patients were divided into groups according to the number LN harvested: <12 and ≥12. Propensity scores were subsequently matched to balance the baseline characteristics.

RESULTS

Of the 954 patients initially selected, 331 were in the <12 LN and 623 were in the ≥12 LN group. After cases were matched, 293 patients were allocated to each group, and all covariates were balanced. For short-term outcomes, the time for surgery was longer in the ≥12 LN group, but there was no significant difference in morbidity between the groups. Overall, relapse-free and cancer-specific survival rates were higher in the ≥12 LN group (P = 0.004, 0.001, and 0.02).

CONCLUSIONS

In patients aged ≥80 years old with stage II-III colon cancer, harvesting ≥12 LN provides a survival benefit, and therefore, limited LN dissection is not recommended in these patients.

DNA mismatch repair in cancer

Microsatellite instability (MSI) refers to the hypermutator phenotype secondary to frequent polymorphism in short repetitive DNA sequences and single nucleotide substitution, as consequence of DNA mismatch repair (MMR) deficiency. MSI secondary to germline mutation in DNA MMR proteins is the molecular fingerprint of Lynch syndrome (LS), while epigenetic inactivation of these genes is more commonly found in sporadic MSI tumors. MSI occurs at different frequencies across malignancies, although original methods to assess MSI or MMR deficiency have been developed mostly in LS related cancers. Here we will discuss the current methods to detect MSI/MMR deficiency with a focus of new tools which are emerging as highly sensitive detector for MSI across multiple tumor types. Due to high frequencies of non-synonymous mutations, the presence of frameshift-mutated neoantigens, which can trigger a more robust and long-lasting immune response and strong TIL infiltration with tumor eradication, MSI has emerged as an important predictor of sensitivity for immunotherapy-based strategies, as showed by the recent FDA's first histology agnostic-accelerated approval to immune checkpoint inhibitors for refractory, adult and pediatric, MMR deficient (dMMR) or MSI high (MSI-H) tumors. Moreover, it is known that MSI status may predict cancer response/resistance to certain chemotherapies. Here we will describe the complex interplay between the genetic and clinical-pathological features of MSI/dMMR tumors and the cancer immunotherapy, with a focus on the predictive and prognostic role of MMR status for immune checkpoint inhibitors (ICIs) and providing some suggestions on how to conceive better predictive markers for immunotherapy in the next future.

Molecular classification and precision therapy of cancer: immune checkpoint inhibitors

On May 23, 2017, the US Food and Drug Administration (FDA) approved a treatment for cancer patients with positive microsatellite instability-high (MSI-H) markers or mismatch repair deficient (dMMR) markers. This approach is the first approved tumor treatment using a common biomarker rather than specified tumor locations in the body. FDA previously approved Keytruda for treatment of several types of malignancies, such as metastatic melanoma, metastatic non-small-cell lung cancer, recurrent or metastatic head and neck cancer, refractory Hodgkin lymphoma, and urothelial carcinoma, all of which carry positive programmed death-1/programmed death-ligand 1 biomarkers. Therefore, indications of Keytruda significantly expanded. Several types of malignancies are disclosed by MSI-H status due to dMMR and characterized by increased neoantigen load, which elicits intense host immune response in tumor microenvironment, including portions of colorectal and gastric carcinomas. Currently, biomarker-based patient selection remains a challenge. Pathologists play important roles in evaluating histology and biomarker results and establishing detection methods. Taking gastric cancer as an example, its molecular classification is built on genome abnormalities, but it lacks acceptable clinical characteristics. Pathologists are expected to act as "genetic interpreters" or "genetic translators" and build a link between molecular subtypes with tumor histological features. Subsequently, by using their findings, oncologists will carry out targeted therapy based on molecular classification.

Differences in Cancer-Specific Mortality of Right- Versus Left-Sided Colon Adenocarcinoma: A Surveillance, Epidemiology, and End Results Database Analysis

Purpose

Studies have shown an increased risk for all-cause mortality with right-sided colon cancer (RCC) as compared with left-sided colon cancer (LCC). However, these studies were unable to directly account for mortality events unrelated to cancer, known as other-cause mortality. We investigated the difference in cancer-specific mortality (CSM) between RCC and LCC at localized, regional, and metastatic stages, according to the Fine and Gray proportional hazards model, while accounting for other-cause mortality as a competing risk.

Methods

Using the SEER database, we identified 90,635 patients with LCC (ie, involving the splenic flexure, descending, sigmoid, and rectosigmoid colon) and 112,679 patients with RCC (ie, involving the cecum, ascending, hepatic flexure, and transverse colon) diagnosed from 1998 to 2013. We performed a competing risk analysis for CSM using the Fine and Gray proportional hazard model, adjusting for age, sex, race, tumor grade, surgery status, year of diagnosis, and tumor laterality, with two-sided testing and a statistical significance threshold of 0.05.

Results

Compared with LCC, RCC demonstrated statistically significant decreased CSM at the localized stage (adjusted hazards ratio [AHR], 0.865; P < .001), equivalent CSM at the regional stage (AHR, 0.990; P = .440), and increased CSM at the metastatic stage (AHR, 1.175; P < .001).

Conclusion

Using a competing risk model, we have shown that RCC, compared with LCC, is associated with lower CSM at the localized stage, equivalent CSM at the regional stage, and higher CSM at the metastatic stage. This pattern may correlate with variation in genetic factors, including known decreased prevalence of microsatellite instability in RCC with regional and metastatic disease.

Family history of colorectal cancer and its impact on survival in patients with resected stage III colon cancer: results from NCCTG Trial N0147 (Alliance)

BACKGROUND

Family history of colon cancer often portends increased risk of disease development; however, the prognostic significance of family history related to disease and survival outcomes is unclear.

METHODS

To investigate the relationship between family history of colorectal cancer and survival outcomes in stage III colon cancer patients, a prospective cohort of 1,935 patients with resected stage III colon cancer enrolled in a randomized controlled trial (N0147), comparing the standard of care FOLFOX to FOLFOX with cetuximab, was studied. Patients completed a baseline questionnaire on family history and were followed every 6 months until death or 5 years after randomization.

RESULTS

We examined the endpoints of disease-free survival (DFS), time to recurrence (TTR) and overall survival (OS), comparing patients with a positive versus negative family history of colorectal cancer. The adjusted hazard ratios (HRs) for patients with a positive family history were 0.95 [95% confidence interval (CI), 0.78-1.16] for DFS, 0.94 (95% CI, 0.76-1.16) for TTR, and 0.92 (95% CI, 0.74-1.15) for OS (all adjusted P>0.47). A non-significant trend toward improved DFS (P=0.17; adjusted P=0.34) was observed when 2 or more relatives were affected as compared to 0 relatives (multivariate HR: 0.72; 95% CI, 0.45-1.15), whereas subjects with histories of 0 or 1 affected relatives had similar DFS (multivariate HR for 1 vs. 0: 1.00; 95% CI, 0.81-1.24). Interactions of the molecular factors KRAS, BRAF, and MMR with family history were also explored. The only significant interaction was for deficient MMR (dMMR) and first-degree relatives with a family history of colorectal cancer (0 vs. 1 vs. 2+ relatives) for a benefit on OS (univariate P=0.001), which remained significant after adjusting for other factors (P=0.029).

CONCLUSIONS

Among patients with stage III resected colon cancer treated with adjuvant FOLFOX, a family history of colorectal cancer did not significantly impact DFS, TTR, or OS outcomes, with the exception of patients with dMMR-expressing tumors.

Primary tumor site and anti-EGFR monoclonal antibody benefit in metastatic colorectal cancer: a meta-analysis

AIM

This meta-analysis aimed to document the impact of primary tumor site on anti-EGFR monoclonal antibody (mAb) benefit in metastatic colorectal cancer.

MATERIALS & METHODS

Tumors with metastatic left-sided colorectal cancer (LCC) were compared with tumors with metastatic right-sided colon cancer (RCC) with respect to anti-EGFR mAb objective response rate (ORR), overall survival (OS) and progression-free survival (PFS) benefit.

RESULTS

Comparing LCC with RCC, LCC was found to have significantly superior anti-EGFR mAb ORR (p < 0.00001), OS (p < 0.00001) and PFS (p < 0.00001) benefit. Additionally, anti-EGFR mAb therapy significantly improved both OS and PFS for LCC compared with no anti-EGFR mAb therapy, but not for RCC. The test of interaction was also apparent for OS (p = 0.0002) and PFS (p = 0.0002).

CONCLUSION

This meta-analysis demonstrated that LCC had markedly superior anti-EGFR mAb treatment benefit compared with RCC.

BRAF-Mutated Colorectal Cancer Exhibits Distinct Clinicopathological Features from Wild-Type BRAF-Expressing Cancer Independent of the Microsatellite Instability Status

In patients with colorectal cancer (CRC), the BRAF V600E mutation has been reported to be associated with several clinicopathological features and poor survival. However, the prognostic implications of BRAF V600E mutation and the associated clinicopathological characteristics in CRCs remain controversial. Therefore, we reviewed various clinicopathological features, including BRAF status, in 349 primary CRCs and analyzed the relationship between BRAF status and various clinicopathological factors, including overall survival. Similar to previous studies conducted in Eastern countries, the incidence of the BRAF V600E mutation in the current study was relatively low (5.7%). BRAF-mutated CRC exhibits distinct clinicopathological features from wild-type BRAF-expressing cancer independent of the microsatellite instability (MSI) status. This mutation was significantly associated with a proximal tumor location (P = 0.002); mucinous, signet ring cell, and serrated tumor components (P < 0.001, P = 0.003, and P = 0.008, respectively); lymphovascular invasion (P = 0.004); a peritumoral lymphoid reaction (P = 0.009); tumor budding (P = 0.046); and peritoneal seeding (P = 0.012). In conclusion, the incidence of the BRAF V600E mutation was relatively low in this study. BRAF-mutated CRCs exhibited some clinicopathological features which were also frequently observed in MSI-H CRCs, such as a proximal location; mucinous, signet ring cell, and serrated components; and marked peritumoral lymphoid reactions.

The Worse Prognosis of Right-Sided Compared with Left-Sided Colon Cancers: a Systematic Review and Meta-analysis

BACKGROUND

Right-sided colon cancers (RCC) and left-sided colon cancers (LCC) are of different embryological origins, and various differences exist between them. However, the survival difference has not been assessed. The aim of this meta-analysis was to quantify the prognostic differences between RCC and LCC.

METHODS

Fifteen studies that compared the prognosis of colon cancer according to tumor location were identified. The effects of tumor location on survival outcome were assessed.

RESULTS

Patients with RCC had a significantly worse prognosis than did those with LCC in overall survival (OS) (hazard ratio (HR) = 1.14, 95 % confidence interval (CI) 1.06-1.22, p < 0.01). Our subgroup analyses demonstrated significant prognostic differences in Western countries (HR = 1.15, 95 % CI 1.08-1.23, p < 0.01), a nationwide database (HR = 1.15, 95 % CI 1.05-1.27, p = 0.01), and a stage-adjusted analysis (HR = 1.14, 95 % CI 1.05-1.24, p < 0.01).

CONCLUSIONS

These findings demonstrate that tumor location is associated with prognosis in colorectal cancer patients, and those with RCC have a significantly worse prognosis than those with LCC in terms of OS. RCC should be treated distinctively from LCC, and the establishment of standardized management for colon cancer by tumor location is needed.

Deficient mismatch repair: Read all about it (Review)

Defects in the DNA mismatch repair (MMR) proteins, result in a phenotype called microsatellite instability (MSI), occurring in up to 15% of sporadic colorectal cancers. Approximately one quarter of colon cancers with deficient MMR (dMMR) develop as a result of an inherited predisposition syndrome, Lynch syndrome (formerly known as HNPCC). It is essential to identify patients who potentially have Lynch syndrome, as not only they, but also family members, may require screening and monitoring. Diagnostic criteria have been developed, based primarily on Western populations, and several methodologies are available to identify dMMR tumours, including immunohistochemistry and microsatellite testing. These criteria have provided evidence supporting the introduction of reflex testing. Yet, it is becoming increasingly clear that tests have a limited sensitivity and specificity and may yet be superseded by next generation sequencing. In this review, the limitations of diagnostic criteria are discussed, and current and emerging screening technologies explained. There is now useful evidence supporting the prognostic and predictive value of dMMR status in colorectal tumours, but much less is known about their value in extracolonic tumours, that may also feature in Lynch syndrome. This review assesses current literature relating to dMMR in endometrial, ovarian, gastric and melanoma cancers, which it would seem, may benefit from large-scale clinical trials in order to further close the gap in knowledge between colorectal and extracolonic tumours.

Post-colonoscopy colorectal cancer (PCCRC) rates vary considerably depending on the method used to calculate them: a retrospective observational population-based study of PCCRC in the English National Health Service

OBJECTIVE

Post-colonoscopy colorectal cancer (PCCRC) is a key quality indicator of colonoscopy. This study compares methods for defining PCCRC rates, proposes a new method of calculating them and quantifies them across the English National Health Service (NHS).

DESIGN

This retrospective observational population-based study involved all individuals with a first primary diagnosis of colorectal cancer made between 2001 and 2010 and treated in the English NHS. Previously published methods for deriving PCCRC rates were applied to the linked routine health data for this population to investigate the effect on the rate. A new method, based on the year of the colonoscopy rather than colorectal cancer diagnosis, was then used to calculate PCCRC rates.

RESULTS

Of 297,956 individuals diagnosed with colorectal cancer, a total of 94,648 underwent a colonoscopy in the 3 years prior to their diagnosis. The application of the published methods and exclusion criteria to the dataset produced significantly different PCCRC rates from 2.5% to 7.7%. The new method demonstrates that PCCRC rates within 3 years of colonoscopy (without exclusions) decreased in the English NHS over 8 years, falling from 10.6% to 7.3% for colonoscopies performed in 2001 and 2007 respectively.

CONCLUSIONS

The method used to determine PCCRC rates significantly affects findings with potential to substantially underestimate rates. To enable international benchmarking there needs to be a standardised method for defining PCCRC. This study proposes a new methodology using colonoscopy as a denominator and between 2001 and 2007 this method indicated an 8.6% PCCRC rate across the English NHS. It also demonstrated PCCRC rates have fallen over time.

Poorly differentiated adenocarcinoma of the colon: subsite location and clinicopathologic features

PURPOSE

Colorectal cancers of the proximal colon are characterized by good prognosis, microsatellite instability (MSI), and poor differentiation. MSI is associated with a favorable prognosis, but poorly differentiated adenocarcinomas (PDAs) have a poor prognosis. In this study, we aimed to investigate this inconsistency by analyzing the heterogeneity of PDAs.

METHODS

A total of 156 surgically resected PDAs were analyzed according to tumor subsite by morphological and immunohistochemical analyses.

RESULTS

Proximal PDAs (n = 86) were significantly associated with females, older age, cytokeratin (CK) 20 downregulation, aberrant MUC5AC expression, and MSI compared with distal PDAs (n = 70). Proximal PDAs tended to show a better overall survival rate than distal PDAs. PDAs with microsatellite stability (MSS) were suggested to progress from well- and moderately differentiated adenocarcinomas (WMDAs), but MSI PDAs typically not. MSI PDAs demonstrated a prognosis marginally better than MSS PDAs, but significantly worse than WMDAs (n = 170). Proximal MSS PDAs had a similar unfavorable prognosis but were significantly associated with females and aberrant MUC5AC expression compared with distal MSS PDAs. MSI may be predictive of prognosis only in proximal PDAs, because nearly all distal PDAs were MSS. In contrast, CK20 downregulation was significantly associated with better prognosis in both subsites.

CONCLUSIONS

Proximal PDAs had a better prognosis than distal PDAs due to a higher incidence of MSI PDAs, whose prognosis was significantly worse than WMDAs. Female and MUC5AC expression were characteristic of proximal PDAs independent of MSI. Subsite-specific features of PDAs may serve for subclassification and predicting prognosis.

Excess of proximal microsatellite-stable colorectal cancer in African Americans from a multiethnic study

PURPOSE

African Americans (AA) have the highest incidence of colorectal cancer compared with other U.S. populations and more proximal colorectal cancers. The objective is to elucidate the basis of these cancer disparities.

EXPERIMENTAL DESIGN

Of note, 566 AA and 328 non-Hispanic White (NHW) colorectal cancers were ascertained in five Chicago hospitals. Clinical and exposure data were collected. Microsatellite instability (MSI) and BRAF (V600E) and KRAS mutations were tested. Statistical significance of categorical variables was tested by the Fisher exact test or logistic regression and age by the Mann-Whitney U test.

RESULTS

Over a 10-year period, the median age at diagnosis significantly decreased for both AAs (68-61; P < 0.01) and NHWs (64.5- 62; P = 0.04); more AA patients were diagnosed before age 50 than NHWs (22% vs. 15%; P = 0.01). AAs had more proximal colorectal cancer than NHWs (49.5% vs. 33.7%; P < 0.01), but overall frequencies of MSI, BRAF and KRAS mutations were not different nor were they different by location in the colon. Proximal colorectal cancers often presented with lymphocytic infiltrate (P < 0.01) and were diagnosed at older ages (P = 0.02). Smoking, drinking, and obesity were less common in this group, but results were not statistically significant.

CONCLUSIONS

Patients with colorectal cancer have gotten progressively younger. The excess of colorectal cancer in AAs predominantly consists of more proximal, microsatellite stable tumors, commonly presenting lymphocytic infiltrate and less often associated with toxic exposures or a higher BMI. Younger AAs had more distal colorectal cancers than older ones. These data suggest two different mechanisms driving younger age and proximal location of colorectal cancers in AAs.

Invasion pattern and histologic features of tumor aggressiveness correlate with MMR protein expression, but are independent of activating KRAS and BRAF mutations in CRC

KRAS/BRAF mutation testing and mismatch repair (MMR) protein immunohistochemistry have an established role in routine diagnostic evaluation of colorectal carcinoma (CRC). However, since the exact impact of these molecular characteristics on tumor morphology and behavior is still subject to research, the aim of our study was to examine associations between molecular and morphologic features that had not been analyzed in this combination before. KRAS (codons 12, 13, and 61) and BRAF (codon 600) mutation status and MMR protein expression were analyzed in a consecutive series of 117 CRC samples using DNA pyrosequencing and immunohistochemistry. Tumor cell budding, infiltration pattern, and peritumoral lymphocytic (PTL) reaction was assessed applying established criteria. Molecular and morphological findings were correlated applying chi-square and Fisher's exact test. We found KRAS or BRAF mutations in 40 and 8 % of samples, while loss of MMR protein expression was observed in 11 %. Tumor budding was significantly associated with infiltrative growth, absence of PTLs, and blood and lymph vessel infiltration. Neither KRAS nor BRAF mutations were associated with a certain growth pattern or budding intensity of CRC, but loss of MMR protein expression was found in context with BRAF mutation, expanding growth, and presence of PTLs. Our results confirm an association between loss of MMR protein expression, presence of activating BRAF mutation, expanding growth, and PTL reaction as well as between tumor budding, infiltrative growth pattern, and tumor aggressiveness; however, there was no such association between the presence of an activating KRAS or BRAF mutation and a distinct invasion pattern or tumor aggressiveness in CRC.

Influence of family history on survival in patients with colon and rectal cancer

OBJECTIVE

We aimed to investigate the association between a family history (FH) of colorectal cancer (CRC) and cancer recurrence and survival in patients with stage III CRC.

METHODS

From April 2001 to December 2007, 1102 patients with stage III CRC were enrolled and their data including FH, clinicopathological characteristics of the tumor were retrospectively analyzed.

RESULTS

Of 971 patients that were finally enrolled, 63 (6.5%) reported CRC in at least one first-degree relative. Death occurred in 12.7% of the CRC patients with an FH and 21.8% in those without an FH. A multivariate analysis showed that patients with an FH of CRC, compared with those without FH, had an adjusted hazard ratios (HR) of 0.674 (P = 0.281) for overall survival (OS) and 0.672 (P = 0.220) for disease-free survival (DFS). However, the location of tumor, preoperative carcinoembryonic antigen (CEA) level, tumor invasion (T) stage and lymph node (N) metastasis significantly affected OS and DFS. Furthermore, whereas the FH of CRC patients was associated with a favorable prognosis in stage III colon cancer (HR 0.224, P = 0.040) but not in rectal cancer (HR 1.225, P = 0.640).

CONCLUSIONS

In patients with stage III CRC, tumor location (especially in the rectum), a high preoperative CEA level and advanced T and N stages indicate a poor prognosis. However, in stage III colon cancer FH is associated with improved survival.

Gut commensal bacteria and regional Wnt gene expression in the proximal versus distal colon

Regional expression of Wingless/Int (Wnt) genes plays a central role in regulating intestinal development and homeostasis. However, our knowledge of such regional Wnt proteins in the colon remains limited. To understand further the effect of Wnt signaling components in controlling intestinal epithelial homeostasis, we investigated whether the physiological heterogeneity of the proximal and distal colon can be explained by differential Wnt signaling. With the use of a Wnt signaling-specific PCR array, expression of 84 Wnt-mediated signal transduction genes was analyzed, and a differential signature of Wnt-related genes in the proximal versus distal murine colon was identified. Several Wnt agonists (Wnt5a, Wnt8b, and Wnt11), the Wnt receptor frizzled family receptor 3, and the Wnt inhibitory factor 1 were differentially expressed along the colon length. These Wnt signatures were associated with differential epithelial cell proliferation and migration in the proximal versus distal colon. Furthermore, reduced Wnt/β-catenin activity and decreased Wnt5a and Wnt11 expression were observed in mice lacking commensal bacteria, an effect that was reversed by conventionalization of germ-free mice. Interestingly, myeloid differentiation primary response gene 88 knockout mice showed decreased Wnt5a levels, indicating a role for Toll-like receptor signaling in regulating Wnt5a expression. Our results suggest that the morphological and physiological heterogeneity within the colon is in part facilitated by the differential expression of Wnt signaling components and influenced by colonization with bacteria.

Survival in stage II/III colorectal cancer is independently predicted by chromosomal and microsatellite instability, but not by specific driver mutations

OBJECTIVES

Microsatellite instability (MSI) is an established marker of good prognosis in colorectal cancer (CRC). Chromosomal instability (CIN) is strongly negatively associated with MSI and has been shown to be a marker of poor prognosis in a small number of studies. However, a substantial group of "double-negative" (MSI-/CIN-) CRCs exists. The prognosis of these patients is unclear. Furthermore, MSI and CIN are each associated with specific molecular changes, such as mutations in KRAS and BRAF, that have been associated with prognosis. It is not known which of MSI, CIN, and the specific gene mutations are primary predictors of survival.

METHODS

We evaluated the prognostic value (disease-free survival, DFS) of CIN, MSI, mutations in KRAS, NRAS, BRAF, PIK3CA, FBXW7, and TP53, and chromosome 18q loss-of-heterozygosity (LOH) in 822 patients from the VICTOR trial of stage II/III CRC. We followed up promising associations in an Australian community-based cohort (N=375).

RESULTS

In the VICTOR patients, no specific mutation was associated with DFS, but individually MSI and CIN showed significant associations after adjusting for stage, age, gender, tumor location, and therapy. A combined analysis of the VICTOR and community-based cohorts showed that MSI and CIN were independent predictors of DFS (for MSI, hazard ratio (HR)=0.58, 95% confidence interval (CI) 0.36-0.93, and P=0.021; for CIN, HR=1.54, 95% CI 1.14-2.08, and P=0.005), and joint CIN/MSI testing significantly improved the prognostic prediction of MSI alone (P=0.028). Higher levels of CIN were monotonically associated with progressively poorer DFS, and a semi-quantitative measure of CIN was a better predictor of outcome than a simple CIN+/- variable. All measures of CIN predicted DFS better than the recently described Watanabe LOH ratio.

CONCLUSIONS

MSI and CIN are independent predictors of DFS for stage II/III CRC. Prognostic molecular tests for CRC relapse should currently use MSI and a quantitative measure of CIN rather than specific gene mutations.

An inducible, isogenic cancer cell line system for targeting the state of mismatch repair deficiency

The DNA mismatch repair system (MMR) maintains genome stability through recognition and repair of single-base mismatches and small insertion-deletion loops. Inactivation of the MMR pathway causes microsatellite instability and the accumulation of genomic mutations that can cause or contribute to cancer. In fact, 10-20% of certain solid and hematologic cancers are MMR-deficient. MMR-deficient cancers do not respond to some standard of care chemotherapeutics because of presumed increased tolerance of DNA damage, highlighting the need for novel therapeutic drugs. Toward this goal, we generated isogenic cancer cell lines for direct comparison of MMR-proficient and MMR-deficient cells. We engineered NCI-H23 lung adenocarcinoma cells to contain a doxycycline-inducible shRNA designed to suppress the expression of the mismatch repair gene MLH1, and compared single cell subclones that were uninduced (MLH1-proficient) versus induced for the MLH1 shRNA (MLH1-deficient). Here we present the characterization of these MMR-inducible cell lines and validate a novel class of rhodium metalloinsertor compounds that differentially inhibit the proliferation of MMR-deficient cancer cells.

Influence of anatomical subsite on the incidence of microsatellite instability, and KRAS and BRAF mutation rates in patients with colon carcinoma

There is a growing amount of data supporting the concept that cancers originating from the proximal and distal colon are distinct clinicopathological entities. The incidence of MSI and BRAF mutation is strongly associated with right sided tumor location, whereas there are conflicting results for KRAS mutation rates. However, to date, no data exist whether and to what extent defined colonic subsites influence MSI status, KRAS and BRAF mutation rates. We selected primary colon cancer from 171 patients operated on at our institution between 2007 and 2010. BRAF, KRAS mutation rates and microsatellite instability were determined and correlated with clinicopathological features and tumor location. MSI-h cancers were significantly associated with poor histological grade but a lower rate of distant metastases. KRAS-mutated tumors were linked to lower T-stage and better differentiation. Colon carcinomas with BRAF mutation were significantly associated with distant metastatic spread and poor histological grade. Furthermore, we found that MSI-h status, KRAS and BRAF mutation rates varied remarkably among the colonic subsites irrespective of right- and left-sided origin, respectively. The results of the current study provide further evidence that a simple classification into right- and left-sided colon carcinoma does not represent the complexity of this tumor entity.

Clinicopathologic features and prognostic analysis of MSI-high colon cancer

PURPOSE

The objectives of the study were to estimate the incidence and clarify the clinicopathologic feature of sporadic microsatellite instability (MSI)-high (MSI-H) colon cancer. Furthermore, the role of MSI in colon cancer prognosis was also investigated.

METHODS

Microsatellite status was identified by genotyping. The clinicopathologic differences between two groups (MSI-H vs. MSI-L/S) and the prognostic value of MSI were analyzed.

RESULTS

From 1993 to 2006, 709 sporadic colon cancer patients were enrolled. MSI-H colon cancers showed significant association with poorly differentiated (28.3% vs. 7.2%, p = 0.001), proximally located (76.7% vs. 34.5%, p = 0.001), more high mucin-containing tumor (10.0% vs. 5.1%, p = 0.001) and female predominance (56.7% vs. 30.2%, p = 0.001). In multivariate analysis, MSI-H is an independent factor for better overall survival (HR, 0.459; 95% CI, 0.241-0.872, p = 0.017).

CONCLUSIONS

Based on the hospital-based study, MSI-H colon cancers demonstrated distinguished clinicopathologic features from MSI-L/S colon cancers. MSI-H is an independent favorable prognostic factor for overall survival in colon cancer.

Detectability of colorectal neoplasia with fluorine-18-2-fluoro-2-deoxy-D-glucose positron emission tomography and computed tomography (FDG-PET/CT)

BACKGROUND

The purpose of this study was to analyze the detectability of colorectal neoplasia with fluorine-18-2-fluoro-2-deoxy-D-glucose positron emission tomography/computed tomography (FDG-PET/CT).

METHODS

Data for a total of 492 patients who had undergone both PET/CT and colonoscopy were analyzed. After the findings of PET/CT and colonoscopy were determined independently, the results were compared in each of the six colonic sites examined in all patients. The efficacy of PET/CT was determined using colonoscopic examination as the gold standard.

RESULTS

In all, 270 colorectal lesions 5 mm or more in size, including 70 pathologically confirmed malignant lesions, were found in 172 patients by colonoscopy. The sensitivity and specificity of PET/CT for detecting any of the colorectal lesions were 36 and 98%, respectively. For detecting lesions 11 mm or larger, the sensitivity was increased to 85%, with the specificity remaining consistent (97%). Moreover, the sensitivity for tumors 21 mm or larger was 96% (48/50). Tumors with malignant or high-grade pathology were likely to be positive with PET/CT. A size of 10 mm or smaller [odds ratio (OR) 44.14, 95% confidence interval (95% CI) 11.44-221.67] and flat morphology (OR 7.78, 95% CI 1.79-36.25) were significant factors that were associated with false-negative cases on PET/CT.

CONCLUSION

The sensitivity of PET/CT for detecting colorectal lesions is acceptable, showing size- and pathology-dependence, suggesting, for the most part, that clinically relevant lesions are detectable with PET/CT. However, when considering PET/CT for screening purposes caution must be exercised because there are cases of false-negative results.

PIK3CA kinase domain mutation identifies a subgroup of stage III colon cancer patients with poor prognosis

BACKGROUND

PIK3CA mutations in the helical domain (in exon 9) and in the kinase domain (exon 20) cause tumor formation by different means. We aimed to determine the effects of each of these mutations on survival of colon carcinoma patients.

METHODS

A large cohort of 685 colon carcinoma patients was tested for PIK3CA mutations in exons 9 and 20 by single nucleotide primer extension (N = 428) or by real time PCR (N = 257).

RESULTS

PIK3CA mutation rate was 13%. 66 of 83 (79.5%) were in exon 9 and 17 of 83 (20.5%) in exon 20. In survival analysis, PIK3CA mutations in exon 9 and 20 had different effects on patient outcome. The PIK3CA exon 20 mutation conferred a poorer disease free survival compared to patients with wild type alleles and exon 9 mutations (Log rank p = 0.04 and p = 0.03 respectively) and cancer specific survival (Log rank p = 0.03 and p = 0.056 respectively) in stage III patients. In stage I and II this negative effect on outcome was not seen.

CONCLUSIONS

PIK3CA mutation in exon 20 is a negative prognostic factor in stage III colon cancer patients. Moreover, this negative effect is not present in stage I and II patients.

Quality assessment and correlation of microsatellite instability and immunohistochemical markers among population- and clinic-based colorectal tumors results from the Colon Cancer Family Registry

The detection of defective mismatch repair (MMR), as assessed by the presence of tumor microsatellite instability (MSI) and/or loss of MMR protein expression by IHC, has been useful for risk assessment, prognosis, and prediction of treatment in patients with colorectal cancer. We analyzed tumors for the presence of defective MMR from 5927 Colorectal Cancer Family Registry patients recruited at six international consortium sites. We evaluated the appropriate percentage instability cutoff used to distinguish the three MSI phenotypes [ie, stable (MSS), low instability (MSI-L), and high instability (MSI-H)]; the sensitivity, specificity, and performance characteristics of individual markers; and the concordance between MSI and IHC phenotypes. Guided by the results of the IHC testing, our findings indicate that the distinction between an MSI-H phenotype from a low-instability or MSS phenotype can best be accomplished by using a cutoff of 30% or greater of the markers showing instability. The sensitivity and specificity of the mononucleotide markers were higher than those of the dinucleotide markers. Specifically, BAT26 and BAT25 had the highest sensitivity (94%) and specificity (98%), and the use of mononucleotide markers alone identified 97% of the MSI-H cases correctly. As expected, the presence of MSI-H correlated with an older age of diagnosis, the presence of tumor in the proximal colon, and female sex.

Molecular tumor clocks to study the evolution of drug resistance

It is likely that drug resistance evolves after transformation. Exactly how these resistant cells arise is uncertain. This review outlines how the evolution of individual human cancers may be inferred by comparing genomic variation from different parts of the same tumor. The past of a tumor may help predict its responses to chemotherapy.

High DNA methylation pattern intratumoral diversity implies weak selection in many human colorectal cancers

BACKGROUND

It is possible to infer the past of populations by comparing genomes between individuals. In general, older populations have more genomic diversity than younger populations. The force of selection can also be inferred from population diversity. If selection is strong and frequently eliminates less fit variants, diversity will be limited because new, initially homogeneous populations constantly emerge.

METHODOLOGY AND RESULTS

Here we translate a population genetics approach to human somatic cancer cell populations by measuring genomic diversity within and between small colorectal cancer (CRC) glands. Control tissue culture and xenograft experiments demonstrate that the population diversity of certain passenger DNA methylation patterns is reduced after cloning but subsequently increases with time. When measured in CRC gland populations, passenger methylation diversity from different parts of nine CRCs was relatively high and uniform, consistent with older, stable lineages rather than mixtures of younger homogeneous populations arising from frequent cycles of selection. The diversity of six metastases was also high, suggesting dissemination early after transformation. Diversity was lower in DNA mismatch repair deficient CRC glands, possibly suggesting more selection and the elimination of less fit variants when mutation rates are elevated.

CONCLUSION/SIGNIFICANCE

The many hitchhiking passenger variants observed in primary and metastatic CRC cell populations are consistent with relatively old populations, suggesting that clonal evolution leading to selective sweeps may be rare after transformation. Selection in human cancers appears to be a weaker than presumed force after transformation, consistent with the observed rarity of driver mutations in cancer genomes. Phenotypic plasticity rather than the stepwise acquisition of new driver mutations may better account for the many different phenotypes within human tumors.

Prognostic and predictive markers in stage II colon cancer: is there a role for gene expression profiling?

Conventional clinical and pathologic risk factors in stage II colon cancer provide limited prognostic information and do not predict response to adjuvant 5-fluorouracil-based chemotherapy. New prognostic and predictive biomarkers are needed to identify patients with highest recurrence risk who will receive the greatest absolute risk reduction from adjuvant chemotherapy. We review below the evidence for conventional risk factors in patients with node-negative colon cancer, followed by a discussion of promising new molecular and genetic markers in this malignancy. Gene expression profiling is an emerging tool with both prognostic and predictive potential in oncology. For patients with stage II colon cancer, the Oncotype DX Colon Cancer test is now commercially available as a prognostic marker, and the ColoPrint assay is expected to be released later this year. Current evidence for both of these assays is described below, concluding with a discussion of potential future directions for gene expression profiling in colon cancer risk stratification and treatment decision making.

Allelotyping identification of genomic alterations in rectal chromosomally unstable tumors without preoperative treatment

Background

Numerous studies reported genomic alterations in colorectal human tumors but few focused on rectal tumors with the specification of preoperative-treated or untreated tumors. The goals of this study were to list chromosome allelic imbalances and correlate their frequency with tumor progression and to identify potential molecular markers of progression in rectal chromosomally unstable tumors without preoperative treatment.

Methods

Genomic alterations of 57 rectal tumors assessed by allelotyping targeting 33 chromosomal loci, were clusterised and compared to those of 151 left colon tumors.

Results

Clustering separated the rectal tumors without preoperative treatment into three subtypes according to the allelic imbalance frequency and genomic alteration associations. The tumors without preoperative treatment displayed a significantly higher allelic imbalance frequency (54%) than the tumors with preoperative treatment (33%), suggesting that treatment could target highly altered tumor clones. Interestingly, the survival analysis identified three potential prognostic molecular survival markers, D1S197, D5S430, and D14S65, for tumors without preoperative treatment.

Conclusion

Based on the genomic status of 33 chromosomal loci, we observed that rectal tumors without preoperative treatment segregate according to the global allelic imbalance frequency but without correlation to the tumor progression. Moreover, the detailed associations of alterations in rectal tumors are different from those described in colon tumors suggesting that rectal and left tumors should be considered as separate entities. Finally, potential prognostic genomic molecular markers for survival are proposed which status could specify the clinical course of the tumors.

Surgical quality and nodal ultrastaging is associated with long-term disease-free survival in early colorectal cancer: an analysis of 2 international multicenter prospective trials

BACKGROUND

The National Quality Forum has endorsed a minimum of 12 lymph node (LN) as a surrogate measure of quality in colorectal cancer (CRC). The prognostic value of ultrastaging hematoxylin and eosin (H&E) negative LNs (N0) using pan-cytokeratin immunohistochemistry (pan-CK-IHC) is unknown.

PURPOSE

To assess the effect on survival of surgical quality and focused pathologic analysis.

PATIENTS AND METHODS

Between 2001 and 2007, 253 evaluable patients with resectable CRC were enrolled. Multiple sectioning and pan-CK-IHC were performed on N0 LNs (American Joint Commission on Cancer Stage II). Follow-up was performed at 6-month intervals with a 4-year disease-free survival (DFS) primary end-point.

RESULTS

There were 253 patients, 177 N0 and 76 N1/N2 patients, staged conventionally. Thirty-six (20%) N0 patients were upstaged using ultrastaging (N0-->N0i+ [n = 27] and N0-->N1mi [n = 9]). At a mean follow-up of 3.4 +/- 1.6 years, 38 (15%) have recurred. Only 3% (3/108) of patients with > or =12 LNs, negative by H&E and pan-CK-IHC (N0i-), compared with 18% (6/33) with <12 LNs/N0i- (6/33; P = 0.0015) have recurred. Four-year DFS differed significantly according to surgical quality (<12 vs. > or =12 LNs) among Stage II patients only (DFS, <12 vs. > or =12 LNs: Stage I, 90.5% vs. 97.7%, P = 0.22; Stage II, 67.5% vs. 94.7%, P = 0.0036; Stage III, 61% vs. 61%, P = 0.61).

CONCLUSION

This represents the first prospective report demonstrating that both surgical quality and nodal ultrastaging impacts survival in Stage II CRC. Patients with Stage II CRC having > or =12 LNs negative for micrometastases (N0i-) are likely cured by surgery alone. Both surgical and pathologic quality measures are imperative in early CRC to improve patient selection for adjuvant chemotherapy.

Location-related differences in sporadic microsatellite unstable colorectal cancer

BACKGROUND

Microsatellite unstable CRC is associated with female gender, large tumours, and poor differentiation. However, there are few reports about the characteristics and differences of sporadic microsatellite unstable CRC based on tumour location.

AIMS

Site-specific heterogeneity of sporadic microsatellite unstable colorectal cancer (CRC) based on location was elucidated.

METHODS

We enrolled 164 CRC patients with high-frequency microsatellite instability (MSI-H) from the prospective database of 2686 consecutive CRC patients who underwent surgical resection. We analysed microsatellite instability (MSI) and expression of mismatch repair (MMR) proteins (MLH1, MSH2, and MSH6).

RESULTS

Among the 164 MSI-H CRC, 105 (64.0%) were located in the proximal colon and 59 (36.0%) were located in the distal colon. The proximal MSI-H CRC was predominantly in female (p=0.014), had a more aggressive differentiation (p=0.001), was of advanced stage (p=0.035), and had a frequent loss of MLH1 expression (p=0.005) compared to the distal MSI-H CRC.

CONCLUSION

There were different clinicopathologic characteristics and MMR protein expression between proximal and distal MSI-H CRC. These findings suggest that the underlying carcinogenic pathway or molecular background differs according to location, despite being microsatellite unstable CRC.