DNA mismatch repair status and colon cancer recurrence and survival in clinical trials of 5-fluorouracil-based adjuvant therapy

Therapeutic implications of DNA mismatch repair in adjuvant colorectal cancer chemotherapy

SUMMARY Microsatellite instability (MSI) is a molecular marker of defective DNA mismatch repair (MMR) and constitutes an important oncogenic molecular pathway in colorectal cancer that is present in approximately 12–15% of all colorectal malignant tumors. Defective MMR status in colorectal cancer occurs as a result of germline mutations in MMR genes (less than one third of cases) or, more commonly, from somatic hypermethylation of the MLH1 promoter (more than two thirds). MMR deficiency accelerates colorectal oncogenesis by accumulation of secondary mutations in specific target genes. Patients with defective MMR tumors have distinct clinicopathologic characteristics and have been associated with a better stage-adjusted prognosis than patients with proficient MMR tumors. MMR deficiency may predict tumor chemoresistance to adjuvant 5-fluorouracil treatment. Preliminary clinical data suggested that adding oxaliplatin to 5-fluorouracil could restore the benefit of adjuvant chemotherapy in MSI patients. Further studies are needed to clarify the differential chemosensitivity of MSI patients depending on the mechanism of MMR deficiency and the adjuvant chemotherapeutic regimen used.

Extensive characterization of sphere models established from colorectal cancer cell lines

Links between cancer and stem cells have been proposed for many years. As the cancer stem cell (CSC) theory became widely studied, new methods were developed to culture and expand cancer cells with conserved determinants of "stemness". These cells show increased ability to grow in suspension as spheres in serum-free medium supplemented with growth factors and chemicals. The physiological relevance of this phenomenon in established cancer cell lines remains unclear. Cell lines have traditionally been used to explore tumor biology and serve as preclinical models for the screening of potential therapeutic agents. Here, we grew cell-forming spheres (CFS) from 25 established colorectal cancer cell lines. The molecular and cellular characteristics of CFS were compared to the bulk of tumor cells. CFS could be isolated from 72 % of the cell lines. Both CFS and their parental CRC cell lines were highly tumorigenic. Compared to their parental cells, they showed similar expression of putative CSC markers. The ability of CRC cells to grow as CFS was greatly enhanced by prior treatment with 5-fluorouracil. At the molecular level, CFS and parental CRC cells showed identical gene mutations and very similar genomic profiles, although microarray analysis revealed changes in CFS gene expression that were independent of DNA copy-number. We identified a CFS gene expression signature common to CFS from all CRC cell lines, which was predictive of disease relapse in CRC patients. In conclusion, CFS models derived from CRC cell lines possess interesting phenotypic features that may have clinical relevance for drug resistance and disease relapse.

A combined analysis of mismatch repair status and thymidylate synthase expression in stage II and III colon cancer

This study in 716 colon cancer patients evaluates if a combined instead of a single marker analysis of mismatch repair (MMR) status and thymidylate synthase (TS) expression could individualize the treatment decision. The results indicate that a combined analysis of MMR status and TS expression can improve prediction of response to adjuvant 5-fluorouracil (5-FU)-based chemotherapy in stage III colon cancer.

BACKGROUND

Colon cancer with mismatch repair deficiency and low TS expression has been associated with an improved prognosis. Data also indicate that MMR proficient colon cancer with high TS expression has a better response to adjuvant 5-FU-based chemotherapy. This study evaluates if a combined analysis of MMR status and TS expression in colon cancer can add prognostic value and better predict response to adjuvant 5-FU-based chemotherapy. The potential relationship between MMR status and TS expression is also investigated.

PATIENTS AND METHODS

This study includes a subgroup of 716 patients with colon cancer out of 2224 stage II and stage III colorectal cancer patients enrolled in Nordic trials randomized to surgery alone or surgery plus adjuvant 5-FU-based chemotherapy. After immunohistochemical analysis of tumor MMR status and TS expression the patients were divided into 4 groups.

RESULTS

There was a nonsignificant difference in overall survival between group 1 (patients with deficient MMR tumors with low TS) and group 4 (patients with proficient MMR tumors expressing high TS). When comparing group 1 and group 4 patients treated with surgery alone a trend to better overall survival was found in group 1, P=.06. In group 4, stage III patients had a significantly improved survival when receiving adjuvant 5-FU-based chemotherapy compared with surgery alone, P=.01. No relationship was found between MMR status and TS expression.

CONCLUSIONS

A combined instead of a single marker analysis of MMR status and TS expression can improve the prediction of response to 5-FU-based chemotherapy in stage III colon cancer.

Microsatellite instability, KRAS mutations and cellular distribution of TRAIL-receptors in early stage colorectal cancer

Background

The fact that the receptors for the TNF-related apoptosis inducing ligand (TRAIL) are almost invariably expressed in colorectal cancer (CRC) represents the rationale for the employment of TRAIL-receptors targeting compounds for the therapy of patients affected by this tumor. Yet, first reports on the use of these bioactive agents provided disappointing results. We therefore hypothesized that loss of membrane-bound TRAIL-R might be a feature of some CRC and that the evaluation of membrane staining rather than that of the overall expression of TRAIL-R might predict the response to TRAIL-R targeting compounds in this tumor.

Aim and Methods

Thus, we evaluated the immunofluorescence pattern of TRAIL-receptors and E-cadherin to assess the fraction of membrane-bound TRAIL-receptors in 231 selected patients with early-stage CRC undergoing surgical treatment only. Moreover, we investigated whether membrane staining for TRAIL-receptors as well as the presence of KRAS mutations or of microsatellite instability (MSI) had an effect on survival and thus a prognostic effect.

Results

As expected, almost all CRC samples stained positive for TRAIL-R1 and 2. Instead, membrane staining for these receptors was positive in only 71% and 16% of samples respectively. No correlation between KRAS mutation status or MSI-phenotype and prognosis could be detected. TRAIL-R1 staining intensity correlated with survival in univariate analysis, but only membranous staining of TRAIL-R1 and TRAIL-R2 on cell membranes was an independent predictor of survival (cox multivariate analysis: TRAIL-R1: p = 0.019, RR 2.06[1.12–3.77]; TRAIL-R2: p = 0.033, RR 3.63[1.11–11.84]).

Conclusions

In contrast to the current assumptions, loss of membrane staining for TRAIL-receptors is a common feature of early stage CRC which supersedes the prognostic significance of their staining intensity. Failure to achieve therapeutic effects in recent clinical trials using TRAIL-receptors targeting compounds might be due to insufficient selection of patients bearing tumors with membrane-bound TRAIL-receptors.

Molecular profiling for stage II colon cancer

SUMMARY Although nearly 80% of patients with stage II colon cancer are cured by surgery alone, 20% will relapse. One major challenge is to identify individuals who will derive enough benefit from adjuvant therapy to balance the risks, costs and inconvenience. Existing markers, such as microsatellite instability, are predictive and prognostic, but only apply to a small number of patients. Novel technologies that include molecular profiling are emerging tools that may help to identify patients at high risk for recurrence or predict who will derive a greater benefit from adjuvant treatment. This article reviews molecular markers in stage II colon cancer and their potential role in identification of high-risk patients.

Biomarkers in early-stage colorectal cancer: ready for prime time?

BACKGROUND/AIMS

During the last two decades, hundreds of reports have detailed putative prognostic and predictive biomarkers for colorectal cancer (CRC). However, the majority of these studies have been small and retrospective, reporting results that are highly likely to represent false positives. Consequently, their relevance to clinical practice requires definition.

METHODS

Review of published literature on CRC biomarkers, focusing on early-stage disease.

RESULTS

Although most putative biomarkers have failed to be validated in subsequent studies, level I evidence now indicates that tumour microsatellite instability can be used to identify a cohort of patients with stage IIA disease at low risk of relapse who can be spared adjuvant chemotherapy. Emerging data suggest that gene expression arrays may have a role in selecting patients with stage IIA disease and mismatch repair-proficient tumours for chemotherapy following tumour resection.

CONCLUSION

Despite the profusion of biomarker literature, only mismatch repair status can be recommended as routine in current clinical practice. High-quality, adequately powered studies are essential to accurately define the utility of existing and putative biomarkers, and to support their rational application in the clinic.

Clinical management of localized colon cancer with capecitabine

Large randomized trials demonstrated a benefit of adjuvant chemotherapy after resection of the primary colon cancer. It improves overall survival and reduces the risk of death, by 5% in UICC (Union Internationale Contre le Cancer) stage II and approximately 15%-20% in stage III. Fluoropyrimidines have been the standard drugs for the treatment of colon cancer since large randomized controlled trials demonstrated their efficacy and safety in treating patients suffering from this disease. Capecitabine is an orally administered fluoropyrimidine, which is preferably activated in tumor tissue to the active moiety 5-fluorouracil (5FU) and is cytotoxic through inhibition of DNA synthesis. It has proven equivalent efficacy and tolerability despite a changed toxicity profile compared to 5FU with less myelosuppression but more hand-and-foot syndrome. Capecitabine is well tolerated in elderly patients. The oral route of administration avoids frequent clinical visits as well as insertion of central venous catheters. The impact of the particular drug features on daily clinical practice is discussed in this review.

A robust genomic signature for the detection of colorectal cancer patients with microsatellite instability phenotype and high mutation frequency

Microsatellite instability (MSI) occurs in 10-20% of colorectal tumours and is associated with good prognosis. Here we describe the development and validation of a genomic signature that identifies colorectal cancer patients with MSI caused by DNA mismatch repair deficiency with high accuracy. Microsatellite status for 276 stage II and III colorectal tumours has been determined. Full-genome expression data was used to identify genes that correlate with MSI status. A subset of these samples (n = 73) had sequencing data for 615 genes available. An MSI gene signature of 64 genes was developed and validated in two independent validation sets: the first consisting of frozen samples from 132 stage II patients; and the second consisting of FFPE samples from the PETACC-3 trial (n = 625). The 64-gene MSI signature identified MSI patients in the first validation set with a sensitivity of 90.3% and an overall accuracy of 84.8%, with an AUC of 0.942 (95% CI, 0.888-0.975). In the second validation, the signature also showed excellent performance, with a sensitivity 94.3% and an overall accuracy of 90.6%, with an AUC of 0.965 (95% CI, 0.943-0.988). Besides correct identification of MSI patients, the gene signature identified a group of MSI-like patients that were MSS by standard assessment but MSI by signature assessment. The MSI-signature could be linked to a deficient MMR phenotype, as both MSI and MSI-like patients showed a high mutation frequency (8.2% and 6.4% of 615 genes assayed, respectively) as compared to patients classified as MSS (1.6% mutation frequency). The MSI signature showed prognostic power in stage II patients (n = 215) with a hazard ratio of 0.252 (p = 0.0145). Patients with an MSI-like phenotype had also an improved survival when compared to MSS patients. The MSI signature was translated to a diagnostic microarray and technically and clinically validated in FFPE and frozen samples.

The clinical significance of MiR-148a as a predictive biomarker in patients with advanced colorectal cancer

Aim

Development of robust prognostic and/or predictive biomarkers in patients with colorectal cancer (CRC) is imperative for advancing treatment strategies for this disease. We aimed to determine whether expression status of certain miRNAs might have prognostic/predictive value in CRC patients treated with conventional cytotoxic chemotherapies.

Methods

We studied a cohort of 273 CRC specimens from stage II/III patients treated with 5-fluorouracil-based adjuvant chemotherapy and stage IV patients subjected to 5-fluorouracil and oxaliplatin-based chemotherapy. In a screening set (n = 44), 13 of 21 candidate miRNAs were successfully quantified by multiplex quantitative RT-PCR. In the validation set comprising of the entire patient cohort, miR-148a expression status was assessed by quantitative RT-PCR, and its promoter methylation was quantified by bisulfite pyrosequencing. Lastly, we analyzed the associations between miR-148a expression and patient survival.

Results

Among the candidate miRNAs studied, miR-148a expression was most significantly down-regulated in advanced CRC tissues. In stage III and IV CRC, low miR-148a expression was associated with significantly shorter disease free-survival (DFS), a worse therapeutic response, and poor overall survival (OS). Furthermore, miR-148a methylation status correlated inversely with its expression, and was associated with worse survival in stage IV CRC. In multivariate analysis, miR-148a expression was an independent prognostic/predictive biomarker for advanced CRC patients (DFS in stage III, low vs. high expression, HR 2.11; OS in stage IV, HR 1.93).

Discussion

MiR-148a status has a prognostic/predictive value in advanced CRC patients treated with conventional chemotherapy, which has important clinical implications in improving therapeutic strategies and personalized management of this malignancy.

ESMO Consensus Guidelines for management of patients with colon and rectal cancer. a personalized approach to clinical decision making

Colorectal cancer (CRC) is the most common tumour type in both sexes combined in Western countries. Although screening programmes including the implementation of faecal occult blood test and colonoscopy might be able to reduce mortality by removing precursor lesions and by making diagnosis at an earlier stage, the burden of disease and mortality is still high. Improvement of diagnostic and treatment options increased staging accuracy, functional outcome for early stages as well as survival. Although high quality surgery is still the mainstay of curative treatment, the management of CRC must be a multi-modal approach performed by an experienced multi-disciplinary expert team. Optimal choice of the individual treatment modality according to disease localization and extent, tumour biology and patient factors is able to maintain quality of life, enables long-term survival and even cure in selected patients by a combination of chemotherapy and surgery. Treatment decisions must be based on the available evidence, which has been the basis for this consensus conference-based guideline delivering a clear proposal for diagnostic and treatment measures in each stage of rectal and colon cancer and the individual clinical situations. This ESMO guideline is recommended to be used as the basis for treatment and management decisions.

How many diseases are colorectal cancer?

The development of personalised therapy and mechanism-targeted agents in oncology mandates the identification of the patient populations most likely to benefit from therapy. This paper discusses the increasing evidence as to the heterogeneity of the group of diseases called colorectal cancer. Differences in the aetiology and epidemiology of proximal and distal cancers are reflected in different clinical behaviour, histopathology, and molecular characteristics of these tumours. This may impact response both to standard cytotoxic therapies and mechanism-targeted agents. This disease heterogeneity leads to challenges in the design of clinical trials to assess novel therapies in the treatment of "colorectal cancer."

High incidence of microsatellite instability and loss of heterozygosity in three loci in breast cancer patients receiving chemotherapy: a prospective study

Background

The aim of the study was to evaluate potential chemotherapy-induced microsatellite instability, loss of heterozygosity, loss of expression in mismatch repair proteins and associations with clinical findings in breast cancer patients, especially resistance to chemotherapy and/or development of other tumors in the four years following chemotherapy treatment.

Methods

A comprehensive study of chemotherapy-related effects with a follow-up period of 48 months post treatment was conducted. A total of 369 peripheral blood samples were collected from 123 de novo breast cancer patients. Microsatellite instability and loss of heterozygosity in five commonly used marker loci (including Tp53-Alu of the tumor suppressor gene TP53) were analyzed in blood samples. Sampling was conducted on three occasions; 4–5 weeks prior to the first chemotherapy session (pre-treatment), to serve as a baseline, followed by two consecutive draws at 12 weeks intervals from the first collection. Mismatch repair protein expression was evaluated in cancer tissues using immunohistochemistry for three mismatch-repair related proteins.

Results

A total of 70.7% of the patients showed microsatellite instability for at least one locus, including 18.6% marked as high-positive and 52.1% as low-positive; 35.8% showed loss of heterozygosity in addition to microsatellite instability, while 29.3% exhibited microsatellite stability. The following incidence rates for microsatellite instability and loss of heterozygosity were detected: 39.1% positive for Tp53-Alu, 31.1% for locus Mfd41, and 25.3% for locus Mfd28. A higher occurrence of loss of heterozygosity was noted with alleles 399 and 404 of Tp53-Alu. The mismatch repair protein expression analysis showed that the chemotherapy caused a loss of 29.3% in hMLH1 expression, and 18.7% and 25.2% loss in hMSH2 and P53 expression, respectively. A strong correlation between low or deficient hMSH2 protein expression and occurrence of mismatch repair/loss of heterozygosity events in Mfd41, Tp53-Alu, and Mfd28 was evident. A significant association between mismatch repair/loss of heterozygosity and incidence of secondary tumors was also established.

Conclusion

Our results suggest that microsatellite instability, loss of heterozygosity, and deficiency in mismatch repair may serve as early prognostic factors for potential chemotherapy-related side effects in breast cancer patients.

Biomarkers, bundled payments, and colorectal cancer care

Changes in the management of cancers such as colorectal cancer (CRC) are urgently needed, as such cancers continue to be one of the most commonly diagnosed cancers; CRC accounts for 21% of all cancers and is responsible for mortalities second only to lung cancer in the United States. A comprehensive science-driven approach towards markedly improved early detection/screening to efficacious targeted therapeutics with clear diagnostic and prognostic markers is essential. In addition, further changes addressing rising costs, stemming from recent health care reform measures, will be brought about in part by changes in how care is reimbursed. For oncology, the advances in genomics and biomarkers have the potential to define subsets of patients who have a prognosis or response to a particular type of therapy that differs from the mean. Better definition of a cancer's behavior will facilitate developing care plans tailored to the patient. One method under study is episode-based payment or bundling, where one payment is made to a provider organization to cover all expenses associated with a discrete illness episode. Payments will be based on the average cost of care, with providers taking on a risk for overutilization and outliers. For providers to thrive in this environment, they will need to know what care a patient will require and the costs of that care. A science-driven "personalized approach" to cancer care has the potential to produce better outcomes with reductions in the use of ineffectual therapies and costs. This promising scenario is still in the future, but progress is being made, and the shape of things to come for cancer care in the age of genomics is becoming clearer.

The utility of diagnostic biopsy specimens for predictive molecular testing in colorectal cancer

AIMS

If stratified medicine is to be applied in the neoadjuvant setting, predictive testing will have to be undertaken on preoperative diagnostic biopsy specimens. The aim of this study was to evaluate whether a diagnostic biopsy was adequately representative of the main tumour in colorectal cancer.

METHODS AND RESULTS

Thirty cases of paired biopsy and subsequent resection specimens were randomly selected. Samples were screened for mutation in KRAS (codons 12/13, 61, and 146), BRAF (codon 600 and exon 11), PIK3CA (exons 1, 9, and 20), TP53 (exons 5-8), and microsatellite instability, using the quick multiplex consensus or standard polymerase chain reaction (PCR) protocols followed by high-resolution melting analysis. A total of 570 paired PCR tests were performed for mutation detection, and identical results were obtained in both biopsy and resection specimens in 569 tests (>99% concordance). Four cases (13%) showed microsatellite instability, and, in all four cases, instability was seen at identical mononucleotide markers in both biopsy and matched resection specimens.

CONCLUSIONS

This is the first study to show that diagnostic biopsy specimens, even though they are a tiny sample of the tumour, are sufficiently representative for use in predictive testing for early driver mutations in colorectal cancer.

Prognostic and predictive significance of proliferation in 867 colorectal cancers

AIM

Recently, the Oncotype DX recurrence score, which measures a gene expression signature including markers of tumour proliferation, was validated as a prognostic signature in colorectal cancer. This study aimed to evaluate whether the Ki67 proliferation index can provide similar prognostic and predictive information.

METHODS

Tissue microarrays were constructed from triplicate cores of colorectal cancer. Immunohistochemistry for Ki67 was performed with the SP6 antibody and the percentage of positive tumour cells scored. Prognostic significance was evaluated in 867 cancers (601 events) using Cox proportional hazards models.

RESULTS

The Ki67 labelling index, divided at the median, was not a statistically or clinically significant prognostic factor in univariate analyses of 5-year overall survival (HR 0.98, 95% CI 0.84 to 1.15, p=0.84). Multivariate analyses were similarly non-significant. However, in Dukes' stage C patients, the high Ki67 subgroup derived a greater 5-year overall survival benefit from chemotherapy (HR 0.32, 95% CI 0.21 to 0.51, p<0.0001) than the low subgroup (HR 0.57, 95% CI 0.37 to 0.89, p=0.011).

CONCLUSIONS

The Ki67 proliferation index is not a useful prognostic factor in colorectal cancer, but deserves further evaluation as a predictive factor for the incremental benefit derived from adjuvant chemotherapy.

Guidelines for biomarker testing in colorectal carcinoma (CRC): a national consensus of the Spanish Society of Pathology (SEAP) and the Spanish Society of Medical Oncology (SEOM)

This consensus statement, conceived as a joint initiative of the Spanish Society of Pathology and the Spanish Society of Medical Oncology, makes diagnostic and treatment recommendations for the management of patients with hereditary, localised and advanced CRC based on the current scientific evidence on biomarker use. This consensus statement thus provides an opportunity to improve healthcare efficiency and resource use, which will benefit these patients. Based on the currently available data on this subject, this expert group recommends testing for microsatellite instability (MSI) in patients with localised CRC, as this is a strong predictive factor for deciding on adjuvant treatment. However, although the ColoPrint(®) and Oncotype Dx(®) gene expression signatures have been shown to have prognostic value, no consensus yet exists concerning their use in clinical practice. For advanced CRC, it is essential to test for KRAS mutation status before administering an anti-EGFR treatment, such as cetuximab or panitumumab. However, testing for other biomarkers, such as BRAF, EGFR, PI3K and PTEN mutations, should not be done routinely, because this does not influence treatment planning at the present time. Other important issues addressed include organisational requirements and the quality controls needed for proper testing of these biomarkers as well as the legal implications to be borne in mind when testing some biomarkers.

Time-dependent trends in lymph node yield and impact on adjuvant therapy decisions in colon cancer surgery: an international multi-institutional study

BACKGROUND

Lymph node yield (LNY) and accuracy of nodal assessment are critical to staging and treatment planning in colon cancer (CC). A nationally agreed upon 12-node minimum is a quality standard in CC. The impact of this quality measure on LNY and impact on therapeutic decisions are evaluated in two international, multi-center, prospective trials comprising a well-characterized cohort assembled over 8 years (2001-2009) with long-term follow-up.

HYPOTHESIS

Quality adherence through increased LNY improves staging accuracy and impacts adjuvant therapy decisions.

METHODS

Retrospective analysis of prospective data to assess time-dependent LNY, the dependent variable in multivariate linear regression analysis adjusted for age, gender, body-mass-index (BMI), tumor size/stage/grade, anatomic location and surgery date.

RESULTS

Two-hundred-forty-five patients with non-metastatic CC, median age 70 years, BMI 26 kg/m(2), tumor size 4.0 cm, and LNY 17 nodes were studied. Seventy-two percent had T3 (70 %)/T4 (2 %) tumors. Adherence to the 12-node minimum was 70 %(2001-2002), 81 % (2003-2004), 90 % (2005-2006), 94 % (2007-2008). LNY significantly increased over time (Median LNY: 2001-2004 = 15 vs. 2005-2008 = 17; P < 0.001) on multivariate analysis controlling for tumor size (P < 0.001), and right-sided tumor location (P < 0.001). Adjuvant therapy administration and indication for chemotherapy according to LNY (<12 vs. 12 + LNs = 33 % vs. 39 %; P = 0.48) and time period (2001-2004 vs. 2005-2008 = 39 % vs. 37 %; P = 0.89) remained unchanged.

CONCLUSIONS

Despite the independent predictors of nodal yield (tumor location and size), year of study still had a significant impact on nodal yield. Despite increased quality adherence and LNY over time, there appears to be a delayed impact on adjuvant therapy decisions once quality standard adherence takes effect.

Association between recurrent metastasis from stage II and III primary colorectal tumors and moderate microsatellite instability

Colorectal cancer cells frequently have low levels of microsatellite instability (MSI-L) and elevated microsatellite alterations at selected tetranucleotide repeats (EMAST), but little is known about the clinicopathologic significance of these features. We observed that patients with stage II or III colorectal cancer with MSI-L and/or EMAST had shorter times of recurrence-free survival than patients with high levels of MSI (P = .0084) or with highly stable microsatellites P = .0415), based on Kaplan-Meier analysis. MSI-L and/or EMAST were independent predictors of recurrent distant metastasis from primary stage II or III colorectal tumors (Cox proportional hazard analysis: hazard ratio, 1.83; 95% confidence interval, 1.06-3.15; P = .0301).

CpG Island Methylation, Microsatellite Instability, and BRAF Mutations and Their Clinical Application in the Treatment of Colon Cancer

There have been significant developments in colon cancer research over the last few years, enabling us to better characterize tumors individually and classifying them according to certain molecular or genetic features. Currently, we are able to use KRAS mutational status as a guide to therapy with anti-epidermal growth factor receptor antibodies. Other molecular features under research include BRAF mutation, microsatellite instability, and CpG island methylation. These three molecular features are often associated with tumors that have overlapping phenotypes and can be present simultaneously in the same tumor. However, they carry different prognostic and predictive qualities, making analysis of their interaction relatively complex. Much research thus far has examined the clinical relevance of microsatellite instability in helping determine prognosis and the predictive value of adjuvant 5-fluorouracil chemotherapy in stages II and III colon cancers. BRAF mutation appears to be a biomarker for poor prognosis. CpG island methylation is tightly associated with microsatellite instable tumors and BRAF mutation, but its clinical utility remains uncertain. Hereby, we examine preclinical and clinical data that supports the utilization of all three phenotypes in future research applied to clinical practice.

Novel prognostic biomarkers in colorectal cancer

The main predictor of outcome of patients with colorectal cancer (CRC) remains the TNM staging system. Biomarkers, i.e. biological indicators of disease progression or of responsiveness to a pharmacological intervention, are expected to be of help in the management of CRC. Despite high expectations, biomarkers have not entered into clinical practice due to contradictory results of large-scale studies and to some complexity in data interpretation. Here we briefly review the main genetic and immunological changes that have been considered potential CRC biomarkers and that might be considered for further testing aimed at clinical use, at least in specific disease settings.

Molecular testing in colorectal cancer: diagnosis of Lynch syndrome and personalized cancer medicine

Currently, molecular testing in colorectal cancer (CRC) is aimed at detecting Lynch syndrome and predicting response to anti-epidermal growth factor receptor (EGFR) therapies. However, CRC is a complex disease, with at least 3 molecular pathways of carcinogenesis. The importance of the EGFR signaling pathway in colorectal carcinogenesis is underscored by the availability of anti-EGFR monoclonal antibodies for the treatment of some metastatic CRCs. Potentially, mutations in any of the genes in the EGFR signaling pathway may be associated with prognosis and may predict response to anti-EGFR or other targeted therapies. Although not currently the standard of care, molecular testing of CRCs is expanding to include mutational analysis of the genes in the EGFR pathway, in addition to more widely performed tests for identifying cancers with high microsatellite instability. Multiplex molecular prognostic panels for therapeutic decision making in stage II CRCs also represent expanding use of molecular testing for this common cancer.

Benefits and adverse events in younger versus older patients receiving adjuvant chemotherapy for colon cancer: findings from the Adjuvant Colon Cancer Endpoints data set

PURPOSE

Limited data exist regarding the outcomes of adjuvant therapy in younger patients with stage II and III colon cancer. We examined disease-free survival (DFS), overall survival (OS), recurrence-free interval (RFI), and grade 3+ adverse events (AEs) in younger patients in the 33,574 patient Adjuvant Colon Cancer Endpoints Group data set.

PATIENTS AND METHODS

Individual patient data from 24 randomized phase III clinical trials were obtained for survival outcomes, which included 10 clinical trials for AE outcomes. Two age-based cutoff points were used to define younger patients: age younger than 40 years and younger than 50 years. Adjuvant therapy benefit analyses were limited to the nine clinical trials in which the investigational chemotherapeutic arm demonstrated benefit.

RESULTS

One thousand seven hundred fifty-eight patients (5.2%) were younger than 40 years, 5,817 patients (17.3%) were younger than 50 years, and only 299 patients (0.9%) were younger than 30 years. No meaningful differences in sex or stage were noted in younger versus older patients. Younger and older patients did not differ in RFI (age, < 40 years: hazard ratio [HR], 1.0; P = .62 and age < 50 years: HR, 1.02; P = .35). Younger patients (both cutoff points), had longer OS and DFS than older patients. In trials demonstrating adjuvant therapy benefit, similar DFS benefit was observed by age. Younger patients experienced less leukopenia and stomatitis, but more frequent nausea/vomiting.

CONCLUSION

Among patients on clinical trials, younger and older patients with stage II and III colon cancer had similar RFI and adjuvant therapy benefit. Younger patients have longer OS and DFS, which is likely primarily because of fewer competing causes of death. Adjuvant therapy is beneficial for colon cancer in patients younger than 50 years who meet typical clinical trial eligibility criteria.

Combined metallothioneins and p53 proteins expression as a prognostic marker in patients with Dukes stage B and C colorectal cancer

Our study aimed to evaluate metallothionein and p53 expression in colorectal cancer and to correlate their combined expression with selected clinical and pathologic variables of the disease, to define their prognostic significance. Colorectal cancer specimens from 99 patients were retrospectively analyzed by immunohistochemistry for metallothionein and p53 expression. Survival curves were generated according to the Kaplan-Meier method, and univariate survival distributions were compared with the use of the log-rank test. Multivariate models were computed using Cox proportional hazards regression. This research was approved by the institutional review boards of all centers. Tumors showing concomitant high metallothionein expression and negative p53 (metallothionein(H)/p53(-)) were significantly inversely related to depth of invasion, frequency of nodal metastasis, and Dukes stage (P < .01). In univariate analysis, patients with metallothionein(H)/p53(-) phenotype showed a better overall survival (hazard ratio [HR], 2.83; P < .05) and disease-free survival (HR, 2.03; P < .05). In multivariate analysis, considering staging, metallothionein, and metallothionein + p53 variables, in 83 patients with Dukes stages B and C, metallothionein(H)/p53(-) combination was the sole factor showing an independent prognostic value for overall survival (HR, 3.88; P < .1) and disease-free survival (HR, 2.56; P < .1). In conclusion, the combined analysis of metallothionein and p53 may enhance the prognostic power of each individual marker by predicting the progression of the disease and contributing to a better identification of patients at low risk for mortality, especially for those with Dukes stage B and C colorectal cancer.

Molecular pathways: microsatellite instability in colorectal cancer: prognostic, predictive, and therapeutic implications

Microsatellite instability (MSI) is the molecular fingerprint of the deficient mismatch repair (MMR) system, which characterizes ∼15% of colorectal cancers. MSI develops as a result of germline mutations in MMR genes or, more commonly, from epigenetic silencing of MLH1 in sporadic tumors occurring in a background of methylation of CpG islands in gene promoter regions and in tumors that frequently show hotspot mutations in the BRAF oncogene. MSI tumors have distinct phenotypic features and have been consistently associated with a better stage-adjusted prognosis compared with microsatellite stable tumors. MSI negatively predicts response to 5-fluorouracil and may also determine responsiveness to other drugs used for treatment of colorectal cancers. Recent data have expanded the molecular heterogeneity of MSI tumors and may contribute to our understanding of differential chemosensitivity. The ability to identify deficient MMR has important implications for patient management, and it holds promise for therapeutic exploitation and for the development of novel therapeutics.

Predictive and prognostic roles of BRAF mutation in stage III colon cancer: results from intergroup trial CALGB 89803

PURPOSE

Alterations in the RAS-RAF-MAP2K (MEK)-MAPK signaling pathway are major drivers in colorectal carcinogenesis. In colorectal cancer, BRAF mutation is associated with microsatellite instability (MSI), and typically predicts inferior prognosis. We examined the effect of BRAF mutation on survival and treatment efficacy in patients with stage III colon cancer.

METHODS

We assessed status of BRAF c.1799T>A (p.V600E) mutation and MSI in 506 stage III colon cancer patients enrolled in a randomized adjuvant chemotherapy trial [5-fluorouracil and leucovorin (FU/LV) vs. irinotecan (CPT11), FU and LV (IFL); CALGB 89803]. Cox proportional hazards model was used to assess the prognostic role of BRAF mutation, adjusting for clinical features, adjuvant chemotherapy arm, and MSI status.

RESULTS

Compared with 431 BRAF wild-type patients, 75 BRAF-mutated patients experienced significantly worse overall survival [OS; log-rank P = 0.015; multivariate HR = 1.66; 95% CI: 1.05-2.63]. By assessing combined status of BRAF and MSI, it seemed that BRAF-mutated MSS (microsatellite stable) tumor was an unfavorable subtype, whereas BRAF wild-type MSI-high tumor was a favorable subtype, and BRAF-mutated MSI-high tumor and BRAF wild-type MSS tumor were intermediate subtypes. Among patients with BRAF-mutated tumors, a nonsignificant trend toward improved OS was observed for IFL versus FU/LV arm (multivariate HR = 0.52; 95% CI: 0.25-1.10). Among patients with BRAF wild-type cancer, IFL conferred no suggestion of benefit beyond FU/LV alone (multivariate HR = 1.02; 95% CI: 0.72-1.46).

CONCLUSIONS

BRAF mutation is associated with inferior survival in stage III colon cancer. Additional studies are necessary to assess whether there is any predictive role of BRAF mutation for irinotecan-based therapy.

Personalized treatment of colorectal cancer

In the last 15 years, significant progress in the management of colorectal cancer (CRC) has been achieved with several new agents licensed extending median overall survival for stage IV disease to about 2 years. Treatment of CRC is stage-specific, multidisciplinary, and based on patient and tumor characteristics. Although especially early stages (0-III, according to Union for International Cancer Control) are treated with curative intent, patients with limited stage IV disease (liver and/or lung or localized peritoneal metastases) might still be curable in a multimodality approach including surgery, perioperative chemotherapy and/or radiotherapy. Despite the broad variety of prognostic factors, treatment decisions and selection of drugs are mainly based on clinicopathologic variables for early stage CRC, extent of disease, potential resectability, patients' eligibility to receive aggressive treatments including chemotherapy, surgery, and very few molecular markers such as KRAS mutational status for advanced disease. However, a tailored approach for the treatment of CRC taking into account all mentioned factors is currently recommended by national and international guidelines and will be discussed in this review.

Mucinous adenocarcinomas: poor prognosis in metastatic colorectal cancer

PURPOSE

Mucinous histology of metastatic colorectal cancer (CRC) has been associated with poor prognosis, however this has never been assessed in large well-defined study populations treated with the current used systemic agents. We investigated the prognostic value of mucinous histology in two large phase III studies in metastatic CRC.

PATIENTS AND METHODS

The study population included 1010 metastatic CRC patients who were treated with chemotherapy and targeted therapies in two phase III studies. Patients were classified according to the histology of the primary tumour in mucinous adenocarcinomas (MC) and non-mucinous adenocarcinomas (AC).

RESULTS

Patients with MC (n=99) were older, had more often a normal serum lactate dehydrogenase (LDH), extrahepatic localisation of metastases, larger primary tumour diameter and a higher T classification compared to patients with AC (n=911). A deficient mismatch repair system and BRAF mutations were observed in 17% and 22% of patients with MC, compared to 3% and 7% in patients with AC, respectively. Clinical outcome was investigated in both studies separately, showing a worse overall survival (OS), progression free survival and overall response rate in patients with MC compared to patients with AC. Patients with MC received less cycles of treatment compared to AC, but did not suffer from a higher incidence of grade 3/4 toxicity. In multivariate analysis, mucinous histology was as an independent negative prognostic factor for OS, resulting in a combined hazard ratio of 1.78 (95%confidence interval (CI) 1.35-2.35).

CONCLUSIONS

Patients with metastatic mucinous CRC have distinct clinicopathological features and poor response to chemotherapy and targeted agents. The strong negative prognostic value of MC warrants the use of this pathological feature as a stratification factor for clinical trials in metastatic CRC.

Association of obesity with DNA mismatch repair status and clinical outcome in patients with stage II or III colon carcinoma participating in NCCTG and NSABP adjuvant chemotherapy trials

PURPOSE

Although the importance of obesity in colon cancer risk and outcome is recognized, the association of body mass index (BMI) with DNA mismatch repair (MMR) status is unknown.

PATIENTS AND METHODS

BMI (kg/m(2)) was determined in patients with TNM stage II or III colon carcinomas (n = 2,693) who participated in randomized trials of adjuvant chemotherapy. The association of BMI with MMR status and survival was analyzed by logistic regression and Cox models, respectively.

RESULTS

Overall, 427 (16%) tumors showed deficient MMR (dMMR), and 630 patients (23%) were obese (BMI ≥ 30 kg/m(2)). Obesity was significantly associated with younger age (P = .021), distal tumor site (P = .012), and a lower rate of dMMR tumors (10% v 17%; P < .001) compared with normal weight. Obesity remained associated with lower rates of dMMR (odds ratio, 0.57; 95% CI, 0.41 to 0.79; P < .001) after adjusting for tumor site, stage, sex, and age. Among obese patients, rates of dMMR were lower in men compared with women (8% v 13%; P = .041). Obesity was associated with higher recurrence rates (P = .0034) and independently predicted worse disease-free survival (DFS; hazard ratio [HR], 1.37; 95% CI, 1.14 to 1.64; P = .0010) and overall survival (OS), whereas dMMR predicted better DFS (HR, 0.59; 95% CI, 0.47 to 0.74; P < .001) and OS. The favorable prognosis of dMMR was maintained in obese patients.

CONCLUSION

Colon cancers from obese patients are less likely to show dMMR, suggesting obesity-related differences in the pathogenesis of colon cancer. Although obesity was independently associated with adverse outcome, the favorable prognostic impact of dMMR was maintained among obese patients.

Micromanaging the classification of colon cancer: the role of the microRNAome

Recent advances in our understanding of the microRNAome (miRNAome) have provided further insights into the molecular pathogenesis of colorectal cancer and shown a potential role for miRNAs in distinguishing molecular subtypes. The mucosa-adenoma-carcinoma model can now integrate miRNAs into the known genetic alterations that drive the progression of colorectal neoplasia.