Context-dependent interpretation of the prognostic value of BRAF and KRAS mutations in colorectal cancer

An invasion front gene expression signature for higher-risk patient selection in stage IIA MSS colon cancer

Stage II colon cancer (CC) encompasses a heterogeneous group of patients with diverse survival experiences: 87% to 58% 5-year relative survival rates for stages IIA and IIC, respectively. While stage IIA patients are usually spared the adjuvant chemotherapy, some of them relapse and may benefit from it; thus, their timely identification is crucial. Current gene expression signatures did not specifically target this group nor did they find their place in clinical practice. Since processes at invasion front have also been linked to tumor progression, we hypothesize that aside from bulk tumor features, focusing on the invasion front may provide additional clues for this stratification. A retrospective matched case-control collection of 39 stage IIA microsatellite-stable (MSS) untreated CCs was analyzed to identify prognostic gene expression-based signatures. The endpoint was defined as relapse within 5 years vs. no relapse for at least 6 years. From the same tumors, three different classifiers (bulk tumor, invasion front, and constrained baseline on bulk tumor) were developed and their performance estimated. The baseline classifier, while the weakest, was validated in two independent data sets. The best performing signature was based on invasion front profiles [area under the receiver operating curve (AUC) = 0.931 (0.815-1.0)] and contained genes associated with KRAS pathway activation, apical junction complex, and heme metabolism. Its combination with bulk tumor classifier further improved the accuracy of the predictions.

Impact of colorectal cancer screening on survival after metachronous metastasis

BACKGROUND

An increasing proportion of colorectal cancer (CRC) cases in Europe are detected by screening with faecal immunochemical testing (FIT). Previous studies showed that population screening with FIT leads to a decrease in CRC incidence and to detection at an earlier stage. However, approximately twenty percent of patients with CRC without metastases at initial diagnosis still develop metachronous metastases. We investigated the association between detection mode of the primary tumor and overall survival (OS) after metachronous metastasis in patients with CRC.

METHODS

Nationwide registry-based data was obtained of 794 patients who developed metachronous metastases after being diagnosed with stage I-III CRC between January and June 2015. With multivariable Cox PH regression modelling, we analyzed the (causal) association between detection mode of the primary tumor (FIT screen-detected versus non-screen-detected) and OS after metachronous metastasis while adjusting for potential confounders.

RESULTS

Median OS and five-year OS after metachronous metastasis were significantly higher for patients with screen-detected (n = 152) vs. non-screen-detected primary tumors (n = 642): 38.3 vs. 19.2 months, and 35.4% vs. 18.8%, respectively, p < 0.0001). After adjustment for potential confounders, the association between detection mode and OS after metachronous metastasis remained significant (HR 0.70 [95% CI 0.56-0.89]).

CONCLUSIONS

Screen-detection of the primary tumor was independently associated with longer OS after metachronous metastasis. This may support the clinical utility of the population screening program and it shows the prognostic value of detection mode of the primary tumor once metachronous metastasis is diagnosed.

Colorectal cancer-associated fibroblasts promote metastasis by up-regulating LRG1 through stromal IL-6/STAT3 signaling

Cancer-associated fibroblasts (CAFs) have been shown to play a strong role in colorectal cancer metastasis, yet the underlying mechanism remains to be fully elucidated. Using CRC clinical samples together with ex vivo CAFs-CRC co-culture models, we found that CAFs induce expression of Leucine Rich Alpha-2-Glycoprotein 1(LRG1) in CRC, where it shows markedly higher expression in metastatic CRC tissues compared to primary tumors. We further show that CAFs-induced LRG1 promotes CRC migration and invasion that is concomitant with EMT (epithelial-mesenchymal transition) induction. In addition, this signaling axis has also been confirmed in the liver metastatic mouse model which displayed CAFs-induced LRG1 substantially accelerates metastasis. Mechanistically, we demonstrate that CAFs-secreted IL-6 (interleukin-6) is responsible for LRG1 up-regulation in CRC, which occurs through a direct transactivation by STAT3 following JAK2 activation. In clinical CRC tumor samples, LRG1 expression was positively correlated with CAFs-specific marker, α-SMA, and a higher LRG1 expression predicted poor clinical outcomes especially distant metastasis free survival, supporting the role of LRG1 in CRC progression. Collectively, this study provided a novel insight into CAFs-mediated metastasis in CRC and indicated that therapeutic targeting of CAFs-mediated IL-6-STAT3-LRG1 axis might be a potential strategy to mitigate metastasis in CRC.

The recurring features of molecular subtypes in distinct gastrointestinal malignancies-A systematic review

In colorectal cancer (CRC), pancreatic ductal adenocarcinoma (PDAC) and gastric cancer (GC) multiple studies of inter-tumor heterogeneity have identified molecular subtypes, which correlate with clinical features. Our aim was to investigate the attributes of molecular subtypes across three different gastrointestinal cancer types. We performed a systematic search for publications on molecular subtypes or classifications in PDAC and GC and compared the described subtypes with the established consensus molecular subtypes of CRC. Examining the characteristics of subtypes across CRC, PDAC and GC resulted in four categories of subtypes. We describe uniting and distinguishing features within a mesenchymal, an epithelial, an immunogenic and a metabolic and digestive subtype category. We conclude that molecular subtypes of CRC, PDAC and GC display relevant overlap in molecular features and clinical outcomes. This finding encourages quantitative studies on subtypes across different cancer types and could lead to a paradigm shift in future treatment strategies.

Adjuvant Chemotherapy in Elderly Colorectal Cancer Patients

The value of adjuvant chemotherapy in elderly patients has been the subject of many overviews, with opinions varying from “not effective”, since randomized trials have not been performed, to “as effective as in young individuals”, based upon many retrospective analyses of randomized trials that have included patients of all ages. In the absence of randomized trials performed specifically with elderly patients, retrospective analyses demonstrate that the influence on the time to tumour recurrence (TTR) may be the same as in young individuals, but that endpoints that include death for any reason, such as recurrence-free survival (RFS), disease-free survival (DFS), and overall survival (OS), are poorer in the elderly. This is particularly true if oxaliplatin has been part of the treatment. The need for adjuvant chemotherapy after colorectal cancer surgery in elderly patients is basically the same as that in younger patients. The reduction in recurrence risks may be similar, provided the chosen treatment is tolerated but survival gains are less. Adding oxaliplatin to a fluoropyrimidine is probably not beneficial in individuals above a biological age of approximately 70 years. If an oxaliplatin combination is administered to elderly patients, three months of therapy is in all probability the most realistic goal.

Biomarker-guided therapy for colorectal cancer: strength in complexity

The number of molecularly stratified treatment options available to patients with colorectal cancer (CRC) is increasing, with a parallel rise in the use of biomarkers to guide prognostication and treatment decision-making. The increase in both the number of biomarkers and their use has resulted in a progressively complex situation, evident both from the extensive interactions between biomarkers and from their sometimes complex associations with patient prognosis and treatment benefit. Current and emerging biomarkers also reflect the genomic complexity of CRC, and include a wide range of aberrations such as point mutations, amplifications, fusions and hypermutator phenotypes, in addition to global gene expression subtypes. In this Review, we provide an overview of current and emerging clinically relevant biomarkers and their role in the management of patients with CRC, illustrating the intricacies of biomarker interactions and the growing treatment opportunities created by the availability of comprehensive molecular profiling.

The Association of Tumor Laterality and Survival After Cytoreduction for Colorectal Carcinomatosis

BACKGROUND

Primary tumor location has emerged as an important surrogate for tumor biology in metastatic colorectal cancer treated with systemic chemotherapy. It is unclear if primary tumor location is associated with survival after cytoreductive surgery (CRS) with or without heated intraperitoneal chemotherapy (HIPEC) for colorectal carcinomatosis.

METHODS

Study of a contemporary cohort merged data from the California Cancer Registry, 2004-2012, and the Office of Statewide Health Planning and Development inpatient database. For patients undergoing CRS/HIPEC, clinicopathologic variables, treatment characteristics, and survival were compared by right versus left colon primary site. Survival was analyzed by Cox proportional hazards.

RESULTS

Of 272 patients identified, 128 (47.1%) had right-sided tumors. Left- and right-sided cohorts had similar patient, tumor, and treatment factors. Patients with left-sided primary tumors had significantly prolonged overall survival (mean 34 versus 15.5 mo, P = 0.0010). Factors independently associated with decreased overall survival included age >80 (HR 7.0, P < 0.0001), advanced T4 stage (HR 3.6, P = 0.0031), and positive lymph nodes (HR 2.2, P = 0.0004). Metachronous peritoneal involvement (HR 0.38, P < 0.0001) and left-sided primary tumors (HR 0.72, P = 0.041) were independently associated with improved overall survival.

CONCLUSIONS

This study identifies location of primary tumor as an important determinant of long-term survival after CRS/HIPEC. Patients with left-sided tumors have a more favorable prognosis.

Consequences of a high incidence of microsatellite instability and BRAF-mutated tumors: A population-based cohort of metastatic colorectal cancer patients

Background

Immunotherapy for patients with microsatellite‐instable (MSI‐H) tumors or BRAF‐inhibitors combination treatment for BRAF‐mutated (mutBRAF) tumors in metastatic colorectal cancer (mCRC) is promising, but the frequency of these molecular changes in trial patients are low. Unselected population‐based studies of these molecular changes are warranted.

Methods

A population‐based cohort of 798 mCRC patients in Scandinavia was studied. Patient and molecular tumor characteristics, overall survival (OS) and progression‐free survival (PFS) were estimated.

Results

Here, 40/583 (7%) tumor samples were MSI‐H and 120/591 (20%) were mutBRAF; 87% of MSI‐H tumors were mutBRAF (non‐Lynch). Elderly (>75 years) had more often MSI‐H (10% vs 6%) and MSI‐H/mutBRAF (9% vs 4%) tumors. Response rate (5% vs 44%), PFS (4 vs 8 months), and OS (9 vs 18 months) after first‐line chemotherapy was all significantly lower in patients with MSI‐H compared to patients with microsatellite stable tumors. MSI‐H and mutBRAF were both independent poor prognostic predictors for OS (P = 0.049, P < 0.001) and PFS (P = 0.045, P = 0.005) after first‐line chemotherapy. Patients with MSI‐H tumors received less second‐line chemotherapy (15% vs 37%, P = 0.005).

Conclusions

In unselected mCRC patients, MSI‐H and mutBRAF cases were more common than previously reported. Patients with MSI‐H tumors had worse survival, less benefit from chemotherapy, and they differed considerably from recent third‐line immunotherapy trial patients as they were older and most had mutBRAF tumor (non‐Lynch).

Clinical and Molecular Comparative Study of Colorectal Cancer Based on Age-of-onset and Tumor Location: Two Main Criteria for Subclassifying Colorectal Cancer

Our aim was to characterize and validate that the location and age of onset of the tumor are both important criteria to classify colorectal cancer (CRC). We analyzed clinical and molecular characteristics of early-onset CRC (EOCRC) and late-onset CRC (LOCRC), and we compared each tumor location between both ages-of-onset. In right-sided colon tumors, early-onset cases showed extensive Lynch syndrome (LS) features, with a relatively low frequency of chromosomal instability (CIN), but a high CpG island methylation phenotype. Nevertheless, late-onset cases showed predominantly sporadic features and microsatellite instability cases due to BRAF mutations. In left colon cancers, the most reliable clinical features were the tendency to develop polyps as well as multiple primary CRC associated with the late-onset subset. Apart from the higher degree of CIN in left-sided early-onset cancers, differential copy number alterations were also observed. Differences among rectal cancers showed that early-onset rectal cancers were diagnosed at later stages, had less association with polyps, and more than half of them were associated with a familial LS component. Stratifying CRC according to both location and age-of-onset criteria is meaningful, not only because it correlates the resulting categories with certain molecular bases, but with the confirmation across larger studies, new therapeutical algorithms could be defined according to this subclassification.

Right or Left Primary Site of Colorectal Cancer: Outcomes From the Molecular Analysis of the AGITG MAX Trial

BACKGROUND

For metastatic colorectal cancer, previous reports have described differences in biology and outcome, including response to biologic agents, based on whether the primary tumor is right- or left-sided. We explored the molecular markers from the AGITG MAX trial.

PATIENTS AND METHODS

The AGITG MAX trial was a randomized study comparing capecitabine versus capecitabine + bevacizumab versus capecitabine + bevacizumab + mitomycin C as first-line therapy in advanced colorectal cancer. Patients were classified as having right-sided (caecum to transverse colon) or left-sided (descending colon to rectum) disease according to anatomic location. Baseline characteristics and previously described molecular profiles were compared by side of primary tumor. Survival outcomes were analyzed by the Kaplan-Meier approach and proportional hazards regression modeling.

RESULTS

Among the 471 patients, the location of primary tumor was known in 440 patients (93%). Molecular profile was known in 298 patients (63%). Twenty-eight percent had right-sided primary tumors. Major differences between right and left are as follows: female 49% versus 33% (P < .01), BRAF mutant 16% versus 3.5% (P ≤ .001), and phosphatase and tensin homolog (PTEN) loss 27.6% versus 53% (P = .01). There were no differences in RAS mutation, PIK3CA mutation, or high versus low expression of assessed angiogenic markers. Right-sided primary lesion predicted a poor outcome for median overall survival: right-sided disease 13.2 months versus left-sided disease 20 months (P = .001; hazard ratio [HR] = 0.67; 95% confidence interval [CI], 0.53-0.85), but not for progression-free survival (HR 0.96; 95% CI, 0.78-1.20). The relative treatment effect did not differ significantly according to location of primary tumor: right primary tumor HR (bevacizumab containing arm vs. capecitabine monotherapy arm) was 0.82 (95% CI, 0.54-1.22), and left primary HR (bevacizumab containing arm vs. capecitabine monotherapy arm) was 0.51 (95% CI, 0.4-0.63) (interaction P = .10).

CONCLUSION

There are more negative prognostic factors in patients with right-sided primary tumors, in particular high BRAF mutations, and these patients have inferior overall survival compared to those with a left-sided primary tumor. There was no suggestion that side of primary site had any impact on bevacizumab effect on progression-free survival.

Mutation Status and Immunohistochemical Correlation of KRAS, NRAS, and BRAF in 260 Chinese Colorectal and Gastric Cancers

KRAS, NRAS and BRAF are kinases involved in the RAS-RAF-MAPK signaling pathway and also potential tumor-driven genes. Patients with KRAS/NRAS/BRAF mutations are resistant to anti-EGFR monoclonal antibody therapy. The main purpose of this study is to investigate the mutation status and distribution of KRAS/NRAS/BRAF in Chinese colorectal and gastric cancers, and to explore the histopathological changes and related immunohistochemical marker changes caused by these mutations. The mutation status of KRAS (exons 2, codon 12/13), NRAS (exons 2/3/4, codon 12/13/59/61/117/146) and BRAF (exons 15, codon 600) were detected by amplification refractory mutation system polymerase chain reaction (ARMS-PCR) in 86 colon cancer, 140 rectal cancer and 34 gastric cancer tissues. Then, the frequencies and distribution of KRAS/NRAS/BRAF mutations were described in detail. Furthermore, the relationship between KRAS/NRAS/BRAF mutations and the features of histopathological and related immunohistochemical markers were analyzed. The results showed that KRAS/NRAS/BRAF mutation rates in colon cancer were 44.2, 1.2, and 3.5%; in rectal cancer were 37.1, 4.3, and 0.7%; in gastric cancer were none, none and 2.9%. The mutation rate of KRAS in female (48.8%) is significantly higher than that of male (27.8%), and the mutation rate increased with the higher degree of differentiation. Additionally, the mutation rate of BRAF detected by ARMS-PCR (1.77%) was significantly lower than that by immunohistochemistry (4.11%). It also showed that the KRAS/NRAS/BRAF mutation status had a certain relationship with the expression of some immunohistochemical markers. This study provides more data support for clinical research on KRAS/NRAS/BRAF mutation in CRCs or gastric cancers.

Prognostic value of the combination of microsatellite instability and BRAF mutation in colorectal cancer

Purpose

The aim of this study was to investigate the prognostic value of the combination of microsatellite instability (MSI) and BRAF V600E mutation in colorectal cancer (CRC).

Materials and methods

We compare the prognosis difference among CRC patients with four subtypes according to MSI and BRAF mutation, ie, microsatellite stable/BRAF wild type (MSS/BRAFwt), MSS/BRAF mutation (MSS/BRAFmut), MSI/BRAFwt, and MSI/BRAFmut, by pooling the previous related reports and public available data sets till December 2017 for the first time.

Results

Twenty-seven independent studies comprising 24,067 CRC patients were included. Meta-analysis suggested that, compared with MSS/BRAFwt subtype, MSS/BRAFmut was associated with shorter overall survival (OS) (N=25, HR = 2.018, 95% CI = 1.706-2.388, P=2.220E-16), while there was a trend of association of MSI/BRAFmut with OS (N=13, HR = 1.324, 95% CI = 0.938-1.868, P=1.096E-01) and no association of MSI/BRAFwt with OS (N=17, HR = 0.996, 95% CI = 0.801-1.240, P=9.761E-01). Compared with MSI/ BRAFwt subtype, MSI/BRAFmut was a poor factor for OS (N=22, HR = 1.470, 95% CI = 1.243-1.740, P=7.122E-06). Compared with MSS/BRAFmut subtype, both MSI/BRAFwt (N=11, HR = 0.560, 95% CI = 0.433-0.725, P=1.034E-05) and MSI/BRAFmut (N=16, HR = 0.741, 95% CI = 0.567-0.968, P=2.781E-02) were favorable for OS. Subgroup analysis revealed similar results in all subgroups except the subgroup of stage IV cancer, in which MSI showed poor effects on OS in BRAF wild-type patients (N=6, HR = 1.493, 95% CI = 1.187-1.879, P=6.262E-04) but not in BRAF-mutated patients (N=5, HR = 1.143, 95% CI = 0.789-1.655, P=4.839E-01). Meta-analysis regression and test of interaction revealed no interaction of MSI with BRAF mutation when evaluating the associations of MSI/BRAF mutation subtypes with OS in CRC.

Conclusion

Among the four subtypes according to MSI and BRAF mutation, MSS/BRAFmut was a poor prognostic factor, while MSS/BRAFwt and MSI/BRAFwt were comparable and favorable and MSI/BRAFmut was moderate in CRC. The combination of MSI/BRAF mutations could facilitate the planning of individualized treatment strategies and prognosis improvement in CRC.

Prediction of overall survival in stage II and III colon cancer beyond TNM system: a retrospective, pooled biomarker study

Background

TNM staging alone does not accurately predict outcome in colon cancer (CC) patients who may be eligible for adjuvant chemotherapy. It is unknown to what extent the molecular markers microsatellite instability (MSI) and mutations in BRAF or KRAS improve prognostic estimation in multivariable models that include detailed clinicopathological annotation.

Patients and methods

After imputation of missing at random data, a subset of patients accrued in phase 3 trials with adjuvant chemotherapy (n = 3016)-N0147 (NCT00079274) and PETACC3 (NCT00026273)-was aggregated to construct multivariable Cox models for 5-year overall survival that were subsequently validated internally in the remaining clinical trial samples (n = 1499), and also externally in different population cohorts of chemotherapy-treated (n = 949) or -untreated (n = 1080) CC patients, and an additional series without treatment annotation (n = 782).

Results

TNM staging, MSI and BRAFV600E mutation status remained independent prognostic factors in multivariable models across clinical trials cohorts and observational studies. Concordance indices increased from 0.61-0.68 in the TNM alone model to 0.63-0.71 in models with added molecular markers, 0.65-0.73 with clinicopathological features and 0.66-0.74 with all covariates. In validation cohorts with complete annotation, the integrated time-dependent AUC rose from 0.64 for the TNM alone model to 0.67 for models that included clinicopathological features, with or without molecular markers. In patient cohorts that received adjuvant chemotherapy, the relative proportion of variance explained (R2) by TNM, clinicopathological features and molecular markers was on an average 65%, 25% and 10%, respectively.

Conclusions

Incorporation of MSI, BRAFV600E and KRAS mutation status to overall survival models with TNM staging improves the ability to precisely prognosticate in stage II and III CC patients, but only modestly increases prediction accuracy in multivariable models that include clinicopathological features, particularly in chemotherapy-treated patients.

Ezrin expression combined with MSI status in prognostication of stage II colorectal cancer

Currently used factors predicting disease recurrence in stage II colorectal cancer patients are not optimal for risk stratification. Thus, new biomarkers are needed. In this study the applicability of ezrin protein expression together with MSI status and BRAF mutation status were tested in predicting disease outcome in stage II colorectal cancer. The study population consisted of 173 stage II colorectal cancer patients. Paraffin-embedded cancer tissue material from surgical specimens was used to construct tissue microarrays (TMAs) with next-generation technique. The TMA-slides were subjected to following immunohistochemical stainings: MLH1, MSH2, MSH6, PMS2, ezrin and anti-BRAF V600E antibody. The staining results were correlated with clinicopathological variables and survival. In categorical analysis, high ezrin protein expression correlated with poor disease-specific survival (p = 0.038). In univariate analysis patients having microsatellite instabile / low ezrin expression tumors had a significantly longer disease-specific survival than patients having microsatellite stable / high ezrin expression tumors (p = 0.007). In multivariate survival analysis, the presence of BRAF mutation was associated to poor overall survival (p = 0.028, HR 3.29, 95% CI1.14–9.54). High ezrin protein expression in patients with microsatellite stable tumors was linked to poor disease-specific survival (p = 0.01, HR 5.68, 95% CI 1.53–21.12). Ezrin protein expression is a promising biomarker in estimating the outcome of stage II colorectal cancer patients. When combined with microsatellite status its ability in predicting disease outcome is further improved.

What We Know About Stage II and III Colon Cancer: It's Still Not Enough

The introduction of oxaliplatin as adjuvant treatment for stage III colon cancer in 2004 has been the last practice changing progress in adjuvant treatment for patients with early colon cancer. Since then, many prognostic and predictive biomarkers have been studied, but only DNA mismatch repair status has been validated as having an important prognostic value. Accordingly, TNM and clinical-pathological patterns, such as pT4 lesions and lymph node sampling <12 nodes, are the main factors that guide physicians' choice regarding adjuvant treatment. More recently, many biomarkers showed promising results: POLE, ErbB2, CDX2, SMAD4, BRAF and KRAS. In addition to these, immune-contexture, molecular classification, and gene signatures could become new ways to better classify colon cancer patients with more discriminatory power than TNM. The aim of this review is to report the state-of-the-art of prognostic and predictive factors in the adjuvant setting and which of these could modify clinical practice and maybe replace TNM classification.

Association of DNA Mismatch Repair and Mutations in BRAF and KRAS With Survival After Recurrence in Stage III Colon Cancers : A Secondary Analysis of 2 Randomized Clinical Trials

Importance

The association of biomarkers with patient survival after recurrence (SAR) of cancer is poorly understood but may guide management and treatment.

Objective

To determine the association of DNA mismatch repair (MMR) status and somatic mutation in the B-Raf proto-oncogene (c.1799T>A [V600E]; BRAFV600E) or exon 2 of the KRAS proto-oncogene (KRAS) in the primary tumor with SAR in patients with stage III colon carcinomas treated with adjuvant chemotherapy.

Design, Setting, and Participants

Patients with resected stage III colon cancers were randomized to adjuvant FOLFOX (folinic acid [leucovorin calcium], fluorouracil, and oxaliplatin) chemotherapy with or without cetuximab (North Central Cancer Treatment Group N0147 trial) or adjuvant FOLFOX chemotherapy with or without bevacizumab (National Surgical Adjuvant Breast and Bowel Project C-08 trial). Associations of biomarkers with SAR were analyzed using Cox proportional hazards models adjusted for clinicopathologic features and time to recurrence (data collected February 10, 2004, to August 7, 2015).

Main Outcomes and Measures

The primary study outcome was survival after recurrence of cancer. A secondary outcome measure was the effect of the site of the primary tumor on the association of biomarkers with SAR.

Results

Among 871 patients with cancer recurrence in the N0147 trial (472 men [54.2%] and 399 women [45.8%]; mean [SD] age, 57.8 [11.2] years) and 524 in the C-08 trial (269 men [51.3%] and 255 women [48.7%]; mean [SD] age, 57.0 [11.7] years), multivariable analysis revealed that patients whose tumors had deficient vs proficient MMR had significantly better SAR (adjusted hazard ratio [AHR], 0.70; 95% CI, 0.52-0.96; P = .03). Patients whose tumors harbored mutant BRAFV600E (AHR, 2.45; 95% CI, 1.85-3.25; P < .001) or mutant KRAS (AHR, 1.21; 95% CI, 1.00-1.47; P = .052) had worse SAR compared with those whose tumors had wild-type copies of both genes, although only results for BRAFV600E achieved statistical significance. Significant interactions were found for MMR (P = .03) and KRAS (P = .02) by primary tumor site for SAR. Improved SAR was observed for patients with deficient MMR tumors of the proximal vs distal colon (AHR, 0.57; 95% CI, 0.40-0.83; P = .003), and worse SAR was observed for tumors of the distal colon with mutant KRAS in codon 12 (AHR, 1.76; 95% CI, 1.30-2.38; P < .001) and codon 13 (AHR, 1.76; 95% CI, 1.08-2.86; P = .02).

Conclusions and Relevance

In patients with recurrence of stage III colon cancer, deficient MMR was significantly associated with better SAR, and this benefit was limited to primary tumors of the proximal colon. Mutations in BRAFV600E were significantly associated with worse SAR, and worse SAR for BRAFV600E or KRAS mutant tumors was more strongly associated with distal cancers. These biomarkers have implications for patient management at recurrence.

Trial Registration

clinicaltrials.gov Identifiers: NCT00079274 and NCT00096278.

The prognostic value of simultaneous tumor and serum RAS/RAF mutations in localized colon cancer

The impact of RAS/RAF mutations in localized colon cancer needs clarification. Based on analysis of tumor-specific DNA, this study aimed at elucidating the prognostic influence of mutational status in tumor and serum using an extended panel of mutations. The study retrospectively included 294 patients with curatively resected stage I-III adenocarcinoma of the colon. Mutations in tumor and serum were determined at time of surgery. Analyses were performed with droplet digital PCR technology. Hazard ratio (HR) for the association between mutational status and survival was estimated in multivariate analysis taking known prognostic factors into account. Mutational status in tumor did not on its own have significant prognostic impact (P = 0.22). Patients with a RAS mutation simultaneously in tumor and serum had a significantly worse prognosis, overall survival (OS) (HR = 2.30, 95% CI = 1.27-4.15, P = 0.0057), and disease-free survival (DFS) (HR = 2.18, 95%CI = 1.26-3.77, P = 0.0053). BRAF mutation in the serum and proficient mismatch repair (pMMR) protein in tumor also indicated significantly worse prognosis, OS (HR = 3.45, 95% CI = 1.52-7.85, P = 0.0032) and DFS (HR = 3.61, 95% CI = 1.70-7.67, P = 0.0008). In conclusion, RAS mutations in serum, and BRAF mutation in serum combined with pMMR in tumor were strong independent prognostic factors in patients with RAS/RAF mutated tumors.

The significance of tumor-associated immune response in molecular taxonomy, prognosis and therapy of colorectal cancer patients

The importance of host immune response in colorectal cancer (CRC) has been constantly revealed through the last 10 years. A number of relevant immune markers have been introduced as prognostic and are now been used alone or in combination with each other in clinical practice. Efforts establishing a worldwide consensus on the implications of immune-profiles in conjunction to other factors are designed in the right direction in order to more effectively categorize patients with CRC in groups that might benefit from currently used or future applied therapies. On the other hand, a number of clinical trials have evolved the application of immunotherapies in patients with CRC both in the adjuvant and palliative setting.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Serrated colorectal cancer: Molecular classification, prognosis, and response to chemotherapy

Molecular advances support the existence of an alternative pathway of colorectal carcinogenesis that is based on the hypermethylation of specific DNA regions that silences tumor suppressor genes. This alternative pathway has been called the serrated pathway due to the serrated appearance of tumors in histological analysis. New classifications for colorectal cancer (CRC) were proposed recently based on genetic profiles that show four types of molecular alterations: BRAF gene mutations, KRAS gene mutations, microsatellite instability, and hypermethylation of CpG islands. This review summarizes what is known about the serrated pathway of CRC, including CRC molecular and clinical features, prognosis, and response to chemotherapy.

The consensus molecular subtypes of colorectal cancer

Colorectal cancer (CRC) is a frequently lethal disease with heterogeneous outcomes and drug responses. To resolve inconsistencies among the reported gene expression-based CRC classifications and facilitate clinical translation, we formed an international consortium dedicated to large-scale data sharing and analytics across expert groups. We show marked interconnectivity between six independent classification systems coalescing into four consensus molecular subtypes (CMSs) with distinguishing features: CMS1 (microsatellite instability immune, 14%), hypermutated, microsatellite unstable and strong immune activation; CMS2 (canonical, 37%), epithelial, marked WNT and MYC signaling activation; CMS3 (metabolic, 13%), epithelial and evident metabolic dysregulation; and CMS4 (mesenchymal, 23%), prominent transforming growth factor-β activation, stromal invasion and angiogenesis. Samples with mixed features (13%) possibly represent a transition phenotype or intratumoral heterogeneity. We consider the CMS groups the most robust classification system currently available for CRC-with clear biological interpretability-and the basis for future clinical stratification and subtype-based targeted interventions.

First-in-Man Dose-Escalation Study of the Selective BRAF Inhibitor RG7256 in Patients with BRAF V600-Mutated Advanced Solid Tumors

BACKGROUND

BRAF mutations are a validated target for cancer therapy. A second-generation BRAF inhibitor with an improved preclinical safety profile (RG7256) was evaluated in a first-in-man study in order to determine the safety, efficacy, pharmacokinetics and pharmacodynamics in patients with BRAF V600-mutated advanced solid tumors.

PATIENTS AND METHODS

Patients received RG7256 orally over 8 dose levels from 200 mg once a day (QD) to 2400 mg twice a day (BID) (50-, 100- and 150-mg tablets) using a classic 3 + 3 dose escalation design.

RESULTS

In total, 45 patients were enrolled; most (87 %) had advanced melanoma (94 % BRAF V600E). RG7256 was rapidly absorbed, with limited accumulation and dose-proportional increase in exposure up to 1950 mg BID. The maximal tolerated dose (MTD) was not reached. The most common drug-related adverse events (AEs) were dyspepsia (20 %), dry skin (18 %), rash (18 %), fatigue (16 %) and nausea (13 %), mainly grade 1. Three patients (7 %) developed cutaneous squamous cell carcinoma. Photosensitivity, arthralgia and increased liver enzyme levels were each observed in only one patient each. Of 44 evaluable patients, 14 (32 %) had a partial response (melanoma and thyroid cancer). At high dose levels (>1200 mg BID), 10 of 16 (63 %) patients had a partial response. A decrease in maximum standardized uptake value (SUVmax) on FDG-PET of ≥25 % was observed in 19 of 37 patients. On-treatment reductions in pERK were documented in eight of ten paired tumor samples.

CONCLUSIONS

RG7256 has a favorable safety profile compared to other BRAF inhibitors while maintaining clinical activity, and MTD was not reached. The excessive pill burden needed to provide the desired exposure, and thus concerns about patient compliance, limited further development of this agent. Study Identifier: ClinicalTrials.gov (NCT01143753).

Analysis of Molecular Markers by Anatomic Tumor Site in Stage III Colon Carcinomas from Adjuvant Chemotherapy Trial NCCTG N0147 (Alliance)

PURPOSE

To determine the frequency and prognostic association of molecular markers by anatomic tumor site in patients with stage III colon carcinomas.

EXPERIMENTAL DESIGN

In a randomized trial of adjuvant FOLFOX ± cetuximab, BRAF(V600E) and KRAS (exon 2) mutations and DNA mismatch repair (MMR) proteins were analyzed in tumors (N = 3,018) in relationship to tumor location, including subsite. Cox models were used to assess clinical outcome, including overall survival (OS).

RESULTS

KRAS codon 12 mutations were most frequent at the splenic flexure and cecum; codon 13 mutations were evenly distributed. BRAF mutation frequency sharply increased from transverse colon to cecum in parallel with deficient (d) MMR. Nonmutated BRAF and KRAS tumors progressively decreased from sigmoid to transverse (all P < 0.0001). Significantly, poorer OS was found for mutant KRAS in distal [HR, 1.98; 95% confidence interval (CI), 1.49-2.63; P < 0.0001] versus proximal (1.25; 95% CI, 0.97-1.60; P = 0.079) cancers. BRAF status and outcome were not significantly associated with tumor site. Proximal versus distal dMMR tumors had significantly better outcome. An interaction test was significant for tumor site by KRAS (P(adjusted) = 0.043) and MMR (P(adjusted) = 0.010) for OS. Significant prognostic differences for biomarkers by tumor site were maintained in the FOLFOX arm. Tumor site was independently prognostic with a stepwise improvement from cecum to sigmoid (OS: P(adjusted) = 0.001).

CONCLUSIONS

Mutation in BRAF or KRAS codon 12 was enriched in proximal cancers whereas nonmutated BRAF/KRAS was increased in distal tumors. Significant differences in outcome for KRAS mutations and dMMR were found by tumor site, indicating that their interpretation should occur in the context of tumor location.

Randomized phase III clinical trial comparing the combination of capecitabine and oxaliplatin (CAPOX) with the combination of 5-fluorouracil, leucovorin and oxaliplatin (modified FOLFOX6) as adjuvant therapy in patients with operated high-risk stage II or stage III colorectal cancer

BACKGROUND

The aim of the trial was to compare two active adjuvant chemotherapy regimens in patients with early stage colorectal cancer (CRC).

METHODS

Patients were assigned to oxaliplatin, leucovorin and 5-FU for 12 cycles (group A, FOLFOX6) or oxaliplatin and capecitabine for eight cycles (group B, CAPOX). Primary endpoint was disease-free survival (DFS). Tumors were classified as mismatch repair proficient (pMMR) or deficient (dMMR) according to MLH1, PMS2, MSH2 and MSH6 protein expression. KRAS exon two and BRAF V600E mutational status were also assessed.

RESULTS

Between 2005 and 2008, 441 patients were enrolled, with 408 patients being eligible. After a median follow-up of 74.7 months, 3-year DFS was 79.8 % (95 % CI 76.5-83.4) in the FOLFOX group and 79.5 % (95 % CI 75.9-83.1) in the CAPOX group (p = 0.78). Three-year OS was 87.2 % (95 % CI 84.1-91.1) in the FOLFOX and 86.9 % (95 % CI 83.4-89.9) in the CAPOX group (p = 0.84). Among 306 available tumors, 11.0 % were dMMR, 34.0 % KRAS mutant and 4.9 % BRAF mutant. Multivariate analysis showed that primary site in the left colon, earlier TNM stage and the presence of anemia at diagnosis were associated with better DFS and overall survival (OS), while grade one-two tumors were associated with better OS. Finally, a statistically significant interaction was detected between the primary site and MMR status (p = 0.010), while KRAS mutated tumors were associated with shorter DFS. However, the sample was too small for safe conclusions.

CONCLUSIONS

No significant differences were observed in the efficacy of FOLFOX versus CAPOX as adjuvant treatment in high-risk stage II or stage III CRC patients, but definitive conclusions cannot be drawn because of the small sample size.

TRIAL REGISTRATION

ANZCTR 12610000509066 . Date of Registration: June 21, 2010.

Personalizing colon cancer adjuvant therapy: selecting optimal treatments for individual patients

For more than three decades, postoperative chemotherapy-initially fluoropyrimidines and more recently combinations with oxaliplatin-has reduced the risk of tumor recurrence and improved survival for patients with resected colon cancer. Although universally recommended for patients with stage III disease, there is no consensus about the survival benefit of postoperative chemotherapy in stage II colon cancer. The most recent adjuvant clinical trials have not shown any value for adding targeted agents, namely bevacizumab and cetuximab, to standard chemotherapies in stage III disease, despite improved outcomes in the metastatic setting. However, biomarker analyses of multiple studies strongly support the feasibility of refining risk stratification in colon cancer by factoring in molecular characteristics with pathologic tumor staging. In stage II disease, for example, microsatellite instability supports observation after surgery. Furthermore, the value of BRAF or KRAS mutations as additional risk factors in stage III disease is greater when microsatellite status and tumor location are taken into account. Validated predictive markers of adjuvant chemotherapy benefit for stage II or III colon cancer are lacking, but intensive research is ongoing. Recent advances in understanding the biologic hallmarks and drivers of early-stage disease as well as the micrometastatic environment are expected to translate into therapeutic strategies tailored to select patients. This review focuses on the pathologic, molecular, and gene expression characterizations of early-stage colon cancer; new insights into prognostication; and emerging predictive biomarkers that could ultimately help define the optimal adjuvant treatments for patients in routine clinical practice.

Establishment and characterization of models of chemotherapy resistance in colorectal cancer: Towards a predictive signature of chemoresistance

Current standard treatments for metastatic colorectal cancer (CRC) are based on combination regimens with one of the two chemotherapeutic drugs, irinotecan or oxaliplatin. However, drug resistance frequently limits the clinical efficacy of these therapies. In order to gain new insights into mechanisms associated with chemoresistance, and departing from three distinct CRC cell models, we generated a panel of human colorectal cancer cell lines with acquired resistance to either oxaliplatin or irinotecan. We characterized the resistant cell line variants with regards to their drug resistance profile and transcriptome, and matched our results with datasets generated from relevant clinical material to derive putative resistance biomarkers. We found that the chemoresistant cell line variants had distinctive irinotecan- or oxaliplatin-specific resistance profiles, with non-reciprocal cross-resistance. Furthermore, we could identify several new, as well as some previously described, drug resistance-associated genes for each resistant cell line variant. Each chemoresistant cell line variant acquired a unique set of changes that may represent distinct functional subtypes of chemotherapy resistance. In addition, and given the potential implications for selection of subsequent treatment, we also performed an exploratory analysis, in relevant patient cohorts, of the predictive value of each of the specific genes identified in our cellular models.

Prognosis of stage II and III colon cancer treated with adjuvant 5-fluorouracil or FOLFIRI in relation to microsatellite status: results of the PETACC-3 trial

BACKGROUND

Although colon cancer (CC) with microsatellite instability (MSI) has a more favorable prognosis than microsatellite stable (MSS) CC, the impact varies according to clinicopathological parameters. We studied how MSI status affects prognosis in a trial-based cohort of stage II and III CC patients treated with 5-fluorouracil (5-FU)/leucovorin or FOLFIRI.

MATERIALS AND METHODS

Tissue specimens of 1254 patients were tested for 10 different loci and were classified as MSI-high (MSI-H) when three or more loci were unstable and MSS otherwise. Study end points were overall survival (OS) and relapse-free survival (RFS).

RESULTS

In stage II, RFS and OS were better for patients with MSI-H than with MSS CC [hazard ratio (HR) 0.26, 95% CI 0.10-0.65, P = 0.004 and 0.16, 95% CI 0.04-0.64, P = 0.01). In stage III, RFS was slightly better for patients with MSI-H CC (HR 0.67, 95% CI 0.46-0.99, P = 0.04), but the difference was not statistically significant for OS (HR 0.70, 95% CI 0.44-1.09, P = 0.11). Outcomes for patients with MSI-H CC were not different between the two treatment arms. RFS was better for patients with MSI-H than with MSS CC in the right and left colon, whereas for OS this was significant only in the right colon. For patients with KRAS- and BRAF-mutated CC, but not for double wild-type patients, RFS and OS were significantly better when the tumors were also MSI-H. An interaction test was statistically significant for KRAS and MSI status (P = 0.005), but not for BRAF status (P = 0.14).

CONCLUSIONS

Our results confirm that for patients with stage II CC but less so for those with stage III MSI-H is strongly prognostic for RFS and OS. In the presence of 5-FU treatment, stage II patients with MSI-H tumors maintain their survival advantage in comparison with MSS patients and adding irinotecan has no added benefit. CLINICALTRIALS.GOV IDENTIFIER: NCT00026273.

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.

Left-sided primary tumors are associated with favorable prognosis in patients with KRAS codon 12/13 wild-type metastatic colorectal cancer treated with cetuximab plus chemotherapy: an analysis of the AIO KRK-0104 trial

Purpose

AIO KRK-0104 investigated first-line therapy of metastatic colorectal cancer (mCRC) with cetuximab, capecitabine and irinotecan versus cetuximab, capecitabine and oxaliplatin. This analysis investigated the impact of primary tumor location on outcome of patients.

Patients and methods

Left-sided primary tumors were defined as tumors from rectum to left flexure, while tumors in the remaining colon were regarded right sided. Overall survival (OS), progression-free survival (PFS) and response rate were correlated with primary tumor location. A Cox regression model was used to evaluate interaction between primary tumor location and KRAS mutation.

Results

Of 146 patients of the AIO KRK-0104 trial, 100 patients presented left-sided (of those 68 KRAS codon 12/13 wild-type) and 46 patients right-sided primary tumors (of those 27 KRAS codon 12/13 wild-type). Left-sided tumors were associated with significantly longer OS (p = 0.016, HR = 0.63) and PFS (p = 0.02, HR = 0.67) as compared to right-sided tumors. These effects were present in the KRAS codon 12/13 wild-type population (HR OS: 0.42; HR PFS: 0.54), while no impact of primary tumor location was evident in patients with KRAS codon 12/13 mutant tumors (HR OS: 1.3; HR PFS: 1.01). A significant interaction of KRAS status and primary tumor location concerning OS and PFS was observed.

Conclusion

Our findings suggest that primary tumor location and KRAS codon 12/13 mutational status interact on the outcome of patients with mCRC receiving cetuximab-based first-line therapy. Left-sided primary tumor location might be a predictor of cetuximab efficacy.