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

Complete response of metastatic microsatellite-stable BRAF V600E colorectal cancer to first-line oxaliplatin-based chemotherapy and immune checkpoint blockade

The randomized METIMMOX trial (NCT03388190) examined if patients with previously untreated, unresectable abdominal metastases from microsatellite-stable (MSS) colorectal cancer (CRC) might benefit from potentially immunogenic, short-course oxaliplatin-based chemotherapy alternating with immune checkpoint blockade (ICB). Three of 38 patients assigned to this experimental treatment had metastases from BRAF-mutant MSS-CRC, in general a poor-prognostic subgroup explored here. The ≥70-year-old females presented with ascending colon adenocarcinomas with intermediate tumor mutational burden (6.2-11.8 mutations per megabase). All experienced early disappearance of the primary tumor followed by complete response of all overt metastatic disease, resulting in progression-free survival as long as 20-35 months. However, they encountered recurrence at previously unaffected sites and ultimately sanctuary organs, or as intrahepatic tumor evolution reflected in the terminal loss of initially induced T-cell clonality in liver metastases. Yet, the remarkable first-line responses to short-course oxaliplatin-based chemotherapy alternating with ICB may offer a novel therapeutic option to a particularly hard-to-treat MSS-CRC subgroup.

Microsatellite instability should not determine candidacy for cytoreductive surgery and hyperthermic intraperitoneal chemoperfusion in patients with peritoneal metastases from colorectal cancer

INTRODUCTION

Cytoreductive surgery and hyperthermic intraperitoneal chemoperfusion (CRS+/-HIPEC) is a multimodal therapeutic option for the management of peritoneal metastases (PM). Treatment outcomes for colorectal cancer (CRC) PM patients undergoing CRS+/-HIPEC with microsatellite instability (MSI) remains unknown. We examined the patient characteristics and outcomes in patients with MSI CRC following CRS+/-HIPEC.

METHODS

This was a retrospective cohort study of a prospectively maintained database of all CRC PM patients undergoing CRS+/-HIPEC (2010-2020). Categorical and continuous variables were analyzed using the chi square test and independent samples t-test, respectively. Survival was evaluated with the Kaplan-Meier analysis.

RESULTS

There were 324 patients diagnosed with CRC PM undergoing CRS+/-HIPEC (MSI n=23, microsatellite stable (MSS) n=301). There was no statistically significant difference in patient demographics, tumor characteristics, or perioperative factors between the two groups. There was a trend towards improved survival in the MSI group with a median OS of 96.7 month compared to patients with MSS disease (median OS 51.4 months, p=0.10). Patients with MSI demonstrated median PFS 8.5 months compared to 11.4 months in the MSS cohort (p=0.28).

CONCLUSION

Patients with CRC PM, regardless of MSI or MSS status, demonstrate similar OS and PFS after CRS+/-HIPEC. MSI status should not change a patient's candidacy for CRS+/-HIPEC.

Survival of Patients with Deficient Mismatch Repair Versus Proficient Mismatch Repair Metastatic Colorectal Cancer Receiving Curative-Intent Local Treatment of Metastases in a Nationwide Cohort

BACKGROUND

It is unclear whether curative-intent local therapy of metastases is of similar benefit for the biological distinct subgroup of patients with deficient mismatch repair (dMMR) metastatic colorectal cancer (mCRC) compared with proficient mismatch repair (pMMR) mCRC.

PATIENTS AND METHODS

In this nationwide study, recurrence-free (RFS) and overall survival (OS) were analyzed in patients with dMMR versus pMMR mCRC who underwent curative-intent local treatment of metastases between 2015 and 2018. Subgroup analyses were performed for resection of colorectal liver metastases (CRLM) and cytoreductive surgery ± hyperthermic intraperitoneal chemotherapy (CRS ± HIPEC). Multivariable regression was conducted.

RESULTS

Median RFS was 11.1 months [95% confidence interval (CI) 8.5-41.1 months] for patients with dMMR tumors compared with 8.9 months (95% CI 8.1-9.8 months) for pMMR tumors. Two-year RFS was higher in patients with dMMR versus pMMR (43% vs. 21%). Results were similar within subgroups of local treatment (CRLM and CRS ± HIPEC). Characteristics differed significantly between patients with dMMR and pMMR mCRC; however, multivariable analysis continued to demonstrate dMMR as independent factor for improved RFS [hazard ratio (HR): 0.57, 95% CI 0.38-0.87]. Median OS was 33.3 months for dMMR mCRC compared with 43.5 months for pMMR mCRC, mainly due to poor survival of patients with dMMR in cases of recurrence in the preimmunotherapy era.

CONCLUSION

Patients with dMMR eligible for curative-intent local treatment of metastases showed a comparable to more favorable RFS compared with patients with pMMR, with a clinically relevant proportion of patients remaining free of recurrence. This supports local treatment as a valuable treatment option in patients with dMMR mCRC and can aid in shared decision-making regarding upfront local therapy versus immunotherapy.

Prognostic value of Lynch syndrome, BRAFV600E , and RAS mutational status in dMMR/MSI-H metastatic colorectal cancer in a pooled analysis of Dutch and French cohorts

BACKGROUND

Current knowledge on prognostic biomarkers (especially BRAFV600E /RAS mutations) in metastatic colorectal cancer (mCRC) is mainly based on mCRC patients with proficient mismatch repair (pMMR) tumors. It is uncertain whether these biomarkers have the same prognostic value in mCRC patients with deficient mismatch repair (dMMR) tumors.

METHODS

This observational cohort study combined a population-based Dutch cohort (2014-2019) and a large French multicenter cohort (2007-2017). All mCRC patients with a histologically proven dMMR tumor were included.

RESULTS

In our real-world data cohort of 707 dMMR mCRC patients, 438 patients were treated with first-line palliative systemic chemotherapy. Mean age of first-line treated patients was 61.9 years, 49% were male, and 40% had Lynch syndrome. BRAFV600E mutation was present in 47% of tumors and 30% harbored a RAS mutation. Multivariable regression analysis on OS showed significant hazard rates (HR) for known prognostic factors as age and performance status, however showed no significance for Lynch syndrome (HR: 1.07, 95% CI: 0.66-1.72), BRAFV600E mutational status (HR: 1.02, 95% CI: 0.67-1.54), and RAS mutational status (HR: 1.01, 95% CI: 0.64-1.59), with similar results for PFS.

CONCLUSION

BRAFV600E and RAS mutational status are not associated with prognosis in dMMR mCRC patients, in contrast to pMMR mCRC patients. Lynch syndrome is also not an independent prognostic factor for survival. These findings underline that prognostic factors of patients with dMMR mCRC are different of those with pMMR, which could be taken into consideration when prognosis is used for clinical decision-making in dMMR mCRC patients and underline the complex heterogeneity of mCRC.

The Role of Targeted Therapy in the Multi-Disciplinary Approach to Colorectal Liver Metastasis

Colorectal cancer (CRC) is the second most common cause of cancer-related mortality in the United States. Among newly diagnosed patients with CRC, 20% will present with metastatic disease and another 25% will develop metastases. The surgical resection of the primary tumor and metastatic disease sites confers the best chance at long-term survival. Unfortunately, many patients will recur after resection or present with unresectable disease. As such, metastatic CRC is commonly treated with a combination of surgery, systemic therapy, and/or liver-directed therapies. Despite best efforts, 5-year survival for unresectable metastatic CRC is only about 20%. CRC is a heterogeneous disease and the underlying genetic differences inform behavior, treatment strategy, and prognosis. Given the limitations of cytotoxic chemotherapy and the growing role of molecular profiling, research has focused on identifying and developing targeted therapies. We herein review how genetic profiling informs prognosis, crucial cell-signaling pathways that play a role in CRC carcinogenesis, and currently approved targeted therapies for metastatic CRC.

Impact of Primary Tumor Location and Genomic Alterations on Survival Following Cytoreductive Surgery and Hyperthermic Intraperitoneal Chemoperfusion for Colorectal Peritoneal Metastases

BACKGROUND

Colorectal cancer leads to peritoneal metastases (CRPM) in 10% of cases. Cytoreductive surgery with hyperthermic intraperitoneal chemoperfusion (CRS-HIPEC) improves survival. Primary tumor location and abnormalities in RAS, BRAF, and mismatch repair/microsatellite stability (MMR/MSI) may affect post-CRS-HIPEC survival, but studies have not been consistent. We estimated the effects of primary tumor site and genomic alterations on post-CRS-HIPEC survival.

METHODS

This retrospective cohort study included CRS-HIPEC cases for CRPM at a high-volume center from 2001 to 2020. Next-generation sequencing and microsatellite testing defined the RAS, BRAF, and MMR/MSI genotypes. Adjusted effects of tumor sidedness and genomics on survival were evaluated using a multivariable Cox proportional hazards model. We analyzed these variables' effects on progression-free survival and the effects of immune checkpoint-inhibitors.

RESULTS

A total of 250 patients underwent CRS-HIPEC with testing for RAS, BRAF, and MMR/MSI; 50.8% of patients were RAS-mutated, 12.4% were BRAF-mutated, and 6.8% were deficient-MMR/MSI-high (dMMR/MSI-H). Genomic alterations predominated in right-sided cancers. After adjustment for comorbidities and oncological and perioperative variables, rectal origin [hazard ratio (HR) 1.9, p = 0.01], RAS mutation (HR 1.6, p = 0.01), and BRAF mutation (HR 1.7, p = 0.05) were associated with worse survival. RAS mutation was also associated with shorter progression-free survival (HR 1.6, p = 0.01 at 6 months post-operatively), and dMMR/MSI-H status was associated with superior survival (HR 0.3, p = 0.01 at 2 years). dMMR/MSI-H patients receiving immune checkpoint-inhibitors trended toward superior survival.

CONCLUSIONS

Rectal origin, RAS mutations, and BRAF mutations are each associated with poorer survival after CRS-HIPEC for CRPM. Patients with CRPM and dMMR/MSI-H status have superior survival. Further research should evaluate benefits of immune checkpoint-inhibitors in this subgroup.

Immune checkpoint blockade therapy for BRAF mutant metastatic colorectal cancer: the efficacy, new strategies, and potential biomarkers

BRAF mutant metastatic colorectal cancer has long been considered a tumor with a poor prognosis and a poor response to chemotherapy. Despite the efficacy of targeted therapy with multi-targeted blockade of the mitogen-activated protein kinase (MAPK) signaling pathway has brought a glimmer of hope to this group of patients, the need to improve treatment efficacy remains unmet, especially for the microsatellite stability/DNA proficient mismatch repair (MSS/pMMR) subtype. BRAF mutant colorectal cancer patients with high microsatellite instability/DNA deficient mismatch repair (MSI-H/dMMR) have high tumor mutation burden and abundant neoantigen, who are deemed as ones that could receive expected efficacy from immunotherapy. Generally, it is believed that MSS/pMMR colorectal cancer is an immunologically "cold" tumor that is insensitive to immunotherapy. However, targeted therapy combined with immune checkpoint blockade therapy seems to bring light to BRAF mutant colorectal cancer patients. In this review, we provide an overview of clinical efficacy and evolving new strategies concerning immune checkpoint blockade therapy for both MSI-H/dMMR and MSS/pMMR BRAF mutant metastatic colorectal cancer and discuss the potential biomarkers in the tumor immune microenvironment for predicting immunotherapeutic response in BRAF mutant colorectal cancer.

Development and validation of a nomogram for predicting metachronous peritoneal metastasis in colorectal cancer: A retrospective study

BACKGROUND

Peritoneal metastasis (PM) after primary surgery for colorectal cancer (CRC) has the worst prognosis. Prediction and early detection of metachronous PM (m-PM) have an important role in improving postoperative prognosis of CRC. However, commonly used imaging methods have limited sensitivity to detect PM early. We aimed to establish a nomogram model to evaluate the individual probability of m-PM to facilitate early interventions for high-risk patients.

AIM

To establish and validate a nomogram model for predicting the occurrence of m-PM in CRC within 3 years after surgery.

METHODS

We used the clinical data of 878 patients at the Second Hospital of Jilin University, between January 1, 2014 and January 31, 2019. The patients were randomly divided into training and validation cohorts at a ratio of 2:1. The least absolute shrinkage and selection operator (LASSO) regression was performed to identify the variables with nonzero coefficients to predict the risk of m-PM. Multivariate logistic regression was used to verify the selected variables and to develop the predictive nomogram model. Harrell’s concordance index, receiver operating characteristic curve, Brier score, and decision curve analysis (DCA) were used to evaluate discrimination, distinctiveness, validity, and clinical utility of this nomogram model. The model was verified internally using bootstrapping method and verified externally using validation cohort.

RESULTS

LASSO regression analysis identified six potential risk factors with nonzero coefficients. Multivariate logistic regression confirmed the risk factors to be independent. Based on the results of two regression analyses, a nomogram model was established. The nomogram included six predictors: Tumor site, histological type, pathological T stage, carbohydrate antigen 125, v-raf murine sarcoma viral oncogene homolog B mutation and microsatellite instability status. The model achieved good predictive accuracy on both the training and validation datasets. The C-index, area under the curve, and Brier scores were 0.796, 0.796 [95% confidence interval (CI) 0.735-0.856], and 0.081 for the training cohort and 0.782, 0.782 (95%CI 0.690-0.874), and 0.089 for the validation cohort, respectively. DCA showed that when the threshold probability was between 0.01 and 0.90, using this model to predict m-PM achieved a net clinical benefit.

CONCLUSION

We have established and validated a nomogram model to predict m-PM in patients undergoing curative surgery, which shows good discrimination and high accuracy.

Clinicopathological characteristics of high microsatellite instability/mismatch repair-deficient colorectal cancer: A narrative review

Colorectal cancers (CRCs) with high microsatellite instability (MSI-H) and deficient mismatch repair (dMMR) show molecular and clinicopathological characteristics that differ from those of proficient mismatch repair/microsatellite stable CRCs. Despite the importance of MSI-H/dMMR status in clinical decision making, the testing rates for MSI and MMR in clinical practice remain low, even in high-risk populations. Additionally, the real-world prevalence of MSI-H/dMMR CRC may be lower than that reported in the literature. Insufficient MSI and MMR testing fails to identify patients with MSI-H/dMMR CRC, who could benefit from immunotherapy. In this article, we describe the current knowledge of the clinicopathological features, molecular landscape, and radiomic characteristics of MSI-H/dMMR CRCs. A better understanding of the importance of MMR/MSI status in the clinical characteristics and prognosis of CRC may help increase the rates of MMR/MSI testing and guide the development of more effective therapies based on the unique features of these tumors.

Correlation of Immunological and Histopathological Features with Gene Expression-Based Classifiers in Colon Cancer Patients

The purpose of this study was to evaluate the association between four distinct histopathological features: (1) tumor infiltrating lymphocytes, (2) mucinous differentiation, (3) tumor-stroma ratio, plus (4) tumor budding and two gene expression-based classifiers—(1) consensus molecular subtypes (CMS) plus (2) colorectal cancer intrinsic subtypes (CRIS). All four histopathological features were retrospectively scored on hematoxylin and eosin sections of the most invasive part of the primary tumor in 218 stage II and III colon cancer patients from two independent cohorts (AMC-AJCC-90 and AC-ICAM). RNA-based CMS and CRIS assignments were independently obtained for all patients. Contingency tables were constructed and a χ2 test was used to test for statistical significance. Odds ratios with 95% confidence intervals were calculated. The presence of tumor infiltrating lymphocytes and a mucinous phenotype (>50% mucinous surface area) were strongly correlated with CMS1 (p < 0.001 and p = 0.008) and CRIS-A (p = 0.006 and p < 0.001). The presence of mucus (≥ 10%) was associated with CMS3: mucus was present in 64.1% of all CMS3 tumors (p < 0.001). Although a clear association between tumor-stroma ratio and CMS4 was established in this study (p = 0.006), still 32 out of 61 (52.5%) CMS4 tumors were scored as stroma-low, indicating that CMS4 tumors cannot be identified solely based on stromal content. Higher budding counts were seen in CMS4 and CRIS-B tumors (p = 0.045 and p = 0.046). No other associations of the measured parameters were seen for any of the other CRIS subtypes. Our analysis revealed clear associations between histopathologic features and CMS or CRIS subtypes. However, identification of distinct molecular subtypes solely based on histopathology proved to be infeasible. Combining both molecular and morphologic features could potentially improve patient stratification.

Assessing Oncologists' Adoption of Biomarker Testing in Metastatic Colorectal Cancer Using Real-World Data

BACKGROUND

Despite national guideline recommendations for universal biomarker testing (KRAS, NRAS, BRAF, and mismatch repair and microsatellite instability [MMR/MSI]) in all patients with metastatic colorectal cancer (mCRC), little is known regarding adherence to these recommendations in routine practice.

METHODS

We retrospectively reviewed patients with mCRC diagnosed between January 1, 2013, and December 27, 2018, from a de-identified electronic health record-derived database. We analyzed disparities in KRAS, NRAS, BRAF, and MMR/MSI testing by race, age, sex, and insurance status using χ2 tests and t tests. We evaluated changes in biomarker testing over time with attention to changes around dates of landmark publications and guideline updates using χ2 tests and Cochran-Armitage tests.

RESULTS

A total of 20 333 patients were identified of which 66.6% had test results for any biomarker. Rates of test results for all 4 biomarkers statistically significantly increased over time (P < .001). However, as of June 30, 2018, the rate of test results was only 46% for NRAS, 56% for KRAS, and 46% for BRAF. As of December 31, 2017, the rate of MMR/MSI testing was 59%. Higher documented testing rates were associated with younger age, lower Eastern Cooperative Oncology Group performance status, and commercial insurance. There were no clinically meaningful and/or statistically significant differences in documented testing rates by tumor sidedness, race, sex, or initial stage.

CONCLUSIONS

Increased rates of documented testing for NRAS, BRAF, and MMR/MSI in mCRC was seen between 2013 and 2018 reflecting adoption of guideline recommendations. However, the rate of documented testing remains lower than expected and warrants additional research to understand the extent to which this may represent a clinical practice quality concern.

Stage-dependent prognostic shift in mismatch repair-deficient tumors: Assessing patient outcomes in stage II and III colon cancer

Introduction

Deficient mismatch repair (dMMR) or high microsatellite instability (MSI-H) is associated with an improved prognosis in colon cancer stage II but poor prognosis in stage IV colon cancer. The clinical significance of dMMR in colon cancer stage III is not established.

Methods

Tissue microarrays (TMAs) from 544 patients with colon cancer stage II and III with clinicopathological and survival data were stained for mismatch repair (MMR) proteins, CD3, CD8, and programmed death ligand-1 (PD-L1), and programmed death ligand- 1 (PD-L1). Patient outcomes were reviewed.

Results

In stage III colon cancer, dMMR was a marker of poor disease-free survival (DFS) (Kaplan–Meier, mean survival in months: dMMR: 28.76 (95% CI 18.46–39.05) vs. pMMR 40.91 (37.20–44.63), p=0.014, multivariate Cox regression: hazard ratio (HR) 4.17 (95% CI 2.02–8.61), p<0.001). In stage II colon cancer, there was a tendency toward improved DFS for dMMR patients (dMMR: 57.14 (95% CI 54.66–59.62) vs. pMMR 53.54 (95% CI 51.48–55.60), p=0.015, multivariate Cox regression HR 0.24 (95% CI 0.06-1.04), p=0.057). CD3, CD8, and PD-L1 expression was not associated with prognosis of dMMR patients. Multivariate Cox regression analysis showed a significant interaction between the MMR phenotype and stage (p=0.001).

Conclusion

dMMR is associated with an improved prognosis in stage II colon cancer but is no longer associated with a favorable prognosis in stage III colon cancer.

SPTSSA Is a Prognostic Marker for Glioblastoma Associated with Tumor-Infiltrating Immune Cells and Oxidative Stress

Background. SPTSSA encodes the small subunit A of serine palmitoyltransferase. It catalyzes the formation of sphingoid long-chain base backbone of sphingolipids. Its role in glioma prognosis and tumor-infiltrating immune cells remains unclear. Methods. We analyzed SPTSSA expression and association with clinical prognosis using GEPIA and CGGA database. Then, GSEA was performed to identify relevant biological functions of SPTSSA. The correlations between SPTSSA expression and tumor immune infiltrates were investigated using CIBERSORT and TIMER. Finally, IHC and IF were performed to confirm the value of prognosis and the correlation with immune infiltration. Results. SPTSSA expression was significantly upregulated in diffuse glioma compared to normal tissues and associated with poor survival in GEPIA and CGGA database. Then, we identified biological processes and signaling pathways associated with SPTSSA expression. The result showed that SPTSSA enriched in the GO term like oxidative stress. Finally, we showed that SPTSSA expression was significantly associated with tumor-infiltrating immune cells and overall survival via IHC. Conclusion. These findings suggest that SPTSSA expression might be used as a prognostic biomarker for glioma and potential target for novel glioma therapy.

Systematic review of randomised clinical trials and observational studies for patients with RAS wild-type or BRAFV600E-mutant metastatic and/or unresectable colorectal cancer

Approximately 8-10% of metastatic colorectal cancer (mCRC) tumours harbour BRAF^V600E mutations. Eleven randomised controlled trials (RCTs) and 24 non-RCTs were identified. Seven studies evaluated BRAF inhibitors. Single-agent BRAF inhibitors had minimal efficacy, whereas BRAF inhibitor plus anti-EGFR therapy improved outcomes. In BEACON CRC, overall survival (OS) was significantly longer for patients receiving encorafenib plus cetuximab ± binimetinib when compared with irinotecan/FOLFIRI plus cetuximab as second- and third-line therapy. Seven prospective non-RCTs reported worse OS and progression-free survival (PFS) for patients with BRAF^V600E-mutant vs BRAF wild-type mCRC. Eight RCTs reported that PFS and OS were generally shorter for patients with BRAF^V600E-mutant mCRC vs those with KRAS or RAS wild-type mCRC. Patients with BRAF^V600E-mutant mCRC have worse outcomes with conventional therapy vs patients with BRAF wild-type tumours. BRAF inhibitors in conjunction with anti-EGFR therapy improves outcomes for patients with BRAF^V600E-mutant mCRC vs conventional therapy or a BRAF inhibitor alone.

Impact of KRAS, BRAF and microsatellite instability status after cytoreductive surgery and HIPEC in a national cohort of colorectal peritoneal metastasis patients

BACKGROUND

Patients with metastatic colorectal cancer (mCRC) carrying BRAF (mutBRAF) or KRAS mutation (mutKRAS) have an inferior prognosis after liver or lung surgery, whereas the prognostic role in the context of peritoneal metastasis (PM) after cytoreductive surgery (CRS) and hyperthermic intraperitoneal chemotherapy (HIPEC) has been less investigated.

METHODS

In total, 257 patients with non-appendiceal PM-CRC were included from the Norwegian National Unit for CRS-HIPEC.

RESULTS

In total, 180 patients received CRS-HIPEC with Mitomycin C, 77 patients received palliative surgery only. In the CRS-HIPEC group, mutBRAF was found in 24.7%, mutKRAS 33.9% and double wild-type 41.4% without differences in survival. MSI was found in 29.3% of mutBRAF cases. Patients with mutBRAF/MSI had superior 5-year survival compared to mutBRAF with MSS (58.3% vs 25.2%, P = 0.022), and better 3-year disease-free survival (DFS) compared to mutKRAS (48.6% vs 17.2%, P = 0.049). Peritoneal Cancer Index and the number of lymph node metastasis were prognostic for OS, and the same two, location and gender prognostic for DFS in multivariate analysis.

CONCLUSIONS

PM-CRC with CRS-HIPEC patients has a surprisingly high proportion of mutBRAF (24.7%). Survival was similar comparing mutBRAF, mutKRAS and double wild-type cases, whereas a small subgroup with mutBRAF and MSI had better survival. Patients with mutBRAF tumours and limited PM should be considered for CRS-HIPEC.

KRAS-G12C Mutation in One Real-Life and Three Population-Based Nordic Cohorts of Metastatic Colorectal Cancer

Background

KRAS mutations, present in over 40% of metastatic colorectal cancer (mCRC), are negative predictive factors for anti-EGFR therapy. Mutations in KRAS-G12C have a cysteine residue for which drugs have been developed. Published data on this specific mutation are conflicting; thus, we studied the frequency and clinical characteristics in a real-world and population-based setting.

Methods

Patients from three Nordic population-based cohorts and the real-life RAXO-study were combined. RAS and BRAF tests were performed in routine healthcare, except for one cohort. The dataset consisted of 2,559 patients, of which 1,871 could be accurately classified as KRAS, NRAS, and BRAF-V600E. Demographics, treatments, and outcomes were compared using logistic regression. Overall survival (OS) was estimated with Kaplan–Meier, and differences were compared using Cox regression, adjusted for baseline factors.

Results

The KRAS-G12C frequency was 2%–4% of all tested in the seven cohorts (mean 3%) and 4%–8% of KRAS mutated tumors in the cohorts (mean 7%). Metastasectomies and ablations were performed more often (38% vs. 28%, p = 0.040), and bevacizumab was added more often (any line 74% vs. 59%, p = 0.007) for patients with KRAS-G12C- vs. other KRAS-mutated tumors, whereas chemotherapy was given to similar proportions. OS did not differ according to KRAS mutation, neither overall (adjusted hazard ratio (HR) 1.03; 95% CI 0.74–1.42, reference KRAS-G12C) nor within treatment groups defined as “systemic chemotherapy, alone or with biologics”, “metastasectomy and/or ablations”, or “best supportive care”, RAS and BRAF wild-type tumors (n = 548) differed similarly to KRAS-G12C, as to other KRAS- or NRAS-mutated (n = 66) tumors.

Conclusions

In these real-life and population-based cohorts, there were no significant differences in patient characteristics and outcomes between patients with KRAS-G12C tumors and those with other KRAS mutations. This contrasts with the results of most previous studies claiming differences in many aspects, often with worse outcomes for those with a KRAS-G12C mutation, although not consistent. When specific drugs are developed, as for this mutation, differences in outcome will hopefully emerge.

The molecular characteristics of high-grade gastroenteropancreatic neuroendocrine neoplasms

High-grade (HG) gastroenteropancreatic (GEP) neuroendocrine neoplasms (NEN) are rare but have a very poor prognosis and represent a severely understudied class of tumours. Molecular data for HG GEP-NEN are limited, and treatment strategies for the carcinoma subgroup (HG GEP-NEC) are extrapolated from small-cell lung cancer (SCLC). After pathological re-evaluation, we analysed DNA from tumours and matched blood samples from 181 HG GEP-NEN patients; 152 neuroendocrine carcinomas (NEC) and 29 neuroendocrine tumours (NET G3). Based on the sequencing of 360 cancer-related genes, we assessed mutations and copy number alterations (CNA). For NEC, frequently mutated genes were TP53 (64%), APC (28%), KRAS (22%) and BRAF (20%). RB1 was only mutated in 14%, but CNAs affecting RB1 were seen in 34%. Other frequent copy number losses were ARID1A (35%), ESR1 (25%) and ATM (31%). Frequent amplifications/gains were found in MYC (51%) and KDM5A (45%). While these molecular features had limited similarities with SCLC, we found potentially targetable alterations in 66% of the NEC samples. Mutations and CNA varied according to primary tumour site with BRAF mutations mainly seen in colon (49%), and FBXW7 mutations mainly seen in rectal cancers (25%). Eight out of 152 (5.3%) NEC were microsatellite instable (MSI). NET G3 had frequent mutations in MEN1 (21%), ATRX (17%), DAXX, SETD2 and TP53 (each 14%). We show molecular differences in HG GEP-NEN, related to morphological differentiation and site of origin. Limited similarities to SCLC and a high fraction of targetable alterations indicate a high potential for better-personalized treatments.

Mismatch Repair Status in Patient-Derived Colorectal Cancer Organoids Does Not Affect Intrinsic Tumor Cell Sensitivity to Systemic Therapy

DNA mismatch repair deficiency (dMMR) in metastatic colorectal cancer (mCRC) is associated with poor survival and a poor response to systemic treatment. However, it is unclear whether dMMR results in a tumor cell-intrinsic state of treatment resistance, or whether alternative mechanisms play a role. To address this, we generated a cohort of MMR-proficient and -deficient Patient-Derived Organoids (PDOs) and tested their response to commonly used drugs in the treatment of mCRC, including 5-fluorouracil (5-FU), oxaliplatin, SN-38, binimetinib, encorafenib, and cetuximab. MMR status did not correlate with the response of PDOs to any of the drugs tested. In contrast, the presence of activating mutations in the KRAS and BRAF oncogenes was significantly associated with resistance to chemotherapy and sensitivity to drugs targeting oncogene-activated pathways. We conclude that mutant KRAS and BRAF impact the intrinsic sensitivity of tumor cells to chemotherapy and targeted therapy. By contrast, tumor cell-extrinsic mechanisms-for instance signals derived from the microenvironment-must underlie the association of MMR status with therapy response. Future drug screens on rationally chosen cohorts of PDOs have great potential in developing tailored therapies for specific CRC subtypes including, but not restricted to, those defined by BRAF/KRAS and MMR status.

Prognostic role of tumour-infiltrating lymphocytes and macrophages in relation to MSI, CDX2 and BRAF status: a population-based study of metastatic colorectal cancer patients

BACKGROUND

Tumour-infiltrating CD3, CD8 lymphocytes and CD68 macrophages are associated with favourable prognosis in localised colorectal cancer, but the effect in metastatic colorectal cancer (mCRC) is not established.

METHODS

A Scandinavian population-based cohort of non-resectable mCRC patients was studied. Tissue microarrays (n = 460) were stained with CD3, CD8 and CD68 using fluorescence-based multiplex immunohistochemistry. Associations with clinicopathological variables, overall survival (OS) and progression-free survival were estimated.

RESULTS

Two-thirds of microsatellite instable (MSI) and one-fourth of microsatellite stable (MSS) tumours displayed the highest quartile density of CD8. For CD3 high vs low cases, median OS was 20 vs 16 months (HR: 0.76, 95% CI: 0.59, 0.76, p = 0.025) with 3-year OS of 27 vs 13%. For CD68 high vs low cases, median OS was 23 vs 15 months (HR: 0.69, 95% CI: 0.54, 0.88, p = 0.003) with 3-year OS of 28 vs 12%. MSI, BRAF mutation and CDX2 loss were negative prognostic markers independent of tumour immune infiltration.

CONCLUSIONS

In mCRC, high lymphocyte infiltration was found in proportions of MSI and MSS tumours-potential subgroups of immunotherapy response. Tumour-infiltrating CD3 lymphocytes and CD68 macrophages were associated with median and long-term survival. MSI was a significant negative prognostic marker despite high immunogenicity.

MTOR/4EBP1 signaling and MMR status in colorectal cancer: New correlations and arising perspectives

This is the first study aiming to investigate mTOR signaling and its relation to mismatch repair status (MMR status) in colorectal cancer (CRC). MMR status and the phosphorylated proteins, pmTOR and p4EBP1, have been immunohistochemically analyzed in 108 formalin-fixed, paraffin-embedded CRC specimens. The correlations between them and with clinicopathological data, MAPK pathway (KRAS, NRAS, BRAF) as well as their impact on patients' overall survival have been statistically analyzed. Our results indicated that positive pmTOR expression was significantly associated with KRAS mutations (p = 0.004). From multivariate survival analysis, only p4EBP1 expression emerged as independent adverse prognostic factor for overall survival (HR, 3.322; 95%CI, 1.110-9.945; p = 0.032). Furthermore, MMR deficient carcinomas tend to express low p4EBP1 protein levels (p = 0.002). A survival analysis stratified by MMR status and p4EBP1 expression, showed that MMR proficient tumours with high p4EBP1 expression had the worst overall survival compared with the other examined subgroups (p = 0.019). In conclusion, MAPK and PI3k/Akt pathways seem to be simultaneously overactivated in CRC. P4EBP1 could be used as a prognostic biomarker. By further analyzing the significant association between MMR status and p4EBP1 expression, we suggest that MMR deficient tumours could represent a subpopulation most likely to derive treatment benefit from mTOR inhibition.

BRAF V600E Mutation in First-Line Metastatic Colorectal Cancer: An Analysis of Individual Patient Data From the ARCAD Database

BACKGROUND

First-line therapeutic strategies for patients with BRAFV600E-mutated (BRAFmt) metastatic colorectal cancer (mCRC) mainly rely on subgroup analyses from randomized controlled trials (RCTs). We aimed to assess the prognostic and predictive impact of BRAFmt on the efficacy of targeted therapies with first-line chemotherapy.

METHODS

Individual patient data from first-line RCTs with BRAF and KRAS status data in the ARCAD database were pooled. Progression-free survival and overall survival (OS) were assessed using Kaplan-Meier and Cox models. Outcomes were compared between treatment groups that were concurrently randomly assigned whenever possible.

RESULTS

A total of 6391 patients from 10 RCTs were included: 573 BRAFmt (9.0%), 2059 KRASmt (32.2%), and 3759 double wild type (58.8%). BRAFmt mCRC patients experienced statistically significantly poorer OS than those with KRASmt (adjusted hazard ratio [HRadj] = 1.46, 95% confidence interval [CI] = 1.30 to 1.64) and patients with double wild-type tumors (HRadj = 2.14, 95% CI = 1.94 to 2.36). Anti-EGFR agents did not improve progression-free survival or OS of BRAFmt mCRC patients, based on 4 RCTs testing chemotherapy with or without anti-epidermal growth factor receptor (anti-EGFR) (HRadj = 0.96, 95% CI = 0.71 to 1.30; and HRadj = 0.85, 95% CI = 0.66 to 1.14, respectively).

CONCLUSIONS

Our data suggest that the addition of anti-EGFR agents to chemotherapy is ineffective as first-line treatment for BRAFmt mCRC patients.

Perspectives on Immunotherapy of Metastatic Colorectal Cancer

Colorectal cancer, especially liver metastasis, is still a challenge worldwide. Traditional treatment such as surgery, chemotherapy and radiotherapy have been difficult to be further advanced. We need to develop new treatment methods to further improve the poor prognosis of these patients. The emergence of immunotherapy has brought light to mCRC patients, especially those with dMMR. Based on several large trials, some drugs (pembrolizumab, nivolumab) have been approved by US Food and Drug Administration to treat the patients diagnosed with dMMR tumors. However, immunotherapy has reached a bottleneck for other MSS tumors, with low response rate and poor PFS and OS. Therefore, more clinical trials are underway toward mCRC patients, especially those with MSS. This review is intended to summarize the existing clinical trials to illustrate the development of immunotherapy in mCRC patients, and to provide a new thinking for the direction and experimental design of immunotherapy in the future.

Clinical Value of Consensus Molecular Subtypes in Colorectal Cancer: A Systematic Review and Meta-Analysis

Background

The consensus molecular subtypes (CMSs) of colorectal cancer (CRC) capture tumor heterogeneity at the gene-expression level. Currently, a restricted number of molecular features are used to guide treatment for CRC. We summarize the evidence on the clinical value of the CMSs.

Methods

We systematically identified studies in Medline and Embase that evaluated the prognostic and predictive value of CMSs in CRC patients. A random-effect meta-analysis was performed on prognostic data. Predictive data were summarized.

Results

In local disease, CMS4 tumors were associated with worse overall survival (OS) compared with CMS1 (hazard ratio [HR] = 3.28, 95% confidence interval = 1.27 to 8.47) and CMS2 cancers (HR = 2.60, 95% confidence interval = 1.93 to 3.50). In metastatic disease, CMS1 consistently had worse survival than CMS2-4 (OS HR range = 0.33-0.55; progression-free survival HR range = 0.53-0.89). Adjuvant chemotherapy in stage II and III CRC was most beneficial for OS in CMS2 and CMS3 (HR range = 0.16-0.45) and not effective in CMS4 tumors. In metastatic CMS4 cancers, an irinotecan-based regimen improved outcome compared with oxaliplatin (HR range = 0.31-0.72). The addition of bevacizumab seemed beneficial in CMS1, and anti-epidermal growth factor receptor therapy improved outcome for KRAS wild-type CMS2 patients.

Conclusions

The CMS classification holds clear potential for clinical use in predicting both prognosis and response to systemic therapy, which seems to be independent of the classifier used. Prospective studies are warranted to support implementation of the CMS taxonomy in clinical practice.

Metastatic colorectal cancer: Advances in the folate-fluoropyrimidine chemotherapy backbone

Notwithstanding recent treatment advances in metastatic colorectal cancer (mCRC), chemotherapy with a combination of a fluoropyrimidine and a folate agent, often 5-fluorouracil (5-FU) and leucovorin, remains the backbone of treatment regimens for the majority of patients with mCRC. This is despite a recent focus on molecular-targeted treatments and patient stratification according to mutational status or expression levels of specific genes. Intracellular folate concentration was discovered to be pivotal in the cytotoxic efficacy of 5-FU, paving the way to the current standard combination therapy approach. Subsequent discovery that systemic chemotherapy agents, such as irinotecan and oxaliplatin, can further increase the efficacy of 5-FU-based treatments led to the development of several combination chemotherapy regimens, including FOLFOX, FOLFIRI and FOLFOXIRI. Subsequent efforts to optimise 5-FU-based treatments have focused on 5-FU analogues, initially capecitabine and the combination drug tegafur/gimeracil/oteracil (S-1) and then TAS-102, which has recently been evaluated in phase 3 clinical trials for refractory colorectal cancer. Further approaches taken to improve the efficacy of 5-FU chemotherapy regimens have focused on optimising the route and dosing schedules and regulating folate metabolism. Pharmacokinetic variability caused by the requirement for metabolic conversion of leucovorin has been central to recent research, and the development of agents such as arfolitixorin which bypass the need for metabolic conversion remains promising for future therapeutic candidates. In this review, we summarise the evidence leading to the current treatment regimens employing 5-FU and leucovorin, focusing on recent approaches taken to optimise and refine treatments to improve clinical outcomes in patients with mCRC.

Systematic Review of Treatments for Colorectal Metastases in Elderly Patients to Guide Surveillance Cessation Following Hepatic Resection for Colorectal Liver Metastases

BACKGROUND

Although included in surveillance programmes for colorectal cancer (CRC) metastases, elderly patients are susceptible to declines in health and quality of life that may render them unsuitable for further surveillance. Deciding when to cease surveillance is challenging.

METHODS

There are no publications focused on surveillance of elderly patients for CRC metastases. A systematic review of studies reporting treatment outcomes for CRC metastases in elderly patients was performed to assess the risk-benefit balance of the key objectives of surveillance; detecting and treating CRC metastases.

RESULTS

Sixty-eight eligible studies reported outcomes for surgery and chemotherapy in the elderly. Liver resections and use of chemotherapy, including biologics, are more conservative and have poorer outcomes in the elderly compared with younger patients. Selected studies demonstrated poorer quality-of-life (QoL) following surgery and chemotherapy. Studies of ablation in elderly patients are limited.

DISCUSSION

The survival benefit of treating CRC metastases with surgery or chemotherapy decreases with advancing age and QoL may decline in the elderly. The relatively lower efficacy and detrimental QoL impact of multimodal therapy options for detected CRC metastases in the elderly questions the benefit of surveillance in some elderly patients. Care of elderly patients should thus be customized based on their preference, formal geriatric assessment, natural life-expectancy, and the perceived risk-benefit balance of treating recurrent CRC metastases. Clinicians may consider surveillance cessation in patients aged 75 years and above if geriatric assessment is unsatisfactory, patients decline surveillance, or patient fitness deteriorates catastrophically.

Recent Advances in Our Knowledge of mCRC Tumor Biology and Genetics: A Focus on Targeted Therapy Development

Metastatic colorectal cancer (mCRC) remains a highly lethal malignancy although considerable progress has resulted from characterizing molecular alterations such as RAS mutation status and extent of microsatellite instability (MSI) to guide optimal use of available therapies. The availability of gene expression profiling, next generation sequencing technologies, proteomics analysis and other technologies provides high resolution information on individual tumors, including metastatic lesions to better define intra-tumor and inter-tumor heterogeneity. Recent literature applying this information to further customize personalized therapies is reviewed. Current biomarker-based stratification used to select optimal therapy that is personalized to the mutation profile of individual tumors is described. Recent literature using whole exome sequencing of metastatic lesions and primary CRC tumors and other advanced technologies to more fully elucidate the tumor biology specific to mCRC sub-types and to develop more precise therapies that improve outcomes is also reviewed.

A review of the sensitivity of metastatic colorectal cancer patients with deficient mismatch repair to standard-of-care chemotherapy and monoclonal antibodies, with recommendations for future research

In 5% of metastatic colorectal cancer (mCRC) patients, tumours display a deficient mismatch repair (dMMR) system. Immunotherapy is beneficial in dMMR mCRC patients and has recently been approved by the Food and Drug Administration for patients with unresectable or metastatic dMMR CRC. Although dMMR and proficient MMR (pMMR) CRC tumours are biologically distinct, they are commonly treated with the same chemotherapy and monoclonal antibodies. This includes dMMR mCRC patients who did not respond to immunotherapy (20-30%). However, it is unclear if these treatments are equally beneficial in dMMR mCRC. Of note, dMMR mCRC patients have a worse prognosis compared to pMMR, which may in part be caused by a lower response to treatment. To avoid unnecessary exposure to ineffective treatments and their associated toxicity, it is important to identify which systemic treatments are most beneficial in dMMR mCRC patients, thus improving their outcome. Indeed, future treatment strategies are likely to involve combinations of immunotherapy, chemotherapy and monoclonal antibodies. In this evidence-based review, we summarize clinical trials reporting treatment efficacy of different types of chemotherapy and monoclonal antibodies in dMMR mCRC patients. We also review the biological rationale behind a potential differential benefit of chemotherapy with or without monoclonal antibodies in dMMR mCRC patients. A barrier in the interpretation of preclinical results is the choice of model systems. They largely comprise traditional models, including cell lines and xenografts, rather than more representative models, such as patient-derived organoids. We provide concrete recommendations for clinical investigators and fundamental researchers to accelerate research regarding which systemic therapy is most effective in dMMR mCRC patients.

A phase 2 trial of trifluridine/tipiracil plus nivolumab in patients with heavily pretreated microsatellite-stable metastatic colorectal cancer

Background

Microsatellite‐stable (MSS) colorectal cancer (CRC) tends to be poorly immunogenic, with limited treatment options. In MSS CRC xenograft models, trifluridine/tipiracil (FTD/TPI) plus programed death 1 inhibitors resulted in synergistic antitumor activity and increased tumor immunogenicity. This phase 2 study evaluated FTD/TPI plus nivolumab in patients with MSS metastatic CRC.

Methods

This single‐arm, safety lead‐in study used a Simon's two‐stage design (enrolling 6 patients in the safety lead‐in, proceeding to stage 2 if ≥2 of the first 15 patients achieved a partial or complete response per immune‐related response criteria [irRC] within 6 months). Patients with histologically proven MSS mCRC, and disease progression after ≥2 prior chemotherapy regimens received FTD/TPI (35 mg/m² twice daily; days 1–5 and 8–12 every 28 days) plus nivolumab (3 mg/kg every 2 weeks).

Results

Between August 2016 and January 2017, 18 patients (50% men; median age 56.5 years) were enrolled; 72% had colon cancer and 56% had KRAS mutations. All patients received treatment (median, 2.5 cycles [range, 1–8]). No dose‐limiting toxicities were observed in the study. The most frequent adverse events (AEs) of any cause and grade were nausea (67%), diarrhea (61%), and neutropenia (50%); 13 patients (72%) experienced grade ≥3 AEs. No patients discontinued treatment because of AEs. No patient achieved a tumor response (either per Response Evaluation Criteria in Solid Tumors [RECIST] or irRC), and the study did not progress to the second stage. Stable disease was achieved in 8 patients per irRC and in 10 patients per RECIST. Median progression‐free survival was 2.2 months (95% CI, 1.8–6.0 months) per irRC and 2.8 months (95% CI, 1.8–5.1 months) per RECIST.

Conclusion

Patients with refractory MSS metastatic CRC failed to experience clinical benefit with FTD/TPI plus nivolumab, although safety data in this population indicated tolerability and feasibility of this combination.

Trial registration number

NCT02860546.

Precision Medicine for the Management of Therapy Refractory Colorectal Cancer

In this analysis, we examined the efficacy, feasibility, and limitations of molecular-based targeted therapies in heavily pretreated metastatic colorectal cancer (mCRC) patients after failure of all standard treatments. In this single-center, real-world retrospective analysis of our platform for precision medicine, we mapped the molecular profiles of 60 mCRC patients. Tumor samples of the patients were analyzed using next-generation sequencing panels of mutation hotspots, microsatellite instability testing, and immunohistochemistry. All profiles were reviewed by a multidisciplinary team to provide a targeted treatment recommendation after consensus discussion. In total, we detected 166 mutations in 53 patients. The five most frequently found mutations were TP53, KRAS, APC, PIK3CA, and PTEN. In 28 cases (47% of all patients), a molecularly targeted therapy could be recommended. Eventually, 12 patients (20%) received the recommended therapy. Six patients (10%) had a clinical benefit. The median time to treatment failure was 3.1 months. Our study demonstrates the feasibility and applicability of using targeted therapies in daily clinical practice for heavily pretreated mCRC patients. This could be used as a targeted treatment option in half of the patients.

BRAF Mutation in Colorectal Cancers: From Prognostic Marker to Targetable Mutation

Simple Summary

Colorectal cancer with a mutation in an oncogene BRAF has paid much attention, as it comprises a population with dismal prognosis since two decades ago. A series of research since then has successfully changed this malignancy to be treatable with specific treatment. Here we thoroughly overviewed the basic, translational and clinical studies on colorectal cancer with BRAF mutation from a physician’s viewpoint. Accumulating lines of evidence suggest that intervention of the trunk cellular growth signal transduction pathway, namely EGFR-RAS-RAF-MEK-ERK pathway, is a clue to controlling this disease. However, it is not so straightforward. Recent studies unveil the diverse and plastic nature of this signal transduction pathway. We will introduce our endeavor to conquer this condition, based on newly arriving datasets, and discuss how we could open the door to future development of CRC treatment.

Abstract

The Raf murine sarcoma viral oncogene homolog B (BRAF) mutation is detected in 8–12% of metastatic colorectal cancers (mCRCs) and is strongly correlated with poor prognosis. The recent success of the BEACON CRC study and the development of targeted therapy have led to the determination of BRAF-mutated mCRCs as an independent category. For nearly two decades, a growing body of evidence has established the significance of the BRAF mutation in the development of CRC. Herein, we overview both basic and clinical data relevant to BRAF-mutated CRC, mainly focusing on the development of treatment strategies. This review is organized into eight sections, including clinicopathological features, molecular features, prognosis, the predictive value of anti-epidermal growth factor receptor (EGFR) therapy, resistant mechanisms for BRAF-targeting treatment, the heterogeneity of the BRAF mutation, future perspectives, and conclusions. A characterization of the canonical mitogen-activated protein kinase (MAPK) pathway is essential for controlling this malignancy, and the optimal combination of multiple interventions for treatments remains a point of debate.

Contemporary treatment approaches for metastatic colorectal cancer driven by BRAF V600 mutations

The treatment of metastatic colorectal cancer (mCRC) harboring BRAF V600 mutations is challenging. These tumors are often refractory to standard treatment. Therefore, the patients may exhibit rapid clinical deterioration, depriving them of the chance to receive salvage therapy. In newly diagnosed patients with good performance status, the administration of an intensive chemotherapy regimen like FOLFOXIRI (5-fluorouracil, leucovorin, oxaliplatin, and irinotecan) along with the antiangiogenic agent bevacizumab can modify this aggressive behavior of the disease and improve patient clinical outcomes. The recently published results of the BEACON (Binimetinib, Encorafenib, and Cetuximab Combined to Treat BRAF-Mutant Colorectal Cancer) study demonstrated that a combination therapy consisting of BRAF, epidermal growth factor receptor, and mitogen-activated protein kinase kinase inhibitors could be a useful second-or third-line alternative. This review summarizes the current treatment strategies for BRAF-mutant mCRC.

Survival of patients with deficient mismatch repair metastatic colorectal cancer in the pre-immunotherapy era

Background

Metastatic colorectal cancer patients with deficient mismatch repair (dMMR mCRC) benefit from immunotherapy. Interpretation of the single-arm immunotherapy trials is complicated by insignificant survival data during systemic non-immunotherapy. We present survival data on a large, comprehensive cohort of dMMR mCRC patients, treated with or without systemic non-immunotherapy.

Methods

Two hundred and eighty-one dMMR mCRC patients (n = 54 from three prospective Phase 3 CAIRO trials; n = 227 from the Netherlands Cancer Registry). Overall survival was analysed from diagnosis of mCRC (OS), from initiation of first-line (OS1) and second-line (OS2) systemic treatment. Cox regression analysis examined prognostic factors. As comparison for OS 2746 MMR proficient mCRC patients were identified.

Results

Of 281 dMMR patients, 62% received first-line and 26% second-line treatment. Median OS was 16.0 months (13.8–19.6) with antitumour therapy and 2.5 months (1.8–3.5) in untreated patients. OS1 was 12.8 months (10.7–15.2) and OS2 6.2 months (5.4–8.9) in treated dMMR patients. Treated dMMR patients had a 7.6-month shorter median OS than pMMR patients.

Conclusion

Available data from immunotherapy trials lack a control arm with standard systemic treatment. Given the poor outcome compared to the immunotherapy results, our data strongly suggest a survival benefit of immunotherapy in dMMR mCRC patients.

Finding the hot spot: identifying immune sensitive gastrointestinal tumors

Although researchers have been trying to harness the immune system for over 100 years, the advent of immune checkpoint blockers (ICB) marks an era of significant clinical outcomes in various metastatic solid tumors, characterized by complete and durable responses. ICBs are monoclonal antibodies that target either of a pair of transmembrane molecules in tumors or T-cells involved in immune evasion. Currently 2 ICBs targeting the checkpoint program death 1 (PD-1), nivolumab and pembrolizumab, and one cytotoxic lymphocyte antigen-4 (CTLA-4) inhibitor (ipilimumab) are approved in gastrointestinal malignancies. We review herein the current evidence on predictive biomarkers for ICB response in gastrointestinal tumors. A review of literature based on the National Cancer Institute list of FDA-approved drugs for neoplasms and FDA-approved therapies at the FDA website was performed. An initial literature review was based on the American Association for Clinical Research meeting 2019, the American Society of Clinical Oncology meeting 2019 and the European Society of Medical Oncology 2019 proceedings. A systematic search of PubMed was performed involving MeSH browser terms such as biomarkers, immunotherapy, gastrointestinal diseases and neoplasms. When appropriate, American and British terms were used in the search. The most relevant predictor of response to ICBs is microsatellite instability (MSI) and the data is strongest for colorectal cancer. At least 3 prospective trials show evidence of PD-L1 as a predictive biomarker for ICB response in gastroesophageal malignancies. At least one prospective trial has described tumor mutational burden high (TMB-H), independent of MSI, as predictive of response in anal and biliary tract carcinomas. DNA Polymerase Epsilon (POLE) or delta (POL-D) mutations have been implicated in a subset of MSS colorectal cancer with TMB-H but this biomarker requires prospective validation. There is evolving data based on retrospective observations that gene alterations predicting acquired resistance and hyper-progression. Ongoing clinical research is assessing the role of the human microbiome and RNA-editing complex mutations as predictive biomarkers of response to ICBs. MSI has the strongest predictive power among current biomarkers for ICB response in gastrointestinal cancers. Data continue to accumulate from ongoing clinical trials and new biomarkers are emerging from pre-clinical studies, suggesting that drug combinations targeting pathways complimentary to the PD-1/PD-L1 axis inhibition will define a robust field of clinical research.

Population-based Screening for BRAF V600E in Metastatic Colorectal Cancer Reveals Increased Prevalence and Poor Prognosis

PURPOSE

BRAF ^V600E mutations portend poor prognosis in metastatic colorectal cancer (mCRC); however, the true prevalence and prognosis are unknown, as unwell patients may not undergo BRAF sequencing.

EXPERIMENTAL DESIGN

We reviewed a population-based cohort of 1,898 patients with colorectal cancer that underwent reflexive IHC mismatch repair (MMR) and BRAF ^V600E testing. Outcomes among IHC-detected BRAF ^V600E mCRC (BRAF _IHC) were compared with patients with next-generation sequencing (NGS)-identified BRAF ^V600E-mutated mCRC from two institutions (BRAF _NGS) with patients spanning from 2004 to 2018.

RESULTS

All-stage population prevalence of BRAF ^V600E was 12.5% (238/1,898) and did not differ between early and metastatic stages (P = 0.094). Prevalence among mCRC was 10.6% (61/575), of whom 51 (83.6%) were referred to oncology and 26 (42.6%) had NGS testing. BRAF _IHC had worse median overall survival (mOS) than BRAF _NGS [5.5 vs. 20.4 months; HR, 2.90; 95% confidence interval (CI), 1.89-4.45; P < 0.0001], which persisted in multivariate analysis (P < 0.0001). Across a combined NGS and IHC cohort, BRAF ^V600E tumors with deficient MMR showed worse mOS compared with MMR proficient tumors (8.9 vs. 17.2 months; HR, 1.46; 95% CI, 0.96-2.27; P = 0.043). In this combined cohort, first-line progression-free survival was 5.9 months, with minimal differences between regimens. Within the population-based cohort, attrition between treatment lines was high with only 60.7% receiving first-line chemotherapy and 26.2% receiving second line.

CONCLUSIONS

Patients with BRAF ^V600E-mutated mCRC have a worse prognosis than previously suggested, potentially arising from referral bias for testing. High attrition between lines of therapy suggests efficacious therapies need to be prioritized early for patients to benefit.

Molecular characterization of a large unselected cohort of metastatic colorectal cancers in relation to primary tumor location, rare metastatic sites and prognosis

Background: We have reported that BRAF V600E mutations and microsatellite instability-high (MSI-H) are more prevalent in a population-based cohort of metastatic colorectal cancer (mCRC) patients than has been reported from clinical trials or hospital-based patient groups. The aim was to explore if other mutations in mCRC differ in prevalence between these cohorts in relation to mismatch repair status and primary tumor location and if presence of bone or brain metastases is associated with any mutations.Material and methods: A population-based cohort of 798 mCRC patients from three regions in Scandinavia was used. Forty-four cancer related genes were investigated in a custom designed Ampliseq hotspot panel. Differences in survival were analyzed using the Kaplan-Meier estimator and the Cox regression analysis.Results: Determination of mutations was possible in 449/501 patients for 40/44 genes. Besides BRAF V600E, seen in 19% of the tumors, none of the other mutations appeared more prevalent than in trial cohorts. BRAF V600E and MSI-H, seen in 8%, were associated with poor prognosis as was right-sided primary tumor location (39%) when compared to left-sided and rectum together; however, in a multivariable regression, only the BRAF mutation retained its statistical significance. No other mutations were associated with poor prognosis. ERBB2 alterations were more common if bone metastases were present at diagnosis (17% vs. 4%, p = .011). No association was found for brain metastases. Fifty-two percent had an alteration that is treatable with an FDA-approved targeted therapy, chiefly by EGFR-inhibitor for RAS wild-type and a check-point inhibitor for MSI-H tumors.Conclusions: Right-sided tumor location, BRAF V600E mutations, but no other investigated mutation, and MSI-H are more commonly seen in an unselected cohort than is reported from clinical patient cohorts, likely because they indicate poor prognosis. Half of the patients have a tumor that is treatable with an already FDA-approved targeted drug for mCRC.

CDX2: A Prognostic Marker in Metastatic Colorectal Cancer Defining a Better BRAF Mutated and a Worse KRAS Mutated Subgroup

Background: Survival of metastatic colorectal cancer (mCRC) patients has improved, but mainly for trial patients. New predictive and prognostic biomarkers validated in the general mCRC population are needed. Caudal-type homeobox 2 (CDX2) is an intestine-specific transcription factor with potential prognostic and predictive effect, but the importance in mCRC has not been fully investigated.

Methods: Immunohistochemistry analysis of CDX2 was performed in a Scandinavian population-based cohort of mCRC (n = 796). Frequency, clinical and tumor characteristics, response rate, progression-free survival, and overall survival (OS) were estimated.

Results: Loss of CDX2 expression was found in 87 (19%) of 452 stained cases, in 53% if BRAF mutated (BRAFmut) and in 9% if KRAS mutated (KRASmut). CDX2 loss was associated with microsatellite instability, BRAFmut, and poor differentiation and inversely associated with KRASmut. Patients with CDX2 loss received less first-line (53 vs. 64%, p = 0.050) and second-line (23 vs. 39%, p = 0.006) chemotherapy and secondary surgery (1 vs. 9%, p = 0.019). Median progression-free survival and OS for patients given first-line combination chemotherapy was 4 and 10 months if CDX2 loss vs. 9 and 24 months if CDX2 expressed (p = 0.001, p < 0.001). Immediate progression on first-line combination chemotherapy was seen in 35% of patients with CDX2 loss vs. 10% if CDX2 expressed (p = 0.003). Median OS in patients with BRAFmut or KRASmut and CDX2 expressed in tumor (both 21 months) was comparable to wild-type patients (27 months). However, if CDX2 loss, median OS was only 8 and 11 months in BRAFmut and KRASmut cases, respectively, and 10 months in double wild-type patients. In multivariate analysis, CDX2 loss (hazard ratio: 1.50, p = 0.027) and BRAFmut (hazard ratio: 1.62, p = 0.012) were independent poor prognostic markers for OS.

Conclusion: In a population-based cohort of mCRC patients, CDX2 loss is an independent poor prognostic marker. Expression of CDX2 defines a new subgroup of BRAFmut cases with a much better prognosis. Loss of CDX2 defines a small group of KRASmut cases with a worse prognosis. Patients with CDX2 loss receive less palliative chemotherapy with less benefit and rarely reach secondary surgery.

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).