Comprehensive genomic sequencing detects important genetic differences between right-sided and left-sided colorectal cancer

Mucin phenotype and genetic alterations in non-V600E BRAF-mutated colorectal cancer

Colorectal cancer (CRC) is a heterogeneous disease that develops through stepwise accumulation of genetic alterations and progresses via several distinct pathways. However, the tumorigenesis of CRCs with BRAF non-V600E mutations remains unclear. Here, we aimed to elucidate the tumorigenesis of CRCs with BRAF non-V600E mutations, focusing on differences in mucin phenotype and genetic alterations between CRCs with non-V600E and V600E mutations. We investigated 201 patients with CRC and performed panel testing of 415 genes to identify BRAF mutations. Patients were classified into five mucin phenotypes - large-intestinal, small-intestinal, gastric, mixed, and unclassified - using immunohistochemistry for CD10, MUC2, MUC5AC, and MUC6. BRAF mutations were identified in 24 of 201 patients' samples, of which 13 (6.5%) had a V600E mutation (V600E-mutant) and 11 (5.5%) had non-V600E mutations (non-V600E-mutant). MUC5AC expression was significantly associated with V600E mutations (P = 0.040), while CD10 expression was significantly associated with non-V600E mutations (P = 0.010). The small-intestinal mucin phenotype was significantly associated with non-V600E mutations (P = 0.031), while the mixed mucin phenotype was significantly associated with V600E mutations (P = 0.027). Regarding genetic alterations, focusing on the WNT signaling pathway, APC mutation was significantly associated with non-V600E mutations (P < 0.001), while RNF43 mutation was significantly associated with V600E mutations (P = 0.020). Considering the differences in mucin phenotype and genetic alterations, different modes of tumorigenesis are assumed for CRC with BRAF V600E mutation and non-V600E mutations. These findings are important in understanding the biology and treatment strategies for BRAF-mutant CRC.

NOS2 Polymorphism in Aspect of Left and Right-Sided Colorectal Cancer

Background: The NOS2 gene polymorphism rs2297518 is associated with an increased level of NO, which could contribute to colorectal cancer (CRC) development. We hypothesized that the potential influence of the NOS2 gene polymorphism on cancer development may vary between right-sided and left-sided colon cancers, and rectal cancers. The aim of this study was to determine the rs2297518 polymorphism influence on colorectal cancer development with regard to tumor localization. Methods: This case-control study included 199 patients with CRC and 120 controls. The qPCR endpoint genotyping was conducted using the TaqMan® genotyping assay. Results: This study revealed significant differences in tumor characteristic and in the minor alelle A frequency in the NOS2 genotype between colorectal cancers with different localizations. The mucinous adenocarcinoma was diagnosed significantly more often in right-sided cancers than in left-sided (30.6% vs. 10.9%, p = 0.009) and rectal cancers (30.6% vs. 7.1%, p = 0.0003). The minor allele A of the NOS2 genotype was observed more frequently in right-sided cancers than in left-sided cancers (44.9% vs. 23.1%, p = 0.0137) and more frequently in rectal cancers than in left-sided cancers (40.0% vs. 23.1%, p = 0.0285). Conclusions: In conclusion, the results support the hypothesis that the SNP rs2297518 of the NOS2 gene influences colorectal cancer development with regard to tumor localization.

A Belgian Population-Based Study Reveals Subgroups of Right-Sided Colorectal Cancer with a Better Prognosis Compared to Left-sided Cancer

BACKGROUND

Patients with left-sided colorectal cancer (L-CRC) are known to have a significantly better prognosis than those with right-sided CRC (R-CRC). It has been hypothesized that RAS, BRAF mutations, or deficient mismatch repair status (MMR) might be responsible for the prognostic effect of primary tumor location (PTL). This study aims to evaluate the prognostic effect of PTL in the Belgian population and to determine the role of biomarkers (MMR, BRAF, and RAS status) in this effect.

PATIENTS AND METHODS

We performed a retrospective analysis of Belgian Cancer Registry data. First, we studied the prognostic effect of PTL on 5-year relative survival of 91 946 patients diagnosed with CRC (all stages) from 2004-2015. Second, we investigated the interaction between biomarkers and the prognostic effect of PTL in 1818 patients diagnosed with stage IV CRC in 2014-2015.

RESULTS

L-CRC was associated with a significantly better 5-year relative survival compared to R-CRC in all stages and ages combined (68.4%, 95% CI, 67.7-69.1% vs 65.6%, 95% CI, 64.7-66.4%). Also, when stratified by age, sex, and stage, the prognosis of L-CRC was better compared to R-CRC in most subgroups. Only in stage II and certain subgroups of elderly patients, the opposite was observed. Furthermore, our data showed that none of the biomarkers had a significant interaction with the effect of PTL on survival.

CONCLUSION

This population-based study confirms that L-CRC is associated with significantly better relative survival compared to R-CRC, in all stages and ages combined. Furthermore, in stage IV L-CRC is associated with a longer survival than R-CRC, regardless of MMR, RAS, and BRAF status.

TIMP1 promotes cell proliferation and invasion capability of right-sided colon cancers via the FAK/Akt signaling pathway

Although right-sided colorectal cancer (CRC) shows a worse prognosis than left-sided CRC, the underlying mechanism remains unclear. We established patient-derived organoids (PDOs) from left- and right-sided CRCs and directly compared cell proliferation and invasion capability between them. We then analyzed the expression of numerous genes in signal transduction pathways to clarify the mechanism of the differential prognosis. Cell proliferation activity and invasion capability in right-sided cancer PDOs were significantly higher than in left-sided cancer PDOs and normal PDOs, as revealed by Cell Titer Glo and transwell assays, respectively. We then used quantitative RT-PCR to compare 184 genes in 30 pathways among right-sided and left-sided cancer and normal PDOs and found that the TIMP1 mRNA level was highest in right-sided PDOs. TIMP1 protein levels were upregulated in right-sided PDOs compared with normal PDOs but was downregulated in left-sided PDOs. TIMP1 knockdown with shRNA significantly decreased cell proliferation activity and invasion capability in right-sided PDOs but not in left-sided PDOs. Moreover, TIMP1 knockdown significantly decreased pFAK and pAkt expression levels in right-sided PDOs but not in left-sided PDOs. A database analysis of The Cancer Genome Atlas revealed that TIMP1 expression in right-sided CRCs was significantly higher than in left-sided CRCs. Kaplan-Meier survival analysis showed significantly shorter overall survival in high-TIMP1 patients versus low-TIMP1 patients with right-sided CRCs but not left-sided CRCs. Our data suggest that TIMP1 is overexpressed in right-sided CRCs and promotes cell proliferation and invasion capability through the TIMP1/FAK/Akt pathway, leading to a poor prognosis. The TIMP1/FAK/Akt pathway can be a target for therapeutic agents in right-sided CRCs.

Upregulated WTAP expression in colorectal cancer correlates with tumor site and differentiation

Few reports exist regarding the expression and function of Wilms’ tumor 1-associated protein (WTAP) in colorectal cancer (CRC), and the evidence is controversial. Our analysis explored the expression of WTAP in CRC tissue, and analyzed its clinical and prognostic significance. WTAP expression was significantly higher in CRC tissue than in colorectal adenoma and normal colorectal tissue. WTAP was highest in left colon tumor samples and negatively associated with tumor differentiation, as well as depth of tumor invasion. In multiple logistic regression analysis, independent predictors of WTAP expression in CRC included tumor in the left colon (odds ratio = 2.634; 95% confidence interval: 1.129–6.142; P = 0.025) and poorly differentiated tissue (0.072; 0.014–0.367; P = 0.002). No clear relationship was observed between CRC patient prognosis and WTAP expression. We suggest that WTAP expression is upregulated in CRC, highly expressed in left colon cancer and negatively correlated with tumor differentiation.

Differences in T cell immune-related lncRNA and mRNA expression patterns between right- and left-sided colorectal cancers

BACKGROUND

Right-sided colorectal cancer (RCRC) and left-sided colorectal cancer (LCRC) harbor different genetic alterations associated with immune response.

OBJECTIVE

This study aimed to analyze the differences in T cell immune-related RNA expression patterns between RCRC and LCRC.

METHODS

The differentially expressed genes (DEGs) and lncRNAs (DElncRNAs) between LCRC and RCRC were screened from the Cancer Genome Atlas (TCGA) database. A correlation analysis between DEGs or DElncRNAs and differential T cells was also performed to obtain T cell-related genes, followed by miRNA prediction. The mRNA-lncRNA network and the competitive endogenous RNA (ceRNA) network were subsequently constructed, and the expression level of mRNA in the ceRNA network was verified using GSE104645.

RESULTS

RCRC patients had a poorer prognosis and were older than LCRC patients. In total, 923 DEGs and 328 DElncRNAs were screened between LCRC and RCRC patients. Compared to RCRC patients, LCRC patients showed a decrease in CD8⁺ T cells. In addition, 26 miRNAs, 8 mRNAs, and 10 lncRNAs were included in the ceRNA network. Finally, the validation analysis revealed that CDHR1 and PRLR were significantly downregulated, while TRIB2 was upregulated in RCRC patients compared to LCRC patients.

CONCLUSION

The analysis of T cell immune-related RNA expression might provide new insights into the underlying molecular mechanisms of the differences between LCRC and RCRC.

Profiling of host genetic alterations and intra-tumor microbiomes in colorectal cancer

Some bacteria are symbiotic in tumor tissues, and metabolites of several bacterial species have been found to cause DNA damage. However, to date, the association between bacteria and host genetic alterations in colorectal cancer (CRC) has not been fully investigated. We evaluated the association between the intra-tumor microbiome and host genetic alterations in 29 Japanese CRC patients. The tumor and non-tumor tissues were extracted from the patients, and 16S rRNA genes were sequenced for each sample. We identified enriched bacteria in tumor and non-tumor tissues. Some bacteria, such as Fusobacterium, which is already known to be enriched in CRC, were found to be enriched in tumor tissues. Interestingly, Bacteroides, which is also known to be enriched in CRC, was enriched in non-tumor tissues. Furthermore, it was shown that certain bacteria that often coexist within tumor tissue were enriched in the presence of a mutated gene or signal pathway with mutated genes in the host cells. Fusobacterium was associated with many mutated genes, as well as cell cycle-related pathways including mutated genes. In addition, the patients with a high abundance of Campylobacter were suggested to be associated with mutational signature 3 indicating failure of double-strand DNA break repairs. These results suggest that CRC development may be partly caused by DNA damage caused by substances released by bacterial infection. Taken together, the identification of distinct gut microbiome patterns and their host specific genetic alterations might facilitate targeted interventions, such as modulation of the microbiome in addition to anticancer agents or immunotherapy.

Histopathological characteristics and artificial intelligence for predicting tumor mutational burden-high colorectal cancer

BACKGROUND

Tumor mutational burden-high (TMB-H), which is detected with gene panel testing, is a promising biomarker for immune checkpoint inhibitors (ICIs) in colorectal cancer (CRC). However, in clinical practice, not every patient is tested for TMB-H using gene panel testing. We aimed to identify the histopathological characteristics of TMB-H CRC for efficient selection of patients who should undergo gene panel testing. Moreover, we attempted to develop a convolutional neural network (CNN)-based algorithm to predict TMB-H CRC directly from hematoxylin and eosin (H&E) slides.

METHODS

We used two CRC cohorts tested for TMB-H, and whole-slide H&E digital images were obtained from the cohorts. The Japanese CRC (JP-CRC) cohort (N = 201) was evaluated to detect the histopathological characteristics of TMB-H using H&E slides. The JP-CRC cohort and The Cancer Genome Atlas (TCGA) CRC cohort (N = 77) were used to develop a CNN-based TMB-H prediction model from the H&E digital images.

RESULTS

Tumor-infiltrating lymphocytes (TILs) were significantly associated with TMB-H CRC (P < 0.001). The area under the curve (AUC) for predicting TMB-H CRC was 0.910. We developed a CNN-based TMB-H prediction model. Validation tests were conducted 10 times using randomly selected slides, and the average AUC for predicting TMB-H slides was 0.934.

CONCLUSIONS

TILs, a histopathological characteristic detected with H&E slides, are associated with TMB-H CRC. Our CNN-based model has the potential to predict TMB-H CRC directly from H&E slides, thereby reducing the burden on pathologists. These approaches will provide clinicians with important information about the applications of ICIs at low cost.

RNF43 mutation is associated with aggressive tumor biology along with BRAF V600E mutation in right-sided colorectal cancer

Right-sided colorectal cancer (RCRC) demonstrates worse survival outcome compared with left-sided CRC (LCRC). Recently, the importance of RNF43 mutation and BRAF V600E mutation has been reported in the serrated neoplasia pathway, which is one of the precancerous lesions in RCRC. It was hypothesized that the clinical significance of RNF43 mutation differs according to primary tumor sidedness. To test this hypothesis, the clinicopathological characteristics and survival outcome of patients with RNF43 mutation in RCRC and LCRC were investigated. Stage I–IV CRC patients (n=201) were analyzed. Genetic alterations including RNF43 using a 415-gene panel were investigated. Clinicopathological characteristics between RNF43 wild-type and RNF43 mutant-type were analyzed. Moreover, RNF43 mutant-type was classified according to primary tumor sidedness, i.e., right-sided RNF43 mutant-type or left-sided RNF43 mutant-type, and the clinicopathological characteristics between the two groups were compared. RNF43 mutational prevalence, spectrum and frequency between our cohort and TCGA samples were compared. RNF43 mutation was observed in 27 out of 201 patients (13%). Multivariate analysis revealed that age (≥65), absence of venous invasion, and BRAF V600E mutation were independently associated with RNF43 mutation. Among the 27 patients with RNF43 mutation, 12 patients were right-sided RNF43 mutant-type and 15 left-sided RNF43 mutant-type. Right-sided RNF43 mutant-type was significantly associated with histopathological grade 3, presence of lymphatic invasion, APC wild, BRAF V600E mutation, microsatellite instability-high (MSI-H), and RNF43 nonsense/frameshift mutation compared with left-sided RNF43 mutant-type. Similarly, RNF43 nonsense/frameshift mutations were more frequently observed in RCRC compared with LCRC in the TCGA cohort (P=0.042). Right-sided RNF43 mutant-type exhibited significantly worse overall survival than RNF43 wild-type and left-sided RNF43 mutant-type (P=0.001 and P=0.023, respectively) in stage IV disease. RNF43 mutation may be a distinct molecular subtype which is associated with aggressive tumor biology along with BRAF V600E mutation in RCRC.

Clinical and prognostic differences between surgically resected right-sided and left-sided colorectal cancer

PURPOSE

A growing body of evidence suggests that right-sided colorectal cancer (RCRC) differs from left-sided colorectal cancer (LCRC) in certain clinicopathological features. Therefore, we investigated the difference between RCRC and LCRC in a series of 899 patients.

METHODS

We reviewed data retrospectively, from 899 patients who underwent R0-resection for stage II and III CRC and compared the clinicopathological factors between patients with RCRC and LCRC.

RESULTS

The patients with RCRC tended to be older, more likely female, with a larger tumor, higher pathological T stage, and a greater proportion of their tumors were poorly differentiated adenocarcinoma, mucinous adenocarcinoma, or signet ring cell carcinoma than the patients with LCRC,. Recurrence-free survival (RFS) of the patients with RCRC tended to be higher than that of the patients with LCRC and was significantly better among patients with stage II cancer. The overall survival (OS) was similar for patients with RCRC and LCRC, irrespective of cancer stage.

CONCLUSION

Compared with the patients with LCRC, those with RCRC had several oncologically unfavorable factors, with better RFS in stage II and similar OS in stages II and III. These results suggest that the biological aggressiveness of RCRC is lower than that of LCRC in stage II; however, it can increase after relapse.

SMAD4 alteration associates with invasive-front pathological markers and poor prognosis in colorectal cancer

Aims

SMAD4 acts as a tumour suppressor, and the loss of SMAD4 is associated with poor prognosis in colorectal cancer (CRC) patients. Although next‐generation sequencing (NGS) enabled us to detect numerous genetic alterations in a single assay, the clinical significance of SMAD4 alteration detected with NGS has not been fully investigated. The aim of this study was to evaluate the clinicopathological characteristics and clinical significance of SMAD4 alteration detected with NGS in CRC.

Methods and results

We retrospectively investigated 201 patients with stage I–IV CRC, by using a 415‐gene panel. To analyse the relationship between SMAD4 alteration and other clinicopathological characteristics, we evaluated clinicopathological variables, including invasive‐front pathological markers: tumour budding, poorly differentiated cluster, and Crohn‐like lymphoid reaction. Fifty‐six patients (28%) had SMAD4 alteration: 24 and 32 patients had SMAD4 mutation and deletion, respectively. SMAD4 alteration was significantly associated with T category (P = 0.027), N category (P = 0.037), M category (P = 0.028), and invasive‐front pathological markers, such as poorly differentiated cluster grade 3 (P = 0.020) and absence of Crohn‐like lymphoid reaction (P = 0.004). Immunohistochemistry revealed that SMAD4 alteration was significantly associated with loss of SMAD4 (P = 0.023). In 90 patients with stage I–III disease, SMAD4 alteration was significantly associated with poor prognosis for relapse‐free and overall survival (P = 0.047; P = 0.022, respectively). Conversely, in 111 patients with stage IV disease, SMAD4 alteration was not significantly associated with overall survival.

Conclusion

SMAD4 alteration is associated with invasive‐front pathological markers and poor prognosis in stage I–III CRC patients.

BRAF V600E and SRC mutations as molecular markers for predicting prognosis and conversion surgery in Stage IV colorectal cancer

Comprehensive genomic sequencing (CGS) enables us to detect numerous genetic alterations in a single assay. We aimed to identify molecular markers for predicting prognosis and conversion surgery in Stage IV colorectal cancer (CRC) using CGS. One-hundred eleven patients with Stage IV CRC who underwent primary tumor resection were analyzed. We retrospectively investigated genetic alterations using CGS of a 415-gene panel. Clinicopathological variables and genetic alterations were analyzed to identify independent prognostic factors of overall survival (OS). Forty-five of 111 patients had R0 resection; of these, 11 patients underwent conversion surgery. Univariate and multivariate analyses identified histopathological grade 3, R0 resection, BRAF V600E mutation, and SRC mutation as independent prognostic factors for OS (P = 0.041, P = 0.013, P = 0.005, and P = 0.023, respectively). BRAF V600E and SRC mutations were mutually exclusive, and SRC mutation was significantly associated with left-sided tumor and liver metastasis compared to BRAF V600E mutation (P = 0.016 and P = 0.025, respectively). Eleven of the 74 initially unresectable patients underwent conversion surgery for R0 resection, yet none harbored BRAF V600E or SRC mutations. BRAF V600E and SRC mutations are important molecular markers which can predict prognosis and conversion surgery in Stage IV CRC.

A Simplified Genomic Profiling Approach Predicts Outcome in Metastatic Colorectal Cancer

The response of metastatic colorectal cancer (mCRC) to the first-line conventional combination therapy is highly variable, reflecting the elevated heterogeneity of the disease. The genetic alterations underlying this heterogeneity have been thoroughly characterized through omic approaches requiring elevated efforts and costs. In order to translate the knowledge of CRC molecular heterogeneity into a practical clinical approach, we utilized a simplified Next Generation Sequencing (NGS) based platform to screen a cohort of 77 patients treated with first-line conventional therapy. Samples were sequenced using a panel of hotspots and targeted regions of 22 genes commonly involved in CRC. This revealed 51 patients carrying actionable gene mutations, 22 of which carried druggable alterations. These mutations were frequently associated with additional genetic alterations. To take into account this molecular complexity and assisted by an unbiased bioinformatic analysis, we defined three subgroups of patients carrying distinct molecular patterns. We demonstrated these three molecular subgroups are associated with a different response to first-line conventional combination therapies. The best outcome was achieved in patients exclusively carrying mutations on TP53 and/or RAS genes. By contrast, in patients carrying mutations in any of the other genes, alone or associated with mutations of TP53/RAS, the expected response is much worse compared to patients with exclusive TP53/RAS mutations. Additionally, our data indicate that the standard approach has limited efficacy in patients without any mutations in the genes included in the panel. In conclusion, we identified a reliable and easy-to-use approach for a simplified molecular-based stratification of mCRC patients that predicts the efficacy of the first-line conventional combination therapy.

Next generation sequencing-based gene panel tests for the management of solid tumors

Next generation sequencing (NGS) has been an invaluable tool to put genomic sequencing into clinical practice. The incorporation of clinically relevant target sequences into NGS-based gene panel tests has generated practical diagnostic tools that enable individualized cancer-patient care. The clinical utility of gene panel testing includes investigation of the genetic basis for an individual's response to therapy, such as signaling pathways associated with a response to specific therapies, microsatellite instability and a hypermutated phenotype, and deficiency in the DNA double-strand break repair pathway. In this review, we describe the concept of precision cancer medicine using target sequences in gene panel tests as well as the importance of the control of sample quality in routine NGS-based genomic testing. We describe geographic and ethnic differences in cancer genomes, and discuss issues that need to be addressed in the future based on our experiences in Japan.

Redefining synchronous colorectal cancers based on tumor clonality

To analyze the possible clonal origin of a part of Synchronous colorectal cancer (SCRC), we studied 104 paired-SCRCs from 52 consecutive patients without hereditary forms of CRC. We used a Single-Nucleotide Polymorphism array to characterize the genomic profiles, and subsequently used a statistical application to define them according to clonality within the same individual. We categorized the ensuing groups according to colonic location to identify differential phenotypes. The SCRC Monoclonal group (M) (19 cases) was divided into Monosegmental (MM) and Pancolonic (MP) groups. The SCRC Polyclonal group (P) (33 cases) was also divided into Monosegmental (PM) and Pancolonic (PP), the first exhibiting preference for left colon. The MM group showed a high rate of mucinous tumors, the lowest mean-number of tumors and associated-polyps, and the worst prognosis. The MP group included the largest mean-number of associated-polyps, best prognosis and familial cancer component. The PM group seemed to be a "frontier" group. Finally, the PP group also exhibited a mucin component, the highest mean-number of tumors (4.6) compared with the mean-number of polyps (7.7), poor prognosis and sporadic cases. Most relevant differential genomic regions within M groups were gains on 1q24 and 8q24, and deletions on 1p21 and 1p23 for MM, while within P were the gains on 7q36 and deletions on 1p36 for PM. The statistical application employed seems to define clonality more accurately in SCRC -more likely to be polyclonal in origin-, and together with the tumor locations, helped us to configure a classification with prognostic and clinical value.

The prognostic significance of the expression of monocarboxylate transporter 4 in patients with right- or left-sided colorectal cancer

AIM

Monocarboxylate transporter 4 (MCT4) is a proton pump that exchanges lactate through the plasma membrane. The present study investigated the clinical significance of the expression of MCT4 in patients with right- or left-sided colorectal cancer (CRC).

METHODS

Surgical specimens from 237 CRC patients were immunohistochemically stained with polyclonal anti-MCT4 antibodies. The relationships among the MCT4 expression, the clinicopathological factors, and the prognosis were evaluated.

RESULTS

Thirty-six (62.1%) of 58 patients with right-sided CRC and 95 (53.1%) of 179 patients with left-sided CRC showed the high expression of MCT4. The MCT4 expression was significantly correlated with gender and lymph node metastasis in patients with right-sided CRC, and size, depth of invasion, distant metastasis, and tumor-node-metastasis stage in patients with left-sided CRC. A univariate analysis demonstrated that the expression of MCT4 was a significant prognostic factor in both right- and left-sided CRC patients. A multivariate analysis demonstrated the expression of MCT4 was a significantly independent prognostic factor in patients with left-sided CRC, but not in those with right-sided CRC.

CONCLUSIONS

Our results suggest that the high expression of MCT4 is a useful marker for tumor progression and a poor prognosis in CRC patients, especially those with left-sided CRC.

Radiomics analysis of pre-treatment [18F]FDG PET/CT for patients with metastatic colorectal cancer undergoing palliative systemic treatment

BACKGROUND

The aim of this study was to assess radiomics features on pre-treatment [¹⁸F]FDG positron emission tomography (PET) as potential biomarkers for response and survival in patients with metastatic colorectal cancer (mCRC).

METHODS

Patients with mCRC underwent [¹⁸F]FDG PET/computed tomography (CT) prior to first- or third-line palliative systemic treatment. Tumour lesions were semiautomatically delineated and standard uptake value (SUV), metabolically active tumour volume (MATV), total lesion glycolysis (TLG), entropy, area under the curve of the cumulative SUV-volume histogram (AUC-CSH), compactness and sphericity were obtained.

RESULTS

Lesions of 47 patients receiving third-line systemic treatment had higher SUV_max, SUV_peak, SUV_mean, MATV and TLG, and lower AUC-CSH, compactness and sphericity compared to 52 patients receiving first-line systemic treatment. Therefore, first- and third-line groups were evaluated separately. In the first-line group, anatomical changes on CT correlated negatively with TLG (ρ = 0.31) and MATV (ρ = 0.36), and positively with compactness (ρ = -0.27) and sphericity (ρ = -0.27). Patients without benefit had higher mean entropy (p = 0.021). Progression-free survival (PFS) and overall survival (OS) were worse with a decreased mean AUC [hazard ratio (HR) 0.86, HR 0.77] and increase in mean MATV (HR 1.15, HR 1.22), sum MATV (HR 1.14, HR 1.19), mean TLG (HR 1.16, HR 1.22) and sum TLG (HT1.12, HR1.18). In the third-line group, AUC-CSH correlated negatively with anatomical change (ρ = 0.21). PFS and OS were worse with an increased mean MATV (HR 1.27, HR 1.68), sum MATV (HR 1.35, HR 2.04), mean TLG (HR 1.29, HR 1.52) and sum TLG (HT 1.27, HR 1.80). SUV_max and SUV_peak negatively correlated with OS (HR 1.19, HR 1.21). Cluster analysis of the 10 radiomics features demonstrated no complementary value in identifying aggressively growing lesions or patients with impaired survival.

CONCLUSION

We demonstrated an association between improved clinical outcome and pre-treatment low tumour volume and heterogeneity as well as high sphericity on [¹⁸F]FDG PET. Future PET imaging research should include radiomics features that incorporate tumour volume and heterogeneity when correlating PET data with clinical outcome.

Clinical Significance of BRAF Non-V600E Mutations in Colorectal Cancer: A Retrospective Study of Two Institutions

BACKGROUND

Recent advances in next-generation sequencing have enabled the detection of BRAF V600E mutations as well as BRAF non-V600E mutations in a single assay. The present work aimed to describe the clinicopathological characteristics and clinical outcome of the BRAF non-V600E mutant-type in colorectal cancer (CRC).

PATIENTS AND METHODS

CRC samples from 111 Stage IV patients were analyzed for somatic mutations using a 415-gene comprehensive genomic sequencing panel. Patients were classified according to BRAF status as wild-type, V600E mutant-type, or non-V600E mutant-type. Differences between clinicopathological characteristics and genetic alterations were analyzed among the three groups. Overall survival (OS) and the response to anti-EGFR therapy were also analyzed.

RESULTS

Comprehensive genomic sequencing revealed that 98 patients (88%), 7 patients (6%), and 6 patients (6%) were wild-type, V600E mutant-type, and non-V600E mutant-type, respectively. Non-V600E mutant-type tumors were frequently left-sided (83%), while V600E mutant-type tumors were frequently right-sided (86%; P = 0.025). Non-V600E mutant-type showed better OS than V600E mutant-type (P = 0.038), with no significant difference compared with wild-type tumors. The two patients with non-V600E mutations who underwent repeated metastasectomies showed no evidence of disease at final follow-up. Regarding the efficacy of anti-EGFR therapy, the patient with an I326V mutation had progressive disease (+115%) despite no genetic alterations detected in the EGFR pathway that could drive resistance, suggesting an alternate resistance mechanism.

CONCLUSIONS

Non-V600E mutant-type is more likely to be left-sided and demonstrates better OS than V600E mutant-type. Further preclinical and clinical investigations are needed to clarify the role of non-V600E mutations in CRC.

Right Versus Left Colon Cancer: Resectable and Metastatic Disease

OPINION STATEMENT

Colorectal cancer does not represent a single anatomic entity and side of origin has a key impact on prognosis and response to different systemic therapies. Compared to tumours arising in left colon, right colorectal cancers rely on the activation of different molecular pathways (e.g. BRAF mutation and MSI status). From a clinical point of view, this results in a different response to anti-EGFR agents. Current guidelines suggest the use of cetuximab or panitumumab in RAS wild-type disease and left colon cancer especially for cytoreduction/conversion purposes, since the expected benefit in right colon cancer is absent or clinically modest. The prognostic role of microbiota in colorectal cancer disease deserves more clarification before being considered in common clinical practice. Screening policies could also be affected by these new acquisitions. At the moment, sidedness should be considered as a strong prognostic variable and a surrogate predictor of different activity of anti-EGFR agents in the metastatic setting. Its role in early stages of resected disease is still uncertain.

Differential clinicopathological and molecular features within late-onset colorectal cancer according to tumor location

Background

Since there is a predilection of some clinical and molecular features for a given tumor location, we assessed whether this can be confirmed in late-onset colorectal cancer (LOCRC).

Results

Right colon cancers showed features associated with sporadic Microsatellite Instability: predominance of female cases and BRAF mutations, and an important mucinous component. Left colon cancers developed a higher number of polyps and multiple primary CRCs, showed the strongest familial component, and had better prognosis. Rectal cancers showed a predominantly sporadic phenotype, with worse prognosis and a CpG Island Methylator Phenotype (CIMP)-High. No copy number alterations (CNAs) greater than or equal to 50% were observed in this LOCRC group, and the most recurrent alterations were losses at 5q13 and 14q11, and gains at 7q11, 7q21-q22, 19p13-p12, 19q13 and 20p11-q11. KRAS and PIK3CA were the only mutated genes showing differences according to the tumor location, mainly for right colon cancers.

Materials and Methods

We analyzed clinical and molecular characteristics of LOCRC at different tumor locations in order to determine if there are differential phenotypes related with the location in the colon.

Conclusions

Categorizing LOCRC according to tumor location appears to be an adequate first step to resolving the heterogeneity of this subset of CRC.