First-Line Cetuximab Monotherapy in KRAS/NRAS/BRAF Mutation-Negative Colorectal Cancer Patients

Distinct Driver Pathway Enrichments and a High Prevalence of TSC2 Mutations in Right Colon Cancer in Chile: A Preliminary Comparative Analysis

Colorectal cancer (CRC) is the second leading cause of cancer deaths globally. While ethnic differences in driver gene mutations have been documented, the South American population remains understudied at the genomic level, despite facing a rising burden of CRC. We analyzed tumors of 40 Chilean CRC patients (Chp) using next-generation sequencing and compared them to data from mainly Caucasian cohorts (TCGA and MSK-IMPACT). We identified 388 mutations in 96 out of 135 genes, with TP53 (45%), KRAS (30%), PIK3CA (22.5%), ATM (20%), and POLE (20%) being the most frequently mutated. TSC2 mutations were associated with right colon cancer (44.44% in RCRC vs. 6.45% in LCRC, p-value = 0.016), and overall frequency was higher compared to TCGA (p-value = 1.847 × 10-5) and MSK-IMPACT cohorts (p-value = 3.062 × 10-2). Limited sample size restricts definitive conclusions, but our data suggest potential differences in driver mutations for Chilean patients, being that the RTK-RAS oncogenic pathway is less affected and the PI3K pathway is more altered in Chp compared to TCGA (45% vs. 25.56%, respectively). The prevalence of actionable pathways and driver mutations can guide therapeutic choices, but can also impact treatment effectiveness. Thus, these findings warrant further investigation in larger Chilean cohorts to confirm these initial observations. Understanding population-specific driver mutations can guide the development of precision medicine programs for CRC patients.

Molecular Network of Colorectal Cancer and Current Therapeutic Options

Colorectal cancer (CRC), a leading cause of cancer-related mortalities globally, results from the accumulation of multiple genetic and epigenetic alterations in the normal colonic and rectum epithelium, leading to the progression from colorectal adenomas to invasive carcinomas. Almost half of CRC patients will develop metastases in the course of the disease and most patients with metastatic CRC are incurable. Particularly, the 5-year survival rate of patients with stage 4 CRC at diagnosis is less than 10%. Although genetic understanding of these CRC tumors and paired metastases has led to major advances in elucidating early driver genes responsible for carcinogenesis and metastasis, the pathophysiological contribution of transcriptional and epigenetic aberrations in this malignancy which influence many central signaling pathways have attracted attention recently. Therefore, treatments that could affect several different molecular pathways may have pivotal implications for their efficacy. In this review, we summarize our current knowledge on the molecular network of CRC, including cellular signaling pathways, CRC microenvironment modulation, epigenetic changes, and CRC biomarkers for diagnosis and predictive/prognostic use. We also provide an overview of opportunities for the treatment and prevention strategies in this field.

Modern Approaches to Testing Drug Sensitivity of Patients' Tumors (Review)

Drug therapy is still one of the basic techniques used to treat cancers of different etiology. However, tumor resistance to drugs is a pressing problem limiting drug treatment efficacy. It is obvious for both modern fundamental and clinical oncology that there is the need for an individual approach to treating cancer taking into account the biological properties of a tumor when prescribing chemo- and targeted therapy. One of the promising strategies is to increase the antitumor therapy efficacy by developing predictive tests, which enable to evaluate the sensitivity of a particular tumor to a specific drug or a drug combination before the treatment initiation and, thus, make individual therapy selection possible.

The present review considers the main approaches to drug sensitivity assessment of patients’ tumors: molecular genetic profiling of tumor cells, and direct efficiency testing of the drugs on tumor cells isolated from surgical or biopsy material. There were analyzed the key directions in research and clinical studies such as: the search for predictive molecular markers, the development of methods to maintain tumor cells or tissue sections viable, i.e. in a condition maximum close to their physiological state, the development of high throughput systems to assess therapy efficiency. Special attention was given to a patient-centered approach to drug therapy in colorectal cancer.

Molecular testing for colorectal cancer: Clinical applications

Molecular genetic analysis is an integral part of colorectal cancer (CRC) management. The choice of systemic therapy for CRC is largely based on the results of tumor molecular testing. Evaluation of the KRAS and NRAS gene status is mandatory for consideration of anti-epidermal growth factor receptor (EGFR) therapy. Tumors with the BRAF V600E substitution are characterized by aggressive behaviour, may require intensified cytotoxic regimens and benefit from combined BRAF and EGFR inhibition. The inactivation of DNA mismatch repair (MMR), or MUTYH gene, or DNA polymerase epsilon results in excessive tumor mutational burden; these CRCs are highly antigenic and therefore sensitive to immune checkpoint inhibitors. Some CRCs are characterized by overexpression of the HER2 oncogene and respond to the appropriate targeted therapy. There are CRCs with clinical signs of hereditary predisposition to this disease, which require germline genetic testing. Liquid biopsy is an emerging technology that has the potential to assist CRC screening, control the efficacy of surgical intervention and guide disease monitoring. The landscape of CRC molecular diagnosis is currently undergoing profound changes due to the increasing use of next generation sequencing.

Drug-Drug Interactions of Irinotecan, 5-Fluorouracil, Folinic Acid and Oxaliplatin and Its Activity in Colorectal Carcinoma Treatment

The combination of folinic acid, 5-fluorouracil, oxaliplatin and/or irinotecan (FOLFOXIRI) is the standard of care for metastatic colorectal cancer (CRC). This strategy inhibits tumor growth but provokes drug resistance and serious side effects. We aimed to improve FOLFOXIRI by optimization of the dosing and the sequence of drug administration. We employed an orthogonal array composite design and linear regression analysis to obtain cell line-specific drug combinations for four CRC cell lines (DLD1, SW620, HCT116, LS174T). Our results confirmed the synergy between folinic acid and 5-fluorouracil and additivity, or even antagonism, between the other drugs of the combination. The drug combination administered at clinical doses resulted in significantly higher antagonistic interactions compared to the low-dose optimized drug combination (ODC). We found that the concomitant administration of the optimized drug combination (ODC) was comparatively active to sequential administration. However, the administration of oxaliplatin or the active metabolite of irinotecan seemed to sensitize the cells to the combination of folinic acid and 5-fluorouracil. ODCs were similarly active in non-cancerous cells as compared to the clinically used doses, indicating a lack of reduction of side effects. Interestingly, ODCs were inactive in CRC cells chronically pretreated with FOLFOXIRI, suggesting the occurrence of resistance. We were unable to improve FOLFOXIRI in terms of efficacy or specificity. Improvement of CRC treatment should come from the optimization of targeted drugs and immunotherapy strategies.

An Update of Efficacy and Safety of Cetuximab in Metastatic Colorectal Cancer: A Narrative Review

Colorectal cancer is the second most common cancer, representing 13% of all diagnosed cancers. Cetuximab is a recombinant chimeric monoclonal IgG1 antibody and epidermal growth factor receptor (EGFR) inhibitor. Cetuximab is approved for the first-line treatment in combination with chemotherapy or as a single agent in patients who have failed or are intolerant to chemotherapy in patients with EGFR-expressing, RAS wild-type metastatic colorectal cancer. Cetuximab efficacy emerged from studies that were conducted to approve the drug. Cetuximab is well tolerated; its toxicities are caused by its mechanism of action and the most common adverse reaction is skin toxicity. The main purpose of this manuscript is to present an update on the evidence-based summary of efficacy and safety and on the cost-effectiveness of cetuximab. Furthermore, it suggests a management of adverse drug reactions to improve the tolerability of the drug.