A Real-World Application of Liquid Biopsy in Metastatic Colorectal Cancer: The Poseidon Study

Liquid biopsy in colorectal cancer: Onward and upward

Colorectal cancer (CRC) remains a leading cause of cancer-related deaths worldwide. In recent years, liquid biopsy has emerged as one of the most interesting areas of research in oncology, leading to innovative trials and practical changes in all aspects of CRC management. RNAs and cell free DNA (cfDNA) methylation are emerging as promising biomarkers for early diagnosis. Post-surgical circulating tumour DNA (ctDNA) can aid in evaluating minimal residual disease and personalising adjuvant treatment. In rectal cancer, ctDNA could improve response assessment to neoadjuvant therapy and risk stratification, especially in the era of organ-preservation trials. In the advanced setting, ctDNA analysis offers the opportunity to monitor treatment response and identify driver and resistance mutations more comprehensively than traditional tissue analysis, providing prognostic and predictive information. The aim of this review is to provide a detailed overview of the clinical applications and future perspectives of liquid biopsy in CRC.

The Importance of Feasibility Assessment in the Design of ctDNA Guided Trials - Results From the OPTIPAL II Study

INTRODUCTION

Both quantitative and molecular changes in ctDNA can hold important information when treating metastatic colorectal cancer (mCRC), but its clinical utility is yet to be established. Before conducting a large-scale randomized trial, it is essential to test feasibility. This study investigates whether ctDNA is feasible for detecting patients who will benefit from treatment with epidermal growth factor receptor inhibitors and the prognostic value of circulating tumor DNA (ctDNA) response.

MATERIALS AND METHODS

Patients with mCRC, who were considered for systemic palliative treatment and were eligible for ctDNA analysis. Mutational testing on cell-free DNA (cfDNA) was done by ddPCR. ctDNA response from baseline to the third treatment cycle was evaluated in patients with detectable ctDNA at baseline. ctDNA maximum response was defined as undetectable ctDNA at the third treatment cycle, ctDNA partial response as any decrease in the ctDNA level, and ctDNA progression as any increase in the ctDNA level.

RESULTS

Forty-nine patients were included. The time to test results for mutational testing on cfDNA was significantly shorter than on tumor tissue (p < .001). Progression-free survival were 11.2 months (reference group), 7.5 months (HR = 10.7, p= .02), and 4.6 months (HR = 11.4, p= .02) in patients with ctDNA maximum response, partial response, and progression, respectively. Overall survival was 31.2 months (reference group), 15.2 months (HR = 4.1, p= .03), and 9.0 months (HR = 2.6, p= .03) in patients with ctDNA maximum response, partial response, and progression, respectively.

CONCLUSION

Pretreatment mutational testing on cfDNA in daily clinic is feasible and can be applied in randomized clinical trials evaluating the clinical utility of ctDNA. Early dynamics in ctDNA during systemic treatment hold prognostic value.

The ideal reporting of RAS testing in colorectal adenocarcinoma: a pathologists' perspective

RAS gene mutational status represents an imperative predictive biomarker to be tested in the clinical management of metastatic colorectal adenocarcinoma. Even if it is one of the most studied biomarkers in the era of precision medicine, several pre-analytical and analytical factors may still impasse an adequate reporting of RAS status in clinical practice, with significant therapeutic consequences. Thus, pathologists should be aware on the main topics related to this molecular evaluation: (i) adopt diagnostic limit of detections adequate to avoid the interference of sub-clonal cancer cell populations; (ii) choose the most adequate diagnostic strategy according to the available sample and its qualification for molecular testing; (iii) provide all the information regarding the mutation detected, since many RAS mutation-specific targeted therapeutic approaches are in development and will enter into routine clinical practice. In this review, we give a comprehensive description of the current scenario about RAS gene mutational testing in the clinic focusing on the pathologist's role in patient selection for targeted therapies.

Implementation Challenges and Disparities in Molecular Testing for Patients With Stage IV NSCLC: Perspectives from an Urban Safety-Net Hospital

The advent of next-generation sequencing (NGS), including both tissue assays and circulating tumor DNA (ct-DNA), has been pivotal in improving outcomes for patients with non-small cell lung cancer (NSCLC). Although molecular testing is standard of care for advanced NSCLC, challenges still exist in its implementation. This Perspective examines barriers to the widespread implementation of NGS from the vantage point of a single urban safety-net institution, with a particular focus on examining racial disparities in NGS completion. We conducted a review of patients at our institution from January 2015 through January 2022 and examined molecular testing patterns before and after the publication of updated molecular testing guidelines from the International Association for the Study of Lung Cancer (IASLC), Association for Molecular Pathology (AMP), and College of American Pathologists (CAP) in March of 2018. While NGS increased over time, we found that 43% of patients in the March 2018 through January 2022 group still did not receive NGS, and the most common reasons for the absence of testing included a lack of physician ordering and insufficient tissue on biopsy. We did not note any racial disparities in completion or time-to-adoption of NGS. Patients with squamous cell carcinoma (SCC) histology were noted to receive liquid NGS markedly less often than patients with non-squamous histology in the March 2018 through January 2022 period. Based on our own data and a review of findings from colleagues in the field, we advocate for additional physician educational programming, increased use of ct-DNA biopsy, automated (reflexive) NGS tissue testing on receipt of biopsy, and consideration for the broader molecular profiling of patients with SCC histology.

Liquid biopsy for KRAS, NRAS and BRAF mutation testing in advanced colorectal cancer patients: the Argentinean experience

Objective: To analyze the frequency of KRAS, NRAS and BRAF hotspot mutations in circulating tumor DNA (ctDNA) from patients with metastatic colorectal cancer (mCRC). Methods: Observational, descriptive and retrospective study in mCRC patients with available ctDNA-based genotype of KRAS, NRAS and BRAF. Results: The frequencies of plasma mutations for KRAS, NRAS and BRAF were 34% (± 7), 4% (± 3) and 4% (± 3), respectively. Median overall survival of plasma-tested RAS/BRAF-mutated patients was 26.6 months (95% CI: 14.4-not estimable [NE]), while RAS/BRAF wild-type patients did not reach the median survival during follow-up. Median progression-free survival for RAS/BRAF wild-type and RAS/BRAF-mutated patients was 12 (95% CI: 7-NE) and 4 months (95% CI: 4-NE), respectively. Conclusion: Our work supports the utility of KRAS, NRAS and BRAF analysis in liquid biopsy from mCRC patients.

Microsatellite Instable Colorectal Adenocarcinoma Diagnostics: The Advent of Liquid Biopsy Approaches

The introduction of immunotherapy has revolutionized the oncological targeted therapy paradigm. Microsatellite instability (MSI) identifies a subgroup of colorectal cancers (CRCs) which respond to treatment with immune checkpoint inhibitors. Tissue biopsy is currently the gold standard for the assessment of MSI/Mismatch Repair deficiency (MMRd) by means immunohistochemistry or molecular assays. However, the application of liquid biopsy in the clinic may help to overcome several limitations of tissue analysis and may provide great benefit to the diagnostic scenario and therapeutic decision-making process. In the context of MSI/MMRd CRC, the use of liquid biopsy may allow to establish MSI/MMR status if tissue sampling cannot be performed or in case of discordant tissue biopsies. Liquid biopsy may also become a powerful tool to monitor treatment response and the onset resistance to immunotherapy over time and to stratify of MSI/MMRd patients according to their risk of relapse and metastases. The aim of this review is to summarize the main technical aspects and clinical applications, the benefits, and limitations of the use of liquid biopsy in MSI/MMRd colorectal cancer patients.