Liquid Biopsy Detects Early Molecular Response and Predicts Benefit to First-Line Chemotherapy plus Cetuximab in Metastatic Colorectal Cancer: PLATFORM-B Study

Unveiling acquired resistance to anti-EGFR therapies in colorectal cancer: a long and winding road

Emergence of acquired resistance limits the efficacy of the anti-EGFR therapies cetuximab and panitumumab in metastatic colorectal cancer. In the last decade, preclinical and clinical cohort studies have uncovered genomic alterations that confer a selective advantage to tumor cells under EGFR blockade, mainly downstream re-activation of RAS-MEK signaling and mutations in the extracellular domain of EGFR (EGFR-ECD). Liquid biopsies (genotyping of ctDNA) have been established as an excellent tool to easily monitor the dynamics of genomic alterations resistance in the blood of patients and to select patients for rechallenge with anti-EGFR therapies. Accordingly, several clinical trials have shown clinical benefit of rechallenge with anti-EGFR therapy in genomically-selected patients using ctDNA. However, alternative mechanisms underpinning resistance beyond genomics -mainly related to the tumor microenvironment-have been unveiled, specifically relevant in patients receiving chemotherapy-based multi-drug treatment in first line. This review explores the complexity of the multifaceted mechanisms that mediate secondary resistance to anti-EGFR therapies and potential therapeutic strategies to circumvent acquired resistance.

Sequential RAS mutations evaluation in cell-free DNA of patients with tissue RAS wild-type metastatic colorectal cancer: the PERSEIDA (Cohort 2) study

PURPOSE

RAS (KRAS/NRAS) mutational status on a tumor biopsy is mandatory to guide the best treatment in metastatic colorectal cancer (mCRC). Determining the RAS mutational status by tumor-tissue biopsy is essential in guiding the optimal treatment decision for mCRC. RAS mutations are negative predictive factors for the use of EGFR monoclonal antibodies. Cell-free DNA (cfDNA) analysis enables minimally invasive monitoring of tumor evolution.

METHODS/PATIENTS

PERSEIDA was an observational, prospective study assessing cfDNA RAS, BRAF and EGFR mutations (using Idylla™) in first-line mCRC, RAS wild-type (baseline tumor-tissue biopsy) patients (cohort 2). Plasma samples were collected before first-line treatment, after 20 ± 2 weeks, and at disease progression.

RESULTS

117 patients were included (103 received panitumumab + chemotherapy as first-line treatment). At baseline, 7 (6.8%) patients had RAS mutations, 4 (3.9%) BRAF mutations and no EGFR mutations were detected (cfDNA, panitumumab + chemotherapy subpopulation [panitumumab + Ch]). The baseline RAS mutational status concordance between tissue and liquid biopsies was 94.0% (93.2%, panitumumab + Ch). At 20 weeks, only one patient in the study (included in the panitumumab + Ch) had an emerging cfDNA RAS mutation. No emerging BRAF or EGFR mutations were reported. At disease progression, 6 patients had emergent mutations not present at baseline (RAS conversion rate: 13.3% [6/45]; 15.0% [6/40], panitumumab + Ch).

CONCLUSIONS

The concordance rate between liquid and solid biopsies at baseline was very high, as previously reported, while our results suggest a considerable emergence of RAS mutations during disease progression. Thus, the dynamics of the genomic landscape in ctDNA may provide relevant information for the management of mCRC patients.

Ongoing Clinical Trials and Future Research Scenarios of Circulating Tumor DNA for the Treatment of Metastatic Colorectal Cancer

Liquid biopsy using circulating tumor DNA (ctDNA) has emerged as a minimally invasive, timely approach to provide molecular diagnosis and monitor tumor evolution in patients with cancer. Since the molecular landscape of metastatic colorectal cancer (mCRC) is substantially heterogeneous and dynamic over space and time, ctDNA holds significant advantages as a biomarker for this disease. Numerous studies have demonstrated that ctDNA broadly recapitulates the molecular profile of the primary tumor and metastases, and have mainly focused on the genotyping of RAS and BRAF, that is propaedeutic for anti-EGFR treatment selection. However, ctDNA soon broadened its scope towards the assessment of early tumor response, as well as the identification of drug resistance biomarkers to drive potential molecular actionability. In this review article, we provide an overview of the current state-of-the-art of this methodology and its applications, focusing on ongoing clinical trials that employ ctDNA to prospectively guide treatment in patients with mCRC.

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.

Circulating Tumor DNA and Management of Colorectal Cancer

Although the incidence of colorectal cancer (CRC) has decreased as a result of increased screening and awareness, it still remains a major cause of cancer-related death. Additionally, early detection of CRC recurrence by conventional means such as CT, endoscopy, and CEA has not translated into an improvement in survival. Liquid biopsies, such as the detection circulating tumor DNA (ctDNA), have been investigated as a biomarker for patients with CRC in terms of prognosis and recurrence, as well as their use to guide therapy. In this manuscript, we provide an overview of ctDNA as well as its utility in providing prognostic information, using it to guide therapy, and monitoring for recurrence in patients with CRC. In addition, we discuss the influence the site of disease may have on the ability to detect ctDNA in patients with metastatic CRC.

Plasma Assay of Cell-Free Methylated DNA Markers of Colorectal Cancer: A Tumor-Agnostic Approach to Monitor Recurrence and Response to Anticancer Therapies

BACKGROUND

Radiographic surveillance of colorectal cancer (CRC) after curative-intent therapy is costly and unreliable. Methylated DNA markers (MDMs) detected primary CRC and metastatic recurrence with high sensitivity and specificity in cross-sectional studies. This study evaluated using serial MDMs to detect recurrence and monitor the treatment response to anti-cancer therapies.

METHODS

A nested case-control study was drawn from a prospective cohort of patients with CRC who completed curative-intent therapy for CRC of all stages. Plasma MDMs were assayed vis target enrichment long-probe quantitative-amplified signal assays, normalized to B3GALT6, and analyzed in combination with serum carcinoembryonic antigen to yield an MDM score. Clinical information, including treatment and radiographic measurements of the tumor burden, were longitudinally collected.

RESULTS

Of the 35 patients, 18 had recurrence and 17 had no evidence of disease during the study period. The MDM score was positive in 16 out of 18 patients who recurred and only 2 of the 17 patients without recurrence. The MDM score detected recurrence in 12 patients preceding clinical or radiographic detection of recurrent CRC by a median of 106 days (range 90-232 days).

CONCLUSIONS

Plasma MDMs can detect recurrent CRC prior to radiographic detection; this tumor-agnostic liquid biopsy approach may assist cancer surveillance and monitoring.

Circulating Tumor DNA to Drive Treatment in Metastatic Colorectal Cancer

In the evolving molecular treatment landscape of metastatic colorectal cancer (mCRC), the identification of druggable alterations is pivotal to achieve the best therapeutic opportunity for each patient. Because the number of actionable targets is expanding, there is the need to timely detect their presence or emergence to guide the choice of different available treatment options. Liquid biopsy, through the analysis of circulating tumor DNA (ctDNA), has proven safe and effective as a complementary method to address cancer evolution while overcoming the limitations of tissue biopsy. Even though data are accumulating regarding the potential for ctDNA-guided treatments applied to targeted agents, still major gaps in knowledge exist as for their application to different areas of the continuum of care. In this review, we recapitulate how ctDNA information could be exploited to drive different targeted treatment strategies in mCRC patients, by refining molecular selection before treatment by addressing tumor heterogeneity beyond tumor tissue biopsy; longitudinally monitoring early-tumor response and resistance mechanisms to targeted agents, potentially leading to tailored, molecular-driven, therapeutic options; guiding the molecular triage towards rechallenge strategies with anti-EGFR agents, suggesting the best time for retreatment; and providing opportunities for an "enhanced rechallenge" through additional treatments or combos aimed at overcoming acquired resistance. Besides, we discuss future perspectives concerning the potential role of ctDNA to fine-tune investigational strategies such as immuno-oncology.

The emergence of RAS mutations in patients with RAS wild-type mCRC receiving cetuximab as first-line treatment: a noninterventional, uncontrolled multicenter study

ABSRTACT

BACKGROUND: Patients treated with anti-epidermal growth factor receptor (anti-EGFR) will ultimately develop acquired resistance promoted by clonal selection, mainly the emergence of mutations in the MAPK pathway (mostly RAS mutations). Baseline assessment of RAS mutations in the blood of patients correlates well with RAS tumour tissue testing and is currently an alternative option in routine clinical practice to guide first-line therapy. The aim of this study was the prevalence of acquired genomic alterations detected in the auxiliary tool of ctDNA testing and investigated the role of RAS ctDNA status for detecting tumour response and predicting benefit to anti-EGFR therapy.

METHODS

Only patients with concordant wild-type formalin-fixed, paraffin-embedded (FFPE) tumour tissue and baseline ctDNA RAS wild-type were included. RAS mutations in plasma were evaluated using MassARRAY platform. Blood samples were collected at baseline, every 3 months during first-line treatment, and at disease progression. The primary endpoint was the detection rate of RAS mutations during cetuximab treatment. The correlation between response and survival outcomes and the emergence of circulating RAS mutations was also analysed.

RESULTS

The detection rate of RAS mutations during treatment was 9.3% (10/108). RAS mutations detection occurred a median of 3 months prior to radiologic documentation. The subgroup of patients with RAS mutations exhibited significantly inferior progression-free survival and overall survival (P = 0.002 and 0.027, respectively) but the baseline characteristics, response rates, disease control rates, and metastatectomy were not significant (all P > 0.05).

CONCLUSIONS

We demonstrated that RAS ctDNA status might be a valuable biomarker for detecting early tumour response and predicting benefit to anti-EGFR therapy.

CLINICAL TRIAL REGISTRATION

NCT03401957 (January 17, 2018).

Clinical application of circulating tumour DNA in colorectal cancer

Liquid biopsies that detect circulating tumour DNA (ctDNA) have the potential to revolutionise the personalised management of colorectal cancer. For patients with early-stage disease, emerging clinical applications include the assessment of molecular residual disease after surgery, the monitoring of adjuvant chemotherapy efficacy, and early detection of recurrence during surveillance. In the advanced disease setting, data highlight the potential of ctDNA levels as a prognostic marker and as an early indicator of treatment response. ctDNA assessment can complement standard tissue-based testing for molecular characterisation, with the added ability to monitor emerging mutations under the selective pressure of targeted therapy. Here we provide an overview of the evidence supporting the use of ctDNA in colorectal cancer, the studies underway to address some of the outstanding questions, and the barriers to widespread clinical uptake.

Circulating Tumor DNA in the Management of Early-Stage Breast Cancer

Liquid biopsies refer to the isolation and analysis of tumor-derived biological material from body fluids, most commonly blood, in order to provide clinically valuable information for the management of cancer patients. Their non-invasive nature allows to overcome the limitations of tissue biopsy and complement the latter in guiding therapeutic decision-making. In the past years, several studies have demonstrated that circulating tumor DNA (ctDNA) detection can be used in the clinical setting to improve patient prognosis and monitor therapy response, especially in metastatic cancers. With the advent of significant technological advances in assay development, ctDNA can now be accurately and reliably identified in early-stage cancers despite its low levels in the bloodstream. In this review, we discuss the most important studies that highlight the potential clinical utility of ctDNA in early-stage breast cancer focusing on early diagnosis, detection of minimal residual disease and prediction of metastatic relapse. We also offer a concise description of the most sensitive techniques that are deemed appropriate for ctDNA detection in early-stage cancer and we examine their advantages and disadvantages, as they have been employed in various studies. Finally, we discuss future perspectives on how ctDNA could be better integrated into the everyday oncology practice.

Truncal Dynamics May Trump: Serial ctDNA to Predict Early Therapeutic Response

SUMMARY

Promising utility of using serial ctDNA in metastatic colorectal cancer to both refine patient selection, reduce toxicity due to chemotherapy, and to evaluate emerging resistance mechanisms may lead the way to novel therapeutic strategies. However, important questions remain in validating its use as a predictive biomarker of treatment response. See related article by Vidal et al., p. 379.