Multicenter Validation Study to Implement Plasma Epidermal Growth Factor Receptor T790M Testing in Clinical Laboratories

The Perceived Value of Liquid Biopsy: Results From a Canadian Validation Study of Circulating Tumor DNA T790M Testing-Patient's Willingness-to-Pay: A Brief Report

Introduction

Liquid biopsy is recommended to diagnose molecular resistance to targeted therapy in patients with lung cancer. Nevertheless, not all jurisdictions provide funding and patient access. We report patients' perceived value of liquid biopsy in targeted therapy resistance.

Methods

Canadian patients participating in a national EGFR T790M liquid biopsy validation study completed structured interviews measuring perceived value and willingness-to-pay for plasma circulating tumor DNA testing as an alternative to tumor biopsy using open-ended and iterative bidding approaches.

Results

A total of 60 patients with advanced lung cancer participated with a median age of 64 years (range: 31-87 y); 69% were Asian and 45% female. All had received prior EGFR tyrosine kinase inhibitor; 17% also received chemotherapy. All patients preferred to have plasma testing over repeat tumor biopsy. In the context of the Canadian publicly funded system, patients estimated that a median of 300 (interquartile range: 150-800) Canadian dollars was a reasonable price to pay for liquid biopsy. Patients were personally willing to pay a median 100 (interquartile range: 33-350) Canadian dollars.

Conclusions

In a system that covers the cost of standard diagnostic tests, patients with lung cancer indicated high willingness-to-pay out-of-pocket for liquid biopsy in the setting of acquired targeted therapy resistance. Patients have high perceived value of plasma genotyping and prefer it to repeat tumor biopsy.

A Micro-Costing Framework for Circulating Tumor DNA Testing in Dutch Clinical Practice

Circulating tumor DNA (ctDNA) is a promising new biomarker with multiple potential applications in cancer care. Estimating total cost of ctDNA testing is necessary for reimbursement and implementation, but challenging because of variations in workflow. We aimed to develop a micro-costing framework for consistent cost calculation of ctDNA testing. First, the foundation of the framework was built, based on the complete step-wise diagnostic workflow of ctDNA testing. Second, the costing method was set up, including costs for personnel, materials, equipment, overhead, and failures. Third, the framework was evaluated by experts and applied to six case studies, including PCR-, mass spectrometry-, and next-generation sequencing-based platforms, from three Dutch hospitals. The developed ctDNA micro-costing framework includes the diagnostic workflow from blood sample collection to diagnostic test result. The framework was developed from a Dutch perspective and takes testing volume into account. An open access tool is provided to allow for laboratory-specific calculations to explore the total costs of ctDNA testing specific workflow parameters matching the setting of interest. It also allows to straightforwardly assess the impact of alternative prices or assumptions on the cost per sample by simply varying the input parameters. The case studies showed a wide range of costs, from €168 to €7638 ($199 to $9124) per sample, and generated information. These costs are sensitive to the (coverage of) platform, setting, and testing volume.

Integrating circulating-free DNA (cfDNA) analysis into clinical practice: opportunities and challenges

In the current era of precision medicine, the identification of genomic alterations has revolutionised the management of patients with solid tumours. Recent advances in the detection and characterisation of circulating tumour DNA (ctDNA) have enabled the integration of liquid biopsy into clinical practice for molecular profiling. ctDNA has also emerged as a promising biomarker for prognostication, monitoring disease response, detection of minimal residual disease and early diagnosis. In this Review, we discuss current and future clinical applications of ctDNA primarily in non-small cell lung cancer in addition to other solid tumours.

Plasma-Based Genotyping in Advanced Solid Tumors: A Comprehensive Review

Molecular genotyping for advanced solid malignancies has transformed the clinical management of patients with metastatic disease. Treatment decisions in a growing number of tumors require knowledge of molecularly driven alterations in order to select optimal targeted therapy. Although genomic testing of tumor tissue is the gold standard for identifying targetable genomic alterations, biopsy samples are often limited or difficult to access. This has paved the way for the development of plasma-based approaches for genomic profiling. Recent advances in the detection of plasma-circulating tumor DNA (ctDNA) have enabled the integration of plasma-based molecular profiling into clinical practice as an alternative or complementary tool for genomic testing in the setting of advanced cancer, to facilitate the identification of driver mutations to guide initial treatment and diagnose resistance. Several guidelines now recommend the use of plasma where tumor tissue is limited to identify a targetable genomic alteration. Current plasma-based assays can evaluate multiple genes in comprehensive panels, and their application in advanced disease will be increasingly incorporated into standard practice. This review focuses on current and future applications of plasma ctDNA-based assays in advanced solid malignancies, while highlighting some limitations in implementing this technology into clinical practice.

Reflex ROS1 IHC Screening with FISH Confirmation for Advanced Non-Small Cell Lung Cancer-A Cost-Efficient Strategy in a Public Healthcare System

ROS1 rearrangements are identified in 1-2% of lung adenocarcinoma cases, and reflex testing is guideline-recommended. We developed a decision model for population-based ROS1 testing from a Canadian public healthcare perspective to determine the strategy that optimized detection of true-positive (TP) cases while minimizing costs and turnaround time (TAT). Eight diagnostic strategies were compared, including reflex single gene testing via immunohistochemistry (IHC) screening, fluorescence in-situ hybridization (FISH), next-generation sequencing (NGS), and biomarker-informed (EGFR/ALK/KRAS wildtype) testing initiated by pathologists and clinician-initiated strategies. Reflex IHC screening with FISH confirmation of positive cases yielded the best results for TAT, TP detection rate, and cost. IHC screening saved CAD 1,000,000 versus reflex FISH testing. NGS was the costliest reflex strategy. Biomarker-informed testing was cost-efficient but delayed TAT. Clinician-initiated testing was the least costly but resulted in long TAT and missed TP cases, highlighting the importance of reflex testing. Thus, reflex IHC screening for ROS1 with FISH confirmation provides a cost-efficient strategy with short TAT and maximizes the number of TP cases detected.

A Pan-Canadian Validation Study for the Detection of EGFR T790M Mutation Using Circulating Tumor DNA From Peripheral Blood

INTRODUCTION

Genotyping circulating tumor DNA (ctDNA) is a promising noninvasive clinical tool to identify the EGFR T790M resistance mutation in patients with advanced NSCLC with resistance to EGFR inhibitors. To facilitate standardization and clinical adoption of ctDNA testing across Canada, we developed a 2-phase multicenter study to standardize T790M mutation detection using plasma ctDNA testing.

METHODS

In phase 1, commercial reference standards were distributed to participating clinical laboratories, to use their existing platforms for mutation detection. Baseline performance characteristics were established using known and blinded engineered plasma samples spiked with predetermined concentrations of T790M, L858R, and exon 19 deletion variants. In phase II, peripheral blood collected from local patients with known EGFR activating mutations and progressing on treatment were assayed for the presence of EGFR variants and concordance with a clinically validated test at the reference laboratory.

RESULTS

All laboratories in phase 1 detected the variants at 0.5 % and 5.0 % allele frequencies, with no false positives. In phase 2, the concordance with the reference laboratory for detection of both the primary and resistance mutation was high, with next-generation sequencing and droplet digital polymerase chain reaction exhibiting the best overall concordance. Data also suggested that the ability to detect mutations at clinically relevant limits of detection is generally not platform-specific, but rather impacted by laboratory-specific practices.

CONCLUSIONS

Discrepancies among sending laboratories using the same assay suggest that laboratory-specific practices may impact performance. In addition, a negative or inconclusive ctDNA test should be followed by tumor testing when possible.

Phase II open-label multicenter study to assess the antitumor activity of afatinib in lung cancer patients with activating epidermal growth factor receptor mutation from circulating tumor DNA: Liquid-Lung-A

BACKGROUND

Mutation analysis of circulating tumor DNA (ctDNA) is used for diagnosing lung cancer. This trial aimed to assess the efficacy of afatinib in treatment-naïve patients with lung cancer harboring epidermal growth factor receptor mutations (EGFRm, exon 19 deletions or exon 21 point mutations) detected based on ctDNA.

METHODS

The primary objective was the objective response rate (ORR) in the response evaluable (RE) population. EGFRm analysis of ctDNA was performed using PANA Mutype. Of the 331 patients screened, ctDNA was positive in 21% (68/331) in the detection of activating EGFRm. Among 81 subjects with tumor EGFRm, 48 showed matched EGFRm in their ctDNA (59% sensitivity).

RESULTS

Therapy with afatinib 40 mg was initiated in 21 (female, 17; adenocarcinoma, 20) patients (intention-to-treat, ITT); dose modifications were made in 15 (71%). The ORR was 74% in the RE population (14/19); 11 patients showed EGFRm only in ctDNA (Group A), whereas 10 exhibited the same EGFRm in their ctDNA and tumor DNA (Group B). There was no significant difference in ORR between Groups A and B (80% and 67% RE, respectively). Median progression-free survival (PFS) was 12.0 months, and no significant difference was observed according to the final afatinib dose, type of EGFRm, and Group A versus B. After progression, T790M mutation was found in 40% (6/15) of patients, and osimertinib was used as a second-line treatment.

CONCLUSIONS

Afatinib showed similar ORR and PFS in patients with lung cancer harboring EGFRm in their ctDNA regardless of tumor EGFRm results.

KEY POINTS

SIGNIFICANT FINDINGS OF THE STUDY: Afatinib showed favorable ORR and PFS regardless of the tumor EGFR mutation status results, similar to the findings of previous trials assessing afatinib as first-line treatment of EGFR-mutated non-small cell lung cancer based on tumor genotyping.

WHAT THIS STUDY ADDS

Our findings emphasize that the survival benefit of afatinib treatment can be achieved not only by appropriate dose reduction with frequent and detailed monitoring of toxicities, but also by using noninvasive (ctDNA) assays in a real-world setting.