Immune checkpoint inhibitors have become important tools for managing non-small-cell lung cancer (NSCLC), could the analysis identify individuals with malignant diseases?
Reported in The Journal of Molecular Diagnostics Molecular, the analysis of small, unfixed tissue samples collected using minimally invasive bronchoscopy, immune checkpoint inhibitors, can identify individuals with malignant disease and yield PD-L1 expression levels.
The tools for managing cancer
Immune checkpoint inhibitors, such as the anti-PD-1 antibody pembrolizumab, have become important tools for managing non-small-cell lung cancer (NSCLC).
Assessing the level of programmed death ligand 1 (PD-L1) expressed by a tumour can assist clinicians in determining how the patient should be treated.
The report describes a novel and rapid approach for quantifying PD-L1 expression levels in tumours that requires only small amounts of tissue that can be collected using minimally-invasive bronchoscopy techniques. This approach can also be used to discriminate malignant from benign tumours and identify mutational status, all of which can guide and refine therapeutic decisions.
Steven Bozinovski, PhD, of the School of Health and Biomedical Sciences, RMIT University, Australia, explains: “The emergence of lung cancer screening trials will result in greater demand to define the molecular nature of suspect lung nodules.
“This test has the potential to save considerable time and money in identifying patients who are most likely to benefit from checkpoint inhibitors such as pembrolizumab.”
Could immune checkpoint inhibitors be the new streamlined approach?
The paper describes a new streamlined approach for comprehensive molecular profiling of bronchial specimens suspected to be NSCLC. Upon collection of a bronchoscopy specimen using brush or biopsy radial probe endobronchial ultrasound (EBUS), a small amount of tissue is placed directly in nucleic acid stabilisation buffer following rapid onsite evaluation of the malignant site.
RNA and DNA are isolated from the specimen and an assay is performed to quantify the expression of matrix metalloproteinase-9 (MMP-9) and its endogenous inhibitor (TIMP3).
The test itself can be performed very quickly, therefore, diagnosis of malignancy and PD-L1 status can be determined within hours following collection. The test and scoring can be readily automated to eliminate tester variability.
“In this study we demonstrate for the first time that the ratio of MMP-9:TIMP3 can accurately differentiate malignant from non-malignant tissue specimens without the need to fix tissue for histological assessment,” adds Bozinovski.
In one case, the MMP9:TIMP3 ratio was elevated more than 300 times while cytology was normal. Nine months later, repeat cytology confirmed that the tumour was indeed malignant.
Assay selects patients with immune checkpoint inhibitors
The assay also quantifies PD-L1 transcript levels, which can have an important impact on the clinical management of NSCLC. Pembrolizumab has FDA approval for the frontline treatment of patients with advanced NSCLC whose tumours have 50% or greater PD-L1 expression as determined using the SP263 immunohistochemistry test. Patients with lower PD-L1 expression levels are more likely to benefit from a combination of pembrolizumab and chemotherapy.
The study demonstrated a strong positive association between transcript levels of PD-L1 as measured by the new assay and the FDA-approved SP263 immunohistochemistry.
According to the researchers, enough genomic DNA from the same specimen should be available to allow multi-panel targeted next-generation sequencing to assess the total mutational burden of the tumour.
Importantly, this is possible because the tissue is unfixed, upholding the integrity of DNA and RNA. In the current report, mutations were detected in the majority of EBUS tumour specimens, including TP53 gene mutations found in 10 of 15 NSCLC samples. Such information may further refine patient selection for a particular treatment regimen.
The test offers additional advantages including rapid turnaround time and automated analysis.
Bozinovski concludes: “We believe our test should significantly enhance the diagnostic utility of EBUS-guided bronchoscopy specimens for the molecular testing of lung cancer patients.”