Clinical implications of circulating cell-free DNA quantification and metabolic tumor burden in advanced non-small cell lung cancer.

OBJECTIVES: This study unravels the significance of cell-free DNA (cfDNA) quantification as a promising measure of the biological behavior/aggressiveness of tumors. Metabolic tumor volume (MTV) and total lesion glycolysis (TLG) measured by positron emission tomography/computed tomography scan enable a precise assessment of metabolic tumor burden. However, their clinical implications in identifying patients who need more aggressive treatment in advanced non-small cell lung cancer (NSCLC) are not fully understood. MATERIALS AND METHODS: In the current prospective trial, we analyzed 101 newly diagnosed advanced NSCLC (stage III-IV) patients with measurable baseline MTV, TLG, and cfDNA quantification. The best cut-offs for cfDNA levels, MTV, and TLG to predict progression-free survival and overall survival were determined using X-tile analysis. RESULTS: There were significant positive correlations between cfDNA and MTV (r = 0.488, p < 0.001) and between cfDNA and TLG (r = 0.554, p < 0.001). High-cfDNA levels and high-MTV/TLG negatively correlated with overall survival (OS) (all p < 0.001). Patients with high-MTV showed similar median OS irrespective of their cfDNA levels (low-cfDNA vs. high-cfDNA=9.2 vs 6.6 months; p > 0.05). However, patients with low-MTV and low-cfDNA levels showed longer OS than those with low-MTV and high-cfDNA levels (low-cfDNA vs. high-cfDNA=49.3 vs 11.5 months; p < 0.001). The patient group with low-TLG also showed similar trends. The cfDNA level was an independent prognostic factor for OS by Cox-proportional hazard analysis. CONCLUSION: Although the patients with high metabolic tumor burden had a poor prognosis, regardless of the biological behavior/aggressiveness of the tumor, patients with low metabolic tumor burden and high cfDNA levels showed a poor prognosis. Taken together, this study indicates a stronger prognostic value of baseline cfDNA levels in identifying patients with advanced NSCLC and personalizing their treatment strategies for better survival.

Basic Concepts and Validation of Digital PCR Measurements.

Use of digital polymerase chain reaction (dPCR) technology is rapidly growing and diversifying into a range of areas in life science. The release of dPCR commercial systems has facilitated access, leading to recognition of the potential advantages compared to previous quantitative PCR technologies, and the scope for novel applications. The capability of dPCR to deliver unprecedented levels of precision, accuracy, and resolution in quantification of nucleic acids has triggered a strong interest by academia and the life sciences industry in use of this technology as a molecular diagnostic tool. However, the performance of dPCR, as for a "classical" PCR assay, essentially still relies on enzyme-based amplification of nucleic acid using specific reagents and instrumentation. This chapter describes basic concepts, key properties, and important factors to consider for the verification and validation of dPCR measurements.