Análisis de la concentración sérica del ADN tumoral en el cáncer de pulmón no microcítico y avanzado: ¿es útil como factor pronóstico?

Quantitative Analysis of Circulating Cell-Free DNA for Correlation with Lung Cancer Survival: A Systematic Review and Meta-Analysis

INTRODUCTION

Despite the growing interest in circulating cell-free DNA (cfDNA), no conclusive evidence exists on the value of quantitative analysis of cfDNA for the prediction of lung cancer survival. We performed a systematic review and meta-analysis of primary studies to estimate the impact of higher baseline cfDNA levels on survival outcomes of patients with lung cancer.

METHODS

A comprehensive search was performed using the PubMed, Web of Knowledge, and Cochrane databases up to March 2016. The methodologic quality of identified studies was assessed by the Newcastle-Ottawa scale. Potential sources of heterogeneity were investigated via subgroup and sensitivity analyses, while publication bias was evaluated by funnel plot and Egger's test.

RESULTS

Among the 17 studies identified, 16 studies (n = 1723 patients) and 5 studies (n = 640) were included in the meta-analysis of overall survival (OS) and progression-free survival (PFS), respectively. Despite the fact that the association with PFS did not reach statistical significance (hazard ratio 1.12% [95% confidence interval 0.91-1.37), the pooled analysis for OS showed evidence of an increased risk of death in patients with higher baseline cfDNA levels (hazard ratio 1.76 [95% confidence interval 1.38-2.25]; p < 0.001). Further subgroup and sensitivity analyses confirmed this relationship, although significant between-study heterogeneity was still detected in most comparisons. The Egger's test revealed no statistical evidence of publication bias in the results.

CONCLUSION

Our findings support the clinical validity of quantitative analysis of cfDNA for the prediction of lung cancer survival. Nevertheless, the establishment of a robust standardized method for determination of optimal cutoff thresholds is required to define the clinical relevance of cfDNA quantification for lung cancer management.

Comparisons between capillary zone electrophoresis and real-time PCR for quantification of circulating DNA levels in human sera

BACKGROUND

Recently, some research results showed that the circulating DNA in serum or plasma had potential for the molecular diagnosis and prognosis of certain cancers. Several methods have been employed for the quantification of circulating DNA. However, the circulating DNA levels obtained by various methods exhibited considerable differences. Additionally, these methods were labor-extensive and time-consuming, and not suitable for the quantification of circulating DNA in numerous samples due to the use of commercial DNA extraction kits for the purification of circulating DNA. We presented a new method for the quantification of circulating DNA in sera by capillary zone electrophoresis (CZE) with laser-induced fluorescence detection (LIF).

METHODS

In the present work, we want to make comparison between CZE-LIF assay and real time PCR for the quantification of circulating DNA levels. Linearity, intra and inter variability of two methods were evaluated.

RESULTS

The intra and inter variability of circulating DNA quantification by real-time PCR were 7.3% and 14.92%, respectively. In CZE assay the intra and inter variability were 4.19% and 6.91%, respectively. The R.S.D. values of the same coated capillary and different coated capillaries were 5.14% and 9.02%, respectively. Our data showed that the circulating DNA levels obtained by two methods had a good correlation. Moreover, we further confirmed that blood samples collection, serum preparation and other treatment procedures had a significant impact on the DNA levels in sera.

CONCLUSION

Our data further illustrated that CZE-LIF is a simple, rapid and sensitive method for the quantification of circulating DNA in human sera, and well suitable for the analysis of a large number of samples in clinical diagnosis.