The predictive and prognostic significance of liquid biopsy in advanced epidermal growth factor receptor-mutated non-small cell lung cancer: A prospective study.

OBJECTIVE: To determine the predictive and prognostic roles of three blood-based biomarkers: circulating tumour DNA (ctDNA), circulating tumour cells (CTC) and carcinoembryonic antigen (CEA), in patients with advanced epidermal growth factor receptor-mutated (EGFR+) lung cancer. MATERIALS AND METHODS: We recruited 28 patients with 103 serial blood samples. We performed mutational analyses for EGFR mutations using droplet digital PCR (ddPCR) on ctDNA. We evaluated the accuracy of EGFR mutation detection in ctDNA compared with tissue biopsy. We also quantified CTCs, ctDNA and CEA in serially collected blood samples, and evaluated the baseline and changes in these blood-based biomarkers with clinical outcomes. RESULTS: EGFR mutation detection in plasma was highly concordant as compared with tissue biopsy. Detectable baseline ctDNA was associated with higher disease burden (p < 0.01). Early disappearance of ctDNA at 4 weeks was associated with radiological response at 12 weeks of treatment (p = 0.01) and improved progression free survival (PFS) (HR 5.47, 95%CI 1.32-22.72, p = 0.02) and overall survival (OS) (HR 5.46, 95%CI 1.28-23.22, p = 0.02). A decrease in CTC count at 4 weeks was associated with improved PFS (HR 3.81, 95%CI 1.13-12.79, p = 0.03) but not OS. 85% of patients with radiological progression had a ctDNA rise compared with 22% of patients with stable disease (p=0.01). ctDNA rise was seen on average 170 days prior to radiological progression. There is a significant association between the rise of CEA level with radiological progression (p=0.001). CONCLUSION: Early change in ctDNA, CTC and CEA levels may be long-term predictors of treatment benefit and failure prior to availability of radiological response data.

Circulating tumour cells--a bona fide cause of metastatic cancer.

Circulating tumour cells (CTCs) are emerging as important prognostic markers and have potential clinical utility as tumour biomarkers for targeted cancer therapy. Although CTCs were proposed more than 100 years ago as potential precursors that may form metastatic lesions, formal evidence that CTCs are indeed capable of initiating metastases is limited. Moreover, the process of CTCs shedding into the circulation, relocating to distant organ sites and initiating metastatic foci is complex and intrinsically inefficient. To partially explain the metastatic process, the concepts of CTCs as metastatic precursors or pre-metastatic conditioners have been proposed; however, it is questionable as to whether these are both variable pathways to metastasis or just markers of metastatic burden. This review explores the evidence for CTCs in the initiation and progression of metastatic cancer and the data supporting these different concepts in an attempt to better understand the role of CTCs in metastasis. A greater understanding of the metastatic potential of CTCs will open new avenues for therapeutic interventions in the future.

Circulating tumour cells and circulating free nucleic acid as prognostic and predictive biomarkers in colorectal cancer.

The detection of circulating tumour cells or circulating free tumour nucleic acids can potentially guide treatment and inform prognosis in colorectal cancer using minimally invasive "liquid biopsies". Current literature supports the notion that high circulating tumour cell counts or presence of tumour nucleic acid correlate with inferior clinical outcomes for patients, but they are not yet part of routine clinical care. Future research evolves around the examination of the molecular phenotype of circulating tumour cells. The key unanswered areas include differentiating between circulating tumour cell presence and their proliferative capacity and dormancy, identifying tumour heterogeneity and understanding the epithelial-mesenchymal transition.