Lianpeng Chang

Application of Circulating Tumor DNA as a Non-Invasive Tool for Monitoring the Progression of Colorectal Cancer

Background Liquid biopsy has been proposed to be a promising noninvasive tool to obtain information on tumor progression. Through a clinical observation of a case series of 6 consecutive patients, we aim to determine the value of circulating tumor DNA (ctDNA) for monitoring the tumor burden during the treatment of colorectal cancer (CRC). Materials and Methods We used capture sequencing of 545 genes to identify somatic alternations in primary tumor tissues of the six CRC patients who underwent radical surgery and in 23 plasma samples collected at serial time points. We compared the mutation patterns and variant allele frequencies (VAFs) between the matched tissue and the plasma samples and evaluated the potential advantage of using ctDNA as a better tumor load indicator to detect disease relapse over carcinoembryonic antigen (CEA), cancer antigen (CA) 19–9 and imaging studies. Results We identified low-frequency mutations with a mean VAF of 0.88% (corresponding to a mean tumor burden of 0.20ng/mL) in the preoperative plasmas of four patients with locally advanced CRC and a subset of mutations shared by their primary tumors. The tumor loads appeared a sudden decrease upon surgery or other adjuvant treatments and then generally maintained at low levels (0.092ng/mL) until disease recurred. ctDNA increased by 13-fold when disease relapsed in one patient while the CEA and CA 19–9 levels remained normal. In this patient, all six somatic mutations identified in the preoperative plasma were detected in the recrudescent plasma again, with five mutations showing allele fraction increase. Conclusions We described a multi-time-point profile of ctDNA of CRC patients during the course of comprehensive treatment and observed a correlation of ctDNA level with the clinically evaluated tumor progression. This demonstrated a new strategy by analyzing the heterogeneous ctDNA to evaluate and monitor the tumor burden in the treatment and follow-up of CRC patients, with potentially better potency than conventional biomarkers.

Comprehensive Molecular Characterization of Young Chinese Patients with Lung Adenocarcinoma Identified a Distinctive Genetic Profile

BACKGROUND Occurrence at a younger age has been demonstrated to be associated with a distinct biology in non-small cell lung cancer. However, genomics and clinical characteristics among younger patients with lung adenocarcinoma remain to be determined. Here we studied the potentially targetable genetic alterations by next-generation sequencing (NGS) assay in young Chinese patients with lung adenocarcinoma. MATERIALS AND METHODS Seventy-one surgically resected lung adenocarcinoma tissue samples from patients aged less than 45 years were collected with informed consent from all patients. Targeted NGS assays were used to identify actionable genetic alterations in the cancer tissues. Additionally, the genomic and clinicopathologic characteristics of 106 patients with lung adenocarcinoma who received NGS testing over the same period were analyzed retrospectively. RESULTS The frequencies of targetable genetic alterations in 177 patients with lung adenocarcinoma were analyzed by defined age categories, which unveiled a distinctive molecular profile in the younger group, aged less than 45 years. Notably, higher frequency of ALK and HER2 genetic alterations were associated with young age. However, a reverse trend was observed for KRAS, STK11 and EGFR exon 20 mutations, which were more frequently identified in the older group, aged more than 46 years. Furthermore, concurrent EGFR/TP53 mutations were much more prevalent in the younger patients (81.6% vs. 46.8%), which might have a poor response to treatment with epidermal growth factor receptor tyrosine kinase inhibitor. CONCLUSION In this study, NGS assay revealed a distinctive genetic profile in younger patients with adenocarcinoma. High frequency of concurrent EGFR/TP53 mutations was found in the younger patients, which especially warranted personalized treatment in this population. IMPLICATIONS FOR PRACTICE Further investigation is needed to understand the genomics and clinical characteristics of young patients with lung adenocarcinoma. In the present study, hybrid capture-based next-generation sequencing assays were used to identify targeted genetic alterations in young lung adenocarcinoma patients. Young patients with lung adenocarcinoma, aged less than 45 years, harbored a higher frequency of ALK and HER2 genetic alterations compared with patients aged more than 46 years. Dramatically, concurrent EGFR/TP53 mutations were much more prevalent in younger patients, which had a poor response to treatment with epidermal growth factor receptor kinase inhibitor. These results reveal a distinctive genetic profile in younger patients with adenocarcinoma, which might improve the treatment of this subpopulation.

Circulating tumor DNA analysis depicts subclonal architecture and genomic evolution of small cell lung cancer

Subclonal architecture and genomic evolution of small-cell lung cancer (SCLC) under treatment has not been well studied primarily due to lack of tumor specimens, particularly longitudinal samples acquired during treatment. SCLC is characterized by early hematogenous spread, which makes circulating cell-free tumor DNA (ctDNA) sequencing a promising modality for genomic profiling. Here, we perform targeted deep sequencing of 430 cancer genes on pre-treatment tumor biopsies, as well as on plasma samples collected prior to and during treatment from 22 SCLC patients. Similar subclonal architecture is observed between pre-treatment ctDNA and paired tumor DNA. Mean variant allele frequency of clonal mutations from pre-treatment ctDNA is associated with progression-free survival and overall survival. Pre- and post-treatment ctDNA mutational analysis demonstrate that mutations of DNA repair and NOTCH signaling pathways are enriched in post-treatment samples. These data suggest that ctDNA sequencing is promising to delineate genomic landscape, subclonal architecture, and genomic evolution of SCLC.Small cell lung cancer (SCLC) may evolve under treatment. But tumor tissues are often not available to study evolution of SCLC. Here, the authors utilize circulating tumor DNA to investigate the genomic evolution and subclonal architecture of SCLC during therapy.