Ultradeep Sequencing of Plasma Cell-Free DNA in Bladder Cancer
In a study reported in the Journal of Clinical Oncology, Christensen et al found that identification of circulating tumor DNA (ctDNA) by ultradeep sequencing of plasma cell-free DNA was highly prognostic for outcome in bladder cancer and permitted early detection of relapse.
The study included 68 patients with locally advanced bladder cancer seen at Aarhus University Hospital. Patient-specific somatic mutations identified by whole-exome sequencing were used to assess ctDNA by ultradeep sequencing (median = 105,000×) of plasma DNA. Plasma samples (n = 656) were obtained at diagnosis, during chemotherapy, before cystectomy, and during surveillance.
Prognostic Ability
Detection of ctDNA at diagnosis prior to chemotherapy was highly prognostic for recurrence-free survival (hazard ratio [HR] = 29.1, P = .001). Detection of ctDNA before cystectomy and after cystectomy was also prognostic for recurrence-free survival (both P < .001), and detection of ctDNA was prognostic for overall survival at all three time points (all P < .001). After cystectomy, ctDNA analysis identified all patients with metastatic relapse during disease monitoring (100% sensitivity and 98% specificity), with a median lead time over radiographic imaging of 96 days being observed.
Among high-risk patients—defined as those who were ctDNA-positive before or during treatment—clearance of ctDNA during chemotherapy was associated with a reduced risk of disease recurrence (P = .023), whereas pathologic downstaging during chemotherapy was not (P = .10). Analysis of tumor-centric biomarkers showed that mutational processes (trinucleotide mutational signature 5) were associated with pathologic downstaging during chemotherapy (P = .024); however, no significant correlations for tumor subtypes, DNA damage response mutations, or other biomarkers were observed.
Overall, ctDNA monitoring remained the strongest predictor of outcome and therapy response in high-risk (ctDNA-positive) patients.
The investigators concluded, “Our results suggest that ctDNA analysis is better associated with treatment efficacy compared with other available methods… ctDNA assessment for early risk stratification, therapy monitoring, and early relapse detection in bladder cancer is feasible and provides a basis for clinical studies that evaluate early therapeutic interventions.”
Lars Dyrskjøt, PhD, of the Department of Molecular Medicine, Aarhus University Hospital, is the corresponding author for the Journal of Clinical Oncology article.
Disclosure: The study was supported by the Danish Cancer Society, Novo Nordisk Foundation, Independent Research Fund Denmark, Aarhus University, and Natera. For full disclosures of the study authors, visit jco.ascopubs.org.
The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.
