Monitoring circulating tumor DNA by recurrent hotspot mutations in bladder cancer

Area of Science:

• Oncology
• Molecular Diagnostics
• Genetics

Background:

• Minimally residual disease in muscle-invasive bladder cancer (MIBC) can be assessed using liquid biopsy.
• Hotspot mutations are prevalent in non-coding regions of MIBC patients.
• Cell-free DNA (cfDNA) analysis offers a method to evaluate MIBC status through hotspot mutations.

Purpose of the Study:

• To evaluate the utility of cfDNA analysis for detecting hotspot mutations in MIBC.
• To assess the potential of cfDNA as a biomarker for predicting disease recurrence in MIBC patients.
• To correlate cfDNA mutation detection with clinical outcomes and imaging diagnostics.

Main Methods:

• Prospective collection of tumor and blood samples from MIBC patients.
• Digital PCR was used to determine the variant allele frequency (VAF) of specific mutations (TERT, PLEKHS1, ADGRG6, WDR74) in tumor and cfDNA.
• Validation of custom primers and probes for mutation detection, and matching of cfDNA VAF with clinical imaging data.

Main Results:

• Out of 37 enrolled MIBC patients, 28 (76%) exhibited hotspot mutations.
• In a follow-up cohort of 21 patients, cfDNA detected recurrence 58 days earlier than CT scan.
• Detection of circulating tumor DNA (ctDNA) post-radical cystectomy correlated with improved recurrence-free survival (P=0.0043) and overall survival (P=0.017).

Conclusions:

• Hotspot mutations in cfDNA serve as a promising biomarker for earlier recurrence prediction compared to CT scans.
• Multiple cfDNA mutation detections enhance the reliability of recurrence prediction in MIBC.
• Negative ctDNA status in patients achieving ypT0 after neoadjuvant chemotherapy was associated with non-recurrence.