GALEAS bladder urine test and methylation biomarkers for bladder cancer

GALEAS is a non-invasive urinary biomarker assay using targeted ultra-deep next-generation sequencing (NGS) to detect somatic gene mutations across a 23-gene panel linked to urothelial bladder cancer (BC) (1):

• aims to serve as a molecular triage tool in urgent haematuria assessment pathways and post-resection non-muscle-invasive bladder cancer (NMIBC) surveillance to safely reduce reliance on invasive flexible cystoscopy
• uses unique molecular identifiers (UMIs) to eliminate false positives from sequencing artifacts or clonal haematopoiesis, enabling reliable detection of low-frequency single nucleotide variants (SNVs)

Core Clinical Findings

Diagnostic Performance of GALEAS Bladder Alone

• high overall accuracy: achieves ~92% sensitivity and ~89% to 92% specificity in clinical haematuria evaluation
• high-grade disease detection: detects over 96% to 97% of high-grade and muscle-invasive bladder cancers, yielding a high negative predictive value (NPV >99%) to rule out aggressive disease
• broad tissue coverage: targeted panel interrogates somatic mutations present in ~96% of all primary urothelial bladder tumours

Value of Adding Methylation Markers to the Panel (2)

• tested hypothesis: researchers investigated whether adding an epigenetic panel (23 hypermethylated DNA loci) could catch false-negative cases missed by the mutation test
• study outcome: adding methylation markers provided no added clinical diagnostic benefit, with combined overall sensitivity remaining unchanged at ~93%
• high concordance: mutation and methylation markers were highly concordant (~85%), and all false-negative GALEAS Bladder urine samples were also completely negative for methylation markers

Key Takeaway for Clinical Practice

• cause of false negatives:
  • false-negative urine DNA results are not caused by missing mutation targets; instead, they occur when low-grade or small tumours shed too few malignant cells into the urine (low tumour cell fraction)
• diagnostic ceiling:
  • because both DNA mutations and methylation markers disappear when shed tumour cells are lacking, adding extra epigenetic markers cannot overcome the physical limit of low cell shedding

References

1. Ward DG, Baxter L, Ott S, Gordon NS, Wang J, Patel P, Piechocki K, Silcock L, Sale C, Zeegers MP, Cheng KK, James ND, Bryan RT. Highly Sensitive and Specific Detection of Bladder Cancer via Targeted Ultra-deep Sequencing of Urinary DNA. European Urology Oncology. 2023;6(1):67-75.
2. Gordon NS, McGuigan EK, Ondasova M, Knight J, Baxter LA, Ott S, Hastings RK, Zeegers MP, James ND, Cheng KK, Goel A, Yu M, Arnold R, Bryan RT, Ward DG. Comparison and combination of mutation and methylation-based urine tests for bladder cancer detection. Biomarker Research. 2024;12(1):133.