HRD assay distinction (Myriad myChoice CDx vs FoundationOne CDx)
Deterministic view of the source YAML entity. Clinical authority remains with the cited source IDs and reviewer sign-off state.
| ID | BIO-HRD-ASSAY-DISTINCTION |
|---|---|
| Type | Biomarker |
| Aliases | GIS vs LOH/TAI/LSTHRD assay distinctionHRD platform comparisonРозмежування HRD-аналізів (Myriad myChoice CDx vs FoundationOne CDx) |
| Status | reviewed 2026-04-29 | pending_clinical_signoff |
| Diseases | None declared |
| Sources | SRC-CIVIC SRC-NCCN-COLON-2025 |
Biomarker Facts
| Biomarker type | composite_score |
|---|---|
| Measurement | MethodTwo FDA-approved companion diagnostic platforms with different scoring systems: (a) Myriad myChoice CDx — Genomic Instability Score (GIS) combining LOH + TAI + LST as a single composite, threshold GIS >=42 for HRD-positive; (b) FoundationOne CDx HRD — reports LOH-high (>=16% genomic LOH) plus BRCA1/2 status; aggregates LOH only, no TAI or LST. Both run on FFPE tumor. Unitscategorical (HRD-positive | HRD-negative); platform-specific cut-points are not interchangeable |
| Related biomarkers | BIO-HRD-STATUS BIO-BRCA1-BRCA2-GERMLINE |
Notes
Scope: this entity is a methodological / assay-distinction layer on top of BIO-HRD-STATUS. The clinical concept (HRD as a PARPi-response predictor) lives in BIO-HRD-STATUS. This entity records the technical caveats clinicians need when interpreting an HRD report from a specific platform. **Why two assays diverge:** - **Myriad myChoice CDx (companion to olaparib + bevacizumab in PAOLA-1 and niraparib in NOVA / PRIMA):** - Composite Genomic Instability Score (GIS) = LOH + TAI + LST - Threshold: GIS >=42 OR BRCA1/2 mutation -> HRD-positive - Captures three independent genome-scarring footprints (LOH = loss of heterozygosity; TAI = telomeric allelic imbalance; LST = large-scale state transitions) - **FoundationOne CDx HRD (companion to rucaparib in ARIEL3 design; olaparib HRRm-positive subset):** - LOH-high threshold: %LOH >=16% across genome - Does NOT include TAI or LST - More permissive on some BRCA-wt high-grade serous tumors, stricter on others — discordance with myChoice runs ~10-20% in head-to-head series **Clinical implications of the discordance:** - A patient classified HRD-positive on one platform may be classified HRD-negative on the other; this is a known pre-analytic lim...
Used By
No reverse references found in the YAML corpus.