# Drug labels must state which biomarker assays were validated and how they compare

Source: https://onco.cc/ideas/idea-tr2-label-assay-concordance/  
OnCo record `idea-tr2-label-assay-concordance` (Idea). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

A drug label says 'for PD-L1 positive patients' but does not say that other tests give different answers. Labels should list the validated tests and how much they disagree.

## Summary

Labels reference the companion diagnostic used in the pivotal trial but not the performance of other assays commonly used in practice, leaving clinicians to guess whether their laboratory's test is equivalent. Requiring a structured concordance section (validated assays, concordance data with other widely used assays, known discordant regions) would surface the uncertainty and drive sponsors to generate bridging data.

## Fields

- Kind: Idea
- Last checked: 2026-09-08
- Hypothesis: Labels with concordance sections will be followed by an increase in published bridging studies and a reduction in the use of unvalidated assay substitutions, measurable in laboratory surveys.
- Rationale: Clinicians substitute assays in practice for cost and availability reasons; the risk of that substitution is currently invisible in the primary document they consult.
- Proposed test: Draft the section for five biomarker-restricted labels using existing concordance literature; survey clinicians and laboratories on utility; propose as a labelling requirement.
- Maturity: speculative
- Actor: regulator

## Sources

- Bottleneck evidence (Biomarkers are not validated or standardised): Fernandez et al., Examination of low ERBB2 protein expression in breast cancer tissue (JAMA Oncology 2022): https://doi.org/10.1001/jamaoncol.2021.7239

## Connected records

- collections: [FDA Oncology Approvals (OCE) & Novel Drug Approvals](https://onco.cc/collections/fda-approvals/)
- ideas: [One digital PD-L1 scale that maps across all the competing assays](https://onco.cc/ideas/idea-tr2-pdl1-digital-calibration/)
- technologies: [Companion diagnostics](https://onco.cc/technologies/companion-diagnostic/)
- terms: [Companion diagnostic](https://onco.cc/terms/companion-diagnostic-term/)
- bottlenecks: [Biomarkers are not validated or standardised](https://onco.cc/bottlenecks/b-biomarker-validation/), [Knowledge reaches practice too slowly](https://onco.cc/bottlenecks/b-knowledge-diffusion/)
- key papers: [Examination of Low ERBB2 Protein Expression in Breast Cancer Tissue](https://onco.cc/key-papers/paper-fernandez-jama-oncol/)

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