Biomarkers beyond PD-L1 — what else predicts your response

Three markers sit alongside PD-L1 as the most established today: tumour mutational burden (TMB), which counts how many mutations a tumour's DNA carries per megabase; microsatellite instability and mismatch-repair status (MSI/dMMR), which reflects whether the tumour's DNA-repair machinery is working normally; and gene-expression profiling, which reads which immune-related genes are switched on inside the tumour to judge whether it looks "immune-hot" or "immune-cold". A pathologist can also count tumour-infiltrating lymphocytes (TILs) directly on a slide — a simple visual clue to how much immune activity is already present.

What makes TMB and MSI/dMMR particularly useful is that both are tumour-agnostic — they can matter for treatment decisions regardless of which organ the cancer started in, unlike PD-L1 cut-offs, which are validated cancer type by cancer type. NCCN and ASCO guidance recognise several of these markers as legitimate additional inputs into an eligibility discussion, not replacements for PD-L1 but complements to it.

None of these markers is interpreted here against your own report. Biomarker testing for CION patients is coordinated through accredited partner pathology and genomic laboratories, and your combined results are reviewed by your treating oncologist and tumour board.

Bands shown are the commonly cited thresholds referenced in NCCN and FDA companion-diagnostic labelling, indicative as of August 2026. Guidelines are updated periodically, and your oncologist confirms which threshold applies to your specific treatment plan — this table is for general education, not an eligibility guarantee.

1. 1

   Existing reports are gathered

   PD-L1, MSI, TMB or any gene-panel results you already have are collected first, so no test is repeated unnecessarily.

2. 2

   Gaps are identified

   If a marker relevant to your cancer type and treatment decision is missing, your oncologist recommends whether it's worth testing for.

3. 3

   Additional testing is coordinated

   Any new sample or send-out test is coordinated through accredited partner pathology and genomic laboratories — not run in-house.

4. 4

   Your tumour board reviews the combined picture

   PD-L1, MSI/TMB, stage, prior treatment and overall health are weighed together — no single marker decides eligibility alone.

5. 5

   Your oncologist explains it in plain language

   You leave the consultation understanding what your specific numbers mean for your options — not holding a stack of unexplained lab printouts.

Genuinely, yes as research — but not yet as a clinical test. Multiple studies have found associations between the diversity of gut bacteria and how patients respond to checkpoint inhibitor immunotherapy, and recent antibiotic use has been linked to weaker responses in observational data across several cancer types. Specific bacterial genera have been highlighted in different studies, but findings vary between research groups and populations, and there is currently no standardised, validated stool test that a lab can run to predict or change your individual response.

The practical takeaway today is narrow but useful: mention any recent or planned antibiotic use to your oncologist before and during immunotherapy, and be cautious of any clinic or product promising to "boost" your response through gut bacteria, probiotics or immunity drips — that claim runs ahead of what validated evidence currently supports.

• Circulating tumour DNA (ctDNA) dynamics — tracking how ctDNA levels change during treatment as an early signal of response, still being validated across cancer types.
• Multi-omics signatures — combining genomic, transcriptomic and other data layers into one predictive score; promising in research cohorts, not yet standardised for clinical use.
• T-cell receptor (TCR) repertoire diversity — measuring the variety of a patient's immune-cell receptors as a proxy for how "ready" the immune system is to respond.
• Radiomic patterns — computer-extracted features from CT/PET scans studied as a non-invasive proxy for tumour immune activity.
• Germline (inherited) genetic markers — early research into whether a patient's own inherited genetics, separate from the tumour's mutations, influences response.

Long-term reliability, and how well these signals compare against each other across different cancers, is genuinely still being worked out. Treat any claim of a definitive "test that predicts your exact response" with caution unless it is one of the established markers your oncologist already discusses with you.

• Tumour-Agnostic Treatment: When the Biomarker Matters More Than the Cancer — how MSI/dMMR and TMB can matter more than which organ the cancer started in.
• What Is EBV, HPV or Hepatitis Status Got to Do With Immunotherapy? — another category of biomarker your report may mention, explained plainly.
• What Is PD-L1 Testing and Why Does It Decide Your Treatment? — the biomarker this page starts from, explained on its own.
• Immunotherapy at CION Cancer Clinics — the full picture of how CION supports patients through the immunotherapy decision and journey.

This page explains general biomarker terminology for education only and does not interpret any individual patient's report. Testing is coordinated at accredited partner laboratories. Bring your reports to a consultation for a doctor's assessment of what they mean for you.

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