Immuno-Oncology Biomarkers Market (2026-2036)

The growth of this market is mainly driven by the expanding use of immune checkpoint inhibitors across tumor types and treatment lines, the increasing number of companion diagnostic approvals linking biomarkers such as PD-L1, tumor mutational burden (TMB), and microsatellite instability (MSI) to immunotherapy eligibility, the adoption of comprehensive genomic profiling that reports multiple immuno-oncology biomarkers in a single test, and the growing use of circulating tumor DNA to monitor response to immunotherapy. In addition, the development of novel immunotherapies, including bispecific antibodies, cell therapies, and cancer vaccines, the emergence of spatial and multiplex tissue biomarkers, and the use of artificial intelligence (AI) in digital pathology to score biomarkers are further supporting the growth of this market.

The Immuno-Oncology Biomarkers Market, also referred to as the immunotherapy biomarkers market, IO companion diagnostics market, or checkpoint inhibitor biomarker testing market, comprises the assays and kits, instruments, software, and testing services used to measure biomarkers that predict, guide, or monitor response to cancer immunotherapies. The market includes immunohistochemistry (IHC) assays for programmed death-ligand 1 (PD-L1) and mismatch repair (MMR) proteins; next-generation sequencing (NGS) tests that measure TMB, MSI, and other genomic biomarkers; PCR-based MSI assays; gene expression signatures of immune activity; multiplex immunofluorescence and spatial assays that profile tumor-infiltrating lymphocytes and the tumor microenvironment; ctDNA tests for monitoring response; and digital pathology and AI software for biomarker scoring. The market ecosystem extends from diagnostic and reagent manufacturers to pathology and reference laboratories, comprehensive genomic profiling providers, pharmaceutical companies that co-develop companion diagnostics, oncologists, and payers.

The market is experiencing steady growth as immune checkpoint inhibitors have become standard treatments across many cancers, including non-small cell lung cancer, melanoma, head and neck, gastric, esophageal, cervical, triple-negative breast, bladder, kidney, and endometrial cancers. Because only a subset of patients respond to immunotherapy, and because these drugs carry significant cost and potential immune-related toxicity, biomarkers are essential for selecting patients, choosing among treatment options, and monitoring response. Each new immunotherapy indication typically requires a companion or complementary diagnostic, generating new testing demand.

PD-L1 testing remains the most widely used immuno-oncology biomarker. In February 2026, Agilent received U.S. Food and Drug Administration (FDA) approval for PD-L1 IHC 22C3 pharmDx as a companion diagnostic for KEYTRUDA (pembrolizumab) in epithelial ovarian, fallopian tube, or primary peritoneal carcinoma, the first immuno-oncology approval in this disease, and in March 2026 received approval in esophageal or gastroesophageal junction carcinoma for tumors with a Combined Positive Score (CPS) of 1 or higher, its eighth FDA-approved companion diagnostic indication with KEYTRUDA. In June 2026, Agilent received FDA approval to run PD-L1 IHC 22C3 pharmDx on its automated Dako Omnis platform for four additional tumor types, esophageal squamous cell carcinoma, triple-negative breast cancer, cervical cancer, and gastric or gastroesophageal junction adenocarcinoma, allowing laboratories to consolidate PD-L1 testing into one automated workflow. Roche offers the VENTANA PD-L1 (SP263) assay, which has FDA-approved non-small cell lung cancer indications for four immunotherapy drugs, including cemiplimab, as well as other PD-L1 assays on its BenchMark platforms. The continued expansion of indications and the consolidation of testing onto automated platforms are supporting stable growth in PD-L1 testing.

Genomic biomarkers measured by NGS are also central to immunotherapy selection. FoundationOne CDx is FDA-approved as a companion diagnostic to identify patients with tumor mutational burden-high (TMB-H) and microsatellite instability-high (MSI-H) solid tumors who may be eligible for KEYTRUDA, enabling genomic immuno-oncology biomarkers to be assessed alongside targeted therapy biomarkers in a single comprehensive genomic profiling test. MSI-H and mismatch repair deficiency (dMMR) are approved tumor-agnostic biomarkers for checkpoint inhibitor therapy, and dMMR tumors are particularly responsive to immunotherapy in colorectal, endometrial, and other cancers. Comprehensive genomic profiling tests from companies such as Foundation Medicine, Caris Life Sciences, Illumina, and Thermo Fisher Scientific report TMB and MSI alongside targeted therapy biomarkers, making genomic immuno-oncology biomarkers more widely available.

Monitoring response to immunotherapy is an emerging area of growth. Imaging can be difficult to interpret during immunotherapy because of pseudoprogression, and ctDNA testing can provide earlier evidence of whether a patient is responding. Natera, which offers the Signatera tumor-informed circulating tumor DNA (ctDNA) test for molecular residual disease and immunotherapy response monitoring, reported Q2 2026 revenue of USD 752.8 million, up 37.7%, with about 296,700 oncology tests processed, and raised its 2026 revenue guidance to USD 2.85 billion to USD 2.91 billion. Medicare issued a draft local coverage determination supporting coverage of Signatera for immunotherapy response monitoring, citing validation showing that the test identified non-responders with high positive predictive value when used with imaging.

New immunotherapy modalities and biomarkers are expanding the market further. Bispecific antibodies, cell therapies, cancer vaccines, and novel checkpoint inhibitors targeting LAG-3, TIGIT, and other pathways require new biomarkers for patient selection. Multiplex immunofluorescence and spatial profiling platforms are being used to characterize the tumor microenvironment and identify spatial biomarkers that predict response more accurately than single-marker IHC, and AI-based digital pathology is being applied to PD-L1 scoring and tumor-infiltrating lymphocyte assessment to improve consistency.

At the same time, the market faces challenges related to the limited predictive accuracy of current biomarkers, differences between assays and scoring systems, and reimbursement. PD-L1 expression is an imperfect predictor of response, and different assays, cutoffs, and scoring methods, such as tumor proportion score and CPS, are used for different drugs and indications. As a result, providers that can deliver standardized, automated, and clinically validated biomarker tests, and that develop new biomarkers for emerging immunotherapies, are expected to capture the largest share of growth over the forecast period.