Immuno-Oncology Diagnostics Market Report (5th Edition): 2027-2031 Forecast, Technology and Partnering Opportunities by Biomarker, Therapy Class, Cancer Type, Technology, Customer and Country - Strategic Analysis of 99 Companies with Executive and Consultant Guides

Immunotherapy testing moves beyond PD-L1. Cell therapies, bispecifics and vaccines need new tests, spatial and AI pathology read the tumour, and blood tests now watch the response over time.

Market Size 2026: USD $7.54B Market Size 2031: USD $13.5B CAGR: 12.4%

Immuno-oncology (IO) diagnostics are the tests used to select, guide and monitor cancer immunotherapy. They began with a single protein stain, PD-L1 immunohistochemistry (IHC), and now include genomic signatures, tests of the tumour microenvironment, blood tests that track the tumour during treatment, and the cell and cytokine tests that cell therapies need.

This report estimates the global market for IO diagnostics at $7.54 billion in 2026, growing 12.4% a year to $13.5 billion in 2031, adding $5.96 billion of new annual spending. Values are at the manufacturer level in constant 2026 U.S. dollars. Immunotherapy keeps moving into new cancers, earlier stages of disease and new drug classes, and each move brings new testing.

2026 was a year of firsts. Natera's Signatera CDx became the first blood-based MRD companion diagnostic, selecting patients for adjuvant Tecentriq in bladder cancer. PD-L1 rules tightened in oesophageal cancer, dostarlimab was approved for dMMR or MSI-H locally advanced rectal cancer, Medicare extended coverage of ctDNA monitoring of immunotherapy, and China approved the first CAR-T for a solid tumour.

Role of Biomarkers in Immuno-Oncology

PD-L1 & Checkpoint Expression testing remains the largest biomarker line at $2.26 billion in 2026, but it grows only 7% a year and its share falls from 30% to 23.5% by 2031. TMB, MSI & dMMR testing grows 10.8% a year to $2.76 billion as mismatch repair testing becomes routine at diagnosis.

The fastest growth is in Tumour Microenvironment & Spatial testing, growing 20.7% a year to $2.02 billion, and ctDNA Response Monitoring, growing 20.5% a year from $716 million to $1.82 billion. Together these two lines take 39% of all new spending. Immune Repertoire & Cell Monitoring grows 14.6% a year to $1.41 billion on the back of cell therapy and minimal residual disease testing.

Cytokine & Immune-Toxicity Monitoring grows 12.4% a year to $1.01 billion as CAR-T and bispecific treatment spreads, while Germline & HLA testing, needed for HLA-restricted therapies, reaches $742 million.

Technologies Used in IO Diagnostics

NGS is the largest technology, growing 14.5% a year to $3.78 billion and taking 31% of new spending. IHC, at $1.84 billion in 2026, grows only 6.8% a year and its share falls from 24.5% to 19%.

Spatial, Digital Pathology & AI is the fastest-growing technology, rising from $566 million to $1.68 billion at 24.4% a year, as multiplex imaging and algorithm-scored slides move from research into drug trials and the first clinical tests.

PCR & Digital PCR grows 11.6% a year to $2.02 billion, flow cytometry grows 12.4% a year to $1.55 billion, tied to cell therapy and blood cancers, and immunoassays grow 10.1% a year to $1.28 billion.

Blood-based tests are becoming part of immunotherapy care. At least four ctDNA assays now have Medicare coverage for monitoring response to checkpoint inhibitors, and a randomised trial is testing whether ctDNA results should change treatment.

Market Drivers

Checkpoint inhibitors still drive most of the market, but newer therapies drive its growth. Testing for checkpoint inhibitors is worth $5.05 billion, 67% of the market, and still accounts for 43% of the growth, yet its share falls to 56.5% by 2031.

Testing linked to bispecifics and T-cell engagers grows 22.2% a year to $2.16 billion, and cell therapy testing (CAR-T, TIL and TCR-T) grows 17.5% to $2.36 billion. Cancer vaccines are the fastest-growing class at 26.4% a year, as personalised neoantigen vaccines need tumour and normal sequencing for every patient.

Narrower labels raise testing needs. Several checkpoint inhibitor labels now require a PD-L1 or MMR/MSI result, and new antigen-targeted cell therapies and bispecifics depend on tissue or blood tests to select patients.

Regulation diverges. In the U.S., the FDA formally rescinded its rule on laboratory-developed tests in 2025, so laboratories can keep offering IO tests without FDA review. In Europe, companion diagnostics are Class C devices under the IVDR.

Market Segmentation

The report forecasts the market by biomarker, therapy class, cancer type, technology, customer and country.

By cancer type, lung cancer is the largest at $2.33 billion, growing 10.5% a year to $3.84 billion. Gastrointestinal cancers grow fastest, at 15.1% a year to $2.36 billion, helped by MSI and dMMR testing in colorectal and rectal cancer and PD-L1 rules in oesophageal and gastric cancer. Blood cancers grow 14.4% a year to $2.36 billion and genitourinary cancers 13.2%.

Melanoma & Skin grows 9.1% a year to $1.68 billion, and Other Solid Tumours 13.5% to $1.35 billion.

By customer, Reference & Central Laboratories are the largest group at $2.82 billion, growing 12.9% a year and taking 40% of new spending. Pharma & CRO spending grows fastest, 14.1% a year to $3.57 billion, as drug developers pay for biomarker work in trials. Hospital Laboratories grow 11.1% to $3.64 billion.

The United States accounts for 43.3% of the world market in 2031, reaching $5.84 billion. China is the fastest-growing country, at 14.8% a year from $660 million to $1.31 billion, as domestic PD-1 drugs, bispecifics and cell therapies multiply. Japan grows 11.5% to $820 million and Germany 11.5% to $664 million.

Competitive Landscape

Agilent and Roche lead PD-L1 and mismatch repair testing, with Agilent strengthening its IHC portfolio by acquiring Biocare Medical in 2026. Foundation Medicine, Caris, Tempus AI, Guardant Health, Natera, NeoGenomics and Labcorp lead in genomic profiling and ctDNA monitoring. The report profiles 99 companies.

The industry is consolidating around platforms and data. Tempus agreed to buy Personalis, Roche agreed to buy PathAI, Waters combined with BD's flow cytometry business, and Quanterix bought Akoya Biosciences.

Spatial biology and AI pathology companies, including 10x Genomics, Bruker Spatial Biology, Quanterix, Lunit and Indica Labs, are moving tumour microenvironment testing from research towards the clinic.

Winning companies combine pharma relationships, regulatory capability and reach into hospital and reference laboratories, and are building multimodal tests that combine DNA, RNA, protein and images.

Future Outlook

Immuno-oncology testing is moving from one test at diagnosis to many signals read together and repeated over time. The largest opportunities are in tests for the newer therapy classes, spatial and AI-scored tissue tests, and blood tests that monitor response.

Personalised cancer vaccines, if approved, would make tumour and normal sequencing a routine step for every treated patient, and multimodal AI scores are starting to compete with single biomarkers such as PD-L1 and TMB.

The main risks are the failure or delay of partners' drugs, payer resistance to new tests, the cost of IVDR certification in Europe and uncertainty over how regulators will treat AI-based tests.

Overall, IO diagnostics remain one of the fastest-growing parts of precision oncology, and the companies that link testing to the newest immunotherapies are best placed.