Cancer Immunotherapy (2026): Types, Success Rates & Side Effects
Medically Reviewed by: OneDayMD Editorial Team | Last Updated: August 2026
Cancer immunotherapy represents a major paradigm shift in oncology — mobilizing a patient's own immune system to recognize and attack cancer cells, rather than relying solely on surgery, radiation, or cytotoxic chemotherapy. Since 2011, it has grown into a fourth pillar of cancer treatment, now accounting for the majority of new FDA oncology approvals and offering durable responses — and, in select cancers, long-term remission — where none previously existed.
Quick Answer (AI & Search Summary)
Cancer immunotherapy is a class of treatments — checkpoint inhibitors, CAR-T and other cell therapies, monoclonal antibodies, bispecific antibodies, cancer vaccines, and immune modulators — that help a patient's own immune system recognize and destroy cancer cells. As of 2025, the FDA has approved 156 cancer immunotherapy products or indications since 2011, and checkpoint inhibitors such as Keytruda (pembrolizumab) now generate more revenue than any other drug in the world ($31.7 billion in 2025). Overall response rates across all comers remain modest — historically cited around 15–20% — but rise sharply in biomarker-selected patients (for example, close to 100% durable complete responses have been reported with dostarlimab in mismatch-repair-deficient rectal cancer). The newest frontiers in 2026 include personalized mRNA neoantigen vaccines, PD-1/VEGF and PD-1/CTLA-4 bispecific antibodies, and the world's first CAR-T cell therapy approved for a solid tumor.
In This Article
- Introduction: The Fourth Pillar
- How Does Immunotherapy Work?
- Major Types of Cancer Immunotherapy
- Which Cancers Are Treated With Immunotherapy?
- 2026 Breakthroughs and New Approvals
- Side Effects of Immunotherapy
- How Is Immunotherapy Given?
- Where and How Often Is It Given?
- How Do You Know If It's Working?
- Success Rates and Response Data
- The Gut Microbiome Connection
- Current Research Directions
- Evidence Grading Summary (CEBM)
- Frequently Asked Questions
- Ask an AI Assistant About Your Situation
- Finding a Clinical Trial
- Conclusion
Introduction: The Fourth Pillar
Until recently, oncology had only three main tools. Surgery has been used for roughly three thousand years. Radiation therapy arrived in 1896. Then, in 1946, mustard-gas research from wartime chemical weapons programs led to the first cancer-killing drugs — the foundation of chemotherapy.
Together, this "cut, burn, and poison" approach cures cancer in roughly half of the people who develop it — a genuine medical achievement, but one that still leaves the other half. Hundreds of thousands of people in the United States alone die of cancer every year.

The fight was never fair. Medicine was pitting relatively blunt drugs against an endlessly creative, mutating version of our own cells — trying to kill the malignant ones while sparing the healthy ones.
Immunotherapy is different. Rather than attacking the tumor directly, it acts on the immune system — the network of cells that has evolved over roughly 500 million years to find and eliminate anything in the body that doesn't belong, including cells that have become infected, mutated, or cancerous.
Which raises an obvious question: if the immune system is built to destroy abnormal cells, why doesn't it eliminate cancer on its own?
The answer is that it often tries to — and frequently succeeds, silently, without our ever knowing a tumor was starting to form. The problem is the rare cell that develops ways to hide from immune surveillance, disable nearby immune cells, or exploit the very checkpoints the immune system uses to avoid attacking healthy tissue. Left undetected, that single cell can eventually become a life-threatening cancer.
For most of the twentieth century, the idea of "waking up" the immune system against cancer was considered scientifically implausible. Even Dr. Siddhartha Mukherjee's widely read 2010 history of oncology, The Emperor of All Maladies, does not discuss cancer immunotherapy in any detail. Within roughly a year of its publication, the first of a new generation of drugs — the immune checkpoint inhibitors — received FDA approval, based on the discovery that tumors hijack specific molecular "off-switches" on T cells to avoid destruction. Blocking those switches, it turned out, could let the immune system finish the job it was designed to do.
The moment this treatment class became widely known to the public was in 2015, when former U.S. President Jimmy Carter announced that melanoma had spread to his liver and brain. Given his age and the extent of disease, most assumed he had months to live. Instead, after several months of surgery, radiation, and the checkpoint inhibitor pembrolizumab (Keytruda), scans showed no detectable cancer. Carter went on to live cancer-free for close to a decade — writing, teaching Sunday school, and building homes with Habitat for Humanity — before he died peacefully at his home at age 100 in December 2024, following an unrelated period of hospice care. His case remains one of the most widely cited examples of durable immunotherapy remission in advanced melanoma.
In 2018, the Nobel Prize in Physiology or Medicine was awarded to Dr. James P. Allison and Dr. Tasuku Honjo for discovering the checkpoint mechanisms that made this new treatment class possible — work the Nobel committee described as having fundamentally changed how cancer is managed. Today, more than 150 individual cancer immunotherapy products or indications have been approved by the FDA since 2011, and more than a thousand additional combinations are in active clinical development.
Background source (paraphrased): The Breakthrough: Immunotherapy and the Race to Cure Cancer (2021)
How Does Immunotherapy Work Against Cancer?
As part of its normal surveillance function, the immune system detects and destroys abnormal cells, likely preventing or slowing the growth of many cancers before they're ever noticed. Immune cells called tumor-infiltrating lymphocytes (TILs) are sometimes found in and around tumors — a sign the immune system is actively responding. People whose tumors contain more TILs generally have better outcomes than those whose tumors don't.
Cancer cells, however, have evolved several mechanisms to suppress this response:
- Checkpoint proteins like PD-1 and CTLA-4 act as "off-switches" on T cells. Tumors exploit these switches to avoid being attacked.
- Genetic changes can make cancer cells less visible to immune surveillance.
- Surface proteins on cancer cells can directly deactivate nearby immune cells.
- Remodeling of the surrounding tissue (the tumor microenvironment) can interfere with how immune cells reach and respond to the tumor.
Checkpoint inhibitors work by blocking these "off-switches," which is often described as releasing the brakes on the immune system — allowing T cells already present in and around the tumor to recognize and destroy cancer cells they were previously prevented from attacking.
Major Types of Cancer Immunotherapy
Several distinct classes of immunotherapy are now in clinical use, and the list has grown meaningfully since this article was first published:
- Immune checkpoint inhibitors — drugs that block checkpoints such as PD-1, PD-L1, and CTLA-4, freeing T cells to attack cancer. Learn more about immune checkpoint inhibitors.
- T-cell transfer therapy (adoptive cell therapy), including CAR-T and TIL therapy — a patient's own immune cells are collected, selected or genetically engineered to better recognize the tumor, expanded in large numbers in a lab, and reinfused. Learn more about T-cell transfer therapy.
- Natural killer (NK) cell-based immunotherapies, including CAR-NK constructs, continue to attract interest for their potential to reduce toxicity relative to CAR-T while retaining efficacy. Learn more about NK cell immunotherapy.
- Monoclonal antibodies — lab-made immune proteins that bind specific targets on cancer cells, marking them for destruction. Learn more about monoclonal antibodies.
- Bispecific antibodies and T-cell engagers — a newer, fast-growing class engineered to bind two different targets at once, typically physically linking a T cell directly to a cancer cell to trigger an attack. Established examples include blinatumomab, teclistamab, mosunetuzumab, and tarlatamab in blood cancers; newer PD-1×CTLA-4 and PD-1×VEGF bispecifics are now being tested across solid tumors as single-molecule alternatives to combination checkpoint therapy.
- Treatment (therapeutic) vaccines, including personalized mRNA neoantigen vaccines — designed to boost the immune response specifically against a patient's existing cancer, distinct from vaccines that prevent disease. Learn more about cancer treatment vaccines.
- Immune system modulators — agents that enhance the immune response either broadly or against specific targets. Learn more about immune system modulators.
Which Cancers Are Treated With Immunotherapy?
Immunotherapy is now approved across dozens of cancer types, though it is still not as universally used as surgery, chemotherapy, or radiation. To check whether it may apply to a specific diagnosis, see the National Cancer Institute's adult cancer treatment summaries and childhood cancer treatment summaries.
Keytruda (pembrolizumab): The World's Best-Selling Drug
Keytruda remains the best-selling pharmaceutical product in the world by a wide margin. Merck reported worldwide Keytruda sales of approximately $31.7 billion in 2025, up 7% year over year, with continued growth expected through 2026 as newer indications — including ovarian cancer and a subcutaneous formulation (Keytruda Qlex) — roll out. Competing checkpoint inhibitors also posted strong 2025 sales: Bristol Myers Squibb's Opdivo (nivolumab) reached roughly $10.05 billion, Roche's Tecentriq (atezolizumab) reached CHF 3.56 billion, and AstraZeneca's Imfinzi (durvalumab) reached about $6.06 billion, up 28% on strong bladder and liver cancer demand.
Keytruda's approved and studied indications include:
- Melanoma (KEYNOTE-006, KEYNOTE-054)
- Non-small cell lung cancer (KEYNOTE-010, -189, -407, -671)
- Head and neck cancer (KEYNOTE-012, -048)
- Renal cell carcinoma (KEYNOTE-426)
- Classical Hodgkin lymphoma (KEYNOTE-204)
- Primary mediastinal large B-cell lymphoma
- Bladder cancer (EV-302/KEYNOTE-A39)
- Microsatellite instability-high (MSI-H) / mismatch-repair-deficient cancers
- Gastric, esophageal, cervical, liver, and biliary tract cancers
- Merkel cell carcinoma and endometrial cancer
- Tumor mutational burden-high (TMB-H) cancers
- Cutaneous squamous cell carcinoma
- Triple-negative breast cancer (ASCENT-04/KEYNOTE-D19)
- Ovarian cancer — a newly approved 2026 indication
"KEYNOTE" is not an acronym — it is simply the code Merck assigns to each clinical trial evaluating pembrolizumab in a given cancer type or setting.
2026 Breakthroughs and New Approvals
Immunotherapy's pace of progress has, if anything, accelerated. The Cancer Research Institute's 2026 tracking report counts 156 total FDA cancer immunotherapy approvals since 2011, with 13 new approvals granted in 2025 alone — 11 of which were PD-1/PD-L1 checkpoint therapies, underscoring how dominant that single molecular axis remains. 2025 also brought the first-ever immunotherapy approval for anal cancer, and the approval of penpulimab — the first Chinese-developed checkpoint inhibitor to reach the U.S. market independently, without first licensing through a Western pharmaceutical company.
Selected developments through mid-2026:
- Dostarlimab (Jemperli) in rectal cancer. Updated data from the original Phase 2 trial show that all 42 patients with locally advanced mismatch-repair-deficient (dMMR) rectal cancer who completed dostarlimab monotherapy achieved a clinical complete response, with 24 patients maintaining that response at 12 months over a median follow-up of roughly 26 months — without chemotherapy, radiation, or surgery. The follow-on registrational trial, AZUR-1, has since met its primary endpoint for durable complete response, and dostarlimab now holds FDA Breakthrough Therapy and Fast Track designations for this use, with global regulatory submissions planned.
- Personalized mRNA cancer vaccines. Five-year data from the KEYNOTE-942 trial, presented at ASCO 2026, showed that a personalized mRNA neoantigen vaccine (mRNA-4157/V940, developed by Moderna and Merck) combined with pembrolizumab cut the risk of melanoma recurrence or death by roughly half compared with pembrolizumab alone. A larger, roughly 1,000-patient Phase 3 program is underway to confirm the finding. Separately, a personalized mRNA vaccine for resected pancreatic cancer (autogene cevumeran, developed with BioNTech and Genentech/MSK) has shown that immune responses in patients who responded to the vaccine have persisted for up to six years, with survival substantially exceeding the roughly 13% five-year survival rate typical of pancreatic cancer in that responder group — though this remains small, early-phase data, and a larger Phase 2 trial is now underway.
- Bispecific antibodies. PD-1×CTLA-4 (cadonilimab) and PD-1×VEGF (ivonescimab) bispecific antibodies — both developed by Akeso — were presented across numerous solid-tumor studies at ASCO 2026, effectively combining what previously required two separate drugs into a single molecule.
- The first CAR-T therapy for a solid tumor. In June 2026, China's National Medical Products Administration approved satricabtagene autoleucel (satri-cel), a Claudin18.2-targeted CAR-T therapy, for Claudin18.2-positive, HER2-negative advanced gastric and gastroesophageal junction cancer after at least two prior lines of treatment — the world's first CAR-T product approved for a solid tumor, based on a confirmatory randomized trial published in The Lancet.
- Broader 2026 FDA approvals have extended immunotherapy to earlier treatment lines and new settings, including upfront durvalumab plus BCG for high-risk non-muscle-invasive bladder cancer, nivolumab plus chemotherapy for pediatric and adult classical Hodgkin lymphoma, adjuvant belzutifan plus pembrolizumab for kidney cancer, ctDNA-guided adjuvant atezolizumab for bladder cancer, and new TROP2-targeted antibody-drug conjugates for triple-negative breast cancer patients who are not candidates for checkpoint inhibitors.
What Are the Side Effects of Immunotherapy?
Immunotherapy side effects largely stem from the same mechanism that makes it effective: an immune system revved up against cancer can also mistakenly attack healthy tissue.
Immune-related adverse events (irAEs)
Common irAEs include skin rash, fatigue, and diarrhea; endocrine disorders such as thyroiditis; and, less commonly, hepatitis or pneumonitis. Serious autoimmune reactions can occur but are uncommon. These effects are not usually life-threatening when caught early — oncologists now follow well-established protocols to monitor for, diagnose, and treat irAEs, often with corticosteroids or other immune-modulating drugs.
Cytokine release syndrome (CRS) and neurotoxicity (ICANS)
CRS is seen primarily with CAR-T and bispecific T-cell engager therapies, resulting from rapid, large-scale immune activation. It is managed with corticosteroids and IL-6 pathway blockers (such as tocilizumab). A related complication, immune effector cell-associated neurotoxicity syndrome (ICANS), is monitored closely in patients receiving cellular therapies and is generally reversible with prompt treatment.
Learn more about immunotherapy side effects.
Related reading: Cardiac Toxicity Associated with Immune Checkpoint Inhibitors: Case Series and Review of the Literature (2019)
How Is Immunotherapy Given?
Different forms of immunotherapy are administered in different ways:
- Intravenous (IV): delivered directly into a vein — the most common route for checkpoint inhibitors and monoclonal antibodies.
- Subcutaneous: injected under the skin; newer formulations such as subcutaneous pembrolizumab (Keytruda Qlex) can reduce infusion time to just a few minutes.
- Oral: some immune modulators come as pills or capsules.
- Topical: a cream applied to the skin, used for very early skin cancers.
- Intravesical: instilled directly into the bladder, as with BCG or durvalumab for early bladder cancer.
Where Do You Go for Immunotherapy, and How Often Is It Given?
Most immunotherapy is administered in a doctor's office, infusion clinic, or hospital outpatient unit — meaning no overnight stay is required for most regimens. Cellular therapies such as CAR-T typically require a short inpatient stay for monitoring after infusion.
How often treatment is given depends on the type of cancer, the specific immunotherapy, and how the patient's body responds. Some regimens are given every few weeks on an ongoing basis; others (like CAR-T or dostarlimab in rectal cancer) are given as a defined, time-limited course. Many are given in cycles — a period of treatment followed by rest, allowing the body to recover and immune cells to regenerate.
How Can You Tell If Immunotherapy Is Working?
Response is tracked through regular physical exams, symptom check-ins, blood tests, and imaging (CT, MRI, or PET scans) to measure tumor size and look for new lesions. Increasingly, blood-based tests for circulating tumor DNA (ctDNA) are being used alongside imaging to detect molecular residual disease earlier than scans alone — now a factor in some FDA-approved adjuvant immunotherapy decisions.
Immunotherapy Success Rates
Immunotherapy is not uniformly effective. Historically, overall response rates across all patients and cancer types have been cited at roughly 15–20% — meaning most patients, taken as an undifferentiated group, do not respond. But that aggregate figure obscures enormous variation by cancer type and biomarker status.
Where response rates are highest
- Melanoma, lung, kidney, bladder, and some head-and-neck cancers now routinely use checkpoint inhibitors as standard care.
- Combination immunotherapy (such as nivolumab plus ipilimumab) has meaningfully improved long-term survival in melanoma and several other tumor types.
- In biomarker-selected populations — most strikingly, dMMR/MSI-H rectal cancer treated with dostarlimab — complete response rates approaching 100% have now been reported and sustained for years.
What predicts response
- PD-L1 expression and tumor mutational burden (TMB) remain the two most widely used biomarkers for predicting benefit.
- Newer AI-based prediction models are being developed to combine imaging, genomic, and pathology data to better identify likely responders before treatment starts.
Immunotherapy Can Fail When Certain Gut Microbes Are Absent
Researchers have found that gut bacteria composition appears to influence how well patients respond to checkpoint inhibitors, which — despite their promise — still fail in a majority of patients. In laboratory studies, germ-free mice failed to respond to checkpoint inhibitor treatment, while mice colonized with specific bacteria such as Bacteroides fragilis responded significantly better. Other researchers have reported similar effects with Bifidobacterium, apparently by helping to prime a more robust anti-cancer immune response.
Consistent with this, antibiotic use around the time of immunotherapy has been associated with worse outcomes in several studies, likely because broad-spectrum antibiotics indiscriminately reduce populations of beneficial gut bacteria along with harmful ones. Even some non-immune-based cancer therapies appear to depend partly on the presence of specific gut microbes for full effectiveness — in some cases because those microbes help directly eliminate tumor cells, and in others because they influence gene expression and genomic stability in the host.
Read more: Gut Microbiome May Be a Game Changer for Cancer Prevention
Current Research Directions
Several major research threads are shaping where immunotherapy goes next:
- Overcoming resistance. Combinations of checkpoint inhibitors with other immunotherapies, targeted therapy, and radiation are being tested to re-sensitize tumors that don't initially respond.
- Predicting response before treatment. Because only a fraction of patients benefit, better biomarkers — genomic, imaging, and AI-driven — remain a top priority.
- Understanding tumor immune evasion in more detail. Each newly discovered evasion mechanism is a potential new drug target.
- Reducing side effects while preserving efficacy, including more selective bispecific and cellular therapy designs.
- Targeting checkpoints beyond PD-1 and CTLA-4, and combining immune checkpoint blockade with anti-angiogenic therapy in a single bispecific molecule (as with PD-1×VEGF agents).
Evidence Grading Summary (CEBM)
Not all immunotherapy claims rest on the same strength of evidence. The table below grades several of the claims made in this article using the Oxford Centre for Evidence-Based Medicine (CEBM) framework, where Level 1 reflects the strongest evidence (systematic reviews of randomized trials) and Level 5 reflects the weakest (mechanistic or expert-opinion evidence).
| Claim | CEBM Tier | Basis |
|---|---|---|
| Checkpoint inhibitors improve survival in melanoma, NSCLC, RCC, bladder, and head/neck cancer | Level 1 | Multiple large randomized controlled trials and meta-analyses (KEYNOTE, CheckMate series) |
| Dual checkpoint blockade (nivolumab + ipilimumab) improves long-term survival | Level 1 | Individual high-quality RCTs (CheckMate-067, CheckMate-214) |
| Dostarlimab achieves durable complete response in dMMR/MSI-H rectal cancer | Level 2 | Single-arm Phase 2 cohort (NCT04165772) plus interim registrational Phase 2 data (AZUR-1) |
| mRNA-4157/V940 + pembrolizumab reduces melanoma recurrence risk | Level 2 | Randomized Phase 2b trial (KEYNOTE-942) with 5-year follow-up; Phase 3 confirmatory trial ongoing |
| Personalized mRNA vaccine (autogene cevumeran) benefits pancreatic cancer patients | Level 4 | Small, uncontrolled Phase 1 case series; Phase 2 trial ongoing |
| Claudin18.2 CAR-T (satri-cel) benefits gastric/GEJ cancer | Level 1 | Confirmatory randomized controlled trial, published and regulatory-approved |
| Gut microbiome composition affects checkpoint inhibitor response | Level 4–5 | Preclinical animal models plus small observational human cohorts; mechanistic plausibility |
| PD-L1 expression and TMB predict likelihood of immunotherapy benefit | Level 2 | Multiple prospective biomarker-stratified trials across tumor types |
Frequently Asked Questions
What is cancer immunotherapy?
Cancer immunotherapy is a category of cancer treatment that works by helping a patient's own immune system recognize and destroy cancer cells, rather than attacking the tumor directly the way surgery, radiation, and chemotherapy do.
What are the main types of immunotherapy?
The main categories are immune checkpoint inhibitors, T-cell transfer therapies (including CAR-T and TIL therapy), NK cell-based therapies, monoclonal antibodies, bispecific antibodies, cancer treatment vaccines (including personalized mRNA vaccines), and immune system modulators.
Which cancers respond best to immunotherapy?
Melanoma, non-small cell lung cancer, kidney cancer, bladder cancer, and several head-and-neck and blood cancers show the most established benefit. Response is especially strong in tumors with high PD-L1 expression, high tumor mutational burden, or mismatch-repair deficiency (MSI-H/dMMR).
What is the overall response rate for immunotherapy?
Across all cancer types and patients, overall response rates have historically been estimated at around 15–20%. In biomarker-selected subgroups, however — such as dMMR/MSI-H rectal cancer treated with dostarlimab — response rates approaching 100% have been reported.
What are the side effects of immunotherapy?
The most common side effects are immune-related adverse events (irAEs) such as rash, fatigue, diarrhea, and thyroid or liver inflammation. Cellular therapies like CAR-T can additionally cause cytokine release syndrome (CRS) and neurotoxicity, both of which are actively monitored for and treatable.
Is immunotherapy a cure for cancer?
For some patients with certain cancers, immunotherapy has produced durable, years-long complete remissions — including cases described as functional cures. It is not curative for most patients, and fewer than half of those treated respond at all, though the field is actively working to expand who benefits.
What's new in cancer immunotherapy in 2026?
Recent developments include sustained complete-response data for dostarlimab in rectal cancer, five-year data showing personalized mRNA melanoma vaccines roughly halve recurrence risk when combined with pembrolizumab, new PD-1×VEGF and PD-1×CTLA-4 bispecific antibodies, and the world's first CAR-T therapy approved for a solid tumor (Claudin18.2-targeted satri-cel, for gastric cancer).
How do I find an immunotherapy clinical trial?
Search the NCI's Find NCI-Supported Clinical Trials database, or call the Cancer Information Service at 1-800-4-CANCER (1-800-422-6237).
Ask an AI Assistant About Your Situation
This article covers immunotherapy broadly, but your own situation — cancer type, stage, biomarkers, and prior treatment — is specific. AI assistants can help you turn general information like this into questions worth bringing to your oncologist. A few starting points:
AI assistants are useful for organizing questions and summarizing publicly available research — they are not a substitute for a qualified oncologist reviewing your actual records, pathology, and imaging.
How Do You Find Clinical Trials Testing Immunotherapy?
To find studies involving immunotherapy, visit the NCI's Find NCI-Supported Clinical Trials search tool, or call the Cancer Information Service, NCI's contact center, at 1-800-4-CANCER (1-800-422-6237). The NCI's list includes all NCI-supported trials taking place across the United States and Canada, including the NIH Clinical Center in Bethesda, MD.
Conclusion — Hope Grounded in Science
Cancer immunotherapy has moved from experimental to foundational in oncology in barely fifteen years. It carries real risks, but those risks are increasingly well characterized and manageable, and its benefits are now proven — and, in 2026, still expanding — across a growing list of cancers.
Source and reference: National Cancer Institute — Immunotherapy
Read more: The Immunotherapy Revolution series
Related Resources
- New Drugs, New Side Effects: Complications of Cancer Immunotherapy
- Targeted Therapy to Treat Cancer
- CAR T Cells: Engineering Patients' Immune Cells to Treat Their Cancers
- Can Immunotherapy Succeed in Glioblastoma?
- Chemotherapy vs Immunotherapy vs Targeted Therapy
- Three Cases of Immune Myocarditis Associated with Camrelizumab Use (2024)
- Interventional oncology: new techniques and new devices (2022)
101 · cancer · immunotherapy · NK cells · pharma · stem cells · CAR-T · CAR-NK · keytruda · dostarlimab
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