CAR-T Cell Therapy: How It Works, Which Cancers It Treats, Benefits, Risks and Availability

Cancer treatment has evolved significantly over the past several decades. While surgery, chemotherapy and radiation therapy remain essential components of cancer care, scientific advances have introduced new approaches that help the body's own immune system recognize and fight cancer more effectively.

One of the most important breakthroughs in modern oncology is CAR-T cell therapy — an advanced form of personalized immunotherapy that uses a patient's own immune cells to target and destroy certain types of cancer.

Unlike conventional treatments that directly attack cancer cells, CAR-T therapy begins by collecting the patient's own T cells, genetically modifying them in a specialized laboratory, and returning them to the body. These engineered immune cells are designed to recognize specific proteins on cancer cells and attack them with greater precision.

For some patients with advanced blood cancers who have not responded to standard treatments, CAR-T therapy has produced durable responses in a subset of patients. Although it is not suitable for every type of cancer or every patient, it represents one of the most significant advances in cancer treatment in recent years. CAR-T therapy is generally considered only for specific diagnoses and at specific stages of treatment, usually after standard therapies have been tried. Whether it is an option in an individual case is determined by the treating oncologist.

In this guide, you'll learn what CAR-T cell therapy is, how it works, which cancers it is currently used to treat, its potential benefits and risks, where it is available around the world, and what researchers hope to achieve in the future.

1. What Is CAR-T Cell Therapy?

CAR-T cell therapy (Chimeric Antigen Receptor T-cell Therapy) is an advanced form of personalized cancer immunotherapy that uses a patient's own immune cells to recognize and destroy cancer cells.

Unlike conventional cancer treatments that directly target tumors, CAR-T therapy works by strengthening the patient's immune system. Instead of administering a traditional drug, doctors collect the patient's own T cells — a type of white blood cell that plays a central role in the body's immune defense. All CAR-T therapies approved today are made from the patient's own cells. Products made from donor cells are still being studied in clinical trials.

Under normal conditions, T cells continuously patrol the body, identifying and eliminating infected or abnormal cells. However, many cancer cells develop sophisticated mechanisms that allow them to hide from the immune system or suppress its activity. As a result, the body's natural defenses may no longer recognize cancer cells as a threat.

CAR-T therapy is designed to overcome this challenge.

After the patient's T cells are collected through a procedure called leukapheresis, they are sent to a specialized laboratory where they are genetically modified. Scientists introduce a new receptor known as a Chimeric Antigen Receptor (CAR) onto the surface of these immune cells. This engineered receptor enables the T cells to recognize a specific protein found on certain cancer cells.

Manufacturing takes time. From cell collection to infusion, the process usually takes several weeks. During this period the patient may receive interim treatment to keep the disease under control. For patients whose disease is progressing rapidly, this timeline is one of the factors the treating team has to weigh.

The modified cells are then multiplied in the laboratory until millions of CAR-T cells are available. Before infusion, the patient receives a short course of lymphodepleting chemotherapy, which reduces the number of existing immune cells and helps the new CAR-T cells expand in the body. This step is itself a form of treatment and carries its own side effects. The engineered cells are then infused back into the patient's bloodstream, where they begin searching for and attacking cancer cells carrying the target protein.

Because CAR-T therapy uses living immune cells that can continue functioning inside the body after infusion, it is often described as a "living medicine." Unlike many conventional drugs that are gradually eliminated from the body, CAR-T cells may remain active for months or even years, helping the immune system maintain its response against cancer.

Today, CAR-T therapy is primarily approved for several types of blood cancers, including certain forms of leukemia, lymphoma, and multiple myeloma. Researchers are actively investigating whether this technology can also be adapted to treat solid tumors and other diseases in the future.

2. How CAR-T Cell Therapy Works: Step by Step

CAR-T cell therapy is a highly personalized treatment that is individually prepared for each patient. Unlike conventional medicines that are manufactured in large batches, every CAR-T therapy product is created using the patient's own immune cells.

Although the manufacturing process is complex, it can be understood in six main steps.

Step 1. Collecting T Cells (Leukapheresis)

The treatment begins with a procedure called leukapheresis.

During this process, blood is drawn from the patient and passed through a specialized machine that separates out the white blood cells containing T cells — the cells that play a key role in the immune system. The remaining blood components are returned to the patient's body.

Leukapheresis is not a surgical operation and usually takes several hours. In some cases a temporary central venous catheter is placed beforehand to allow adequate blood flow.

Step 2. Genetic Modification in the Laboratory

The collected T cells are transported to a specialized manufacturing laboratory.

Scientists use advanced genetic engineering techniques to introduce a new gene into the T cells. This gene instructs the cells to produce a Chimeric Antigen Receptor (CAR) on their surface.

The CAR acts like a highly specialized sensor, allowing the modified T cells to recognize specific proteins found on certain cancer cells.

Step 3. Growing Millions of CAR-T Cells

Once the cells have been genetically modified, they are carefully grown under controlled laboratory conditions.

Over the following days, the modified cells multiply until millions of CAR-T cells are available for treatment. Throughout this process, strict quality and safety checks are performed to ensure that the final product meets clinical standards before it is released for patient use.

Step 4. Preparing the Patient

Shortly before the CAR-T cells are returned, the patient receives a short course of lymphodepleting chemotherapy, usually over three to five days.

Its purpose is not to destroy the tumor, but to reduce the number of existing immune cells so that the new CAR-T cells can expand more effectively in the body.

This is a treatment step in its own right and has its own side effects. It is given in hospital or under close medical supervision.

Step 5. CAR-T Cell Infusion

The prepared cells are returned to the patient through an intravenous line, in a way that resembles a blood transfusion.

The infusion itself usually takes between thirty and sixty minutes and does not require surgery or anesthesia. From the bloodstream, the CAR-T cells travel through the body and begin to recognize cancer cells carrying the target protein.

Although the procedure is short, it takes place in a specialized center, because the following days require close observation.

Step 6. Monitoring After Treatment

The first weeks after infusion are the most important period for monitoring.

Patients usually remain near the treatment center for several weeks so that any complications can be recognized and treated quickly. During this period doctors monitor temperature, blood pressure, neurological status and blood test results.

After this initial phase, monitoring continues over a longer period. Follow-up visits assess how the disease responds, whether the response lasts and how the immune system recovers. Long-term follow-up continues for years.

3. Which Cancers Can CAR-T Cell Therapy Treat?

CAR-T cell therapy is not a universal treatment for all cancers. Today, it is approved primarily for certain blood cancers, where clinical studies have demonstrated significant benefits in carefully selected patients.

Most currently approved CAR-T therapies target CD19, a protein found on the surface of B cells — a type of white blood cell involved in the immune system. Because many blood cancers arise from these cells, CAR-T therapy has been particularly successful in this group of diseases.

Acute Lymphoblastic Leukemia (ALL)

CAR-T therapy has become an important treatment option for some children, adolescents and adults with B-cell acute lymphoblastic leukemia (B-ALL) whose disease has returned after treatment or has not responded to standard therapies.

For some patients, CAR-T therapy has produced long-lasting remissions when few other treatment options remained.

Diffuse Large B-Cell Lymphoma (DLBCL)

One of the most common indications for CAR-T therapy is diffuse large B-cell lymphoma (DLBCL).

Patients whose lymphoma returns after chemotherapy or stem cell transplantation — or does not respond to these treatments — may be candidates for CAR-T therapy if they meet specific clinical criteria.

Other B-Cell Lymphomas

Several other lymphoma subtypes may also be treated with approved CAR-T products, including:

• Primary mediastinal B-cell lymphoma (PMBCL)
• Follicular lymphoma (FL)
• Mantle cell lymphoma (MCL)

Eligibility depends on the exact diagnosis, previous treatments, regulatory approvals in each country, and assessment by a specialist treatment center.

Multiple Myeloma

CAR-T therapy has also changed the treatment landscape for some patients with multiple myeloma.

Unlike products that target CD19, CAR-T therapies for multiple myeloma usually target BCMA (B-cell maturation antigen), a protein commonly found on malignant plasma cells.

For carefully selected patients whose disease has progressed despite multiple previous treatments, CAR-T therapy has produced meaningful responses.

How Often Does It Work?

CAR-T therapy does not work for every patient. Some patients do not respond at all, and among those who do, the disease can return months or years later. Response rates and the durability of response differ substantially between diagnoses, between products and between individual patients. The treating team can explain what is realistically expected in a specific situation.

Are Solid Tumors Treated with CAR-T?

At present, CAR-T therapy is mainly approved for blood cancers.

Researchers around the world are studying whether CAR-T technology can be adapted for solid tumors such as:

• Lung cancer
• Breast cancer
• Ovarian cancer
• Pancreatic cancer
• Brain tumors
• Liver cancer

Although early clinical trials have shown encouraging findings in some cases, CAR-T therapy for most solid tumors remains investigational and is not yet considered standard treatment.

Important Note

Not every patient with these cancers is eligible for CAR-T therapy.

Eligibility depends on multiple factors, including:

• The exact diagnosis
• Previous treatments
• Overall health
• Organ function
• Disease characteristics
• Availability of approved CAR-T products in the patient's country

The decision to recommend CAR-T therapy is made by a multidisciplinary medical team with expertise in hematology, oncology and cellular therapy.

4. How Effective Is CAR-T Cell Therapy?

CAR-T cell therapy has become one of the most significant advances in the treatment of certain blood cancers over the past decade. For some patients whose disease has returned after multiple treatments — or has not responded to standard therapies — it has provided an opportunity to achieve remission when few other options remained.

However, CAR-T therapy is not a cure for every patient, and its effectiveness varies depending on several important factors.

Response Rates Differ Between Diseases

The effectiveness of CAR-T therapy depends on the specific type of cancer being treated, the CAR-T product used, the patient's overall health and previous treatments.

Some blood cancers respond particularly well to CAR-T therapy, while others may respond less consistently. Even among patients with the same diagnosis, treatment outcomes can vary significantly.

Much of what is known about effectiveness comes from clinical trials in carefully selected patients, and results in everyday practice may differ. For this reason, doctors evaluate each patient individually rather than relying on average results alone.

What Does "Remission" Mean?

Many people encounter the word remission when reading about CAR-T therapy.

A complete remission means that, using current medical tests, doctors can no longer detect signs of the cancer after treatment.

This does not always mean the disease has been permanently cured. Some patients remain in remission for many years, while others may experience a relapse and require additional treatment.

For this reason, long-term follow-up remains an essential part of CAR-T therapy.

Why Doesn't CAR-T Work for Everyone?

Although CAR-T therapy has changed the treatment of several blood cancers, it does not produce the same results in every patient.

Several factors may influence treatment response, including:

• The biological characteristics of the cancer
• The patient's immune system
• The amount of cancer present before treatment
• Previous therapies received
• The specific CAR-T product used

Researchers continue to study why some patients experience long-lasting responses while others do not.

How Is Success Measured?

Doctors assess the effectiveness of CAR-T therapy using several methods.

These may include:

• Physical examination
• Blood tests
• Bone marrow examination, when appropriate
• CT, PET-CT or MRI imaging
• Molecular or genetic laboratory tests
• Long-term monitoring for disease recurrence

The goal is not only to determine whether the cancer has responded, but also to monitor how long that response lasts.

Current Clinical Experience

Clinical studies and real-world experience have shown that CAR-T therapy can produce deep and durable responses in selected patients with certain blood cancers.

For some individuals, these responses have lasted for years after a single CAR-T infusion. However, outcomes vary between patients, and researchers continue to improve CAR-T technology in order to increase effectiveness, reduce side effects and extend its use to additional diseases.

Because the field is evolving rapidly, treatment recommendations continue to change as new clinical evidence becomes available.

Important Perspective

CAR-T therapy represents a major milestone in modern cancer treatment, but it should be viewed as one option within a broader treatment strategy rather than a universal solution.

The decision to recommend CAR-T therapy depends on careful evaluation by a specialist medical team, taking into account the patient's diagnosis, previous treatments, overall health and the expected balance between potential benefits and risks.

5. Risks and Side Effects of CAR-T Cell Therapy

Like all cancer treatments, CAR-T cell therapy can cause side effects. Because it activates the immune system in a powerful way, some reactions can be serious and require treatment in a specialized hospital.

Importantly, not every patient experiences severe side effects, and many complications can now be recognized early and managed effectively by experienced medical teams.

For this reason, CAR-T therapy is performed only in specialized centers with trained multidisciplinary teams and close monitoring after the infusion.

Cytokine Release Syndrome (CRS)

The most common serious side effect of CAR-T therapy is cytokine release syndrome (CRS).

When CAR-T cells recognize cancer cells, they release signaling proteins called cytokines that activate the immune system. If this immune response becomes excessive, the patient may develop CRS.

Symptoms may include:

• Fever
• Chills
• Fatigue
• Low blood pressure
• Rapid heartbeat
• Difficulty breathing
• Low oxygen levels

CRS usually develops during the first days after the CAR-T cell infusion. Most cases are mild to moderate, but severe cases require prompt treatment and intensive monitoring.

Today, medications such as tocilizumab and corticosteroids have significantly improved the management of CRS, allowing many patients to recover without long-term complications.

Immune Effector Cell-Associated Neurotoxicity Syndrome (ICANS)

Another important complication is immune effector cell-associated neurotoxicity syndrome (ICANS).

ICANS affects the nervous system and may develop together with CRS or occur separately.

Possible symptoms include:

• Confusion
• Difficulty speaking or finding words
• Tremor
• Sleepiness
• Problems with attention or memory
• Seizures, which are rare
• Temporarily reduced level of consciousness in severe cases

Most patients recover completely with appropriate medical care, although careful neurological monitoring is essential during the first weeks after treatment.

Increased Risk of Infection

Before receiving CAR-T cells, patients usually undergo lymphodepleting chemotherapy, which temporarily reduces immune cells.

In addition, CAR-T therapy itself may affect normal immune function, particularly when it targets B cells.

As a result, patients may have an increased risk of infection for weeks or months after treatment.

Doctors may recommend:

• Preventive antibiotics or antiviral medication
• Immunoglobulin replacement therapy in selected patients
• Regular blood tests
• Vaccination planning after immune recovery, when appropriate

Secondary Cancers

In rare cases, secondary malignancies have been reported after treatment with CAR-T cells, including cancers arising from T cells themselves.

These cases are uncommon, and it is not always possible to determine whether they were caused by the CAR-T product, by previous chemotherapy, or by the underlying disease. Regulatory authorities have nevertheless asked that patients be informed of this risk and followed for a long period after treatment.

This is one of the reasons why long-term follow-up continues for years, not only for months.

B-Cell Aplasia

Many approved CAR-T therapies target CD19, a protein found on both malignant and healthy B cells.

Because healthy B cells may also be eliminated, patients can develop B-cell aplasia, which leads to reduced antibody production.

This is an expected effect of the treatment on healthy B cells rather than an unexpected complication. Some patients require periodic immunoglobulin replacement to reduce the risk of infection until normal immune function recovers.

Blood Cell Counts and Fatigue

Some patients experience:

• Low white blood cell counts
• Low platelet counts
• Anemia
• Fatigue

These effects can persist for weeks or months after treatment. They are monitored with regular blood tests and managed with supportive care when necessary.

Why Is Close Monitoring So Important?

Most serious side effects occur during the first days or weeks after the CAR-T cell infusion.

For this reason, patients usually remain near the treatment center after infusion so that doctors can quickly recognize and treat any complications.

Monitoring may include:

• Frequent physical examinations
• Blood tests
• Neurological assessments
• Monitoring of vital signs
• Additional imaging or laboratory investigations if needed

Weighing Risks Against Expected Benefit

Although the possible side effects of CAR-T therapy can sound alarming, it is important to consider them in context.

Specialized centers have established protocols for recognizing and managing complications, and supportive care has improved considerably in recent years. The decision to recommend CAR-T therapy is based on balancing its potential benefits against its known risks for each individual patient.

For carefully selected patients with certain difficult-to-treat blood cancers, the expected benefit may outweigh these risks. The treating medical team will explain which complications are most relevant in an individual situation and how they will be monitored and managed.

6. Who Can Receive CAR-T Cell Therapy?

CAR-T cell therapy is not suitable for every patient with cancer. Although it has changed the treatment of several blood cancers, eligibility depends on many medical factors and is determined individually for each patient.

The decision is usually made by a multidisciplinary team, which may include hematologists, oncologists, cellular therapy specialists, transplant physicians, radiologists and pathologists. Together they review the diagnosis, previous treatments, overall health and the expected balance between benefits and risks.

Who May Be Eligible?

Patients may be considered for CAR-T cell therapy if they meet several medical criteria. These generally include:

• A cancer type for which an approved CAR-T therapy exists
• Disease that has returned after previous treatment, or has not responded adequately to standard therapies
• Sufficient heart, lung, liver and kidney function to undergo treatment safely
• An overall condition that allows intensive monitoring and follow-up
• No medical conditions that would make CAR-T therapy unacceptably risky

Criteria differ depending on the specific disease, the approved product and national treatment guidelines. Some products are approved only for certain age groups, so age can also affect which options are available.

Meeting the medical criteria does not automatically mean treatment is accessible. An approved CAR-T product may not be available in the patient's country, which is a separate question from medical eligibility.

What Tests Are Performed Before Treatment?

Before CAR-T therapy begins, patients undergo a comprehensive medical evaluation.

The purpose of this evaluation is not only to confirm the diagnosis, but also to ensure that the patient can safely undergo CAR-T therapy and its potential side effects.

This assessment may include:

• Blood tests
• Bone marrow examination, when appropriate
• CT, PET-CT or MRI imaging
• Assessment of heart function
• Lung function tests
• Screening for active infection
• Review of previous cancer treatments and current medications

These investigations help doctors determine whether CAR-T therapy is appropriate and whether any additional treatment is needed beforehand.

A Personalized Treatment Decision

CAR-T cell therapy is one of the most individualized treatments in modern oncology.

Rather than relying on a single test or diagnosis, doctors evaluate the patient's overall medical situation to determine whether the expected benefits outweigh the potential risks.

This individualized approach helps ensure that CAR-T therapy is offered to the right patients and at the right stage of treatment.

7. Where Is CAR-T Cell Therapy Available?

CAR-T cell therapy is available in a growing number of countries, but access remains limited compared with conventional cancer treatments. It is usually provided only in specialized hospitals with experience in cellular therapy, intensive monitoring and the management of serious treatment-related complications.

The list of countries and centers offering CAR-T therapy changes as new products are approved and new centers are certified. Regulatory approval in a country does not mean that every product is available at every cancer center. Approved indications, reimbursement rules and treatment capacity can differ substantially, so current information should be confirmed with the treating oncologist.

Why Is CAR-T Available Only at Certain Centers?

CAR-T therapy requires much more than administering an infusion.

A treatment center must be able to:

• Confirm that the patient meets the medical criteria
• Collect the patient's T cells through leukapheresis
• Coordinate the transport and manufacture of the CAR-T product
• Provide preparatory chemotherapy
• Administer the CAR-T cells safely
• Recognize and manage cytokine release syndrome and neurological complications
• Provide close monitoring and long-term follow-up

For these reasons, CAR-T treatment is generally concentrated in specialist hematology, oncology, transplant or cellular therapy centers. Some approved products can only be administered by appropriately trained teams in certified hospitals.

Availability Depends on More Than the Country

When considering CAR-T therapy, it is not enough to ask whether the treatment exists in a particular country.

The medical team must also confirm:

• Whether a CAR-T product is approved for the patient's specific disease
• Whether the patient meets the product's eligibility criteria
• Whether the center currently accepts new patients
• Whether manufacturing capacity is available
• How long treatment preparation may take
• Whether the hospital treats international patients
• How the treatment and related hospital care will be funded

A product may be approved nationally but temporarily unavailable at a particular center because of manufacturing schedules, limited capacity or reimbursement restrictions.

Germany and Turkey

Germany. Germany was among the first European countries to introduce commercial CAR-T therapy after EU approval in 2018. Treatment is provided only in certified specialist centers. Reimbursement is generally available through the statutory health insurance system for eligible patients, while international patients usually require separate financial arrangements.

Turkey. Turkey also provides CAR-T therapy in selected certified centers with expertise in stem cell transplantation and cellular therapies. Public reimbursement is more limited than in Germany, and both eligibility and funding depend on national regulations and individual clinical circumstances.

Key Point Medical eligibility and treatment availability are different concepts. A patient may be medically eligible for CAR-T therapy even if the treatment is not currently available in their country or at a particular center.

Receiving CAR-T Therapy Abroad

Some patients explore treatment in another country because CAR-T therapy is unavailable locally, because a particular product is not approved where they live, or because they want an evaluation at a more experienced center.

Before traveling, the receiving hospital will normally need to review the diagnosis, pathology findings, imaging, previous treatments, current disease status and general health. The center may request additional examinations before confirming whether the patient can be accepted.

Patients should also clarify which parts of the process must take place at the treatment center. Cell collection, preparatory chemotherapy, CAR-T infusion and early monitoring are closely connected and may require the patient to remain near the hospital for several weeks.

The cost of treatment and the way it is funded vary widely between countries and centers, and are a separate question from medical eligibility.

Questions to Ask a Treatment Center

Before making travel or financial arrangements, patients may ask:

• Is the proposed CAR-T product approved for my diagnosis?
• Is the treatment part of standard care or a clinical trial?
• How many patients with my condition has the center evaluated or treated?
• Which examinations must be completed before arrival?
• How long should I expect to remain near the hospital?
• What happens if my disease progresses while the cells are being manufactured?
• If I am not accepted, what other options would you suggest?
• Which treatment-related services are included in the estimated cost?
• How will follow-up be coordinated after I return home?

The final decision should be based on both medical suitability and the center's ability to provide the complete treatment pathway safely.

8. Conclusion

CAR-T cell therapy represents one of the most important advances in modern cancer treatment. By using a patient's own genetically modified immune cells, it offers a personalized approach that has transformed the treatment landscape for several types of blood cancers.

At the same time, CAR-T therapy is not suitable for every patient or every type of cancer. Careful evaluation by an experienced multidisciplinary medical team is essential to determine whether the potential benefits outweigh the possible risks in an individual situation.

As research continues, new CAR-T products, improved manufacturing methods and broader clinical experience are expected to expand the role of this technology in the years ahead. Researchers are also investigating new targets for blood cancers, approaches for solid tumors and strategies to improve both safety and effectiveness.

For patients and families, understanding how CAR-T therapy works, who may benefit, what risks should be considered and where treatment is available can help support informed discussions with their medical team.

CAR-T therapy should always be considered as part of an individualized treatment plan developed together with qualified healthcare professionals. For anyone wondering whether it may be relevant in their situation, the first step is a discussion with their treating oncologist, who can assess the specific diagnosis, previous treatments and overall clinical circumstances.

Medical Disclaimer

The information presented in this article is intended for educational purposes only and should not be considered a substitute for professional medical advice, diagnosis or treatment.

CAR-T cell therapy is a highly specialized treatment that may not be appropriate for every patient. Treatment decisions depend on the specific diagnosis, previous therapies, overall health, regulatory approvals and evaluation by experienced medical professionals.

Patients should always consult their treating physician or another qualified healthcare professional before making decisions about CAR-T therapy or any other cancer treatment.

References

Clinical guidelines

• National Comprehensive Cancer Network (NCCN). Clinical Practice Guidelines in Oncology. nccn.org
• European Society for Medical Oncology (ESMO). Clinical Practice Guidelines. esmo.org
• American Society of Clinical Oncology (ASCO). Cancer.Net — CAR T-Cell Therapy. cancer.net
• European Hematology Association (EHA). Guidelines and Educational Resources. ehaweb.org

Regulatory authorities

• US Food and Drug Administration (FDA). Approved Cellular and Gene Therapy Products. fda.gov
• European Medicines Agency (EMA). Authorised Advanced Therapy Medicinal Products. ema.europa.eu

Additional reading

• Neelapu SS, Locke FL, Bartlett NL, et al. Axicabtagene Ciloleucel CAR T-Cell Therapy in Refractory Large B-Cell Lymphoma. N Engl J Med. 2017;377(26):2531–2544.
• Maude SL, Laetsch TW, Buechner J, et al. Tisagenlecleucel in Children and Young Adults with B-Cell Lymphoblastic Leukemia. N Engl J Med. 2018;378(5):439–448.
• Schuster SJ, Bishop MR, Tam CS, et al. Tisagenlecleucel in Adult Relapsed or Refractory Diffuse Large B-Cell Lymphoma. N Engl J Med. 2019;380(1):45–56.
• Munshi NC, Anderson LD Jr, Shah N, et al. Idecabtagene Vicleucel in Relapsed and Refractory Multiple Myeloma. N Engl J Med. 2021.