Immunotherapy is an advanced form of cancer treatment that harnesses the body’s own immune system to recognize and destroy cancer cells. Unlike chemotherapy or radiation, which directly target cancer cells, immunotherapy strengthens or “releases the brakes” on the immune system so it can identify and attack cancer more effectively.

This approach has transformed cancer care for many patients. However, like all treatments, it has potential side effects and risks. Understanding the benefits, limitations, and possible side effects of immunotherapy helps patients and families make informed treatment decisions.

What Is Immunotherapy?

Immunotherapy refers to treatments that enhance the immune system’s ability to detect and fight cancer. Under normal circumstances, the immune system can identify abnormal cells. However, cancer cells often develop mechanisms to hide from immune detection or suppress immune responses.

Certain immunotherapy drugs—particularly immune checkpoint inhibitors—work by blocking these escape mechanisms, allowing immune cells to recognize and attack cancer.

Immunotherapy is currently used in several cancers, including:

• Non-small cell lung cancer

• Melanoma

• Kidney cancer

• Bladder cancer

• Head and neck cancers

• Hodgkin lymphoma and other blood cancers

The effectiveness of immunotherapy depends on factors such as cancer type, stage, molecular markers, and overall patient health.

Benefits of Immunotherapy

While immunotherapy does not work for every patient, it has provided meaningful and sometimes long-lasting benefits in many cancers.

• More Targeted Immune Activation: Immunotherapy helps the immune system specifically recognize cancer cells. Unlike chemotherapy—which affects all rapidly dividing cells—immunotherapy is generally more selective. This often results in a different side effect profile compared to traditional chemotherapy.
• Potential for Long-Lasting Responses: One of the most significant advantages is immune memory. Once trained to recognize cancer, the immune system may continue to suppress it even after treatment stops. In some patients, this leads to durable remissions lasting years.
• Effective in Advanced or Metastatic Cancer: In certain late-stage cancers, immunotherapy has shown responses even when chemotherapy has failed. Some patients with metastatic disease experience tumor shrinkage or prolonged disease stabilization.
• Improved Survival in Selected Cancers: In cancers such as advanced melanoma and non-small cell lung cancer, immunotherapy has improved overall survival in carefully selected patients.
• Quality of Life in Some Patients: Because immunotherapy does not typically cause hair loss or severe nausea in most patients, many individuals are able to maintain daily activities. However, this does not mean it is free of risks.

Immunotherapy Side Effects

Immunotherapy side effects are different from chemotherapy side effects.

Because these drugs activate the immune system, side effects often occur when the immune system becomes overactive and attacks healthy tissues. These are called immune-related adverse events (irAEs).

Side effects may occur during treatment or even months after stopping therapy.

Common Side Effects

• Fatigue: The most commonly reported symptom. Patients may feel persistent tiredness not relieved by rest.
• Skin Reactions: Rash, itching, dryness, or skin discoloration are common. Some patients may develop vitiligo, especially in melanoma treatment.
• Flu-Like Symptoms: Fever, chills, and body aches may occur, particularly early in treatment.
• Digestive Symptoms: Diarrhea, abdominal pain, or nausea may indicate inflammation of the intestines (colitis). Severe diarrhea should be reported immediately.
• Hormonal Changes: The immune system may affect glands such as:
  • Thyroid
  • Pituitary
  • Adrenal glands

This can lead to thyroid dysfunction, weight changes, mood changes, or prolonged fatigue. Some patients may require lifelong hormone replacement.

Organ Inflammation

Less commonly, immunotherapy can cause inflammation of:

• Lungs (pneumonitis)

• Liver (hepatitis)

• Kidneys (nephritis)

• Heart (myocarditis – rare but serious)

Early detection and treatment—often with steroids—usually control these reactions.

Immunotherapy Risks

All cancer treatments carry risks. The goal is to balance benefit with safety.

• Autoimmune Reactions: Immunotherapy may trigger autoimmune-like reactions affecting various organs.
• Severe Inflammation: Although uncommon, severe immune reactions can affect organ function and may require hospitalization.
• Delayed Side Effects: Side effects can develop weeks or even months after stopping treatment. This makes long-term follow-up essential.
• Not Effective for Everyone: Some tumors do not respond. Doctors often test biomarkers such as PD-L1 expression or other molecular features to help guide treatment decisions, but these tests do not guarantee response.
• Financial Considerations: Immunotherapy can be costly. Financial planning and insurance counseling may be necessary in many healthcare systems.

Signs Immunotherapy Is Working

Unlike chemotherapy, immunotherapy responses may not be immediate.

Doctors monitor progress using imaging scans and blood tests. Possible indicators include:

• Tumor shrinkage on scans

• Stable disease (no further growth)

• Improvement in cancer-related symptoms

• Durable control lasting months to years

In some cases, tumors may temporarily appear larger before shrinking. This phenomenon is known as pseudoprogression, caused by immune cells entering the tumor.

When to Contact Your Doctor Immediately

Patients receiving immunotherapy should report new or worsening symptoms promptly. Seek medical attention if you experience:

• Persistent fever

• Severe or worsening diarrhea

• Shortness of breath

• Yellowing of the eyes or skin

• Severe fatigue

• Confusion or severe headache

Early treatment of side effects significantly improves outcomes.

Conclusion

Immunotherapy represents a major advancement in modern oncology. For selected patients, it offers targeted immune activation, long-term disease control, and improved survival.

However, immunotherapy is not without risks. Immune-related side effects can affect multiple organs and may occur even after treatment stops. With proper monitoring, early recognition of symptoms, and timely management, most side effects are manageable.

An informed patient is an empowered patient. Discussing potential benefits, risks, and expectations with your oncologist ensures that treatment decisions are personalized and appropriate.

FAQs

1. How quickly does immunotherapy work?

It may take weeks to months. The immune system requires time to mount an effective response.

2. Is immunotherapy better than chemotherapy?

They work differently. Some patients benefit more from immunotherapy, others from chemotherapy, and many receive a combination.

3. Can immunotherapy cure cancer?

In some cancers, it can produce long-term remission. However, it is not guaranteed to cure every patient.

4. Are side effects permanent?

Most are reversible if detected early. Some hormonal side effects may require long-term treatment.

5. Can immunotherapy be combined with other treatments?

Yes. It is often combined with chemotherapy, radiation therapy, or targeted therapy depending on the cancer type.