Keytruda works against cancers where the immune system has been blocked

Keytruda (the drug name is pembrolizumab) is an immunotherapy that helps your immune system recognize and attack cancer cells. It works by removing a "brake" that cancer puts on your immune cells. The U.S. Food and Drug Administration has approved Keytruda for specific cancers where this approach has shown benefit in clinical trials: melanoma, non-small cell lung cancer, head and neck cancers, Hodgkin lymphoma, urothelial (bladder) cancer, microsatellite instability-high cancers, and gastric cancer. It is also used for certain breast cancers and kidney cancers, though approval and use vary by the specific type and stage.

Keytruda is not a first-line treatment for all of these cancers. For some, it is used when other treatments have not worked. For others, it may be combined with chemotherapy or used as a first treatment. The specific role depends on the cancer type, how advanced it is, and what genetic markers your tumor has. Your oncologist will determine whether Keytruda is an option for your particular situation based on your tumor's characteristics and your overall health.

Key Takeaways

  • Keytruda is approved for melanoma, non-small cell lung cancer, head and neck cancers, Hodgkin lymphoma, bladder cancer, and several other cancer types.
  • The drug works by releasing an immune system "brake" that cancer cells use to hide, allowing your immune cells to attack the tumor.
  • Keytruda is not always a first-line treatment; sometimes it is used after other therapies have been tried or combined with chemotherapy.
  • Whether Keytruda will work for you depends on your specific cancer type, stage, tumor genetics, and overall health — your oncologist will assess this.
  • Common side effects come from the immune system becoming overactive and can include fatigue, rash, joint pain, and in rare cases, serious inflammation of organs.

Melanoma and Keytruda

Keytruda was first approved for melanoma, the most serious form of skin cancer. It is used for melanomas that have spread beyond the skin (stage III or IV) or cannot be removed by surgery. In clinical trials, Keytruda extended survival compared to older treatments, and it can shrink tumors in roughly 40 to 50 percent of patients with advanced melanoma.

For earlier-stage melanomas that have been surgically removed, Keytruda is sometimes given after surgery to reduce the risk that cancer will return. This is called adjuvant treatment. Your dermatologist or oncologist will discuss whether this approach makes sense for your situation based on how aggressive your melanoma appears under the microscope.

Lung cancer and Keytruda

Non-small cell lung cancer is the most common type of lung cancer, and Keytruda has a role in treating it. For patients with advanced non-small cell lung cancer that has not been treated before, Keytruda alone or combined with chemotherapy can be a first-line option. For those whose cancer has progressed after chemotherapy, Keytruda is often used as a second-line treatment.

Whether Keytruda will work depends partly on a marker called PD-L1 expression on your tumor cells. Tumors with higher PD-L1 levels tend to respond better to Keytruda. Your oncologist will order a test to measure this before recommending Keytruda. Keytruda is also used for small cell lung cancer, though less commonly and usually after other treatments.

Head and neck cancers, Hodgkin lymphoma, and bladder cancer

Keytruda is approved for head and neck cancers (cancers of the mouth, throat, and surrounding tissues) that have spread or returned after chemotherapy. It is also used as a first-line treatment combined with chemotherapy for some patients with newly diagnosed advanced head and neck cancer.

For Hodgkin lymphoma, Keytruda is used when the cancer has returned after stem cell transplant or when transplant is not an option. It has shown durable responses in this setting, meaning some patients stay in remission for extended periods.

Bladder cancer (urothelial carcinoma) that has spread or cannot be removed surgically can be treated with Keytruda, either alone or combined with chemotherapy. Keytruda is also used to reduce recurrence risk after surgery in certain high-risk bladder cancers.

Other cancers where Keytruda may be used

Keytruda has approval for gastric cancer (stomach cancer) and gastroesophageal junction cancer when combined with chemotherapy, particularly in patients whose tumors have high PD-L1 expression. It is also approved for certain breast cancers, specifically triple-negative breast cancer (a subtype that lacks three common receptors) when combined with chemotherapy.

For kidney cancer, Keytruda is used in combination with other immunotherapy drugs or with targeted therapy drugs, rather than alone. Keytruda is also approved for cancers with a specific genetic marker called microsatellite instability-high (MSI-H), regardless of where the cancer started. This approval is unusual because it is based on a genetic feature rather than the cancer's location in the body.

How Keytruda works differently from chemotherapy

Chemotherapy kills cancer cells directly by damaging their DNA. Keytruda does not kill cancer cells itself. Instead, it blocks a protein called PD-1 on immune cells, which cancer cells normally use to turn off the immune attack. By blocking this interaction, Keytruda allows your T cells (a type of white blood cell) to recognize and destroy cancer cells that were previously hidden.

This mechanism means Keytruda can take longer to work than chemotherapy — sometimes weeks or months — but responses can last longer once they occur. It also means the side effects are different: instead of the nausea and hair loss common with chemotherapy, Keytruda side effects come from your immune system becoming overactive and attacking normal tissue.

Side effects and what to watch for

The most common side effects of Keytruda are fatigue, rash, joint or muscle pain, and decreased appetite. These are usually mild to moderate and manageable. More serious side effects, though less common, occur when the immune system attacks organs: pneumonitis (lung inflammation), colitis (colon inflammation), hepatitis (liver inflammation), or endocrinitis (inflammation of hormone-producing glands).

Serious immune-related side effects happen in roughly 10 to 15 percent of patients receiving Keytruda alone, and more often when it is combined with chemotherapy or other drugs. If you develop shortness of breath, severe diarrhea, yellowing of skin or eyes, or severe fatigue, contact your oncology team immediately. These symptoms can develop weeks or even months after starting Keytruda, so ongoing monitoring is important.

Frequently Asked Questions

Does Keytruda work for all types of cancer?

No. Keytruda is approved only for specific cancers where clinical trials showed benefit. It does not work for all patients with those cancers — response rates vary from 20 to 50 percent depending on the cancer type and whether your tumor has certain genetic markers. Your oncologist will determine if Keytruda is an option for your specific cancer.

How long do you take Keytruda?

Keytruda is given as an intravenous infusion every three or four weeks. How many doses you receive depends on how your cancer responds and whether you develop side effects. Some patients receive it for a year or two and then stop; others continue longer. Your oncologist will reassess your treatment plan regularly with imaging and blood tests.

What does it cost, and will insurance cover it?

Keytruda is expensive — the list price is several thousand dollars per dose — but most insurance plans cover it when prescribed for an approved cancer type. If you are uninsured, the manufacturer offers a patient assistance program. Discuss cost and coverage with your oncology team's financial counselor before starting treatment.

Can Keytruda be used with other cancer treatments?

Yes. Keytruda is often combined with chemotherapy, other immunotherapy drugs, or targeted therapy drugs depending on your cancer type. Combining treatments can improve response rates but also increases the risk of side effects. Your oncologist will decide what combination, if any, is appropriate for your situation.

How do doctors know if Keytruda is working?

Your oncologist will order imaging scans (CT, MRI, or PET scans) every 8 to 12 weeks to measure whether tumors are shrinking, staying the same, or growing. Blood tests may also be used to track tumor markers. Sometimes tumors appear to grow briefly before shrinking — a pattern called pseudoprogression — so your doctor will repeat imaging before deciding whether to stop Keytruda.