Targeted Therapy vs. Chemotherapy: How They Differ

This page is for people comparing targeted therapy and chemotherapy. It explains how each works and why testing often comes first.

Both are drug treatments that reach the whole body, but they work differently. Chemotherapy damages fast-growing cells broadly, which is why it can affect healthy cells too. Targeted therapy is more precise. It is designed to act on specific molecules or genetic changes found mainly in cancer cells. So the two often cause different side effects. Targeted therapy also usually requires testing the cancer first, to find the right target.

Chemotherapy uses drugs that kill or slow cells that divide quickly. Cancer cells divide quickly, so chemo works against them. But some healthy cells divide quickly too, such as those in hair follicles, the gut lining, and bone marrow. That is why chemo can cause hair loss, nausea, and low blood counts.

Targeted therapy is built around a specific feature of a cancer. That may be a protein or a genetic change that helps the cancer grow. The drug is designed to block or interfere with that feature. Because it focuses on something found mainly in cancer cells, it can sometimes spare more healthy cells than chemotherapy.

Targeted therapy only helps when the cancer actually has the target the drug acts on. Biomarker testing, also called molecular testing, checks the tumor or blood for that change. If the target is not there, the drug would not be expected to work. That is why testing guides the choice.

Targeted therapies do not usually cause the classic chemo picture. Depending on the drug, they may cause skin rashes, diarrhea, high blood pressure, or effects on the liver. These still need monitoring, but they tend to look different from chemo side effects.

Neither is simply "better." Not every cancer has a usable target, so targeted therapy is not an option for everyone. Chemotherapy remains highly effective for many cancers. The two are sometimes combined, or given in sequence. The right approach depends on the cancer type, its features on testing, and the goals of treatment. Your care team can walk through those questions with you.

Both kinds of drugs need watching, but the warning signs are not the same.

• Call 911 or go to an emergency department if you have any of these: chest pain, sudden trouble breathing, swelling of the face, lips, or tongue, heavy bleeding, or new confusion or weakness on one side. Do not drive yourself.
• Call your treatment team without waiting, day or night, if you have a temperature of 100.4°F (38°C) or higher, or shaking chills, during chemotherapy. CDC treats this as a medical emergency. Low white cells let an infection turn dangerous within hours. If the team cannot be reached fast, go to an emergency department and tell the staff you are having chemotherapy. Chills, a sore throat, mouth sores, or burning when you urinate during chemotherapy need that same call, even with a normal temperature.
• Call your care team the same day if you notice unusual bruising or bleeding, a rash that is blistering or spreading quickly, or yellowing of the skin or eyes.
• If you are not having chemotherapy, call your care team within a day or two if diarrhea, nausea, or mouth sores keep you from eating and drinking, a home blood pressure reading is much higher than usual, or a skin or nail problem is getting worse.

Do not stop, pause, or change the dose of a targeted therapy pill on your own. Call the team first, even if the answer turns out to be a break.

• National Cancer Institute — Targeted Therapy for Cancer
• National Cancer Institute — Chemotherapy to Treat Cancer
• National Cancer Institute — Infection and Neutropenia During Cancer Treatment
• CDC — Fever during chemotherapy