Immunotherapy and targeted therapy are not the same thing. They are two distinct categories of cancer treatment that work through fundamentally different mechanisms. Immunotherapy activates or enhances your immune system to recognize and attack cancer cells, while targeted therapy directly interferes with specific proteins that cancer cells need to grow and survive. The confusion is understandable, though, because the two categories occasionally overlap, and some treatments blur the line between them.
How Each Treatment Works
The core difference comes down to what each therapy acts on. Immunotherapy works on your immune system. Cancer cells are skilled at hiding from immune defenses or putting the brakes on immune responses. Immunotherapy essentially releases those brakes, allowing your existing immune cells to do the job they were designed for. The treatment doesn’t attack the tumor directly. It empowers your body to do it.
Targeted therapy, by contrast, works directly on the cancer cells themselves. These drugs zero in on specific proteins or genetic mutations that drive a tumor’s growth. For example, some cancers have a mutation that tells cells to keep dividing. A targeted therapy drug binds to that faulty protein and shuts it down. The drug does the killing (or growth-blocking) itself rather than relying on the immune system as an intermediary.
The National Cancer Institute classifies targeted therapy as the foundation of precision medicine, meaning treatments are matched to the specific molecular features of a patient’s tumor. Immunotherapy falls under a separate classification, though some targeted therapies do work by helping the immune system function better, which is where the categories start to merge.
Where the Categories Overlap
Monoclonal antibodies are the biggest source of confusion. These lab-made proteins can be designed to do very different things depending on their target. Some monoclonal antibodies mark cancer cells so your immune system recognizes and destroys them. Others block proteins that cancer cells need to grow. Still others block proteins that suppress immune responses. Cleveland Clinic notes that monoclonal antibodies may be called biologics, targeted therapy, or immunotherapy depending on how they work.
A checkpoint inhibitor like pembrolizumab is a monoclonal antibody, but it’s classified as immunotherapy because it works by blocking a protein (PD-1) that keeps immune cells from attacking cancer. A drug like trastuzumab is also a monoclonal antibody, but it’s classified as targeted therapy because it directly blocks a growth signal (HER2) on cancer cells. Same drug class, different mechanism, different category.
Types of Immunotherapy
Checkpoint inhibitors are the most widely used form of immunotherapy. They block proteins like PD-1 or PD-L1 that act as “off switches” on immune cells. Cancers exploit these switches to avoid detection. Blocking them lets immune cells respond aggressively to the tumor.
T-cell transfer therapy takes a different approach. Immune cells are removed from your tumor, and the ones most active against your cancer are selected, multiplied in a lab, and infused back into your body. CAR-T cell therapy, a version of this, genetically modifies the T cells to better recognize cancer.
Treatment vaccines (distinct from preventive vaccines) boost your immune system’s response to cancer cells that are already present. These are less common than checkpoint inhibitors but represent a growing area of treatment.
Types of Targeted Therapy
Most targeted therapy drugs are small molecule inhibitors, pills that are small enough to enter cancer cells and interfere with proteins inside them. The largest group targets protein kinases, enzymes that act like on/off switches for cell growth. Different inhibitors target different switches: some block signals from growth factor receptors on the cell surface, others interrupt signaling chains inside the cell that tell it to divide, and others cut off a tumor’s blood supply by blocking the formation of new blood vessels.
Multikinase inhibitors hit several of these targets at once. They block blood vessel growth signals while also disrupting other pathways, giving them both anti-growth and anti-blood-supply effects. These drugs tend to have broader activity but are less precisely matched to a single biomarker.
How Doctors Decide Which You Get
The decision depends largely on biomarkers, measurable characteristics of your specific tumor. For targeted therapy, doctors look for known mutations or protein overexpression. A tumor with a BRAF mutation, an EGFR mutation, or HER2 overexpression, for instance, has a clear molecular target that a drug can be designed to hit.
For immunotherapy, the key biomarker is often PD-L1 expression, a measure of how much of the “hide from the immune system” protein a tumor is producing. Tumors with high PD-L1 levels tend to respond better to checkpoint inhibitors. Some checkpoint inhibitors, like pembrolizumab, require confirmed PD-L1 overexpression before they can be prescribed. Others, like nivolumab, do not have that requirement for all cancer types.
In some cases, patients who progress on targeted therapy may then be candidates for immunotherapy. For example, patients with certain lung cancer mutations who initially receive targeted therapy can switch to a PD-L1 blocker if the cancer progresses.
Response Time Differences
Targeted therapies generally produce faster visible results. Because they directly block the signals driving tumor growth, many patients see tumor shrinkage within weeks of starting treatment.
Immunotherapy typically works more slowly. In a study of 522 metastatic melanoma patients on PD-1 checkpoint inhibitors, fewer than 10% achieved a measurable response within the first three months. About 19% responded later, 37% had stable disease (the tumor didn’t grow but didn’t shrink substantially), and roughly 36% did not respond at all. This slower timeline makes sense: immunotherapy is training a biological system to fight, not directly poisoning cancer cells.
However, when immunotherapy does work, the responses can be remarkably durable. Some patients maintain remission for years after stopping treatment, because the immune system has effectively “learned” to recognize the cancer. Targeted therapy responses, while faster, more commonly face the problem of resistance, where the cancer eventually finds a workaround to the blocked pathway.
Side Effects Look Different
Because the two therapies work through different mechanisms, their side effects follow different patterns. Immunotherapy side effects stem from an overactive immune system. When you remove the brakes on immune cells, they sometimes attack healthy tissue too. These immune-related reactions can affect virtually any organ, though skin reactions are among the most common: rashes, eczema-like patches, dry skin, and itching.
Targeted therapy side effects are more predictable because they relate directly to the protein being blocked. The same protein that drives cancer growth often plays a role in normal skin and tissue maintenance. Acne-like rashes are the most frequent skin side effect, appearing in 25% to 85% of patients on certain targeted therapy drugs. The high rate reflects the fact that the targeted protein is active in healthy skin cells too.
Using Both Together
Combining immunotherapy and targeted therapy is increasingly common. The idea is to attack the cancer on two fronts: directly blocking its growth machinery while also unleashing the immune system against it. In HER2-positive stomach and esophageal cancers, for example, the combination of the checkpoint inhibitor pembrolizumab with the targeted therapy trastuzumab (plus chemotherapy) has become a standard first-line treatment. This combination approach reflects a broader trend in oncology: rather than choosing one or the other, doctors are layering therapies that work through complementary mechanisms to improve outcomes.