Targeted therapy (precision medicine)

Unlike chemotherapy, which acts selectively, targeted therapy precisely affects the changes in cancer cells that cause them to grow, divide, and/or spread. Therefore, these drugs are colloquially called smart drugs. This type of treatment was made possible by scientific research, which over time has found molecules on the surface or inside tumor cells that are specific to cancer cells (i.e., they are not found on healthy cells). After the discovery of such molecules, they can be targeted with specific antibodies that bind to them. In this way, we ensure that the drug is delivered directly to the tumor cell without a negative effect on healthy cells in the body, which significantly reduces the risk of side effects of treatment. Drugs used in targeted therapy belong to the group of small molecule drugs or monoclonal antibodies. The advantage of the first group is that these drugs are small enough to enter the cell without major difficulties, so they are primarily used to "target" targets inside the cell. They come in the form of tablets or capsules. Monoclonal antibodies are proteins in composition and are produced in specialized laboratories. They are administered intravenously. They serve to specifically bind to a specific target molecule on a tumor cell, and further effects depend on the specific drug.

Dr. Kust for Laudato TV: What are smart drugs? Who can get smart drugs? Will I have better results with a smart drug than with chemotherapy? What are the side effects of smart drugs? If smart drugs don't work for me, can other types of treatment be used?

Which patients are candidates for targeted therapy? Since this is a highly selective treatment, in the vast majority of cases, before the targeted therapy is applied, the patient's tissue (obtained through an earlier biopsy or surgery) must be tested for the presence of certain target molecules. Only those patients in whom it is found that there is indeed a target on/in the tumor cells that we can "attack" with a targeted drug will be candidates for the use of such a drug, because in other patients the treatment will have no effect and may even be harmful.

Possible mechanisms of action of targeted therapy:

1. Action on the immune system. Due to their importance, these drugs are separated into a separate group, and the form of treatment is called immunotherapy, which you can read about in a separate article.

2. Stopping the growth of tumor cells. Healthy cells divide only when necessary, and to initiate the above process, they need signals delivered by proteins that bind to specific molecules on the cell surface. However, tumor cells can, due to genetic changes, enter a state of constant division without this initial signal (the signaling pathway is constantly activated). Some targeted drugs interfere with the altered proteins, thereby interrupting the signaling pathway that stimulates the cell to divide.

3. Stopping angiogenesis. Tumor tissue needs a large amount of nutrients for growth, and they receive them, like all other cells, through the blood. Since tumor tissue grows much faster than healthy tissue, it also needs a large blood supply and the continuous formation of new blood vessels, which is called angiogenesis. Tumors stimulate angiogenesis by releasing their signaling molecules that act on existing blood vessels. Some targeted drugs interfere with this process and reduce the formation of new blood vessels around the tumor, which prevents them from growing further or causes the tumor to shrink due to the loss of blood supply.

4. Delivery of cytotoxic substances to the tumor. Some targeted drugs are combined with toxins, cytostatics or radiation. After the targeted drug binds to the tumor tissue, the cells take up the cytotoxic substance and the cell dies, while the surrounding healthy cells remain unharmed.

5. Causing cell death. Normal healthy cells regularly die when they are damaged or no longer needed, while tumor cells resist this natural process. Some drugs can restore them to a normal state and the process of dying.

6. Preventing the effects of hormones. You can read about hormone therapy in a separate article.

Figure 1. Presentation of the complexity of the signaling pathways that lead to programmed cell death (apoptosis), by which healthy cells die when they are damaged or no longer needed. Avoiding apoptosis is one of the ways of survival of tumor cells, but with the effect of targeted therapy on one of these control points, an attempt is made to stop this process.

Although targeted therapy is generally well tolerated and has fewer side effects than chemotherapy, side effects can still occur. The most common are diarrhea, liver function, blood clotting disorders, high blood pressure, fatigue, damage to the oral mucosa, changes in nail and hair color, and skin changes (rash or dry skin). Many patients do not have any of these side effects or the side effects are very mild and often do not require intervention. Treatment can be given daily, once a week, or even once a month, depending on the specific drug and treatment protocol.​​

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Immunotherapy

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