In 2020, approximately 10 million cancer-related fatalities were reported worldwide, making it one of the major causes of premature death. Chemotherapy, radiation therapy, and surgery are the three cancer modalities that have formed the cornerstone of cancer treatment for many years and are considered the conventional approaches to treating this illness. Chemotherapy medications are modulated to target both the body’s healthy cells and cancer cells that divide quickly. Over the past 10 years, a new group of treatments have come to the forefront of treating cancer i.e. targeted therapy drugs. Somewhat similar to standard chemotherapy drugs, targeted cancer therapies use pharmacological substances that stimulate cell death, prevent cancer from spreading and inhibit its growth. Researchers have improved treatment options to fight cancer as we know more about the proteins and DNA alterations present on the surface of cancerous cells. Targeted therapies lay emphasis on precision medicine techniques by focusing on the specific molecular alterations that are unique to a given cancer, as opposed to employing a broad approach to treat this illness. Within this line of treatment, doctors aim to customize a therapeutic strategy that targets the proteins that dictate a cancer cell by understanding the DNA modifications that rule cancer, as opposed to the usual one-size-fits-all approach.
What Distinguishes Targeted Therapy From Conventional Treatment Approaches Like Chemotherapy?
Drugs used in targeted therapy function differently from those used in conventional chemotherapy. These drugs target cancer cells while leaving healthy cells unharmed. Drugs used in chemotherapy are cytotoxic, meaning they can harm both cancerous and healthy cells. Chemotherapy medications only target the cancer cells that are already present in the body and may not always stop them from proliferating and reproducing. Chemotherapy medications have severe side effects since they also impact healthy cells. Some of the side effects when a patient receives chemotherapy include loss of hair, extreme fatigue, weakness or numbness, mouth and throat sores, and nausea. Although targeted therapy can cause side effects such as high blood pressure, rashes on the skin, diarrhea, and fatigue, they are not as severe when compared with chemotherapy.
Drugs used in targeted therapy frequently function by preventing cancer cells from replicating. Put simply, this implies that they prevent cancer cells within the body from reproducing and multiplying.
How Does Targeted Therapy Work?
Targeted therapy drugs are designed to recognize and ultimately attack the mutations in cancer cells. They are also curated to block specific signals sent inside a cancer cell that tell it to grow. To develop targeted therapy drugs, researchers and experts try to learn about the genetic properties of a cancer cell that help it grow. Once the targets have been identified in the lab, the drugs are developed to attack that particular cancer. The action of a targeted therapy drug then becomes to:
- Help the immune system to destroy cancer cells: The ability of cancer cells to evade detection by the immune system contributes to their growth. Some targeted treatments have the ability to designate cancer cells, making it simpler for the immune system to locate and eliminate them. Additional personalized treatments may strengthen the patient’s immune system and improve their ability to fight cancer cells.
- Interrupt signals that allow cancer cells to grow: The body’s healthy cells only divide to create new ones when they get specific signals to do so. These signals cause the cells to divide by binding to proteins on the cell surface. However, surface protein alterations in certain cancer cells instruct them to proliferate regardless of the presence of signals. Certain targeted treatments disrupt these proteins, stopping them from instructing the cells to divide. This procedure aids in slowing the uncontrolled growth of cancer.
- Block signals that aid in the formation of blood vessels: Tumors must undergo a process known as angiogenesis in order to generate new blood vessels and expand beyond a specific size. Angiogenesis begins when signals from the tumor are sent. Angiogenesis inhibitors, a class of targeted medicines, obstruct these signals to stop the formation of a blood supply. Tumors remain tiny in the absence of a blood supply. Alternatively, if a tumor already has a blood supply, these treatments may lead to the breakdown of blood vessels, which may shrink the size of the tumor.
Why is Targeted Therapy Also Called Precision Medicine?
Targeted therapy is also referred to as precision medicine. This is because they are created to precisely attack the changes or substances in cancer cells. These substances can be different even when two patients have the same type of cancer. With the help of a biopsy or biomarker testing, certain types of tumors are tested to find the most effective form of treatment. Targeted therapy drugs are usually classified under two categories:
- Small-molecule drugs: These drugs are small enough to enter a cancer cell upon recognition. Once they enter the cancer cell, they then target a specific substance inside the cancer cell and block it.
- Large-molecule drugs: These drugs don’t enter a cancer cell because they are too big. Their primary aim is to attack and weaken the proteins or enzymes on the surface of the cells. Once these proteins or enzymes have been weakened, the drug can then effectively combat the cancer cells in the body.
How Can a Patient Be Determined To Be Eligible for Targeted Therapy ?
Most patients with specific cancers will have a target that is appropriate for a particular targeted therapy, making them good candidates for receiving this form of treatment. For instance, the majority of patients with Chronic Myelogenous Leukemia (CML) have the BCR-ABL fusion gene. With the use of biomarker testing, physicians can determine if a patient is a good candidate for targeted therapy by looking for certain biomarkers. Biomarker testing is the process of looking for genes, proteins, and other materials that might give more details about a cancer. Each patient with cancer exhibits a unique pattern of biomarkers. The effectiveness of certain cancer treatments is influenced by particular biomarkers. Together with your oncologist, biomarker testing may help a patient identify potential sources of treatment.
Targeted Therapy For Different Types of Cancers
Targeted therapy as a line of treatment for cancer is a rapidly growing field of research, and researchers are constantly studying the efficacy of various drugs through clinical trials. Some cancers which have shown positive results when treated with targeted therapy drugs include:
- Breast Cancer: Human epidermal growth factor receptor 2 (HER2) is a protein that is overexpressed in 20% to 25% of breast cancer cases. Tumor cells proliferate due to this protein. There are numerous alternatives for targeted therapy if the malignancy is HER2-positive. Trastuzumab is a drug that is commonly used for non-metastatic HER2-positive breast cancer. A trastuzumab-based regimen, which frequently combines trastuzumab with chemotherapy, is administered to patients with stage I to stage III breast cancer. This is followed by adjuvant HER2-targeted therapy for a full year.
- Chronic Myeloid Leukemia (CML) – The formation of the gene BCR-ABL is the primary cause of nearly all cases of chronic myeloid leukemia. The BCR-ABL protein, an enzyme, is produced as a result of this gene. This protein induces cancer-like behavior in healthy myeloid cells. Imatinib and Dasatinib are targeted therapy drugs that are commonly used for the treatment of this cancer.
- Colorectal Cancer – Epidermal growth factor receptor (EGFR) is a protein that is frequently overexpressed in colorectal cancer. Anti-EGFR medications may help prevent or reduce the spread of cancer. A medication that inhibits vascular endothelial growth factor (VEGF), a tumor-agnostic approach that targets an NTRK fusion, and anti-angiogenesis therapy are further alternatives. This protein aids in blood vessel formation. Fruquintinib is a targeted therapy drug that is commonly used for this cancer.
Summary
Targeted therapy for cancer treatment is a rapidly growing field of research and has shown great promise over the last decade. By targeting proteins that control how cancer cells grow, divide, and spread, targeted therapy specifically targets cancer cells as opposed to the one-size-fits-all approach seen in conventional lines of treatment for cancer.
