Cancer is one of the most common diseases and a major public health problem, taking nearly 10 million lives each year worldwide. There are many conventional cancer treatment methods, however, they are not effective for all types of cancer, and more importantly, they demonstrate severe side effects for the patients' organisms. Therefore, over the past several years, a new generation of cancer treatment has come to the forefront – targeted cancer therapy. So, what is it exactly?
Targeted cancer therapy - drugs that “attack” specific parts of cancer cells called “targets.”
Targeted cancer therapy “targets” – proteins, enzymes, or genes that control cancer cells spreading and division.
Targeted cancer therapy makes the cancer treatment more tumor-specific and demonstrates less severe side effects for the patient's organism.
Most cancers are still treated by combining traditional methods (chemotherapy, radiation therapy, surgery) and targeted therapy.
What is targeted cancer therapy?
Targeted cancer therapy includes various drugs that “attack” specific parts of cancer cells – called “targets”. These “targets” could be proteins, genes (such as particular DNA sequences), or enzymes found either on cancer cell surfaces or inside them. The main goal of targeted cancer therapy is to block cancer signals that make cancerous cells grow, divide, and survive. These therapies make the cancer treatment more tumor-specific and less toxic to the patients With more accuracy and precision, less harm and collateral damage is done.
Cancer types that can be treated using targeted therapy
It is important to note that targeted therapy is not a universal tool. Each type of cancer or even the same type in different patients requires different drugs. To date, more than 80 targeted therapies and drugs have been developed to treat various kinds of cancers. This table shows common types of cancers that can be treated using targeted therapy.
Cancer types which can be treated by targeted therapy drugs
|Body part/tissue||Cancer type|
|Bone and soft tissue||Certain soft tissue sarcomas|
|Breast||BRCA gene mutation breast cancer|
HER2-positive breast cancer
Hormone receptor-positive breast cancer
Triple-negative breast cancer
|Digestive system||Colorectal (colon) cancer|
Gastrointestinal stromal tumor
Stomach cancer (intestinal stomach adenocarcinomas)
Hepatocellular (liver) cancer
Cholangiocarcinoma (gall bladder cancer)
|Head and neck||Laryngeal cancer|
Nasal cavity and paranasal sinus cancer
|Lung||Non-small cell lung cancer|
Small cell lung cancer
|Reproductive system||Cervical cancer|
Cutaneous squamous cell skin cancer
|Thyroid||Anaplastic thyroid cancer|
Medullary thyroid cancer
Papillary/follicular thyroid cancer
|Urinary system||Bladder cancer|
Differences between traditional cancer treatments and targeted cancer therapies
Surgery, radiation therapy, and chemotherapy are the traditional, effective cancer treatment methods. In most cases, surgical removal of the tumor alone is not enough, so radiation therapy and/or chemotherapy are additionally applied before or after surgery.
The main targets of chemotherapy and radiation therapy are rapidly dividing cells, such as cancer cells. However, cancerous cells are not the only type of quickly dividing cells within the body. For example, bone marrow, the digestive tract, and hair follicles are tissues that demonstrate high rates of division. That is why radiation therapy and chemotherapy will not only affect cancer cells but also cause healthy cell death. This harm is often quite significant and exhausting.
This lack of specificity and precision leads to severe side effects, such as pain, nausea, diarrhea, cardiotoxicity, hair loss, darkened or dry skin, and depression of the immune system. In addition, cancer cells that are not killed by traditional methods usually acquire resistance and ultimately result in a more aggressive form of cancer, which becomes very difficult to treat. Thus, not only the patient's organism is weakened, but additionally, cancer gets stronger.
Targeted therapy for cancer is the opposite. Since this therapy aims to "target" cancer cells without affecting normal cells, its toxicity to the body is lower, and the side effects are significantly lighter.
The most common side effects of target therapy
Even though targeted cancer therapy is much more specific to cancer cells, it still has side effects for the organism. The frequency and strength of the side effects mostly depend on the “target” which the drug is intended for.
During the development of targeted therapy drugs, efforts are made to discover and select the “targets” (mutated proteins, specific growth factors, etc.) which are specific only to cancer cells. Unfortunately, in most cases, such specific and unique “targets” cannot be distinguished, therefore the selected ones are also presented in the healthy organism cells, just in a significantly lower amount. Thus, when the drug “attacks” its “target”, various processes determining cell survival and division are disrupted not only in cancer cells but also in healthy ones. This is why targeted drugs also cause side effects.
However, not all patients experience these side effects. As well, the severity of the effects varies individually. The most common targeted therapy side effects include:
- Dry skin/skin rash
- Elevated liver enzymes
- Cardiotoxicity (damage to the heart muscle)
- Extreme sensitivity to ultraviolet light (photosensitivity)
- High blood pressure (hypertension)
- Loss of hair color
- Nail changes
- Problems with wound healing and blood clotting
- Heart rhythm changes
The side effects gradually disappear when the targeted therapy is finished. It is important to remember that targeted therapy drugs, unlike those used in chemo/radiation therapies, are relatively new, so it is still difficult to assess if their use can cause lifelong damage to the heart, lungs, kidneys, reproductive organs, etc.
Finally, many targeted therapy drugs are still not sufficient to completely block their “targets” and thereby successfully destroy cancer cells. Therefore, only a few types of cancers are routinely treated by using only these drugs. In most cases, cancer treatment strategies include both types of therapies – targeted and traditional (chemo or radiation).
Despite the current shortcomings of targeted therapy, it is the way forward to develop highly efficient drugs that affect only cancer cells and do minimal or close to no harm to healthy organism cells.