Understanding Targeted Therapy In Cancer Treatment

Overview

Targeted therapy concerns a kind of cancer treatment that utilizes drugs designed specifically to ‘target’ cancerous cells without affecting normal ones significantly. Typically, cancer cells have genetic changes (or mutations), which differentiate them from normal cells. After a cell undergoes specific gene changes, it no longer acts like a normal cell. Instead, it will divide and grow very fast.

Like other drugs that treat cancer, targeted therapy medications are technically chemotherapy. Unlike standard or traditional chemotherapy (chemo), targeted therapy drugs work differently by focusing on some changes that differentiate cancerous cells from normal ones. As a result, their functions differ from chemo in two ways:

• Unlike traditional chemo that affects both cancerous and healthy cells, targeted therapy only eliminates cancer cells. These drugs affect normal cells to a much lesser extent.
• Targeted drugs usually block cancer cells from replicating or copying themselves, stopping them from dividing and creating new cancerous cells. But conventional chemo kills any dividing (cells in the process of cell division) in the body.

Due to this vital difference, oncologists sometimes use targeted therapy as the initial/frontline treatment. Targeted therapy could also be combined with other cancer treatments. More than 80 targeted therapies have been developed by medical researchers to treat different types of cancer and the numbers are increasing.

How Targeted Therapy Works

Once researchers know the genetic mutation that changes healthy cells into cancerous ones, they pinpoint certain cancer cell parts that can be targeted. Often, the targets may be on the surface of cancer cells. Occasionally, the targets could be substances within cancer cells. Two common targeted therapies and their mode of combatting cancer are:

• Monoclonal antibodies: These are lab-made versions of antibodies, which form part of our immune system. They are proteins that scan one’s body for signs of invading proteins (or antigens), which may come from infections or cancer cells. Antibodies then target these antigens to eliminate the intruders.
• Small-molecule drugs: Binding or attaching themselves to specific targets on the cancer cells, these drugs prevent cancerous cell growth or kill such cells. These molecules, being small, can gain access through the cell wall into the cell itself.

Other Examples of Targeted Therapy

To survive, cancer cells need multiple elements. Some targeted therapies that are programmed to prevent cancerous cells from growing, increasing and surviving include:

• Angiogenesis inhibitors: Like other organs and tissues, cancerous cells and tumors need new blood vessel formation to obtain oxygen and nutrients for survival. To ensure they have ample oxygen and nutrients, cancerous cells emit chemical signals that encourage new blood vessel formation into the tumor. By blocking these signals, angiogenesis inhibitors suspend the formation of new blood vessels into the tumor.
• Proteasome inhibitors: Here, the targeted therapy is focused on certain enzymes termed proteasomes, which digest proteins found inside cancer cells.
• Signal transduction inhibitors: This treatment disrupts the messaging system of cancer cells used for growth and survival. Cancer cells generally use a protein or signalling receptor to flash messages to other proteins within the cell. The signalling receptor gives proteins instructions on dividing and other steps meant for the growth and multiplication of cancer cells.

Are All Types of Cancer Treated with Targeted Therapy?

As said earlier, more than 80 targeted therapies have been developed to treat numerous types of cancer. Targeted therapies have also been developed to treat diverse mutations forming part of the same type of cancer. Targeted therapies can treat various kinds of cancer including:

• Blood cancers – leukaemia, lymphoma and multiple myeloma.
• Brain cancers (e.g., glioblastoma and neuroblastoma).
• Bone and soft tissue cancers, including some soft tissue sarcomas.
• Breast cancers (like BRCA gene mutation, HER2-positive, hormone receptor-positive and triple-negative breast cancer).
• Digestive system cancers such as colorectal (colon) cancer, oesophageal, gastrointestinal stromal tumour, neuroendocrine tumours, non-Hodgkin’s lymphoma, as well as stomach, pancreatic, liver and gall bladder cancers.
• Head-and-neck cancers – laryngeal cancer, nasal cavity and paranasal sinus cancer, nasopharyngeal, oral and oropharyngeal cancers.
• Lung cancers, e.g., small cell lung cancer, non-small cell lung cancer and mesothelioma.
• Reproductive system cancers such as cervical, endometrial and prostate cancers.
• Skin cancers (melanoma and cutaneous squamous cell skin cancer).
• Thyroid cancers (anaplastic thyroid, medullary thyroid and papillary/follicular thyroid cancers).
• Urinary system cancers such as bladder, kidney and prostate cancers.

How Effective is Targeted Therapy?

Though targeted therapy is extremely effective, it may not always be successful. Before a target for this therapy can be identified, which is a complicated process, oncologists must have detailed information regarding the specific cancer. Since this remains a challenging process, the success rates can vary.

Below are a few situations highlighting when targeted therapy won’t work: 

• The tumour has no target that matches this treatment.
• The tumour does not react as expected to the therapy. For instance, targeted therapy may concentrate on blocking the tumour growth with a drug customized for the substance that is driving growth. However, if the tumour does not require this substance to grow, the targeted therapy will be ineffective.
• If tumour cells continue mutating, the targeted therapy ceases to work or won’t be as effective as it was earlier.

What Happens Before the Therapy?

The oncologist will first confirm if targeted therapy is the right approach for the type of cancer you have. Your blood test may be done or some tissue samples taken for biopsies. These samples will be checked for certain gene mutations or changes, seeking targets that will possibly react to specific therapies.

Procedure during Targeted Therapy

Since each person’s situation differs, the oncologist will explain the treatment plan so it’s clear what one can expect. Some general possibilities that could occur during targeted therapy:

• It may require the ingestion of a pill, be administered subcutaneously (an injection under the skin) or by an IV (intravenously or via a vein).
• It could be given along with other treatments, such as chemo or radiation therapy.
• It may be done daily, once a week, several times per week, only once a month or less frequently.
• A brief break from therapy may be permitted/required.

Regular visits to the cancer care facility will be necessary so oncologists can evaluate your progress. Blood tests may be taken while X-rays, computed tomography (CT) scans and allied tests will assess whether the therapy is working well. The doctors will also check if the treatment’s side effects are well managed.

What are the Benefits of this Treatment?

The big benefit is that targeted therapy will eliminate cancer cells without harming your healthy cells. Cancer cells will also be blocked from growing and multiplying. If other treatments have been ineffective, targeted therapies could offer hope.

What are the Side Effects?

While the side effects will differ as per each drug used, some possible ones could include:

• Diarrhoea.
• Dry skin.
• Skin rash.
• Elevated liver enzymes, which could potentially damage the liver.
• Cardiotoxicity – damage to the heart muscle.
• Extreme sensitivity to UV (ultraviolet) light (photosensitivity).
• High blood pressure.
• Loss of hair colour.
• Nail changes.
• Issues with blood clotting and wound healing.
• Interstitial lung disease (also termed pulmonary fibrosis).
• Changes in the heart rhythm.
• Neurological changes

Recovery and Outlook

Side effects after targeted therapy could last throughout the treatment. These side effects could vary across each person. Most side effects will subside some months after the treatment concludes.

For many people, although targeted therapy remains an effective cancer treatment, the success rate can vary substantially. The results will depend on the type and stage of cancer. Since targeted therapy affects people in different ways, the oncological team will guide you regarding what to expect. By seeking treatment from the best cancer hospital, you can improve the possibility of better outcomes.