Chemotherapy

What is this ?

Chemotherapy is the most commonly used cancer treatment. Its effect is cytotoxic, meaning it targets the cell multiplication cycle in a non-specific manner.

Thus, its action affects tumor cells, whose growth is uncontrolled, as well as healthy cells that divide rapidly (mucous membranes, hair, etc.).

The operation

There are a large number of chemotherapy agents available in oncology/hematology. The different phases of the cell cycle during which they act distinguish them from one another.

Indeed, the development of a cancerous tumor initially arises from the degeneration of a single cell, whose proliferation becomes uncontrolled and very rapid. This means that each cell divides into 2, then 4 cells, each of which divides again, and so on in an infinite and exponential manner.

This proliferation is divided into several phases :

• Growth of the cell
• Replication: Doubling of the cell's genetic material
• Mitosis or division into 2 cells (called daughter cells) from the first cell (called the mother cell).

Chemotherapies target these phases of cell activity, which are points of vulnerability, in order to control or even stop the growth of the tumor.

To enhance the effectiveness of the treatment, chemotherapy agents are often combined within what is known as a chemotherapy protocol (named after the initials of the drugs it includes).

These medications can be available in different forms: most commonly intravenous, but also oral, intramuscular, or subcutaneous.

Thus, treatments are organized into cycles of drug administration, with one or more doses given at regular intervals within each cycle.

It is primarily the mode of action of the drug used, as well as the predictable side effects of the treatment, that determine the intervals between cycles, allowing the body time to recover.

Finally, the indication and the patient's response to the treatment determine the number of cycles to be administered. Your oncologist will regularly perform a comprehensive assessment of the disease, including blood tests and imaging (most often every 2 or 3 cycles), to determine whether to continue the treatment.

Catherine, 53, talks about her fight against breast cancer and her chemotherapy treatment.

Side effects

Firstly, the side effects of chemotherapy vary in frequency and intensity depending on the drugs used.

To illustrate this, some of the most common side effects include :

• Allergic reaction
• Risk of reduced fertility or sterility: The medical team may offer a fertility preservation strategy to any affected patient.
• Fatigue
• Alopecia: Hair and body hair loss (not systematic)
• Digestive issues: Nausea/vomiting, diarrhea, mucositis (mouth ulcers and irritations).
• Biological disturbances (visible in blood tests) :
• Toxicity to blood cells. This can cause symptoms such as :
• Anemia, leading to a decrease in hemoglobin (red blood cells),
• Leukopenia, representing a decrease in white blood cells (notably neutrophils that protect against infections),
• Thrombocytopenia, caused by a decrease in platelets with a risk of bleeding.
• Hepatic and renal toxicity: The kidneys and liver are the main organs that metabolize and eliminate chemotherapy. This can result in disturbances of the function of these organs after treatment.

While some side effects are immediate (fatigue, nausea, vomiting), most occur within 7 to 10 days following the administration of the treatment. Premedication treatments can therefore be taken to prevent the onset of most of these side effects.

Your oncologist will strengthen these preventive measures based on each individual's tolerance, and if necessary, the chemotherapy dosage will also be adjusted.

Indications

Chemotherapy is a systemic treatment (as opposed to a local one) that targets cancer wherever it is found in the body.

It is most commonly used in metastatic diseases (meaning cancer that has spread throughout the body), but it can also be used in cases where the disease is confined to a single organ under two specific circumstances.

In « adjuvant »

This means after a radical local treatment aimed at completely removing the tumor (surgery or radiotherapy) to minimize the risk of recurrence.

Indeed, it is well established that the early spread of microscopic cancer cells (not visible on scans or MRIs) into the bloodstream promotes the possibility of distant relapses following local treatment. These cells can then, sometimes after several years, colonize other organs.

A doctor may propose additional treatment a few weeks after the procedure when this risk is considered significant.

In « neoadjuvant »

When the tumor remains localized but appears difficult for the surgeon to remove, the oncologist may recommend initial chemotherapy. The goal of this treatment is to reduce the size of the tumor so that it can be more easily removed.