Definition
The term "chemotherapy"is generally used to indicate the drug treatment of neoplasms. In reality, the meaning of this word is much broader.
At the beginning of the twentieth century, the German microbiologist Paul Ehrlich defined chemotherapy as the use of any chemical substance (of synthetic origin) for the treatment of any pathological manifestation due to infectious agents.
Wanting to be precise, therefore, it is necessary to distinguish between:
- Antibacterial chemotherapy, whose target is made up of pathogenic microorganisms against which defined drugs are used:
- chemotherapy if they are of synthetic origin);
- antibiotics in case they are of natural origin.
- Antineoplastic chemotherapy. The term "antineoplastic" it means "against new growth"The target of this treatment is cancer cells, which they are treated with anticancer drugs (antineoplastic or chemotherapy drugs).
Currently, with the generic word chemotherapy it refers specifically to the treatment of neoplastic pathologies. Instead, the term is used to indicate the treatment of any pathology with the use of any chemical substance pharmacotherapy.
Antineoplastic chemotherapy
The high incidence of tumors on the human body - both in terms of the number of cases found and the high mortality rate that characterizes them - has allowed and made essential a considerable development of antineoplastic chemotherapy.
The purpose of chemotherapy is to slow, and hopefully stop, the uncontrolled cell growth and spread that characterizes malignant tumors.
The drugs used are defined cytotoxic drugs, as they possess a toxic activity towards cells. The toxicity of these drugs generally occurs by interfering with the synthesis and function of DNA, RNA and proteins essential for cellular life.
An ideal antineoplastic drug should be "tissue- and cell-specific"; that is, it should be able to selectively act only on the tissue affected by the disease and only on the tumor cells, leaving the healthy ones unaltered in order not to incur side effects. Unfortunately, the ideal chemotherapy does not yet exist and the undesirable effects often occur. above all, towards those tissues characterized by a large cell turnover.
Combination Antineoplastic Chemotherapy
Combination antineoplastic chemotherapy consists in the use of two or more anticancer drugs (drug cocktail), with the aim of taking advantage of the different ways in which these act on the tumor.
The combined chemotherapy approach is based on the assumption that several drugs, with different mechanisms of action, can give synergistic effects (ie work together to obtain an effect that cannot be obtained if used individually) and / or can delay the onset of resistance to single drug.
Sometimes, due to combined administration, drugs can be administered at lower dosages than would be required if administered individually. The administration of a lower dosage of drugs could result in a reduction of toxicity and side effects.
However, this therapeutic approach may also have disadvantages, such as the possible occurrence of multiple side effects and the possibility of negative interactions between the components of the cocktail once they have been administered.
Resistance to chemotherapy
The phenomenon of resistance to chemotherapy is called the mechanism of Multi-Drug Resistance (Multi-Drug Resistance). This phenomenon is due to the adaptive capacity of some tumors, which are able to develop resistance to drugs, thus leading to the ineffectiveness of the therapy.
This process usually occurs in patients with solid-type tumors and / or who are undergoing multiple courses of chemotherapy.
It seems that the phenomenon of multi-drug resistance is due to the presence of a particular protein on the cell membrane: the P-glycoprotein 1 or Multi-Drug Strength Protein. The task of this protein is to transport the drug out of the tumor cell, thus preventing it from carrying out its cytotoxic action.
Administration
The method by which chemotherapy is administered varies according to the type of cancer, its location, its stage and the patient's condition. The main routes of administration are listed below.
Intravenous route
This method of administration provides access to the bloodstream (venous access), which must be kept open for the time necessary to complete the treatment.
Chemotherapy can be given via:
- Syringe, when the drug is administered in a short time (at most a few minutes);
- Drip, when the drug is to be administered in an interval ranging from thirty minutes to a few hours;
- Infusion pump, when the drug must be administered slowly (drop by drop) even for days;
- Continuous infusion for weeks to months, in which case the patient will always have the infusion pump with them.
Intravenous chemotherapy involves repeated injection of irritants that can cause phlebitis. To try to overcome this problem, alternative methods of intravenous administration have been devised; with these methods the venous access is kept open and it is not necessary to look for a vein every time to administer the drug.
Among these alternative methods we find:
- Needle cannula or peripheral venous catheter: it consists of a thin tube which, through a needle, is inserted into a vein in the hand or arm. With this system both drugs and blood samples can be administered. It can be held for a few days.
- Central venous catheters, are tubes of material compatible with the body (usually silicone or polyurethane) that reach the large veins that are located near the heart. These catheters can be
- external, are inserted under local anesthesia, in a sterile environment;
- interior, are inserted with a minor surgery.
Oral way
Taking oral chemotherapy can be used alone or in combination with intravenous therapies. In the case of capsules or tablets, these can be provided directly to the patient, who can take them at home.
In this case it is important that all the doctor's instructions on how to take it are followed diligently and that the package leaflet is carefully read.
Arterial route
It consists in inserting a cannula inside the main artery that irrigates the area where the tumor is present. It is usually used for liver carcinomas (in this case the chemotherapy drugs are administered through the hepatic artery).
It is a technique that requires a high level of qualification and is practiced only in specialized centers.
Intracavitary route
The administration takes place in a natural cavity of the organism:
- Intravesical way, the chemotherapy is administered directly into the bladder through the use of a catheter;
- Intraperitoneal route, the administration takes place between the two layers constituting the peritoneum (the membrane that covers the wall and the abdominal viscera);
- Via intrapleural, administration takes place between the two layers that make up the pleura (the membrane that lines the chest and lungs).
Intrathecal route
Used only in some types of brain tumors and leukemia. The chemotherapy is administered into the cerebrospinal fluid via the spinal column.
Intramuscular route
It is a little used way. It is practiced at the level of the thigh or buttocks and causes a slower release of the chemotherapy than the intravenous route.
Subcutaneous route
This route is mainly used for haematological drugs. Administration takes place in the thigh, abdomen or arm.
Side effects
The side effects of chemotherapy can be many, as they depend on the type of drugs used and can vary from individual to individual.
Many chemotherapeutics have negative effects especially against those tissues characterized by a high cell turnover, as occurs, for example, in the hair follicles, in the mucous membranes or in the blood.
It is therefore not easy to list every single side effect that can be caused by chemotherapy; below are what are considered to be the main side effects.
Bone marrow suppression and immunosuppression
Bone marrow suppression (or myelosuppression) can be caused both by particular types of bone tumors and by some types of chemotherapy. Some chemotherapeutic agents are in fact able to induce a sort of blockage in the bone marrow, which thus loses the ability to adequately regenerate and renew blood cells.
Myelosuppression can lead to:
- anemia, i.e. a reduction in the amount of hemoglobin in the blood. Hemoglobin is a protein found inside red blood cells that makes it possible to transport oxygen in the blood from the lungs to the rest of the body. Typical symptoms of anemia are particular tiredness or shortness of breath.
- thrombocytopenia, which is a drop in platelets, which are the blood cells responsible for clotting. The decrease in the number of platelets favors the onset of bleeding or bleeding.
- leukopenia, that is, a decrease in white blood cells, which are the cells responsible for the body's immune defenses. A decrease in the amount of white blood cells makes the patient more prone to contracting infections.
Ideally, all drugs used in chemotherapy can cause suppression of the immune system. For this reason, patients are encouraged to wash their hands often, to avoid contact with sick people and to take all possible precautions to try to reduce the risk of contracting infections.
However, many of the infections contracted by patients undergoing chemotherapy are due to the normal bacterial flora present in the gastrointestinal tract, in the mouth and on the skin. These infections can be systemic or localized, such as infection caused by Herpes simplex.
Disorders of the gastrointestinal tract
The mucous membranes that make up the digestive system are subject to rapid cell turnover and, for this reason, they are among those most affected by chemotherapy. It is not unusual for the following to occur:
- Nausea and vomit: in reality, not all chemotherapy drugs cause these symptoms; moreover, for those drugs that cause them, it cannot be predicted whether they will do so, how often and with what intensity, since there is great variability from individual to individual. These symptoms can appear from a few minutes to a few hours after the administration of chemotherapy, they can last for hours and sometimes for a few days.Generally, doctors keep these disorders under control by administering appropriate drugs against vomiting (antiemetics);
- Inflammations and ulcers in the mouth. These symptoms may appear a few days after chemotherapy and usually disappear 3-4 weeks after the end of treatment;
- Alteration of taste. This symptom generally disappears after a few weeks from the end of the treatment;
- Loss of appetite, diarrhea or constipation. Although there may be a loss of appetite, it is still essential to introduce the necessary amount of fluids, especially if chemotherapy has induced diarrhea.
In the event that the treatments trigger constipation, a possible solution is to follow a diet that is rich in fiber.
Tiredness
The sense of fatigue that one feels during chemotherapy is very intense and prolonged, and is called fatigue. The sense of fatigue is considerable and can be due to a number of factors, including the action of drugs, lack of sleep or an inadequate diet.
Hair loss
Not all drugs used in chemotherapy cause this disorder and in any case not all cause it with the same intensity. Often, the hair regains its normal appearance 4-6 months after the end of the therapy, even if, it can happen, that it grows with a different color or that it presents more curls than it was before starting chemotherapy.
Peripheral neuropathy
Peripheral neuropathy is a pathology of the peripheral nervous system. It can involve one or more nerves and can manifest itself with alterations in sensitivity and tingling that mainly involve the hands and feet. It usually disappears a few months after chemotherapy ends.
Damage to other organs
Many drugs used in chemotherapy can cause damage to organs such as the heart, lungs, liver and kidneys. It is the responsibility of doctors to identify the chemotherapy that best suits each individual patient, to try to limit side effects as much as possible.
Chemotherapy drugs: what they are and how they work "
