Definition
The term " chemotherapy " is generally used to indicate the pharmacological treatment of neoplasms. In reality, the meaning of this word is much broader.
At the beginning of the 20th 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.
To be precise, therefore, it is necessary to distinguish between:
- Antibacterial chemotherapy, whose target is pathogenic microorganisms against which defined drugs are used:
- chemotherapy if they are of synthetic origin);
- antibiotics if they are of natural origin.
- Antineoplastic chemotherapy . The term " antineoplastic " means " against new growth ". The target of this treatment is cancer cells, which are treated with anticancer drugs (antineoplastic or chemotherapeutic).
Currently, the generic term chemotherapy refers specifically to the treatment of neoplastic diseases. The term pharmacotherapy is used to indicate the treatment of any disease with the use of any chemical substance.
Antineoplastic chemotherapy
The high incidence of tumors on the human organism - both in terms of the number of cases found and the high mortality rate that characterizes them - has allowed and made essential a remarkable development of antineoplastic chemotherapy.
The purpose of chemotherapy is to slow down, and hopefully block, the uncontrolled cell growth and spread that characterize malignant tumors.
The drugs used are called cytotoxic drugs, as they have a toxic activity towards cells. The toxicity of these drugs is generally expressed by interfering with the synthesis and function of DNA, RNA and proteins indispensable for cellular life.
An ideal antineoplastic drug should be " tissue- and cell-specific "; that is, it should be able to act selectively only on the tissue affected by the pathology and only on the tumor cells, leaving the healthy ones unaffected to avoid collateral effects. Unfortunately, the ideal chemotherapy does not yet exist and the undesirable effects are manifested, often and above all, in respect of those tissues characterized by a great cell turnover.
Combination antineoplastic chemotherapy
Combination antineoplastic chemotherapy consists of using two or more anticancer drugs (drug cocktails), in order to take advantage of the different ways in which they act on the tumor.
The combined chemotherapeutic approach is based on the assumption that more drugs, with different mechanisms of action, can give synergistic effects (that is, work together to obtain an effect that cannot be achieved if used individually) and / or that can delay the onset of resistance to single drug.
Sometimes, thanks to the combined administration, the drugs can be administered with lower dosages than those that would be necessary if they were administered individually. The administration of a lower dosage of drugs could result in a reduction in toxicity and side effects.
However, this therapeutic approach can 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 chemotherapy resistance is called the Multi-Drug Resistance mechanism. This phenomenon is due to the adaptive capacity of some tumors, which are able to develop drug resistance, thus leading to the ineffectiveness of the therapy.
This process usually occurs in patients with solid tumors and / or who are subjected to multiple chemotherapy cycles.
It appears 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 Resistance Protein . The task of this protein is to transport the drug outside the cancer 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, the stage in which it is located 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 administered via:
- Syringe, when the drug is administered quickly (at most a few minutes);
- Drip, when the drug must be administered in an interval that goes from thirty minutes to some hours;
- Infusion pump, when the drug must be administered slowly (drop by drop) even for days;
- Continuous infusion for a period ranging from weeks to months, in this case the patient will always have the infusion pump with him.
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 have to look for a vein each time to administer the drug.
Among these alternative methods we find:
- Agocannula or peripheral venous catheter : it consists of a thin tube that, through a needle, is inserted into a vein of the hand or arm. With this system, both drugs and blood samples can be taken. It can be kept for a few days.
- Central venous catheters, are tubes of material compatible with the organism (usually silicone or polyurethane) that reach the large veins that are near the heart. These catheters can be
- external, they are inserted under local anesthesia, in a sterile environment;
- internal, are inserted with a small surgery.
Oral
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 directives on the method of employment are carefully followed and that the information leaflet is read carefully.
Arterial way
It consists of inserting a cannula into 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.
Via intracavitaria
The administration takes place in a natural cavity of the body:
- Via intravesical, the chemotherapy is administered directly into the bladder through the use of a catheter;
- Via intraperitoneally, the administration occurs between the two layers constituting the peritoneum (the membrane that covers the wall and the abdominal viscera);
- Via intrapleural, the administration occurs between the two layers that constitute the pleura (the membrane that covers the chest and the lungs).
Intrathecal route
Used only in some types of brain tumors and leukemia. Chemotherapy is administered into the cerebrospinal fluid through the spine.
Intramuscular way
It is a little used street. It is practiced at the level of the thigh or buttocks and causes a slower release of the chemotherapy than the intravenous route.
Subcutaneously
This route is mainly used for hematological drugs. Administration takes place at the level of the thigh, abdomen or arm.
Side effects
The side effects of chemotherapy can be multiple, since they depend on the type of drugs used and may vary from individual to individual.
Many chemotherapists have negative effects especially on those tissues characterized by a high cell turnover, as happens, for example, in hair follicles, mucous membranes or blood.
It is therefore not easy to list every single side effect that may be caused by chemotherapy; the following are the main side effects.
Bone marrow suppression and immunosuppression
Bone marrow suppression (or myelosuppression ) can be caused either by particular types of bone tumors or by certain types of chemotherapy. Some chemotherapy drugs are in fact able to induce a sort of blockage in the bone marrow, which thus loses the ability to regenerate and adequately renew the blood cells.
Myelosuppression can lead to:
- anemia, or 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 into the blood, from the lungs to the rest of the body. Typical symptoms of anemia are a particular fatigue or shortness of breath.
- thrombocytopenia, or a drop in platelets, which are the blood cells responsible for coagulation. The fall in the number of platelets favors the onset of bleeding or bleeding .
- leukopenia, ie a decrease in white blood cells, which are the cells responsible for the body's immune defenses. A drop in the amount of white blood cells makes the patient more susceptible to 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 acquired by patients undergoing chemotherapy are due to the normal bacterial flora present in the gastro-intestinal tract, in the mouth and on the skin. These infections can be systemic or localized, such as the infection caused by Herpes simplex .
Disorders of the gastrointestinal tract
The mucous membranes that make up the digestive system are subject to a rapid cellular exchange and, for this reason, are among those most affected by chemotherapy. It is not unusual for them to manifest:
- Nausea and vomiting : in reality not all chemotherapy drugs cause these symptoms; moreover, for those drugs that cause them it cannot be foreseen if they will do it, with what frequency and with what intensity, since a great variability exists from individual to individual. These symptoms can appear from a few minutes up to a few hours after chemotherapy, can last for hours and sometimes for a few days. In general, 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 after 3-4 weeks after the end of treatment;
- Taste alteration . This symptom usually disappears a few weeks after the end of 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.
Fatigue
The sense of fatigue that one experiences during chemotherapy is very intense and prolonged, and is called fatigue . The sense of fatigue is considerable and may be due to a combination of factors, including the action of drugs, lack of sleep or inadequate nutrition.
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 a normal appearance after 4-6 months from the end of the therapy, even if, it can happen, that they grow with a different color or that they appear more curly than they were before starting the 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 changes in sensitivity and tingling that mainly involve hands and feet. It usually disappears after a few months after the end of chemotherapy.
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 doctors' responsibility to identify the chemotherapy that is best suited to each individual patient, to try to limit the side effects as much as possible.
Chemotherapy drugs: what they are and how they work ยป
