Chemotherapy: principles of chemotherapy, side effects, role in oncology
The society developed a stereotype that chemotherapy is used exclusively for the treatment of cancer.In fact, it still struggles with both infectious diseases and parasitic diseases.The common thing is that this struggle consists in influencing an enemy agent( tumor, infectious or parasitic pathogen) with the help of certain chemotherapeutic agents.But today, nevertheless, we will talk about chemotherapy in oncology.
The American children's doctor Sidney Farber, who worked as a pathologist, became the founder of modern oncological chemotherapy. Working in the 50s of the last century in children's hospitals, Farber was carried away by children's and then by adult oncology and thanks to grants he carried out a series of studies of drugs that had a harmful effect on malignant tumors. The discoveries of Farber laid the foundation for the era of chemotherapy, which since then has saved and improved the lives of dozens and hundreds of thousands of oncological .Table of contents: What is the effect of chemotherapy Formal differences in pharmaco- and chemotherapy Classification of chemotherapy Classification of antitumor drugs Chemotherapy methods Side effects of chemotherapy Medication tactics for the occurrence of side effects
What is the effect of chemotherapy drugs
Chemotherapy, the use of whichAnd is the basis of chemotherapy, in its effects are poisons or toxins for tumor cells and act as follows:
- ruins their external and internal structures, preventing cells from living and evolving;
- inhibits the multiplication of cells, thereby preventing new individuals from "flooding" the body and dislodging healthy, normal cells;
- disrupting vital intracellular processes( eg, internal metabolism), kill atypical cells.
and, as a summary result, expel the oncocells, advancing on all three fronts.
In effect, the principle is: "The enemy of my enemy is my friend." This chemical "friend", in addition to the general definition of "chemotherapy", has one more common name - "chemotherapeutic agent".
Formal differences in pharmaco-chemotherapy
Chemotherapy could be attributed to pharmacotherapy - and there, and there, on the "hotbed of evil" they act with the help of medications.But in the pharmacotherapeutic process involved two participants: the body and the drug.In the chemotherapeutic process, the circle of participants expands: it is an organism, a pathogenic agent( in the light of today's topic - atypical cells) and chemotherapy.
There is one more fundamental difference. In the classical manifestation, pharmacotherapy is aimed at, figuratively speaking, to extend a helping hand to the cells of the human body. Pharmaceuticals help cells to multiply, grow, develop, assist in the performance of disturbed or lost functions. Chemotherapy drugs the opposite mission - to crush and destroy an uninvited guest( again in the context of our topic - to kill an atypical cage). A fundamentally important point: chemotherapy, killing someone else's malignant cell, should at the maximum sparing the normal cells of the human body .
Tumors are good and malignant - chemotherapy is used to affect the second type of neoplasm.Chemotherapy drugs are used to influence both the primary malignant focus and the metastasis - cells that have detached from the primary tumor, which have fallen into other organs and have begun their destructive action there. In the treatment of metastatic tumors, chemotherapy is a great help for doctors - the chemotherapy works where the scalpel of the surgeon can not reach for technical reasons, or the tumor so "grows" into the organ that it is not possible to separate it from healthy tissues, because between themThere is no clear boundary.
Classification of chemotherapy
There are many classifications of chemotherapy.Here are the most revealing, which will help to understand the essence and purpose of this method of treatment.
Depending on where the chemotherapy agent is used, chemotherapy can be:
- pre-operative - is used with the purpose to weaken pathogenic cells, "to extinguish" the oncological process, thereby facilitating the technically easier operation for the removal of a malignant tumor;
- postoperative - "cleans" tissues from the foci of tumor cells that could remain in the human body after surgical removal of the main array of malignant tumor( causes: 1) foci are too small, extremely difficult to see with the naked eye, 2) foci are lost in places whereIt is impossible to use a scalpel - for example, because of the critical proximity of blood vessels and nervous branches);
- therapeutic is an independent method of action by which the cells are expelled, if surgery is impossible for some reason;
- prophylactic - to prevent recurrence of the tumor( its reappearance in the same place).
According to the goals that are pursued using this method, chemotherapy happens:
- radical - when the complete destruction of the tumor is expected;
- restraining - with its help try to "slow down" the growth and destructive effect of the tumor;
- palliative - directed not to the tumor itself, but to the symptoms it causes, for example, pain, swelling, inflammation;
- Chemotherapy is waiting for patients who are preparing for a bone marrow transplant and need this "chemical" support so that during the waiting period the tumor does not recur and does not start to show its negative effect again;
- supporting - aimed at maintaining the state of remission - relief of the symptoms characteristic of a particular tumor process
and some others.
The mechanism of action of chemotherapy is:
- cytostatic - inhibits the reproduction of tumor cells, but they remain "alive";
- cytotoxic is more radical, because it kills atypical cells.
Classification of antitumor drugs
The mechanism of action of the classification of antitumor drugs is quite complex.In a simplified form, it looks as follows:
- alkylating antineoplastic drugs are those that act on the DNA of malignant cells by the addition of the so-called alkyl group, which causes the malignant cells to lose the ability to divide at their normal rate( mechlorethamine, Chlorambucil, bendamustine);
- antimetabolites are drugs that interfere with the biochemical reactions of malignant cells, which ensure their multiplication, growth and vital activity( methotrexate, fospurin);
- intercalants - preparations, the structural parts of which are built, like bricks, into the structure of DNA of tumor cells, which disrupts the process of natural cell division( doxorubicin, epirubicin);
- topoisomerase I inhibitors and topoisomerase II inhibitors are preparations that lead to rupture of DNA from tumor cells, disturbances of DNA loops, because of which this "matrix", naturally, can not already stamp valuable tumor cells( etoposide, teniposide);
- inhibitors of microtubule formation are drugs that inhibit the formation of cell particles, which are part of its peculiar "skeleton"( vincristine, vinblastine);
- fission spindle inhibitors are drugs that inhibit the formation of the so-called fission spindle, without which the chromosome discrepancy necessary for normal cell division( colchamine) will not pass.
Methods of involving chemotherapy
The basic methods of administering chemotherapy in the body are the following :
- injection - into the bloodstream, from where chemotherapy with blood flow reaches the "destination";
- is oral in the form of tablets that transit through the gastrointestinal tract also enter the bloodstream and along it - into the organ that needs help;
- application - in the form of labels containing chemotherapy( for tumors of the skin or accessible mucous membranes);
- directly to the organ that needs treatment( under the spinal cord or brain, in the ventricles of the brain, the "shirt" of the heart( pericardium), the abdominal cavity, etc.), or even sightingly into the tumor.
Chemotherapy is applied cyclically - repeatedly at regular intervals. Tumor cells tirelessly multiply( this is the problem of treating malignant neoplasms), this process occurs cyclically, so cells also need to act with an enviable periodicity to prevent them from "crushing" healthy tissue.
Chemotherapy drugs are prescribed alone or in combination with other methods of ejection of tumors( radiochemotherapy, immunochemotherapy, and so on).
Side effects of chemotherapy drugs
Unfortunately, the action of the chemotherapeutic agent has not yet learned to program so that it targets selectively only in atypical cells. Chemopreparation acts to a greater or lesser extent on normal cellular structures of the human body, thereby causing side effects:
- hair loss - due to the fact that the hair bulb is being destroyed;
- nausea and vomiting - due to the action of the chemotherapeutic agent on the tissues of the gastrointestinal tract, as a result of which those secrete serotonin, it acts on the center of the urge to vomit;
- damage to the mucous membranes of the gastrointestinal tract - first of all it manifests itself( manifests itself) by stomatitis( inflammation of the oral mucosa) and diarrhea( due to action on the intestinal wall tissue);
- pain from the internal organs - abdominal organs( spastic pain), heart and so on;Again, pain is observed due to toxic tissue damage;
- death of a part of blood cells( in particular, platelets and leukocytes) - chemotherapy has a destructive effect on blood cells, and also inhibits the formation of , which is why their deficiency is observed;
- change from the nails and surface layers of the skin - the same mechanism: chemotherapy not only destroys cells, but also inhibits their formation;
- memory disorders - due to toxic effects on highly differentiated cells of the central nervous system;While the patient does not remember the facts of life and the details of events, does not remember names.
Medical tactics in the event of side effects
Side effects of chemotherapy are expected, but do not appear in all cases when using chemotherapy.They are not an indication to stop the course. Side effects are contended in such ways:
- reduces the dose of the chemotherapeutic agent;
- prescribes treatment that combats negative manifestations( for example, prescribes drugs that block nerve impulses entering the brain, which causes a feeling of nausea and vomiting);The
- scrupulously controls that the patient adheres to the sleep, rest and especially balanced diet( remember the role of a nutritionist who will choose the optimal diet, taking into account the balance of proteins, fats, carbohydrates and minerals).
By the way, the consequences of the action of chemotherapy are not as scary as they are "painted". For example, dropped eyebrows and eyelashes are restored after 12-14 days after the end of the course of chemotherapy.And the hair on the head can grow even better and more magnificent than they were before the course of treatment.
Kovtonyuk Oksana Vladimirovna, medical reviewer, surgeon, consulting physician