Antineoplastic

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Antineoplastic

 

any one of a group of synthetic or natural substances used in the treatment of malignant tumors. Antineoplastics include alkylating agents (embichine, novembichin, Chlorbutin [chlorambucil], dopan, sarcolysine, Cyclophosphane [cyclophosphamide], myelosan), antimetabolites (methotrexate, 6-mercaptopurine, 5-fluorouracil), antibiotics (bruneomycin, rubomycin), and plant alkaloids (Colchamine [Colcemid], vinblastine, vincristine). These substances arrest the process of mitosis. In addition, enzymes and hormonal preparations are used, including corticosteroids and female and male sex hormones.

Antineoplastics are used only with certain types of tumors. The histological structure that a tumor of a particular organ has is especially significant. There is no universal antineoplastic preparation. As a rule, the effect of the preparation is inversely proportional to the mass of the tumor, that is, the preparation is more easily effective with a small tumor than with a large one. Treatment with antineoplastics is based on the differences between the biochemical properties of normal and tumoral tissues and is directed predominantly toward suppressing the accelerated reproduction of tumoral cells. The differences between normal and tumoral tissues are principally quantitative—rapid cell reproduction is characteristic not only of tumoral elements but also of normal cells of the hematopoietic organs, intestinal epithelium, and skin.

Antineoplastics also affect normal tissues when they act on a tumor. Many antineoplastics are toxic and produce side effects that may or may not be associated with the mechanism of suppressing cell reproduction. These side effects include nausea, vomiting, loss of appetite, diarrhea, stomatitis, and a decrease in the number of leukocytes, thrombocytes, and erythrocytes in the blood. In some cases, this results in the limitation of the dosage or even suspension of treatment.

Antineoplastics are either injected intravenously, administered orally, or injected into the pleural or abdominal cavities. The preparation has a local effect when the injection is intracavitary, although it is to one degree or another absorbed into the blood. In treating skin tumors, antineoplastics can be applied locally. It is possible to increase the effectiveness of the treatment and decrease the toxic effects of the preparation by special injection methods, when the antineoplastic is injected into the vessels that supply the tumor with blood. Antineoplastics are usually administered in stages, with varying time periods separating the stages. Sometimes there is a delayed reaction and the effect of the preparation only occurs after the completion of one stage of treatment.

Polychemotherapy is promising in the treatment of tumors. It consists in the simultaneous or successive use of several preparations that differ in the mechanism of their effect and in their toxic side effects. There has been progress in the treatment of children stricken with acute lymphoid leukemia, largely because of the introduction of therapy combined with antineoplastic preparations. Antineoplastics are also used together with other methods of tumor treatment, for instance, during preoperative and postoperative periods, or with radiotherapy.

REFERENCES

Larionov, L. F. Khimioterapiia zlokachestvennykh opukhoki. Moscow, 1962.
Blokhin, N. N., and N. I. Perevodchikova. “Nekotorye etapy klinicheskoi khimioterapii opukholevykh zabolevanii.” Vestnik AMN SSSR, 1967, no. 5.

V. I. ASTRAKHAN