Principles of Cancer Therapy

Chapter 37 Principles of Cancer Therapy



The standard modalities for the management of gynecologic cancer are surgery, chemotherapy, radiation therapy, and hormonal therapy. In this chapter, the principles of chemotherapy, radiation therapy, and hormonal manipulation are discussed, together with the principles of pain management and end-of-life issues. Targeted therapies and hyperthermia are at present experimental modalities and are not included.



image Cellular Biology


The characteristic feature of malignant tumor growth is its uncontrolled cellular proliferation, which requires replication of DNA. There are two distinct phases in the life cycle of all cells: mitosis (M phase), during which cellular division occurs; and interphase, the interval between successive mitoses.


Interphase is subdivided into three separate phases (Figure 37-1). Immediately following mitosis is the G1 phase, which is of variable duration and is characterized by a diploid content of DNA. DNA synthesis is absent, but RNA and protein synthesis occur. During the shorter S phase, the entire DNA content is duplicated. This is followed by the G2 phase, which is characterized by a tetraploid DNA content and by continuing RNA and protein synthesis in preparation for cell division. When mitosis occurs, a duplicate set of chromosomal DNA is inherited by each daughter cell, thus restoring the diploid DNA content. Following mitosis, some cells leave the cycle temporarily or permanently and enter the G0 or resting phase.



The growth fraction of the tumor is the proportion of actively dividing cells. The higher the growth fraction, the fewer the number of cells in the G0 phase and the faster the tumor-doubling time.


Chemotherapeutic agents and radiation kill cells by first-order kinetics, which means that a constant proportion of cells is killed for a given dosage, regardless of the number of cells present. Both therapeutic modalities are most effective against actively dividing cells because cells in the resting (G0) phase are better able to repair sublethal damage. Unfortunately, both therapeutic modalities also suppress rapidly dividing normal cells, such as those in the gastrointestinal mucosa, bone marrow, and hair follicles.



image Chemotherapy


One of the major advances in medicine since the 1950s has been the successful treatment of certain disseminated malignancies, including choriocarcinoma and germ cell ovarian tumors, with chemotherapy.





CHEMOTHERAPEUTIC AGENTS


The common agents used in the management of gynecologic malignancies may be classified as shown in Table 37-1. This table also contains a summary of the main indications for and side effects of these drugs.









image Radiation Therapy


Radiation may be defined as the propagation of energy through space or matter.





Jun 4, 2016 | Posted by in GYNECOLOGY | Comments Off on Principles of Cancer Therapy

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