Page 86 - Bio Engineering Approaches to Cancer Diagnosis and Treatment

84 CHAPTER 4 Immunotherapy

4.4.1 Chemotherapy
Radiotherapy and surgery are mainly used to eliminate solid tumors or normal
tumors that are located in a particular area. In other word, radiotherapy and surgery
are the therapeutic methods for locoregional diseases. However, these local therapies
are not enough to treat metastatic cancers which involve cancerous cells entering the
blood or lymph, and spreading in different parts of the body or hematologic malig-
nancies. Therefore, systemic treatments are introduced. Chemotherapy is a treatment
for advanced cancers that enter to the blood and lymph nodes, and it is also the
main treatment for hematological cancers, such as leukemia. The mechanism of che-
motherapy drugs for treating cancer is in the field of mitosis—cell division. More
specifically, most chemotherapy agents damage cells with higher division rates, and
since malignant and tumor cells grow faster than other healthy tissue cells, chemo-
therapy has been seen as the main treatment for cancer. But in addition to destroying
and damaging cancer cells, chemotherapy also affects other healthy and normal cells
which are fast growing. For instance, some of the cells in the bone marrow and the
cells of hair follicles are fast division cells, and thus chemotherapy affects them.
Myelosuppression is one of the side effects of chemotherapy. Myelosuppression is
the decrease in production of blood cells (leukocytes, erythrocytes, and thrombo-
cytes) [38].

4.4.1.1 Mechanism of action
Chemotherapy agents are known to be cytotoxic as they damage the cells, and the
mechanism of their behavior is different (Fig. 4.8). Chemotherapy agents mainly
cause apoptosis in cells with rapid cell division rates. These cytotoxic substances
induce apoptosis by destroying DNA or preventing mitotic division [39].

FIGURE 4.8 Mechanism of action of chemotherapy.