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4.4 Chemo immunotherapy 85

4.4.1.2 Chemotherapy regimens and drugs for the treatment
of various cancers
Among the many strategies and chemotherapy drugs that are licensed by the FDA
(Food and Drug Administration), the therapeutic regimen is selected based on the
type of cancer and its progression. General guidelines have been obtained during
clinical studies and clinical trials based on these two criteria. However, the choice of
a proper chemotherapy regimen from various guidelines for cancer depends on sev-
eral other factors in relation to the patient. These factors include age, history of other
illnesses in the patient, previous treatment(s), hematological examination, liver and
kidney function [40]. Table 4.1 shows examples of FDA-approved drugs that have
been used in recent years to treat various cancers in clinical trial.

4.4.1.3 Chemotherapy, definitive treatment for cancer?
Despite the usefulness and importance of chemotherapy, the long history of its use,
as well as the existence of different drugs and methods of treatment, chemotherapy
is ineffective in destroying cancerous cells that do not have rapid cell division rates.
And the known side effects of chemotherapy create barriers against the effectiveness
of it on the destruction of tumor cells. These include the effects of it on healthy tissue
and the normal cells, and the increasing resistance of tumor cells to chemotherapy
drugs. A side effect of chemotherapy is the destruction of healthy cells that have
high division rates. In Section 4.4.1, these effects are briefly cited. As mentioned
above, one of the most prominent reasons for chemotherapy failure is the resistance
of tumor cells to chemotherapy agents. The resistance of cancerous cells to chemo-
therapy drugs is mainly due to two reasons:
1. Some of the cancerous cells have been resistant to the drug from the start of
treatment. That is, tumor cells have been resistant to the drug already.
2. The tumor cells were initially susceptible to the drug, but became resistant to it
during the procedure of the treatment [40,41].

Another cause of chemotherapy failure as a definitive treatment is the presence of
cancer stem cells and their resistance to chemotherapy. This problem, which has been

Table 4.1 FDA-approved drugs that have been used to treat various cancers
in clinical trial.
Agent Type of cancer Reference
Bendamustine Advanced chronic lymphocytic leukaemia (CLL10) [41]
Docetaxel Nonsmall-cell lung cancer (OAK) [42]
FOLFOXIRI Metastatic colorectal cancer [43]
Paclitaxel Metastatic breast cancer [44]
Cyclophosphamide Primary Central Nervous System Lymphoma (PCNSL) [45]
Abiraterone acetate Metastatic castration-resistant prostate cancer [46]
(COU-AA-302)