Chapter 1
Introduction
Mutation is not uncommon in our daily
lives. Most mutated cells either keep their normal cellular functions or
undergo a programmed cell death (apoptosis) and die at some point in time. In
addition, many mutated cells are recognized and rapidly removed by the body’s
immune system. Only a very small portion of mutated cells will evolve further
and become cancerous cells with uncontrollable proliferation; this behavior is
different from that of normal cells. For adult, most normal cells are well
differentiated except for certain types of cells, such as epithelial cells and
bone marrow hematopoietic progenitor cells, which are capable of continuous proliferation;
unlike cancerous cells, the growth of normal cells is highly regulated and
controlled.
Cancer is a group of various diseases
in that some cells are mutated in certain ways so that they grow and divide
continuously. Currently, there are more than 200 known cancers that afflict
humans.
For the treatment of cancer, there are
generally three conventional strategies: surgery, chemotherapy, and
radiotherapy. In this book, we will focus on chemotherapy, radiotherapy, and
their side effects.
Chemotherapy is a systemic treatment
of cancer patients with one or more anticancer drugs (chemical agents) to kill
cancer cells and/or slow down their growth. The name “chemotherapy” comes from chemical agents being used as a therapy for treating cancer.
Chemotherapy plays a critical role in cancer treatment; it is estimated that more than half of all cancer patients receive
chemotherapy.
Depending on the dosage form, cancer
drugs may be administered through several different routes, including
intravenous injection/infusion, oral (mouth) delivery, or a slow release dosage
form embedded in a tissue by implantation. A chemotherapy regimen (a treatment plan
including the dosing and schedule) usually includes the administration of at
least one drug to fight cancer at a predetermined dose according to a suitable
schedule, usually daily, weekly, or every several weeks. Due to the different characteristics of individual cancer drugs, the
chemotherapy regimen for each drug may be different. Because cancer treatment is a delicate
process, it is important to know that staying on the chemotherapy regimen gives
a patient the optimal chance for a successful result.
Many times, additional supplementary
drugs are used simultaneously in a chemotherapy regimen in order to achieve a
better outcome to either increase the anticancer potency or reduce the side
effects of chemotherapy; these drugs are often called adjuvant medications.
Adjuvant drugs that are used to reduce the side effects of cancer therapy,
including chemoprotective and radioprotective agents, will be discussed in Part
III.
Most cancer drugs work by killing
cancer cells or slowing down the growth of cancer cells. Unfortunately, most of
the cancer drugs are not able to clearly distinguish between cancer cells and
normal cells. Therefore, most cancer drugs will damage not only the
fast-growing cancer cells but also the fast-growing normal cells, which include
bone marrow cells, crypt epithelial cells (lining of small intestine), and hair
follicles. In addition, a number of organs (e.g., liver, kidney, and heart) are
often injured by chemotherapy.
In order to have a better understanding
on how anticancer drugs work and what kind of side effects they can cause,
let’s take a look at some anticancer drugs in different categories.
Disclaimer: This blog is written solely for informational purposes. It does not constitute the practice of any medical, nursing or other medical professional health care advice, diagnosis, or treatment. All contents posted are extracted from the book, "SIDE EFFECTS OF CHEMOTHERAPY AND RADIOTHERAPY", prepared by Dr. Jiajiu Shaw, Dr. Frederick Valeriote, and Dr. Ben Chen.
