The National Institute of Health defines cells as “the building blocks of all living things”. Each individual human being is made of trillions of cells, and they have numerous important purposes. Cells perform many specialized tasks, including providing the structure for the human body. They also allow our bodies to absorb the nutrients of the food we eat, and convert those nutrients into energy. Cell reproduction is extremely organized and controlled; when they become old or die, the body replaces them with as many new cells as necessary to keep individuals healthy. However, this process can sometimes go wrong. Genetic material that is carried in cells can become damaged, thus producing mutations and affecting the orderly process of cell growth and reproduction. Individual’s abnormal cells begin dividing uncontrollably, and thus multiplying, instead of dying—all while new cells are still being reproduced. This overabundance of cells in the human body can form tumors, some of which are cancerous. Cancerous cells are also able to metastasize using the body’s blood and lymph system to travel, and can invade different tissue and organs throughout the body, sometimes forming tumors in those areas as well.(Figure1)
Cancers are named according to the type of tissue in which cancer originates i.e. histological type and contains suffix to represent the site. Below are the five broad groups to classify the cancer.
The options for cancer treatment is not limited to single rather a range of options are available. The best option is determined by various factors like age, history, and lifestyle. More often various types of treatment are combined to get the best possible result. The most popular types of cancer treatment are discussed below.
Immunotherapy is a new type of therapy to fight against various types of cancers where body uses own immune system to help fight cancer. The immune system is a group of cells and organs that work together to defend the body against foreign particles such as cancer cells, bacteria, and viruses. The defense mechanism is known as immune response where several kinds of cells like macrophages, lymphocytes, T lymphocytes, dendritic cells, and granulocytes go into action after the entry of foreign particles. These immune cells communicate with each other by a number of special protein molecules known as cytokines. Cytokines can be natural, recombinant, or synthetic. Some of the cytokines are interferons, interleukins, tumor necrosis, and colonystimulating factors. The idea of immunotherapy treatment involves giving larger amounts of proteins either by an injection or infusion so that the cells of immune system acts more effectively to make tumor cells more prominent to the immune system. The active agents of immunotherapy are termed as immunomodulators. Flu, chills, fever, nausea, fatigue, and loss of appetite are some of the common side effects of this type of therapy.
2. Targeted Therapy
Targeted therapy is a selective way of attacking the cancer cells with drugs or other substances. It is a newer type of treatment and is precise and does very little damage to normal cells. It interferes with the proliferation and spread of cancer cells. This form of therapy mainly focus on proteins that are involved in cell signaling pathways regulating the basic cellular functions and activities like cell division, cell movement, cell responses, and cell death. When the signals to divide and grow uncontrollably are blocked, the progression of cancer is halted and may even induce death of the cancer cell through a process called apoptosis. Small-molecule drugs or monoclonal antibodies are the most common targeted therapies. It is convenient for small-molecule drugs to diffuse into the cell to act on the specific targets. Monoclonal antibodies are directed against the targets outside the cell because they cannot penetrate the plasma membrane. In case of chronic myeloid leukemia (CML), BCR-ABL gene is responsible to relay the signal regulating cell proliferation. Continuous proliferation of CML cells can be controlled by targeting BCR-ABL using targeted therapy. In contrast to traditional chemotherapy, targeted therapies are generally better tolerated, but they are associated with several adverse effects, such as acneiform rash, cardiac dysfunction, thrombosis, hypertension, and proteinuria.
Chemotherapy is the use of chemicals to kill the cancer cells or stop them from growing. The chemicals interferes the process of cell division by either damaging the RNA or DNA. Chemotherapy is primarily used to damage the DNA of the affected cancer cells, stop the cell
from replicating by inhibiting the synthesis of new DNA strand, and stop the division of original cell into its daughter cells in mitotic phase of cell division. The drugs for chemotherapy are given in combination of two or three at the same time. These combinations are called regimens. The purpose of regimens differs according to the stage of cancer. For instance, regimens lower the risk of cancer coming back in early stage breast cancer, while it makes cancer shrink or disappear in advanced stage. Chemo therapy not only kills the cancer cells but affects the healthy cells. Damage in the blood cells results in anemia, fatigue, and various kinds of infections. Mouth sores and diarrhea are caused by the damage in the cell at mucous membrane. Another common side effect of chemotherapy is the destruction of cells at hair roots and follicles that ultimately results in loss of hair. The cytotoxic chemotherapy drugs have different method of killing cancer cells. They are classified accordingly to following classes: alkylating agents, heavy metals, antimetabolites, anthracycline, antibiotics, epipodophyllotoxins, plant alkaloids, and antitumor antibiotics.
4. Radiation Therapy
In radiation therapy, high energy particles are used to damage the cancerous cells in the body. The common types of radiation used are X-rays, gamma rays, and charged particles. If the radiation is delivered by a machine outside the body, it is known as external-beam radiation therapy and if the radiation is delivered from radioactive material placed inside the body near cancer calls, it is called brachytherapy or internal radiation therapy. The radiation either damages DNA directly or it creates free radicals inside the cell that actually end up damaging the DNA. Once the DNA is damaged, cancer cells stop dividing and eventually die and will be eliminated by body’s natural processes.
Surgery is a common and oldest technique to treat or even help prevent cancer. The first use of this technique was employed by ancient Egyptians to remove breast tumors in 7th century. If the cancer is benign, it offers the biggest chance for cure as the tumor does not get a chance to spread around the body. However, if the cancer has metastasized, surgery won’t be very beneficial. Some type of surgery is usually performed in most people with cancer. The symptoms of bowel obstruction or spinal cord compression can be controlled by surgery.
Hyperthermia is a type of cancer treatment in which the temperature of tumor-loaded tissue is raised up to 113°F. The applied high temperature is capable of killing the cancer cells with minimal injury to normal cells. It is applied as an adjoining therapy with other established cancer treatments like radiotherapy and chemotherapy. With the use of this form of treatment, cancer cells becomes more sensitive to radiation that otherwise would resist radiation. Heat is applied by using microwave, radiofrequency, and ultrasound to a small specific area such as tumor in the case of local hyperthermia. Metastatic cancer that has spread throughout body is treated by using whole-body hyperthermia by raising the body temperature to 107-108°F using thermal chambers.