Cancer, also called as malignancy is a group of diseases involving abnormal cell growth with the potential to invade or spread to other parts of the body. Throughout our lives, healthy cells in our bodies divide and replace themselves in a controlled fashion. Cancer describes the disease that results when cellular changes cause the uncontrolled growth and division of cells. It starts when a cell is somehow altered so that it multiplies out of control. Some types of cancer cause rapid cell growth while others cause cells to grow and divide at a slower rate. Most of the body’s cells have specific functions and fixed lifespans. While it may sound like a bad thing, cell death is part of a natural and beneficial phenomenon called apoptosis. A cell receives instructions to die so that the body can replace it with a newer cell that functions better. Cancerous cells lack the components that instruct them to stop dividing and to die. As a result, they build up in the bod using oxygen and nutrients that would usually nourish other cells.
Certain forms of cancer result in visible growths called tumors while others such as leukemia do not. A tumor is a mass composed of a cluster of abnormal cells. Most cancers form tumors but not all tumors are cancerous. Benign or noncancerous tumors do not spread to other parts of the body and do not create new tumors. Malignant or cancerous tumors crowd out healthy cells, interfere with body functions and draw nutrients from body tissues. Cancers continue to grow and spread by direct extension or through a process called metastasis, whereby the malignant cells travel through the lymphatic or blood vessels eventually forming new tumors in other parts of the body.
The term “cancer” encompasses more than 100 diseases affecting nearly every part of the body and all are potentially life threatening. The major types of cancer are carcinoma, sarcoma, melanoma, lymphoma and leukemia. Carcinomas – the most commonly diagnosed cancers originate in the skin, lungs, breasts, pancreas and other organs and glands. Lymphomas are cancers of lymphocytes. Leukemia is cancer of the blood. It does not usually form solid tumors. Sarcomas arise in bone, muscle, fat, blood vessels, cartilage or other soft or connective tissues of the body. They are relatively uncommon. Melanomas are cancers that arise in the cells that make the pigment in skin.
GENETIC INFLUENCE ON CANCER
Genetic factors can contribute to the development of cancer. A person’s genetic code tells their cells when to divide and expire. Changes in the genes can lead to faulty instructions, and cancer can result. Genes also influence the cells’ production of proteins, and proteins carry many of the instructions for cellular growth and division. Some genes change proteins that would usually repair damaged cells. This can lead to cancer. If a parent has these genes, they may pass on the altered instructions to their offspring. Some genetic changes occur after birth, and factors such as smoking and sun exposure can increase the risk. Other changes that can result in cancer take place in the chemical signals that determine how the body deploys or “expresses” specific genes. Finally, a person can inherit a predisposition for a type of cancer. A doctor may refer to this as having a hereditary cancer syndrome. Inherited genetic mutations significantly contribute to the development of 5–10 percent of cancer cases.
Signs and symptoms caused by cancer will vary depending on what part of the body is affected. Some general signs and symptoms associated with but not specific to cancer include the following:
- Lump or area of thickening that can be felt under the skin
- Weight changes including unintended loss or gain
- Unexplained headaches, seizures or vertigo
- Skin changes such as yellowing, darkening or redness of the skin, sores that won’t heal or changes to existing moles
- Changes in bowel or bladder habits
- Persistent cough or trouble breathing
- Difficulty swallowing
- Persistent indigestion or discomfort after eating
- Persistent, unexplained muscle or joint pain
- Persistent, unexplained fevers or night sweats
- Unexplained bleeding or bruising
- Unexplained spinal cord compression or fracture
Cancer is caused by mutations (changes) to the DNA within cells. The DNA inside a cell is packaged into a large number of individual genes, each of which contains a set of instructions telling the cell what functions to perform, as well as how to grow and divide. Errors in the instructions can cause the cell to stop its normal function and may allow a cell to become cancerous.
A gene mutation can instruct a healthy cell to grow and divide more rapidly. This creates many new cells that all have that same mutation. It fails to stop uncontrolled cell growth. Normal cells know when to stop growing so that just the right number of each type of cell exist in the body. Cancer cells lose the controls that tell them when to stop growing. A mutation in a gene allows cancer cells to continue growing and accumulating. DNA repair genes look for errors in a cell’s DNA and make corrections. A mutation in a DNA repair gene may mean that other errors aren’t corrected, leading cells to become cancerous.
Gene mutations can occur due to several reasons
- Inherited genetic mutations that are inherited from parents. This type of mutation accounts for a small percentage of cancers.
- Gene mutations that occur after birth. A number of forces can cause gene mutations, such as smoking, radiation, viruses, cancer-causing chemicals (carcinogens), obesity, hormones, chronic inflammation and a lack of exercise.
The inherited gene mutations and those that are acquired throughout the life work together to cause cancer. An inherited genetic mutation predisposes to cancer, that doesn’t mean it is certain to get cancer. Instead, the presence of one or more other gene mutations cause cancer. The inherited gene mutation could make a person more likely than other people to develop cancer when exposed to a certain cancer-causing substance.
Age, alcohol, Cancer-Causing Substances, Chronic Inflammation, Diet, Hormones, Immunosuppression, Infectious Agents, Obesity, Radiation, Sunlight, Tobacco etc increases the risk of getting cancer in future.
The earlier cancer is diagnosed and treated, the better the chance of its being cured.
Cancer diagnosis begins with a thorough physical exam and a complete medical history. During a physical exam, presence of any abnormalities such as changes in skin colour or enlargement of an organ that may indicate the presence of cancer are examined.
Laboratory studies of blood, urine, and stool can detect abnormalities that may indicate cancer.
When a tumor is suspected, imaging tests such as X-rays, computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, and fiber-optic endoscopy examinations help doctors determine the cancer’s location and size.
To confirm the diagnosis of most cancers, a biopsy needs to be performed in which a tissue sample is removed from the suspected tumor and studied under a microscope to check for cancer cells. Normal cells look uniform, with similar sizes and orderly organization. Cancer cells look less orderly with varying sizes and without apparent organization.
If the diagnosis is positive (cancer is present), other tests are performed to provide specific information about the cancer. This essential follow-up phase of diagnosis is called staging. The most important thing doctors need to know is whether cancer has spread from one area of the body to another. Staging tests and procedures may include imaging tests, such as bone scans or X-rays, to see if cancer has spread. If the initial diagnosis is negative for cancer and symptoms persist, further tests may be needed.
Cancer stages are generally indicated by Roman numerals — I to IV, with higher numerals indicating more advanced cancer. In some cases, cancer stage is indicated using letters or words.
Depending on the type and stage of cancer, treatments to eradicate the tumor or slow its growth may include some combination of surgery, radiation therapy, chemotherapy, hormone therapy or immunotherapy.
Most people with cancer will have some type of surgery. The main goal is to remove tumors, tissue, or areas with cancer cells, such as lymph nodes. Doctors also may do it to diagnose the disease or find out how serious it is. In many cases, surgery offers the best chance of getting rid of the disease, especially if it hasn’t spread to other parts of the body.
Along with a traditional operation, doctors can also fight some types of cancer with:
- Laser surgery (beams of light)
- Electrosurgery (electric currents)
- Cryosurgery (very cold temperatures to freeze cancer cells)
Medications to block pain during and after surgery will be provided. Antibiotics are also ensured to lower the risk of infection.
Chemotherapy is one of the most common treatments for cancer. It uses certain drugs to kill cancer cells or to stop them from growing and spreading to other parts of the body. A doctor might prescribe chemo by itself or with surgery or radiation therapy. Newer kinds of cancer-fighting drugs can also be taken along with chemotherapy. When cancer occurs, more and more cells are produced, and they start to occupy an increasing amount of space until they occupy the space previously inhabited by useful cells. Chemotherapy drugs interfere with a cancer cell’s ability to divide and reproduce. A single drug or a combination of drugs is used. These can be delivered either directly into the bloodstream to attack cancer cells throughout the body or they can be targeted to specific cancer sites. Most chemo medications are given through an injection into a vein. Oral chemos are also preferred nowadays.
Chemotherapy drugs can:
- impair mitosis or prevent cell division
- target the cancer cells’ food source which consists of the enzymes and hormones they need to grow
- trigger the suicide of cancer cells, known medically as apoptosis
- stop the growth of new blood vessels that supply a tumor in order to starve it.
Cancer cells tend to grow fast, and chemo drugs kill fast-growing cells. But because these drugs travel throughout the body, they can affect normal, healthy cells that are fast-growing, too. Damage to healthy cells causes side effects. The normal cells most likely to be damaged by chemo are blood-forming cells in the bone marrow, hair follicles, cells in the mouth, digestive tract, and reproductive system.
The severity of side effects varies greatly from person to person. Some of the most common side effects caused by chemotherapy are:
- Hair loss
- Easy bruising and bleeding
- Anaemia (low red blood cell counts)
- Nausea and vomiting
- Appetite changes
- Mouth, tongue, and throat problems such as sores and pain with swallowing
- Nerve and muscle problems such as numbness, tingling, and pain
- Skin and nail changes such as dry skin and colour change
- Urine and bladder changes and kidney problems
- Weight changes
- Chemo brain, which can affect concentration and focus
- Mood changes
- Changes in libido and sexual function
- Fertility problems
Adverse effects of chemotherapy can be severe. But the benefits of chemotherapy usually outweigh the risk of adverse effects.
Radiation therapy also known as radiotherapy is the common treatment which uses high-energy particles or waves to destroy or damage cancer cells to keep them from spreading. It might be the only treatment or might get it along with surgery or chemotherapy. It uses high doses of radiation to kill cancer cells and shrink tumors.
Radiation therapy kills cancer cells or slows their growth by damaging their DNA. Cancer cells whose DNA is damaged beyond repair stop dividing or die. When the damaged cells die, they are broken down and removed by the body. Radiation therapy does not kill cancer cells right away. It takes days or weeks of treatment before DNA is damaged enough for cancer cells to die. Then, cancer cells keep dying for weeks or months after radiation therapy ends.
There are two main types of radiation therapy, external beam and internal.
- External beam radiation therapy comes from a machine that aims radiation at cancer. The machine is large and may be noisy. It does not touch the patient’s body but can move around sending radiation to a part of the body from many directions. External beam radiation therapy is a local treatment, which means it treats a specific part of the body. For example, if a person has cancer in lung, radiation will be provided only to the chest and not to the whole body.
- Internal radiation therapy is a treatment in which a source of radiation is put inside the body. The radiation source can be solid or liquid.
Internal radiation therapy with a solid source is called brachytherapy. In this type of treatment, seeds, ribbons, or capsules that contain a radiation source are placed in your body, in or near the tumor. Like external beam radiation therapy, brachytherapy is a local treatment and treats only a specific part of your body. With brachytherapy, the radiation source in your body will give off radiation for a while.
Radiation not only kills or slows the growth of cancer cells, it can also affect nearby healthy cells. Side effects depend on the part of the body that is treated. Radiation itself isn’t painful, but afterward pain, fatigue, hair loss, dry mouth and skin rashes around the place of treatment may experienced.
Healthy cells that are damaged during radiation treatment usually recover within a few months after treatment is over. But sometimes people may have side effects that do not improve. Other side effects may show up months or years after radiation therapy is over. These are called late effects.