Cancer: Causes, Types, Treatment
Understanding Cancer and its types
CANCER, a disease if detected early can be cured completely, if not can lead to death. There are thousands of people in the world who suffer from various types of cancers. While some cancers affect the solid organs, others infect the blood, tissues and bones. The most common types of cancer that you know today are of the Breast, lungs, bladder, prostate, oral, thyroid, stomach and esophagus. But apart from these there are several other types of rare and uncommon cancers that people suffer from all around the world.
Before understanding the various types, let’s understand what CANCER is.
What is Cancer and how Cancer Starts?
Cancer is the abnormal growth of cells that spread in an uncontrollable way and spread in the surrounding tissues. It starts when cells begin to grow and multiply to form a lump called a tumor. Each cell of the body has a function to play and is controlled by the central nucleus. The nucleus contains the genes that instruct the cell and make sure that the cells grow in a controllable manner. But certain changes known as MUTATIONS can happen when the cell fails to understand the command and starts to multiply. Mutations can happen as a result of the changes taking place inside the cell or due to external factors.
There are two types of lumps that form when the cell starts dividing abnormally. The lumps or tumors can either be
- Benign tumors- which are non cancerous
- Malignant tumors- which are cancerous
How Cancer Spreads?
The malignant tumors are the ones made up of cancer cells. They grow faster than benign tumors and spread rapidly to other parts of the body and damage the surrounding tissues. This spreading is known as METASTASIS. The cancer cells remain near the tissues from where they develop and this is known as carcinoma in situ. Unlike other cells, the cancer cells need essential nutrients to survive and therefore start ANGIOGENESIS where new blood vessels start to grow in the tumor. Once this happens the cancer starts to grow bigger and spread rapidly in the surrounding tissues.
As it grows it causes pressure and takes up more space in the body. It squeezes through the normal cells and blood vessels and kills them on the way. When it starts growing in the surrounding structure, it is known as local invasion.
What are the types of cancer?
The counting won’t end as there are more than 100 types of cancers affecting people. Some are solid cancers while some affect the blood stream. The types of cancer can be grouped based on the type of cells they start in. The other types of cancers get their names from the organs where they form. All types of cancer affect the cells and spread due to the abnormal growth. The primary difference between normal and cancers cells is that the normal cells grow into a size and stop but cancer cells do not stop dividing.
The categories that types of cancer can be divided into are:
These are the most common types of cancers comprising about 80% of all cancers. They start in the epithelial cells/ tissues. These are those cells which cover the inside and outside surfaces of the body and the organs. There are different types of epithelial cells and develop into different types of Carcinomas. These are
- Squamous Cell Carcinoma forms in the squamous cells. These are the cells which are found below the outer surface of the skin. These are flat cells covering the surface and line the organs such as the stomach, kidney, lungs and bladder. They are also called Epidermoid carcinomas.
- Basal Cell Carcinoma affects the base layer of the human skin, which is the outermost layer of the skin.
- Adenocarcinoma is the cancer that forms in the glandular cells. These cells produce mucus and fluids to keep the body moist. These are commonly found in breasts, colon and prostate.
- Transitional Cell Carcinoma is formed in the transitional epithelium tissue and these are the cells that can expand as the organ grows. These epithelial cells are found in the lining of the bladder, ureter and parts of the urinary system.
Sarcomas are those cancers that start in the connective tissues of the body, i.e., bone, soft tissue, ligaments, cartilage and fibrous tissues. Sarcomas are basically divided into
- Bone sarcomas are commonly known as Osteosarcoma and start from the bone cells. This type of cancer mostly affects children and young adults.
- Soft tissue sarcomas either start in the cartilage (Chondrosarcoma) or the muscles (rhabdomyosarcoma).
Leukemia is the cancer of blood cells. The cancer begins when a huge number of white bold cells are formed in the bone marrow and they build up in the blood. This crowds the normal blood cells and they lose the capacity to fight infections. Leukemias are mostly common among young children. There are four types of Leukemia based on how fast they grow (acute and chronic) and the type of blood cells that get affected (Lymphoblastic and Myeloid)
- Acute Myeloid Leukemia starts in the myeloid blood cells and is characterized by rapid growth of granulocytes and monocytes
- Chronic Myeloid Leukemia also starts in the white blood cells but the growth is comparatively slow.
- Acute Lymphoblastic Leukemia starts from white blood cells called lymphocytes and spread rapidly.
- Chronic Lymphoblastic Leukemia affects the lymphoblastic cells but is a slow growing cancer.
Lymphomas are cancers of the lymphatic system which is an import part of the immune system. They form in the white blood cells known as lymphocytes (made of T cells and B cells) and lead to abnormal building in the lymph nodes and vessels, preventing the cells to fight infection. Lymphomas are of two types
- Hodgkin Lymphoma contain the Reed Stenberg cells which are abnormal lymphocytes and affect the B cells
- Non- Hodgkin Lymphoma also starts in the lymphocytes but can affect both the B cells and the T cells.
5. Multiple Myeloma
Multiple Myeloma is a cancer that s the plasma cells which are the other type of cells of the immune system. The plasma cells are responsible for fighting infections through the antibodies known as immunoglobins. In Multiple Myeloma, the plasma cells multiply abnormally and form tumors in the bone marrow and at times also spill out and spread in the body.
6. Brain and Spinal Cord Cancers
The brain and spinal cord make up the central nervous system. The cancer that affects the brain and spinal cord is based on the cell where the abnormal growth begins and the area where the malignant tumor formed. The most common type of Brain cancers are Gliomas that start in the glial cells.
Melanoma is the cancer that develops in the pigment cells of the skin known as melanocytes. This is the most serious form of skin cancer and form mostly as a result of over exposure to harmful UV rays. This type of cancer can occur anywhere in the body and can also spread rapidly to other parts of the body.
Therefore, cancers can be life threatening if not treated on time. The best way to treat and prevent cancer is early detection and diagnosis. This not only helps in making the treatment more effective but also provides a better cure.
Causes of Cancer
The World Health Organization has listed the following cancer risk factors that are most likely to cause cancer:
- Use of Tobacco (smoking/consumption) and alcohol consumption
- Obesity and overweight
- Dietary habits, insufficient intake of fruits and vegetables
- Physical inactivity
- Environmental and occupational risks that include exposure to harmful radiations
- Chronic infections caused by Hepatitis viruses (HBV, HCV, HPV)
Cancer is one of the top most causes of death in the world today. The most common cancer in the world is Lung cancer and leads to the most number of deaths. To prevent cancer, you need to know its causes. Scientists are still working to find out why some people are more prone to cancer than others. Though it is still not known what develops cancer, hopefully one day we will know the answer. Till then here are the most common causes of cancer.
1. Cancer causing agents in the environment
Cancer is caused as a result of genetic mutations in a cell which occur naturally, but there are many substances in the environment which if a human being is exposed to can damage the DNA. These substances include smoke, gases and radiation from the sun. These harmful substances in the environment are known as carcinogens. Prolonged exposure to such carcinogenic substances alters the metabolism of the body and may instigate the cells to divide faster and lead to DNA damage. The substances that are most likely carcinogens include arsenic, aflatoxins, benzene, asbestos, nickel compounds, emission from vehicles, factories and coke ovens, combustion of coal, wood dust, etc. Extended exposure to asbestos can lead to mesothelioma.
Radiations from radon or other environmental gases can pose a threat to the health of the individual and alter the normal functioning of the cells. The ultra violet radiations are extremely harmful when exposed to for a long time. It is the leading cause of melanoma (skin cancer) and other types of skin malignancies.
2. Smoking of Tobacco
Smoking and consumption of tobacco is one of the primary reasons of many types of cancers and the most common cause for lung cancer. There are a number of carcinogens present in tobacco such as nicotine, hydrogen cyanide, arsenic, benzene, etc. A smoker inhales all of these substances which directly affect the lungs. Excessive use of tobacco also leads to head, neck, oral, stomach, esophagus and pancreatic cancer.
3. Alcohol Consumption
Alcohol consumption can lead to various types of cancers, the most common being liver cancer. The ethanol in alcohol gets converted into acetaldehyde which is a highly toxic chemical. This toxin damages the DNA and prevents the cells to repair the damage. Excessive drinking leads to liver cirrhosis which in turn gives rise to abnormal cancer causing cells. Alcohol consumption is also directly related to breast cancer and also causes cancer of the esophagus, food pipe, larynx and the oral cavity.
4. Chronic Inflammation
Inflammation is a physiological process that occurs when chemicals are released to heal a damaged tissue. The white blood cells allow the cells to divide and repair the injured tissue. When the injury heals, the inflammation process stops. In Chronic inflammation however, the inflammation process begins even when there is no damage and does not stop. The cells keep on dividing and building up abnormal cells. This in turn damages the DNA and leads to cancer. Chronic inflammatory diseases such as Crohn’s disease can lead to colon cancer.
5. Viral and bacterial infections
There are certain infectious agents such as bacteria, viruses and pathogens that also increase the risk of cancer. These types of infections weaken the immune system and cancer cells start to grow in the area of the infection. Chronic infections can be caused by Hepatitis B virus and Hepatitis C virus which leads to liver cancer. Infection caused by the Human Papillo Virus (HPV) is known to cause cervical cancer and Helicobacter Pylori infection is a major cause for stomach and gastric cancer.
6. Hormones and hormonal changes in a woman
Hormones, especially estrogen when produced in excessive levels can have a carcinogenic effect on the human body and lead to cancer. Though estrogen is present in both males and females, it can lead to uterine or breast cancer in women. Studies have shown that the increased levels of both the estrogen and progesterone and prolonged exposure to these hormones increase the risk breast cancer. The increase in exposure can be caused as a result of early menstruation, late menopause, never giving birth or being older during the first pregnancy.
7. Immunosuppression/ Immune system dysfunction
Immunosuppression is the decrease in capability of the immune system to function effectively. A person infected with HIV has a weak immune system and is most likely to get infected with different types of cancers. People receiving organ transplants take immunosuppressive drugs to prevent the immune system from rejecting the organ. However, such drugs weaken the cancer fighting cells and increase the risk of cancers. Both the HIV positive and organ transplant patient can suffer from cancers such as Non Hodgkin’s Lymphoma, liver cancer due to chronic infection of Hepatitis B and C virus and HPV related cancers of the anal and cervix.
8. Overweight and obesity
Being unhealthy and overweight can lead to a lot of diseases such as diabetes, high blood pressure and heart diseases. Eating healthy, maintaining an active lifestyle and managing the right weight are essential to reduce the risk of cancer. Obese people have a high risk of several types of cancers. Studies have shown that he amount of fats in the body can lead to cancer. This includes endometrial cancer (lining of the uterus) in women. Overweight and obese people are also at higher risk of liver, pancreatic, colon, esophageal, kidney and gall bladder cancers.
9. Genetics and inheritance
Cancer is caused as a result of damaged DNA and thus it is a genetic disease. Genes control the functioning of the cells and instruct them to grow and divide. These genetic cancer cells can be inherited by the offspring from the parents. The hereditary cancer gene TP53 consists of germline mutations and causes the Li-Fraumeni syndrome that increases the risk of bone, breast, brain cancer and soft tissue sarcomas. The inherited mutations in BRCA1 and BRCA2 genes increase the risk of breast and ovarian cancer in women and can also lead to pancreatic and prostate cancer in other cases. Mutations in the PTEN gene can cause Cowden syndrome and lead to breast, thyroid and endometrial cancers.
Although there has not been proven studies as to how diet is related to cancer, but a healthy balanced diet can surely cut the risk of cancer. Dietary components such as charred meat, cruciferous vegetables, artificial sweeteners, and those containing antioxidants can trigger the DNA, but there has not been any clear evidence on the same. It has not been proven yet that food habits can cause or protect against cancer, but healthy food habits do help in maintaining an active lifestyle with fewer diseases.
Apart from all the above causes, there are many types of cancers that develop for no known reason. Scientists and doctors have spent years in clinical trials and studies to find a definite cause of cancer but there are still several risks associated with it. While a damaged DNA is responsible for the start of cancer, it is however difficult to arrive at a definite cause that triggers such genetic mutations.