Cancer is a generic term for a large group of diseases that can affect any part of the body. It is a serious disease wherein cells divide uncontrollably. Every year numerous deaths are caused by cancerous tumors. Read here to learn about the causes, mechanisms, and types of prevalent cancers.
Cancer is a leading cause of death worldwide, accounting for nearly 10 million deaths in 2020, or nearly one in six deaths.
The most common types are breast, lung, colon and rectum, and prostate cancers.
Around one-third of deaths from cancer are due to tobacco use, high body mass index, alcohol consumption, low fruit and vegetable intake, and lack of physical activity.
Cancer-causing infections, such as human papillomavirus (HPV) and hepatitis, are responsible for approximately 30% of cancer cases in low- and lower-middle-income countries. Many cancers can be cured if detected early and treated effectively.
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What is cancer?
Cancer is a generic term for a large group of diseases that can affect any part of the body.
Other terms used are malignant tumors and neoplasms.
One defining feature of the disease is the rapid creation of abnormal cells that grow beyond their usual boundaries, and which can then invade adjoining parts of the body and spread to other organs; the latter process is referred to as metastasis. Widespread metastases are the primary cause of death from cancer.
Cancer begins when genetic changes interfere with this orderly process causing cells to start to grow uncontrollably.
- These cells may form a mass called a tumor. A tumor can be cancerous or benign.
- A cancerous tumor is malignant, meaning it can grow and spread to other parts of the body.
- A benign tumor means the tumor can grow but will not spread.
- Some types of cancer do not form a tumor. These include leukemias, most types of lymphoma, and myeloma.
Types of cancer
Doctors divide cancer into types based on where it begins. Four main types of cancer are:
- Carcinomas: A carcinoma begins in the skin or the tissue that covers the surface of internal organs and glands. Carcinomas usually form solid tumors. They are the most common type of cancer. Examples of carcinomas include prostate, breast, lung, and colorectal.
- Sarcomas: A sarcoma begins in the tissues that support and connect the body. A sarcoma can develop in fat, muscles, nerves, tendons, joints, blood vessels, lymph vessels, cartilage, or bone.
- Leukemias: Leukemia is a cancer of the blood. Leukemia begins when healthy blood cells change and grow uncontrollably. The 4 main types of leukemia are acute lymphocytic leukemia, chronic lymphocytic leukemia, acute myeloid leukemia, and chronic myeloid leukemia.
- Lymphomas: Lymphoma is cancer that begins in the lymphatic system. The lymphatic system is a network of vessels and glands that help fight infection. There are 2 main types of lymphomas: Hodgkin lymphoma and non-Hodgkin lymphoma.
There are many other types as well which do not fall under the above categories like the ones affecting the central nervous system.
Also read: Sickle Cell Disease
How cancer spreads?
As a cancerous tumor grows, the bloodstream or lymphatic system may carry cancer cells to other parts of the body.
- During this process, the cancer cells grow and may develop into new tumors.
- This is known as metastasis.
One of the first places cancerous tumor often spreads is to the lymph nodes.
- Lymph nodes are tiny, bean-shaped organs that help fight infection.
- They are located in clusters in different parts of the body, such as the neck, groin area, and under the arms.
It may also spread through the bloodstream to distant parts of the body.
- These parts may include the bones, liver, lungs, or brain.
- Even if it spreads, it is still named for the area where it began.
- For example, if breast cancer spreads to the lungs, it is called metastatic breast cancer, not lung cancer.
What causes cancer?
Cancer arises from the transformation of normal cells into tumor cells in a multi-stage process that generally progresses from a pre-cancerous lesion to a malignant tumor.
These changes are the result of the interaction between a person’s genetic factors and three categories of external agents, including:
- physical carcinogens, such as ultraviolet and ionizing radiation;
- chemical carcinogens, such as asbestos, components of tobacco smoke, alcohol, aflatoxin (a food contaminant), and arsenic (a drinking water contaminant); and
- biological carcinogens, such as infections from certain viruses, bacteria, or parasites.
Tobacco use, alcohol consumption, unhealthy diet, physical inactivity, and air pollution are risk factors for the disease and other non-communicable diseases.
The risk of cancerous tumor can be reduced by:
- not using tobacco;
- maintaining a healthy body weight;
- eating a healthy diet, including fruit and vegetables;
- doing physical activity regularly;
- avoiding or reducing consumption of alcohol;
- getting vaccinated against HPV and hepatitis B if you belong to a group for which vaccination is recommended;
- avoiding ultraviolet radiation exposure (which primarily results from exposure to the sun and artificial tanning devices) and/or using sun protection measures;
- ensuring safe and appropriate use of radiation in health care (for diagnostic and therapeutic purposes);
- minimizing occupational exposure to ionizing radiation; and
- reducing exposure to outdoor air pollution and indoor air pollution, including radon (a radioactive gas produced from the natural decay of uranium, which can accumulate in buildings — homes, schools, and workplaces).
A correct cancer diagnosis is essential for appropriate and effective treatment because every cancer type requires a specific treatment regimen.
Treatment usually includes surgery, radiotherapy, and/or systemic therapy (chemotherapy, hormonal treatments, targeted biological therapies).
- Some of the most common cancer types, such as breast cancer, cervical cancer, oral cancer, and colorectal cancer, have high cure probabilities when detected early and treated according to best practices.
- Some cancer types, such as testicular seminoma and different types of leukemia and lymphoma in children, also have high cure rates if appropriate treatment is provided, even when cancerous cells are present in other areas of the body.
There is a significant variation in treatment availability between countries of different income levels; comprehensive treatment is reportedly available in more than 90% of high-income countries but less than 15% of low-income countries.
India is expected to roll out the indigenously developed CERVAVAC vaccine for the prevention of cervical cancer among girls aged 9-14 years through their schools by mid-2023.
- The decision was based on the National Technical Advisory Group for Immunisation (NTAGI) recommendation to introduce the Human Papillomavirus (HPV) Vaccine in the Universal Immunisation Programme.
- It is India’s first indigenously developed quadrivalent human papillomavirus (qHPV) vaccine that is said to be effective against four strains of the virus – Type 6, Type 11, Type 16, and Type 18.
Cervical cancer is the 4th most common type of cancer among women, globally and 2nd most common among women in India.
But when diagnosed, cervical cancer is one of the most successfully treatable forms of cancer, as long as it is detected early and managed effectively.
The burden of cancers in India
Cancer cases in India increased at an average annual rate of 1.1-2 percent from 2010-2019.
According to a report by the Indian Council for Medical Research on the ‘Burden of cancers in India’, seven cancers accounted for more than 40% of the total disease burden: lung (10.6%), breast (10.5%), esophagus (5.8%), mouth (5.7%), stomach (5.2%), liver (4.6%) and cervix uteri (4.3%).
The National Cancer Grid (NCG) is an initiative of the Government of India through the Department of Atomic Energy and its grant-in-aid institution, the Tata Memorial Centre.
- It started to create a network of cancer centers, research institutes, patient groups, and charitable institutions across India.
- The main objectives are: developing uniform standards of patient care for the prevention, diagnosis, and treatment of cancer; providing specialized training and education in oncology and facilitating collaborative basic, translational and clinical research in cancer.
NCG today has over 270 hospitals in its network across India.
To tackle the challenge of Non-Communicable Diseases (NCD), including cancer, 599 NCD Clinics at the District level and 3,274 NCD Clinics at the Community Health Centre level have been set up under National Programme for Prevention and Control of Cancer, Diabetes, Cardiovascular Diseases, and Stroke (NPCDCS).
Read: Cancer care in India
-Article written by Swathi Satish