Cancer is a disease which occurs when changes in a group of normal cells within the body lead to uncontrolled, abnormal growth forming a lump called a tumour; this is true of all cancers except leukaemia (cancer of the blood). If left untreated, tumours can grow and spread into the surrounding normal tissue, or to other parts of the body via the bloodstream and lymphatic systems, and can affect the digestive, nervous and circulatory systems or release hormones that may affect body function.
Cancer tumours can be divided into three groups: benign, malignant or precancerous
Benign tumours are not cancerous and rarely threaten life. They tend to grow quite slowly, do not spread to other parts of the body and are usually made up of cells quite similar to normal or healthy cells. They will only cause a problem if they grow very large, becoming uncomfortable or press on other organs - for example, a brain tumour inside the skull.
Malignant tumours are faster growing than benign tumours and have the ability to spread and destroy neighbouring tissue. Cells of malignant tumours can break off from the main (primary) tumour and spread to other parts of the body through a process known as metastasis. Upon invading healthy tissue at the new site they continue to divide and grow. These secondary sites are known as metastases and the condition is referred to as metastatic cancer.
Precancerous (or premalignant) describes the condition involving abnormal cells which may (or is likely to) develop into cancer.
Cancer can be classified according to the type of cell they start from. There are five main types:
Carcinoma – Cancer that arises from the epithelial cells (the lining of cells that helps protect or enclose organs). Carcinomas may invade the surrounding tissues and organs and metastasise to the lymph nodes and other areas of the body. The most common forms of cancer in this group are breast, prostate, lung and colon cancer
Sarcoma – A type of malignant tumour of the bone or soft tissue (fat, muscle, blood vessels, nerves and other connective tissues that support and surround organs). The most common forms of sarcoma are leiomyosarcoma, liposarcoma and osteosarcoma
Lymphoma and Myeloma – Lymphoma and Myeloma are cancers that begin in the cells of the immune system. Lymphoma is a cancer of the lymphatic system, which runs all through the body, and can therefore occur anywhere. Myeloma (or multiple myeloma) starts in the plasma cells, a type of white blood cell that produces antibodies to help fight infection. This cancer can affect the cell's ability to produce antibodies effectively
Leukaemia – Leukaemia is a cancer of the white blood cells and bone marrow, the tissue that forms blood cells. There are several subtypes; common are lymphocytic leukaemia and chronic lymphocytic leukaemia
Brain and spinal cord cancers – these are known as central nervous system cancers. Some are benign while others can grow and spread.
Cancers can be caused by a number of different factors and, as with many other illnesses, most cancers are the result of exposure to a number of different causal factors. It is important to remember that, while some factors cannot be modified, around one third of cancer cases can be prevented by reducing behavioural and dietary risks.
With so many different types of cancers, the symptoms are varied and depend on where the disease is located. However, there are some key signs and symptoms to look out for, including:
Unusual lumps or swelling – cancerous lumps are often painless and may increase in size as cancer progresses
Coughing, breathlessness or difficulty swallowing – be aware of persistent coughing episodes, breathlessness or difficulty swallowing
Changes in bowel habit – such as constipation and diarrhoea and/or blood found in the stools
Unexpected bleeding – includes bleeding from the vagina, anal passage, or blood found in stools, in urine or when coughing
Unexplained weight loss – a large amount of unexplained and unintentional weight loss over a short period of time (a couple of months)
Fatigue – which shows itself as extreme tiredness and a severe lack of energy. If fatigue is due to cancer, individuals normally also have other symptoms
Pain or ache – includes unexplained or ongoing pain or pain that comes and goes
New mole or changes to a mole – look for changes in size, shape, or colour and if it becomes crusty or bleeds or oozes
Complications with urinating – include needing to urinate urgently, more frequently, or being unable to go when you need to or experiencing pain while urinating
Unusual breast changes – look for changes in size, shape or feel, skin changes and pain
Appetite loss – feeling less hungry than usual for a prolonged period of time
A sore or ulcer that won’t heal – including a spot, sore wound or mouth ulcer
Heartburn or indigestion – persistent or painful heartburn or indigestion
Heavy night sweats – be aware of very heavy, drenching night sweats
Over a third of all cancers can be prevented by reducing your exposure to risk factors such as tobacco, obesity, physical inactivity, infections, alcohol, environmental pollution, occupational carcinogens and radiation.
Prevention of certain cancers may also be effective through vaccination against the Hepatitis B Virus (HBV) and the Human Papilloma Virus (HPV), helping to protect against liver cancer and cervical cancer respectively.
Reducing exposures to other carcinogens such as environmental pollution, occupational carcinogens and radiation could help prevent further cancers.
There are a number of cancers which can be identified early which helps to improve the chances of successful treatment outcomes, often at lower costs and with fewer (or less significant) side effects for patients. There are cost-effective tests that help detect colorectal, breast, cervical and oral cancers early and further tests are being developed for other cancers.
Check with your doctor for guidance on the national recommendations regarding vaccinations, testing and screenings. These can and do vary from country to country.
The classification of cancer by anatomical extent of the disease, i.e. stage, is essential to patient care, research and cancer control. The UICC TNM staging system is the common language adopted by oncology health professionals to communicate on the cancer extent for individual patients. Once the stage of cancer is known and understood, this is often a basis for deciding appropriate treatment and individual prognosis. It can also be used to inform and evaluate treatment guidelines and constitutes vital information for policy-makers developing or implementing cancer control, prevention plans and research.
The TNM classification focuses on the anatomical extent of the tumour and is determined by assessing the following categories:
Treatment depends on the type of cancer, where your cancer is, how big it is, whether it has spread, and your general health. The general types of treatments include surgery, chemotherapy, radiotherapy, hormone therapy, immunotherapy, and gene therapy.
If cancer has not metastasised (spread), surgery can remove entire cancer which may completely cure the disease. Often, this is effective in removing the prostate or a breast or testicle.
Radiation treatment or radiotherapy uses high-energy rays to reduce a tumour or destroy cancer cells as a stand-alone treatment and in some cases in combination with other cancer treatments.
Chemotherapy uses chemicals to interfere with the way cells divide - damaging of DNA - so that cancer cells will destroy themselves. These treatments target any rapidly dividing cells (not necessarily just cancer cells), but normal cells usually can recover from any chemical-induced damage while cancer cells cannot. Chemotherapy is generally used to treat cancer that has spread or metastasised because the medicines travel throughout the entire body. It is a necessary treatment for some forms of leukaemia and lymphoma.
Immunotherapy uses the body's own immune system to fight the cancer tumour. Immunotherapy may treat the whole body by giving an agent that can shrink tumours.
Several cancers have been linked to some types of hormones, including breast and prostate cancer. Hormone therapy works to change hormone production in the body so that cancer cells stop growing or are killed completely.
The goal of gene therapy is to replace damaged genes with ones that work to address a root cause of cancer: damage to DNA. Other gene-based therapies focus on further damaging cancer cell DNA to the point where the cell destroys themselves. However, gene therapy is new and has not yet resulted in any successful treatments.