Oncology is the medical study and treatment of cancer. A doctor who practices oncology is an oncologist. The term is from the Greek “onkos”: meaning bulk, mass or tumor.
Oncology is concerned with:
- The diagnosis of cancer
- Treatments (i.e. surgery, radiotherapy, chemotherapy , biological and immunological treatments)
- Follow-up of cancer patients after successful treatment
- Palliative care of patients with terminal malignancies
- Screening efforts of general population or of the relatives of patients (in types of cancer that are thought to have a heritable basis, such as breast cancer).
Cancer is defined as the uncontrolled or unregulated growth of cells. The word is derived from “crab” in Latin. In general, one billion cells are required for a cancer lump to reach 1cm diameter or to weigh 1g. This is the limit of detection by imaging techniques.
Cancer can start almost anywhere in the human body, which is made up of trillions of cells. Normally, human cells grow and divide to form new cells as the body needs them. When cells grow old or become damaged, they die, and new cells take their place. When cancer develops, however, this orderly process breaks down. As cells become more and more abnormal, old or damaged cells survive when they should die, and new cells form when they are not needed. These extra cells can divide without stopping and may form growths called tumours.
Many cancers form solid tumours, which are masses of tissue. Cancers of the blood, such as leukaemia, generally do not form solid tumours. Oncologists treat cancers arising from solid tumours whereas Haematologists treat blood-related cancers.
Cancerous tumours are malignant, which means they can spread into, or invade, nearby tissues. In addition as these tumours grow, some cancer cells can break off and travel to distant places in the body through the blood or the lymph system and form new tumours far from the original tumour (“metastasize”).
Unlike malignant tumours, benign tumours do not spread into, or invade, nearby tissues. Benign tumours can sometime be quite large, however. When removed, they usually don’t grow back, whereas malignant tumours sometimes do. Unlike most benign tumours elsewhere in the body, benign brain tumours can be life threatening.
According to the National Cancer Registry 2007-2011 report:
- There were over 103,507 new cancer cases were diagnosed in Malaysia during the period of 2007 to 2011, of which 46,794 (45.2%) were reported in males and 56,713 (54.8%) in females.
- the risk of males getting cancer was 1 in 10 and for females was 1 in 9.
- The commonest cancer among Malaysian males is colorectal (large intestine) cancer, followed by lung cancer, and the third Prostate cancer, which is followed closely by Nasopharyngeal cancer or nose cancer.
- Breast cancer is the most common cancer in females followed by colorectal (large intestine) cancer and cervical cancer.
Cancer prevention is action taken to lower the risk of getting cancer. This can include maintaining a healthy lifestyle, avoiding exposure to known caner-causing substances, and taking medicine or vaccines that can prevent cance from developing.
It is usually not possible to know exactly why one person develops cancer and another doesn’t. But research has shown that certain risk factors may increase a person’s chances of developing cancer. Cancer risk factors include exposure to chemicals or other substances, as well as certain behaviours. They also include things people cannot control, like age and family history (Hereditary Cancer Syndromes). Limiting your exposure to avoidable risk factors may lower your risk of developing certain cancers.
Advancing age is the most important risk factor for cancer overall, and for many individual cancer types. But cancer can occur at any age, e.g. bone cancer is most frequently diagnosed among people under age 20 and certain cancer types are more common in children and adolescent than in adults
Drinking alcohol increases risk for developing cancers of the mouth, throat, esophagus, larynx (voicebox), liver and breast. The more you drink, the higher your risk. The risk of cancer is much higher for those that drink and also use tobacco.
Chemicals that can damage DNA that causes changes to genes that alter cell functions causes cancers. Many factors influence whether a person exposed to a carcinogen will develop cancer, including the amount and duration of the exposure and the individual’s genetic background. Carcinogens can be in the air, the food we eat, the water we drink and materials we use to do our jobs. Examples of carcinogens in our environment include: Aflotoxins, arsenic, asbestos, benzene, cadmium, coal tar, crystallin silica, formaldehyde, hexavalent chromium compounds, Nickel, Radon, secondhand tobacco smoke, soot, strong inorganic acids mists containing sulfuric acid, vinyl chloride, wood dust etc.
People who receive organ transplants take medications to suppress the immune system so the body wont reject the organ. These “immunosuppressive” drugs make the immune system less able to detect and destroy cancer cells or fight off infections that cause cancer. Infection with HIV also weakens the immune system and increases the risk fo certain cancers.
Certain infectious agents, including viruses, bacteria and parasites can cause cancer or increase the risk that cancer will form. Some viruses can disrupt signalling that normally keeps cell growth and proliferation in check. Also , some infections weaken the immune system, making the body less able to fight off other cancer-causing infections. And some viruses, bacteria and parasites can also cause chronic inflammation, which may lead to cancer. Most viruses that are linked to an increased risk of cancer can ve passed from one person to another through blood and/or other body fluids. You can lower your risk of infection by getting vaccinated, not having unprotected sex, and not sharing needles. Examples include Epstein-Barr Virus (EBV), Hepatitis B and Hepatitis C viruses (HBV and HCV), Human immunodeficiency virus (HIV), Human Papillomaviruses (HPVs), Human T-Cell Leukaemia/Lymphoma Virus Type 1 (HTLV-1), Kaposi Sarcoma-Associated Herpesvirus (KSHV), Merkel Cell Polyomavirus )HCPyV), Helicobacter pylori (H.Pylori bacteria), opisthorchis viverrini (parasite) and Schistosoma hematobium (parastite).
Obese people may have an increased risk of seeral types of cancer, including cancers of the breast, colorectal (large intestine), endometrium (lining of uterus), esophagus, kidney, pancreas and gallbladder.
Ionizing radiation has enough energy to damage DNA and cause cancer. High-energy radiation include radon, x-rays, gamma rays, which can be used as part of imaging procedures and even in radiotherapy as part of cancer treatment. You can talk with your oncologist on risk and benefits of radiation therapy and risks for development of second cancer later on.
The sun, sunlamps, and tanning booths all give off ultraviolet (UV) radiation. Exposure to UV radiation causes early aging of the skin and skin damage that can lead to skin cancer. People of all ages and skin tones should limit the amount of time they spend in the sun, and keep in mind that UV radiation is reflected by sand, water, snow and ice and can go through windshields and windows. Usage of hats with wide brim, sunglasses, long sleeves and long pants as well as sunscreen products of sun protection factor (SPF) of at least 15 may help you to minimize harms of UV rays.
It is a leading cause of cancer and of death from cancer. It causes approximately 30 per cent of cancers, including cancer of the lung, mouth, larynx (voice box), cervix, stomach, large intestine (colon & rectum), pancreas, urinary bladder as well as acute myeloid leukaemia. People who use smokeless tobacco (snuff or chewing tobacco) have increased risk of cancers of the mouth, esophagus and pancreas. There is no safe level of tobacco use. People who use any type of tobacco product are strongly urged to quit. People who quit smoking, regardless of their age, have substantial gains in life expectancy compared with those who continue to smoke. Also, quitting smoking at the time of a cancer diagnosis reduces the risk of death.