WHAT IS CANCER? Cancer is not a new disease. Yet knowledge about cancer is not widespread. This is partly because health care providers (Doctor, Nurses & Radiographers) use rather technical terms to describe the disease and its management. And partly because many of us don抰 want to know too much about something that seems so frightening. Scientists are still trying to understand what actually has turned a cell 揷ancerous? The answer may not be available for a long time yet. However it is not very difficult to understand the general nature of cancer. We are made up of cells. In fact we began life when two cells - sperm and ovum - united to form one cell. This divided and divided to form more cells and cause growth. This growth is very carefully controlled by a protein called DNA which is contained in genes. It is this information that allows for healing of a wound. So if cells in a body divide only when necessary and stop when the job is done the total number of cells in the adult body will remain constant. However when a cell starts dividing and when the daughter cells in turn keep dividing without any purpose, then the number of cells in that particular area begins to increase and a lump appears - a cancer. CANCERS SPREAD If the cells that formed the cancerous lump remained only at that site then most cancers could be treated effectively. But cancers cells have another dangerous feature - they can spread. As the cancer grows clumps of cells will invade tissues around them and later invade arteries and veins and can be carried along by them. They could settle in another site far away from the original site. Cancers can also travel along channels called lymphatic and spread to lymph nodes. PRIMARY AND SECONDARY CANCERS The site where the cancer started is called the primary cancer. The site the cancer spreads to is called the secondary cancer. For example a cancer may start in the breast. This is called a primary breast cancer. It may spread to the liver and lungs. These are not new cancers in the liver and lungs but secondaries from the primary breast cancer. ONCOGENES We do not know what it is that transforms a normal cell into a cancerous cell. We know however that there are certain genes-oncogenes that can either promote or suppress cell division. P53 is a suppressor oncogene. In certain breast cancer tissues excessive amounts of a defective P53 gene are present. These cancers are generally believed to be aggressive. It may be possible in the future to regulate growth of cancer cells by modifying these genes. THE CAUSES Likely cause of cancer Estimated proportion of cancer deaths (%) Environmental Cigarette smoking 35 Diet 30 Occupation 2 Background radiation 2 Non-environmental Generic 5 Total 74 Unaccounted 26 From the table above we see that almost 70% of cancers are believed to be caused by 攅nvironmental?factors - which mean these cancers should be preventable. However it is not always possible to link a particular cancer-causing substance (carcinogen) and a cancer as there is usually a long interval - latent period - between the exposure and the cancer. SMOKING It is very clear from the table that the link between cancer and smoking is very strong. In addition to the cancer deaths caused by smoking there are deaths from lung, heart and blood vessel diseases caused by smoking. The risk of dying of lung cancer is directly related to the number of cigarettes smoked, age at starting, and smoking habits (how many puffs per cigarette, length of butt left, type of cigarette including filter and tar content). The risk of developing cancers for those who stop smoking gradually falls and after 15 years is similar to those who have never smoked. FOOD There is a wide difference in the incidence of cancers in different parts of the world. Part of these differences can be attributed to food habits. However the relationship between food and cancers is not as clear as between smoking and cancers. General guidelines on healthy eating would include the following recommendations: • Reduce the amount of animal fats consumed. • Increase roughage by consuming more unprocessed cereals. • Take reasonable amounts of fresh fruits and vegetables. • Maintain reasonable body weight. FOOD WRAPPINGS, FOOD ADDITIVES AND PESTICIDES There is no clear association between these and cancers. The following recommendations, though not based on firm scientific foundations, seem reasonable: ?λτ;/ΦΟΝΤ> Reduce the intake of preserved foods. ?λτ;/ΦΟΝΤ> Avoid food additives. ?λτ;/ΦΟΝΤ> Avoid or quickly unwrap food covered with polyvinyl chloride (cling film) wrapping. ?λτ;/ΦΟΝΤ> Wash fruits and vegetables to remove pesticides. Remember: The health risks of modern processed foods are must less than that from smoking and alcohol. OCCUPATION CAUSES Much of our early understanding of the causes of cancer came from studies of the risks in industry. There is little doubt that exposure to certain chemicals increases the risk of developing cancers. The jobs carrying the greatest risks are those in the petro-chemical industries involving exposure to tars and certain inorganic chemicals. The link between asbestos exposure and lung cancer is well established. Remember: Smoking significantly increases the risks of workers in these industries of actually contracting cancers. RADIATION AND HIGH VOLTAGE POWER LINES Major studies into the risks of people living close to nuclear power stations or high voltage lines have, suggested that at worst there may be some minor increase of leukemia, though no of other tumors. VIRUSES Long term infections with the Hepatitis B & C viruses are well established as causing liver cancers. Hepatitis B vaccination is being carried out to reduce this risk. Less established are the relationship between Herpes Simplex Type ll and cervical cancers. The HIV linked to AIDS may allow cancers to grow by suppressing the immune system. INHERITANCE For most people with cancer, there is no direct inherited cause. Our genetic make-up may increase our chances of developing a cancer upon exposure to certain carcinogens. This may explain why some people who smoke develop lung cancers and others done. There are certain inherited conditions which run in families where the risk of developing a particular type of cancer is high. One such condition is called Multiple Ployposis Coli where multiple fleshy growths in the large intestine may be found in many members of the same family. There is a great risk that these growths could turn malignant and removal of the large intestine is recommended. EARLY DETECTION Early detection of cancers are beneficial for two reasons: ?λτ;/ΦΟΝΤ> the smaller a cancer is when it is diagnosed, the greater the chances of cure. ?λτ;/ΦΟΝΤ> the earlier a cancer is diagnosed, the less extensive will be the treatment. Screening procedures allows a cancer to be diagnosed before they cause any symptoms that is when it is at its smallest. This has proved to be useful in the case of breast cervical cancers. Although screening has been tried in other tumors, there is little or no evidence that current tests pick up cancers early enough to prolong life and for this reason it is not recommended. WARNING SYMPTOMS OF CANCERS Breast: Lump of thickening, nipple discharge. Bowels: Change in bowel habits or bleeding. Lung: Persistent cough, lingering lung infection, coughing up of blood. Mouth, Throat, larynx: Sore that does not heal, difficulty in swallowing, hoarseness Cervix and Womb: Any abnormal vaginal bleeding after intercourse, between periods or after the menopause. Stomach: Indigestion, difficulty in swallowing, persistent vomiting. Bladder or Kidney: Pain or difficulty in passing urine, blood in urine Skin: Ulcer that does not heal, change in size or color of a mole. DIAGNOSIS To confirm a diagnosis of cancer it is almost always necessary to remove a small piece of the tumor for examination; this is called a biopsy. The presence in the blood of certain proteins called tumor markers (e.g. C.E.A., CA-125, P.S.A. etc.) may point to a diagnosis of cancer but are never enough in themselves to establish the diagnosis. Once the diagnosis is made, it may be necessary to carry out further tests such as CT Scans, Bone marrow studies etc. to see if there is evidence of spread of cancer. This is called staging. TREATMENT Treatment of cancer is by surgery, radiotherapy and chemotherapy. Surgery: In cancer surgery is used 1) To make the diagnosis 2) To remove all the tumor or most of the tumor 3) To control symptoms even when a cancer is too advanced to be cured e.g. removing a tumor that is causing severe bowel obstruction and lastly 4) To prevent cancers by removing an organ when the risk of malignant transformation is very high Radiotherapy: This is the use of x-rays to treat cancers. Some cancers are curable by radiotherapy e.g. cancers of the cervix. It is also used to mop up the tumor area after surgery. In incurable cancers radiotherapy can provide relief from pain caused by spread to the bones. Chemotherapy: This involves the use of drugs to destroy cancer cells. Some cancers are curable by chemotherapy e.g. certain lymphomas. In certain cancers especially breast and colon cancers chemotherapy is used in addition to surgery and radiotherapy to prevent spread of the cancers.