Our current understanding of what causes cancer is not complete. It is clear that cancer is not caused by injury such as a bump or a bruise. Although being infected with certain viruses may increase the risk of some types of cancer, cancer is not contagious; no one can catch cancer from another person.
Cancer develops gradually as a result of a complex mix of factors related to environment, lifestyle and heredity. Scientists estimate that 80% of all cancers are related to the use of tobacco products, what we eat and drink, and to a lesser extent, cancer causing (carcinogens) agents in the environment and workplace. Some people are more susceptible to factors that can cause cancer.
Keep in mind that not everyone with a risk factor will get cancer. Most people do not. Below are some factors known to increase the risk of cancer:
Tobacco and Cancer
Tobacco causes cancer. Smoking cigarettes, pipes or cigars, using smokeless tobacco or being regularly exposed to tobacco smoke, causes up to one-third of all cancer deaths.
Smoking accounts for more than 85% of all lung cancer deaths. The risk of developing lung cancer is affected by the number and type of cigarettes smoked and the numbers of years a person has been smoking. Smokers are more likely than nonsmokers to develop larynx (voice box), oesophagus (gullet), pancreas, bladder, kidney, cervix and lung cancers. The risk begins to decrease when a smoker quits.
Chewing tobacco can also cause cancers of the mouth and throat.
Exposure to environmental smoke increases the risk of lung cancer. The risk goes up 30% for the nonsmoking spouse of the person who smokes.
Diet and Cancer
What a person eats may affect his chances of developing cancer. There is a link between a high-fat diet and certain cancers, such as cancer of the breast, colon, uterus, and prostate. Being seriously overweight is linked to increased rates of cancers of the prostate, pancreas, uterus, colon, and ovary. On the other hand, foods containing fiber, such as fruits, vegetables, whole-grain breads and cereals, help to protect against some types of cancer.
Drinking large amounts of alcohol increases the risk of cancer of the mouth, throat, oesophagus and larynx (voice box). People who smoke and drink have a higher risk. Alcohol can also damage the liver and increase the risk of liver cancer.
Chemicals in the Workplace and Cancer
Being exposed to chemicals such as asbestos, nickel, cadmium, uranium, radon, vinyl chloride, benzidene, and benzene can increase the risk of cancer. It is important to follow safety and work rules to avoid contact with dangerous materials.
Cancer is treated with surgery, radiation therapy, chemotherapy, hormone therapy or biological therapy. Patients are often treated by a team of specialists, which may include, among others, a medical oncologist (doctor trained in cancer treatment), surgeon, radiation oncologist (doctor trained in radiotherapy). The doctors may decide to use one or a combination of methods to treat the cancer. The choice of treatment depends on the type, location, stage of cancer, the patient's age and general health, and other factors.
Some patients take part in a clinical trial (research study) using new treatment methods designed to improve cancer treatment.
Surgery is the local treatment to remove the tumour. Tissue around the tumour and nearby lymph nodes may also be removed during the operation. There may be pain after surgery for the first few days but this can be controlled by medication. It is also common for patients to feel tired or weak for a while. The length of time it takes to recover varies from patient to patient.
In radiotherapy, high-energy rays are used to kill cancer cells and stop them from growing and dividing. Like surgery, radiotherapy is a local treatment; it can affect cancer cells only in the treated area. Radiotherapy is usually given on an outpatient basis, 5 days a week, for several weeks. Patients are not radioactive during or after treatment.
The most common side effects are tiredness, skin reactions such as rash or redness, and loss of appetite. Radiation therapy may also cause a temporary lowering of the white blood cell count, cells that help protect the body against infection. The side effects are usually temporary, developing gradually over the weeks of the treatment, and improving gradually after treatment is completed.
Treatment with medicines to kill cancer cells is called chemotherapy. Most of these medications are injected into a vein or a muscle. The medicines flow through the bloodstream to nearly every part of the body, damaging cells that are rapidly dividing and growing. Normal cells that are rapidly dividing and growing, such as white blood cells, will also be affected by chemotherapy. Because cancer cells are often more immature and fragile than normal cells, chemotherapy affects cancer cells more than they do normal healthy cells.
Chemotherapy is generally given in cycles: a treatment period is normally followed by a rest period, then another treatment period, and so on. Most chemotherapy can be given on an outpatient basis.
The specific medicine or combination recommended, as well as the frequency of the treatment, depend on a number of things - the kind of cancer, its location, height and weight, how quickly the healthy normal cells recover from the treatment. Anticancer medication affects all cells that grow rapidly: cancer cells, white and red blood cells, hair and cells which line the digestive tract such as the mouth and intestines. As a result, patients may experience side effects, such as nausea and vomiting, loss of appetite, mouth sores or tiredness. Medication will usually be prescribed to minimise these side effects. These side effects go away after treatment stops.
Some types of cancer, for example, breast cancer and prostate cancer, depend on hormones to grow. For this reason, doctors may recommend therapy that prevents cancer cells from getting or using the hormones they need. Sometimes, the patient has surgery to remove the organs (like the ovaries or testes) that make the hormones. Or drugs are used to stop hormone production or change the way the hormones work.
Hormone therapy may cause nausea, swelling of the limbs or weight gain through water retention. In women, there may be irregular periods and vaginal dryness. In men, there may be impotence or loss of sexual desire.
Biological therapy, also called immunotherapy, uses the body's own immune system to fight infection and disease or protect the body from some of the side effects of other forms of treatment. Monoclonal antibodies, interferon, interleukin-2, and colony-stimulating factors such as GM-CSF and G-CSF, are forms of biological therapy.
These treatments often cause temporary flu-like symptoms such as fever and chills, muscle aches and weakness, loss of appetite and diarrhoea.