Cancer is the second leading cause of death globally accounting for 1 in 6 deaths, the majority (around 70%) in low middle income countries. Demographic (aging population) and lifestyle changes, accelerated urbanisation, partly contribute to this increase in many developing countries including Sri Lanka. To give readers a better understanding of what cancer is and how it could be prevented, the Sunday Observer today has brought this subject on centre stage to raise more awareness in a collective effort that now has the backing of a government that is fully committed to drastically reduce the percentage of cancer patients in Sri Lanka.
Consultant Community Physician National Cancer Prevention Programme (NCPP) Dr Nayana de Alwis explains what cancer is , how it spreads, signs to look for, and most importantly how modifiable risk factors can be reduced to prevent cancer .
Excerpts:
Q. Many of our readers still don’t understand what cancer is. So tell us what is cancer.
 Dr Nayana de Alwis |
A. Cancer is a group of diseases having similar characteristics. Cancer can start anywhere in the body where cells are present. Cells are the basic building blocks of the body. Cells grow and divide to make new cells when the body needs them. In normal circumstances cells divide according to the body’s need and new cells form and replace old cells.
Cancer begins when genetic changes interfere with this orderly process. At the initial stages when very few abnormal cells are formed the body’s immune mechanism identifies them as abnormal and destroys. As cells become more and more abnormal and more and more rapidly proliferating, the body is unable to destroy them. In all types of cancers, cells in the particular organ or part of the body begins to divide in an uncontrollable manner and form a mass called a tumour. A tumour can be cancerous or benign. A cancerous tumour is malignant, meaning it can grow and spread to other parts of the body. A benign tumour means the tumour can grow but will not spread. Some types of cancers do not form tumours e.g: cancers of the blood or lymphatics leukemia, some types of lymphoma and myeloma.
Q. What causes it?
A. Cancer is a genetic disease caused by changes in the genes that control the way cells function, especially, how they grow and divide. Cancer begins when genes in a cell become abnormal and the cell starts to grow and divide out of control.
There are two ways one can have abnormal genes
1. Inherited: An abnormal gene can be passed from the mother or the father at the time of birth which is called inherited gene abnormality. These abnormal cells will proliferate during one’s lifetime to produce cancers. These types of gene abnormalities run through families. That’s why family history of cancer is important in some people. Inherited gene abnormalities are thought to be a direct cause of only a small fraction (5 – 10%) of cancers.
2. Acquired: gene abnormalities also arise during a person’s lifetime as a result of errors that occur during cell division or damage of DNA caused by certain environmental exposure. Acquired gene abnormalities are much more common than inherited gene mutations. About 90 – 95% adult cancers occur due to acquired gene mutations.
Q. How does it spread?
A. When a cancerous tumour grows, the blood stream or lymphatic system may carry dislodged cancer cells to other parts of the body. A cancer spread to a distant place in the body from the original site is called metastatic cancer. Metastatic cancer (secondary deposit) has the same type of cancer cells as the original or primary cancer. E.g: Breast cancer which spreads to the lung and forms a metastatic tumour in the lung is metastatic breast cancer not lung cancer.
One of the first places a cancer spreads is lymph nodes, which are very tiny organs located in clusters in different parts of the body such as neck, groin or under the arm. Their main function is to fight infections.
Cancer may also spread to distant parts of the body through the blood stream and the sites may include bones, liver, lung and brain.
Q. Where do these different types of cancers originate?
A. There are more than 100 types of cancers named according to the organ or tissue where cancer forms.
E.g: Breast cancer starts in the cells of the breast; lung cancer in the cells of the lung and liver cancer in the cells of the liver.
Q. How are cancers different from one another?
A. Some cancers grow fast and spread fast while others grow very slowly. Cancers respond to treatments also in different ways. Some cancers respond better with surgery and some with radiotherapy or different groups of drugs including chemotherapy. Some respond better when treatment modalities are given in combination.
Q. Probable reasons for developing cancers?
A. While definite causative agents have been identified for certain cancers (e.g: Tobacco smoke for lung cancer, Human papilloma virus infection for cervical cancer) there are no definitive causative agents for a majority of cancers.
Q. Risk factors – what are they?
A.risk factor is something which increases a person’s chance of getting a disease. There are known risk factors which increase the chance of developing a cancer. In most instances it is not a single risk factor responsible for the development of a cancer but a combination of different risk factors (multifactorial).. Of these, there are factors which you can change or modify (modifiable) and some cannot be changed or modified (nonmodifiable).
Modifiable risk factors
Smoking - Tobacco smoke is made up of thousands of chemicals, including at least 70 which are known to cause cancer. Following cancers can occur due to tobacco smoke:
Lung, oral, laryngeal, oesophageal, bladder, pancreatic, liver, kidney, colon, rectum and cervical cancers are some. Breathing in other people’s smoke, called passive smoking, also can cause cancers.
Smokeless tobacco/arecanut – it has been scientifically proven that the areca nut and smokeless tobacco in the betel quid contain several carcinogens. The chemical Arecoline in the areca nut and several other carcinogens in the smokeless tobacco are responsible for developing oral cancers in betel chewers. This is one of the main reasons for the high incidence of oral cancers in South East Asian countries including Sri Lanka.
Alcohol – alcohol consumption is positively associated with the development of various cancers including oral, laryngeal, oesophageal, vocal cord, liver and breast cancers. Cancer risk increases with the amount and frequency of drinking. It has also been proved that people who use both alcohol and tobacco (Smoking/smokeless) have a greater risk of developing cancers than people who use either alcohol or tobacco.
Unhealthy dietary habits – Research has found that the people consuming plant foods are at a lower risk of developing cancers than those who consume animal foods. Studies have also shown that people consuming more vegetables and fruits have a less chance of developing colo rectal cancers. Consumption of high fat diets can increase the risk of developing breast, prostate, uterine, ovarian and colon cancers. It is advisable to limit the daily consumption of foods containing fat so that only less than 30% of daily calorie requirement is supplemented by fat.
Animal food – Red meat such as beef, mutton and pork, processed foods (sausages, ham, bacon), grilled and meat prepared under high temperatures are also known to increase the chance of developing cancers of the digestive tract.
Aflatoxin - a toxin released by certain fungi which can contaminate crops while in the field, at harvest and during storage can cause liver cancer.
Artificial flavours used to enhance the taste of the food and other preservatives and colouring products may also act as carcinogens. Hence, it is advisable to select food items prepared adhering to proper standards and guidelines.
Q. Is being overweight and obese also risk factors?
A. Yes. Overweight and obesity are risk factors for many cancers. E.g: breast cancer, colon, oesophageal, uterine, ovarian, renal, pancreatic, gall bladder and prostate cancers.
Q. Lack of regular physical exercise - what role does it play?
A. Regular physical exercises prevent many cancers including colo rectal, breast and uterine cancers. Regular physical exercise indirectly helps prevent cancers by reducing body weight, reducing circulating hormones, especially, oestrogen.
Q. Environmental carcinogens- what are they?
A. Any substance that causes cancer is known as carcinogen. It does not mean that just exposing to a carcinogen would cause cancer, 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. There are many scientifically proven environmental carcinogens, some of them are:
Arsenic, Asbestos, Benzene, Benzidine, Beryllium, Cadmium, coal tar, Crystalline silica, Formaldehyde, second hand tobacco smoke, Vinyl chloride, wood dust, leather dust, ultra violet radiation.
Radiation – Radiation of certain wavelength called ionising radiation has enough energy to damage DNA in the cells and initiate causation of cancer.
Ionising radiation includes Radon, X rays, gamma rays, CT scan, PET scan, Radiotherapy and other high energy radiation. However, the risk of cancer from the medical procedures is very small and the benefit of having them when necessary is always greater than the risk.
Infectious agents – certain microorganisms including viruses, bacteria and parasites can also cause cancer or increase the chance of developing cancer.
eg:
Human papilloma virus – cancer uterine cervix
Hepatitis B and Hepatitis C – liver cancer
Human Immunodeficiency virus (virus causing AIDS)
Q. How many of the cancers you mentioned are preventable and how?
A. About 30 -35% (1/3) of all cancers can be prevented by avoiding possible risk factors and choosing a healthy lifestyle.
Q. Symptoms?
A. Following are some suggestive symptoms and signs of possible cancers. However, they are not specific to cancers; they can be found in non-cancerous disease conditions as well but need further investigations to exclude cancer.
· Prolonged cough / coughing with blood
· Prolonged hoarseness of voice
· A sore/wound that does not heal
· Sudden change or growth of a lump, wart or a nevus
· Thickening or a lump in the breast or elsewhere
· Indigestion or difficulty in swallowing
· Frequent fever, pallor or unexpected loss of weight
· Passing blood- or blood-stained stools
· Unusual bleeding or discharge
Q. Will early detection result in better outcome?
A. Early detection of cancer increases the chances for successful treatments. A significant proportion of cancers can be cured if detected early.
Q. Your message in brief to the public?
A. There is no single way to prevent all cancers. But by choosing healthy lifestyles you can lower your risk of some cancers. Of all cancers about 1/3 can be prevented by adhering to a healthy lifestyle.