Will I get cancer? - Daily Nation

A look at the science and how to lower your risk


Will I get cancer?

As a Kenyan, you have 14 per cent risk of getting cancer before the age of 75.

For the past five years, cancer has been the third leading cause of death in Kenya, with numbers from last year’s Economic Survey showing that in 2017, 16,953 people died of cancer, up from 13,720 deaths in 2013.

Statistics from the World Health Organisation paint an even grimmer picture, with the Globocan 2018 report, showing that 33,978 Kenyans died of cancer in 2018.

Data compiled from the Eldoret and Nairobi Cancer registries, showed that the most common cancers in Kenya are breast, cervical, oesophageal and colorectal (bowel), with the most fatal being oesophageal and cervical cancer, which accounted for 14 per cent and 10 per cent of cancer deaths, respectively. Other fatal cancers were those of the stomach, prostate, bowel and liver.

While cancer is often seen as a disease of age (cells get damaged with age), In Kenya, six out of 10 people who have cancer are under the age of 70.

Further, the National Cancer Control Strategy (2011-2016), estimates that that a Kenyan has a 14 per cent risk of getting cancer before age 75, and a 12 per cent risk of dying from cancer before the same age.

For men, the most common cancers are prostate (15 per cent), oesophagus (12 per cent), colorectal/bowel (six per cent), Kaposi sarcoma (six per cent) and non-Hodgkin lymphoma; while for women, the most common cancers are breast (21 per cent), cervical (18 per cent), oesophageal (seven per cent), colorectal (four per cent), and stomach (four per cent).

EXPOSURE TO CARCINOGENS

There are some aspects of life that predispose people to cancer in ways we have no control over, such as age and genetics.

The longer you live, the more you are exposed to cancer-causing substances (carcinogens), and the more likely your cells are to get damaged and change in ways associated with cancer.

Then there are is the family history factor. If a close relative in your family had breast cancer, for instance, you might have inherited a higher risk of getting that cancer, but that doesn’t mean that you will definitely get cancer; it just means that if you carry the breast cancer gene, you are more likely to develop breast cancer than women with normal breast cancer risk.

Which brings us to the question, can we prevent cancer?

To some extent. While some risks such as age and genes cannot be modified, a third of cancer cases can be prevented by reducing exposure to the risks that make people susceptible to cancer.

These risks include tobacco (the largest single modifiable risk), obesity, physical inactivity, infections, alcohol, environmental pollution, occupational carcinogens and radiation.

When you maintain a healthy weight, adopt a healthy diet, incorporate regular physical activity to your life, reduce alcohol intake and avoid tobacco, you will have a lower risk of getting cancer than someone who leaves these things to chance.

How do Kenyans fare as far as these risks that they can do something about are concerned?

Avoiding tobacco: More than one in 10 Kenyans (13 per cent) report that they smoke or use tobacco, with one in four men (25 per cent), and less than one per cent of women reporting that they smoke.

A 2015 survey on risk factors for non-communicable diseases, including cancer, found that those who smoke daily, puff seven sticks on average, and that the mean age of starting smoking is 21 years.

Cigarettes are called cancer sticks for a reason – tobacco smoke contains at least 80 cancer-causing substances and is responsible for 22 per cent of cancer deaths. And it is not just the smoker who is at risk, inhaling second-hand smoke is just as risky.

When smoke is inhaled, the harmful chemicals pass from the lungs into the bloodstream and into the rest of the body, where they wreak havoc on cells.

The earlier one starts smoking, the more cigarettes smoked and the longer one keeps smoking, the higher the risk of lung, mouth and other cancers.

This is why the world’s tobacco control strategies (that include zero advertising, higher tobacco taxes, plain packaging, warning signs on packaging, and smoking only in designated smoking zones) came into being.

Maintaining healthy weight: Being overweight or obese (with body mass index above 25) has been linked to increased risk for 12 cancers, including bowel, pancreatic, endometrial, oesophageal, liver, kidney, gall bladder, breast, ovarian and thyroid cancer.

While overall obesity rate is six per cent, 33 per cent of women are overweight, while 10 per cent are obese. Excess weight is thought to contribute to cancer through inflammation, which can cause DNA damage, leading to cancer.

Moreover, fat tissue is linked to higher levels of oestrogen, associated with breast, endometrial and ovarian cancers, especially in postmenopausal women.

Healthier diet: Diets high in red meat, processed meats (sausages, bacon, salami, ham, frankfurters), salted foods and low in fruits and vegetables have been linked to colorectal cancer.

The World Health Organisation classifies processed meat as a group 1 carcinogen, while red meat (beef, pork, lamb, mutton, goat) is classified in group 2A (probably causes cancer).

Eating about three-quarter kilos of red meat a week increases your risk, as does every 50 grammes of processed meat consumed per day. The risk in red meat has been linked to processing and cooking (especially barbecuing and pan-frying), which causes carcinogenic chemicals such as N-nitroso compounds and polycyclic aromatic hydrocarbons (PAH), to form.

Moreover, nitrite and nitrate preservatives used on processed meat produce the same harmful N-nitroso compound.

The World Health Organisation’s classification of red meat as probably carcinogenic, means that other explanations for the observation that linked it to cancer, could not be ruled out. The recommendation then, is not to go vegetarian, but to reduce red meat intake to about a quarter kilo a week, and substitute it with chicken, fish, eggs, beans, lentils and mushrooms.

Physical inactivity: Seventeen per cent of Kenyans report being inactive, with 15 per cent of men and 19 per cent of women reporting being inactive.

Physical activity works together with maintaining healthy weight and consuming a healthier diet, to reduce excess body fat and the cancer risks associated with it.

Being physically active, described as at least 150 minutes of moderate-intensity aerobic activity, 75 minutes of vigorous-intensity aerobic physical activity, or a combination, every week, can help reduce the risks of developing colon, breast and endometrial cancers.

Reducing alcohol intake: Men in Kenya take an average of 7.4 litres of pure alcohol, women take 1.3 litres, according to 2014 figures from the World Health Organisation. Alcohol increases the risk of bowel (colorectal) cancer, breast, mouth, pharynx and larynx (mouth and throat) cancer, oesophageal cancer, liver and stomach cancer. The more you drink, the higher the risk, though even moderate alcohol intake increases risk.

Infections: Viruses can cause changes in cells that make them more likely to be cancerous, as in the case of cervical cancer, which is caused by human papillomavirus infection. Hepatitis B and C virus can cause liver cancer and non-Hodgkin lymphoma, while the Epstein-Barr virus has been linked to lymphoma.

Helicobacter pylori infection, which causes inflammation of the stomach lining, has been linked to stomach cancer, while HIV/AIDS has been associated with Kaposi’s sarcoma.

Some of these infections can be prevented through vaccination. For instance, vaccinating children against the hepatitis B virus helps protect them against liver cancer, and while most children in Kenya have received the vaccine (83 per cent), a number who missed out remain unprotected.

For cervical cancer, vaccination against the human papillomavirus (HPV) which causes 99.7 per cent of cancer cases, has a protective effect. The HPV vaccine is usually given at age nine , before girls become sexually active, and exposed to the virus which is transmitted during sex.

The government has announced plans to vaccinate girls aged nine to 14 years from May to protect them against HPV infection.

Radiation: Prolonged and unprotected (without sunscreen) exposure to ultraviolet radiation from the sun can lead to skin cancer.

Exposure to ionising radiation from radon, x-rays, gamma rays and others may also increase the risk of cancer, especially for those who are exposed to radiation at work.

Screening: When cancer is identified early, there are higher chances that treatment will be successful, cheaper and with fewer side effects. Moreover, 30 per cent of treatable cancers can be cured if detected early.

However, in Kenya, eighty per cent of the cancers are caught at advanced stage. For some cancers, early detection begins with regular screening. For breast cancer, women are advised to conduct a monthly self breast exam to detect lumps, and to have a yearly clinical breast exam, with a yearly mammogram starting at age 45, in addition.

For cervical cancer, women should have their first test by age 30, and then have a regular exam every five years. There are also screening tests for prostate cancer and colorectal cancer.

Sources: Kenya Stepwise Survey for NCD Risk Factors; World Health Organisation; National Cancer Control Strategy; GloboCan 2018, National Cancer Institute (US)

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Signs and symptoms

Eighty per cent of reported cases of cancer are diagnosed at advanced stages, when very little can be achieved in terms of cure.

This has been attributed to the low awareness of cancer signs and symptoms, among other reasons. Some signs to watch out for:

  1. Unusual lumps or swelling that may be painless and increase in size
  2. Persistent coughing, breathlessness or difficulty swallowing
  3. Changes in bowel movements – constipation, diarrhoea or blood in stool
  4. Unexpected bleeding from the vagina or anus; blood in stool or urine or when coughing
  5. Unexplained and unintentional weight loss over a short period of time
  6. Fatigue. Extreme tiredness and severe lack of energy, usually with other symptoms
  7. Unexplained pain that comes or goes or unexplained ongoing pain
  8. New mole or changes in size, shape or colour of mole or skin. Mole that becomes crusty or bleeds or oozes
  9. Needing to urinate urgently, more frequently or unable to pass urine or pain when urinating
  10. Unusual changes in breast size, shape, feel, skin changes and pain

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How does cancer develop

The human body is made of a trillion of cells, which grow old and die, or get damaged and die, and are replaced by new cells.

When the mechanism that regulates normal cell growth and death works, cells grow and divide to form new cells as the body needs them, and die when the body doesn’t.

If some cells keep dividing without stopping (divide and grow out of control) and spread to surrounding tissues, that’s when cancer begins. The normal process has broken down and the abnormal takes over.

The abnormality happens because of changes in the cell’s genetic material, which cause a breakdown in the normal mechanism that regulates cell growth and death. These changes are caused by age or when genes interact with risk factors such as radiation, tobacco, aflatoxins, or viruses, among others.

In the abnormality and breakdown, old and damaged cells no longer die. They survive and new cells, without specific function, form when they are not needed.

These extra cells divide without stopping and may form growths called tumours (solid masses of tissue), though blood cancers do not. If the tumour is benign, it usually poses no harm, unless it is interfering with other body organs.

If it is malignant (cancerous), it can spread or invade nearby tissues. And as it grows, it spreads by breaking off, travelling through the blood or lymph system and making a new home in a location away from the original tumour.

There are more than 100 diseases characterised by uncontrolled growth and spread of abnormal cell, which we know as cancer, and they are categorised into several types based on where they begin.

Carcinoma begins in the skin or tissues that cover organs.

Sarcoma begins in bone, cartilage, fat, muscle blood vessels or other connective tissue.

Leukemia starts in blood-forming tissues such as bone marrow. Lymphoma and multiple myeloma begin in cells of the immune system.

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Carcinogens: Cancer-causing substances

Carcinogens are substances that change how a cell behaves, thereby increasing the chances of developing cancer.

The International Agency for Research on Cancer has listed more than 100 group 1 carcinogens, after evaluating the cancer causing potential of more than 900 substances.

Some of the substances are categorised in group 2A, which means they are probably carcinogenic, while those in group 2B are possibly carcinogenic.

Substances in group 3 are unclassifiable as carcinogenic, while those in group 4 are probably not carcinogenic. The following fall in the list of known carcinogens (group 1).

  1. Acetaldehyde (from consuming alcoholic beverages)
  2. Aflatoxins
  3. Alcoholic beverages
  4. Aluminium production
  5. Arsenic and inorganic arsenic compounds
  6. Asbestos (all forms) and mineral substances (such as talc or vermiculite) that contain asbestos
  7. Coal (indoor emissions from household combustion, gasification)
  8. Coal-tar (distillation, pitch)
  9. Engine exhaust, diesel
  10. Ethanol in alcoholic beverages
  11. Leather dust
  12. Outdoor air pollution
  13. Processed meat
  14. Salted fish (Chinese style)
  15. Tobacco smoking, smokeless, second-hand smoke
  16. Wood dust