3.4 Cancer

Introduction (ESG5Q)

Cancer is a group of diseases characterised by uncontrolled cell division which leads to growth of abnormal tissue. This means that a cancer is essentially a disease of mitosis. Cancer begins when a single cell is transformed, or converted from a normal cell to a cancer cell. Cancer cells grow and divide uncontrollably to form a mass of cancer cells called a tumour. As the tumours grow, they squash healthy cells, steal their nutrients and prevent them from working normally. Cancer cells differ from normal cells in a number of ways:

1. Cancer cells don't listen to signals to stop growing: Normal cells listen to signals from the body to stop growing and dividing. However cancer cells do not respond to signals from the body and keep on dividing.
2. Cancer cells grow new blood vessels: As the tumour grows larger, it begins to release proteins from the cell to attract new blood vessels. Blood vessels draw nutrients away from healthy cells and therefore starve them while allowing the growth of the tumour. The new blood vessels also enable cancer cells to enter the bloodstream and spread to other parts of the body.
3. Cancer cells spread around the body: Another feature of cancer cells is that they can spread around the body (metastasise). Tumours that have the ability to spread to other parts of the body are called malignant. Cancer cells can spread to surrounding tissues via the bloodstream or via the lymph system.

As previously mentioned, cancer cells are malignant which means they are able to invade tissues and spread to other parts of the body. Some tumours cannot spread to other tissues and are called benign tumours. Benign tumours are non-cancerous.

Types of cancers

Cancer can affect almost any tissue in the body. A list of some common cancers includes:

• Breast cancer
• Lung cancer
• Oesophageal cancer
• Leukaemia (blood cancer)
• Melanoma (skin cancer)

Causes of cancer (ESG5R)

Beliefs and attitudes concerning cancer (ESG5S)

There are some common misconceptions about cancer

• It is people's fault if they get cancer: Although there are ways to try and decrease your risk of getting cancer, it is not always possible. Cancer is caused by random mutations in DNA, and sometimes people get cancer purely by chance.
• Cancer is a death sentence: Sometimes when the cancer is very advanced there is not much to be done to save a person, but there are many cancers that respond well to treatment when detected early. Depending on the type and the stage of the cancer, people can survive cancer and go on to live healthy happy lives.
• If someone in your family has cancer you might get it too: Although there are some cancers that are more common in certain families due to an inherited genetic mutation, a family history of cancer does not mean than you will also get cancer. However, if a certain type of cancer runs in your family it is good to see a doctor for regular screenings.
• Cancer is contagious and you can catch it from others: Cancer cannot be spread from one person to another.
• A positive attitude can cure cancer: There is plenty of evidence that a positive attitude can help a person with cancer feel better and stay healthier for longer, however it is not the only factor that determines whether someone will recover or not.
• Only old people get cancer: Although cancer is more common in older people, children and babies can also get cancer. Leukaemia is a common childhood cancer.
• Only females get breast cancer: Although breast cancer is more common in females, males can also get breast cancer.
• Only pale people get skin cancer: Although skin cancer is more common in people with light skin (melanin, the pigment that makes your skin dark is also protective), people with dark skin can also get skin cancer.

Cancer treatment (ESG5T)

Cancer is usually treated using conventional methods that are based on Western evidence-based medicine. However, many people like to use a holistic approach to treat cancer, and therefore also use indigenous methods to manage symptoms. The following sections will introduce some conventional and indigenous methods for treating cancer.

Conventional methods (ESG5V)

The conventional medical approaches to treating cancer include radiation therapy, chemotherapy and surgery.

1. Radiation therapy

Radiation therapy is the use of high energy electromagnetic radiation to kill cancer cells. The radiation damages the DNA inside the cancer cells, causing them to die. Radiation damages healthy cells too; therefore the treatment is targeted directly at the tumour.

2. Chemotherapy

Chemotherapy is the use of special drugs to treat cancer. Most chemotherapy drugs are cytotoxic (toxic to cells) and work by damaging the cell's DNA. Chemotherapy specifically tries to prevent cell division, and so it is very toxic to cancer cells which are characterised by uncontrolled cell division. However, unfortunately, these drugs also damage healthy cells that divide rapidly, such as blood cells and cells found in hair follicles, lining the mouth, stomach and intestine and the skin. Because of the damage to rapidly dividing healthy cells, the side-effects from chemotherapy include hair loss, mouth ulcers, nausea, sores, anaemia and infections due to a lowered immune system.

A combination of drugs which act in slightly different ways to halt cell division are often given together. Patients often receive chemo according to a regime, where they receive doses of chemo for a time period, followed by a break that allows the healthy cells in their bodies to recover. Usually a chemo regime consists of a few cycles of chemotherapy doses and breaks for recovery.

3. Surgery

Surgery involves removal of either the whole tumour, part of the tumour and sometimes even whole organs or body parts. When a small section of the tumour is removed this is called biopsy. Frequently surgery is followed by either radiation therapy or chemotherapy and sometimes both.

Indigenous methods (ESG5W)

In addition to the conventional methods of treatment described, many people seek alternative forms of treatment. In South Africa, individuals commonly use traditional medicines like African Potato (Hypoxis hemerocallidea) and "Cancer bush" (Sutherlandia frutescens), to boost the immune system while undergoing conventional treatments.

The cancer bush (Sutherlandia frutescent, uNwele) is an indigenous medicinal plant which the Khoi and Nama people used to wash wounds and to reduce high fevers. The early settlers also used this bush to treat chicken pox, eye problems and internal cancers. Cancer patients often lose weight and suffer muscle wastage and a tonic made from this bush may improve appetite, decrease anxiety and slow down the weight loss.

Prevention of cancer (ESG5X)

The risk of developing any one of the many types of cancer can be reduced by eating a healthy diet, exercising regularly and avoiding smoking and alcohol. The sooner cancer is detected the easier it is to treat. Therefore it is also advisable for people to get regular screenings. Here are some guidelines to lower your risk of developing cancer:

• Avoid smoking: avoid smoking cigarettes and avoid enclosed areas where people smoke (this avoids passive smoking).
• Avoid alcohol: limit alcohol, as excessive alcohol consumption can lead to increased risk of oesophageal, liver and breast cancer.
• Healthy diet: avoid (or limit) very processed foods or burnt food, both of which contain carcinogens.
• Regular physical activity: partake in physical activity on a regular basis. Regular exercise improves general health and helps one to maintain an ideal body weight, thereby lowering the risk of many cancers.
• Sun protection: limit exposure to the sun and damage by ultraviolet radiation. Try to stay out of the sun between 10 am and 3 pm, wear high SPF sunscreen that protects against UVA and UVB, and wear a hat, sunglasses, and protective clothing.
• Regular screenings: cell or tissue abnormalities can sometimes be detected before they become cancerous. Regular pap smears can prevent cervical abnormalities developing into cervical cancer and getting moles and skin conditions checked can prevent dangerous skin cancer. Cancer can also be detected at the early treatable stages by going for regular mammograms (for breast cancer), or prostate exams (for prostate cancer) as adults. The frequency of these exams will be age and risk dependent.

Ways to decrease cancer risk
Avoid smoking	Avoid excessive alcohol consumption	Eat a healthy diet
Regular physical activity	Sun protection	Regular screenings

Cancer and smoking

Aim

Investigating the relationship of smoking and cancer.

Instructions

Look at the graph below and answer the questions that follow:

Questions

1. In what year was the first incidence of lung cancer seen in male smokers?
2. How many years was this after the introduction of cigarettes?
3. In which year did the average number of cigarettes smoked per year reach a peak?
4. Approximate how many years it takes most male smokers to develop cancer? Clue: Compare the number of years seen between the two line graphs for 1000, 2000, 3000 and 4000 cigarettes per year. Add the years together and divide by 4 to get the average time (in years) taken for smokers to develop cancer.
5. What can you say about the shape of the two graphs? Do they look similar or different? What does this mean?
6. What was the death rate from lung cancer in 1950? Express your answer as a percentage and show your working.
7. Suggest a reason why the number of cigarettes smoked shows a decrease after 1945.