Cancers are caused by uncontrolled cell division and growth. Initially learners will need to be told what cancer is, and how cancer cells differ from normal cells. They will also need to understand how a tumour can be benign or malignant. The key characteristic of a malignant tumour is the ability to metastasise to other organs via the bloodstream or lymph.
A brief discussion of the causes of cancers with learners is necessary. Teachers should emphasise that learners can control some of the behaviours that cause cancer. Finally teachers should address the beliefs and attitudes of various communities and groups about cancer. This is an excellent opportunity to hold a class discussion, and we encourage teachers to invite questions and stories from learners and not to focus on only some of the common misconceptions outlined in this book.
The various treatments of cancer including traditional, other non-conventional treatments also need to be discussed. The advancement of medical biotechnology e.g. radiotherapy, chemotherapy needs to be introduced to the learners, but no detail is required.
Websites to visit
Short video from the Khan Academy: "Cancer : An introduction to cancer and how it is the by-product of broken DNA replication"
Inside Cancer (very good summary of cancer and related issues) and
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:
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.
Figure 3.4: Benign tumours are unable to metastasise. Malignant tumours are able to metastasise away from the original tumour site.
Types of cancers
Cancer can affect almost any tissue in the body. A list of some common cancers includes:
Cancers often spread to different organs, however it remains the same type of cancer as the original cancer, it is simply referred to as a metastasis. Therefore melanoma (skin cancer) that spreads to the liver is not liver cancer, but a melanoma metastasis to the liver.
Cancer is caused by agents called carcinogens. Carcinogens cause cancer by damaging DNA which can no longer code for the important regulatory functions of the cell cycle. Some viruses can also increase the likelihood of getting certain types of cancer. Human papillomavirus (HPV), the disease that causes genital warts, can increase a woman's risk of cervical cancer, and infection with hepatitis B or C increases the risk of liver cancer. In addition, some people are born with genetic mutations that they have inherited from their parents that increase their chances of getting cancer. However a genetic predisposition to cancer does not mean that you will get cancer. If you have a family history of cancer it simply means it is more important for you to limit your exposure to carcinogens. Examples of some carcinogens include:
Carcinogens can cause a DNA mutation that occurs in one of several genes that normally function to control growth. E.g the BRCA1, or "Breast Cancer Gene". The BRCA1 gene normally functions to suppress tumour formation; but if a genetic mutation occurs it does not work properly, and tumour formation can begin. Mutations in this gene does not mean that a person will develop breast cancer, but they have an increased risk for breast cancer.
There are some common misconceptions about cancer
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.
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.
Figure 3.5: Radiation therapy uses high energy electromagnetic radiation to kill cancer cells.
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.
Figure 3.6: Chemotherapy is the use of chemical treatments targeted at cancer cells.
Chemotherapy targets cells that are rapidly dividing so patients undergoing chemotherapy often lose their hair and feel nauseous (because the intestinal lining in the stomach is killed).
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.
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.
![]() Figure 3.7: African potato is used as a remedy against cancer in some forms of traditional medicine. | ![]() Figure 3.8: "Cancer bush" used in certain forms of indigenous treatments for cancer. |
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.
Some people are born with mutations in genes involved in regulating the cell cycle. For example in colorectal cancer (cancer of the colon) some people have mutations in the mismatch repair genes. Mismatch repair genes fix damaged DNA. If they are not working properly it enhances a person's risk of getting cancer. People who have a close family member who got cancer when they were under 40 years of age need to be regularly tested for damaged genes.
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:
Ways to decrease cancer risk | ||
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Avoid smoking | Avoid excessive alcohol consumption | Eat a healthy diet |
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Regular physical activity | Sun protection | Regular screenings |
Watch this video about how our bodies help protect us from cancer despite the constant bombardment of environmental carcinogens.
Investigating the relationship of smoking and cancer.
Look at the graph below and answer the questions that follow:
Figure 3.9: Graph showing correlation between smoking and lung cancer (courtesy NHI).
Cancer and Smoking
Approximately 1918-1919 (1)
Approximately 18 years - 19 years (1)
Around 1945 (accept one year either way) (1)
The average is about 20 years. (4)
They are very similar in shape (where the smoking graph shows an increase in the average number of cigarettes smoked per year, the incidence of lung cancer increased), but are approximately 20 years apart. The fact that the two lines converge (get closer together) near the top, indicates that the more cigarettes one smokes, the less time it takes for lung cancer to develop. (3)
125 deaths per people (3)
Fewer people were smoking after the Second World War – it became widely known that smoking damages one’s health, so they stopped / gave up. The ones who were still smoking may also have decided to cut down / reduce the number they smoke. (2)
Aim
To research and present information on one of the human cancers
Resources required
Instructions
Using the resources available, you are required to research ONE of the cancers affecting humans. In particular you are required to:
Research on Cancer
This can be an extremely complex research task, or one that is relatively easily managed, depending on how the teacher approaches the task. It is recommended that the following guidelines be used:
Major causes: Describe two to four causes. It is recommended that learners list these in order of importance. Each cause should be approximately one short paragraph of about 4 lines. More marks will be allocated to four, rather than two causes.
Common beliefs / attitudes: Find and briefly describe three commonly held beliefs about the causes, treatment, progression and origins of cancer. These do not have to be accurate, but they do have to be substantiated. Learners are required to indicate sources for where these beliefs / attitudes were found. It is also expected that learners indicate whether these are in fact accurate or incorrect.
Treatment:Briefly describe two forms of treatment for the specific type of cancer that was researched. It is not expected that learners name specific drugs or give dosages of radiation or drugs.
Prevalence: Sources must be acknowledged when quoting statistics. Teachers are to check that learners give stats for the SPECIFIC type of cancer they researched, not for cancers in general. Teachers should guard against plagiarism in copying pie charts and other graphs directly off the Internet – learners should be asked to give their sources if doing so is deemed acceptable by the staff, or they may be required to hand in only HAND DRAWN graphs and other charts. It is suggested that learners be told SPECIFICALLY what graphs to hand in, e.g. you MUST have at least one graph to support your research, but you may not submit more than three.
Section | 5 Excellent. Clear, detailed, neat | 4 Good. Well-researched, less detail | 3 Average. Tried, but made errors | 2 Not so good. Some gaps in knowledge | 1 Very weak. Very few facts | 0 Not done / no proof given |
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