Cancer (Grade 10 NSC Matric Life Sciences): Revision Notes

Cancer

Introduction

Cancer is a serious group of diseases that affects millions of people worldwide. Understanding what cancer is and how it develops is essential for making informed decisions about health and lifestyle choices.

Cancer occurs when the normal process of cell division goes wrong. Instead of cells dividing in a controlled way to help our bodies grow and repair tissues, cancer represents uncontrolled cell division that leads to the growth of abnormal tissue. This makes cancer essentially a disease caused by mutations in genes that control the cell cycle.

The cancer process begins when a single normal cell becomes transformed or converted into a cancer cell. Once this transformation happens, the cell starts to behave very differently from healthy cells. These cancer cells then multiply uncontrollably, forming a mass of abnormal cells called a tumour.

As tumours grow larger, they begin to interfere with the normal functioning of healthy tissues around them. They compete with healthy cells for nutrients and space, which can prevent normal tissues from working properly.

Characteristics of cancer cells

Cancer cells behave very differently from normal, healthy cells in our bodies. There are three key ways that cancer cells differ from normal cells:

1. Cancer cells don't listen to signals to stop growing

Normal cells in our body receive chemical signals that tell them when to stop dividing and growing. This is important because it prevents tissues from growing too large. However, cancer cells have lost the ability to respond to these "stop" signals. They continue dividing and growing even when they should stop, leading to the formation of tumours.

2. Cancer cells grow new blood vessels

As a tumour becomes larger, it needs more nutrients to continue growing. Cancer cells release special proteins that signal the body to grow new blood vessels towards the tumour. These new blood vessels bring nutrients and oxygen to feed the growing cancer cells. This increases competition for nutrients and oxygen in surrounding tissues, which can cause healthy cells to become weak or die.

3. Cancer cells spread around the body

One of the most dangerous features of cancer cells is their ability to spread to other parts of the body through a process called metastasis. Cancer cells can break away from the original tumour and travel through the bloodstream or lymphatic system to form new tumours in different organs or tissues.

Benign vs malignant tumours

Not all tumours are the same. There are two main types of tumours: benign and malignant, and understanding the difference between them is crucial.

Benign tumours are non-cancerous growths that remain in one location. These tumours:

• Stay contained within their original location
• Do not invade neighbouring tissues
• Cannot spread to other parts of the body
• Are generally not life-threatening
• Can often be removed completely with surgery

Malignant tumours are cancerous growths that can spread throughout the body. These tumours:

• Can invade and damage neighbouring tissues
• Have the ability to metastasise (spread) to distant parts of the body
• Enter the bloodstream and lymphatic system to reach new locations
• Can form secondary tumours in different organs
• Are much more dangerous and difficult to treat

Types of cancer

Cancer can develop in almost any tissue or organ in the human body. Some of the most common types of cancer include:

• Breast cancer - affects breast tissue
• Lung cancer - develops in lung tissue
• Oesophageal cancer - affects the tube connecting the throat to the stomach
• Leukaemia - a type of blood cancer affecting white blood cells
• Melanoma - a serious form of skin cancer

Causes of cancer

Cancer is caused by substances and factors called carcinogens. These carcinogens damage the DNA inside our cells, which contains the instructions that control how cells grow and divide. When DNA is damaged, cells can lose their ability to function normally and may become cancerous.

There are several different types of carcinogens that can increase the risk of developing cancer:

• Cigarette smoke - contains many harmful chemicals
• Radiation (including X-rays and radioactive materials)
• UV light - from sun exposure and tanning beds
• Some chemicals in processed foods - certain preservatives and substances may increase cancer risk
• Dangerous chemicals - in the workplace or environment

It's worth noting that viruses can also increase cancer risk. For example, Human Papillomavirus (HPV) can increase the risk of cervical cancer, and Hepatitis B can increase the risk of liver cancer.

Common misconceptions about cancer

There are many false beliefs about cancer that can cause unnecessary fear or prevent people from seeking proper treatment. Here are some important facts to clear up common misconceptions:

Additional important facts to remember:

• Cancer is not contagious - it cannot be spread from person to person, although some infections that increase cancer risk can be transmitted
• Cancer affects all ages - while more common in older adults, people of all ages, including children and young adults, can develop cancer
• Men can get breast cancer too - although much more common in women, men can also develop breast cancer
• All skin types can develop skin cancer - while people with lighter skin are at higher risk, people with darker skin can also develop skin cancer

Cancer treatment

There are several approaches to treating cancer, ranging from conventional medical treatments to traditional remedies that some people use alongside modern medicine.

Conventional methods

Modern medicine offers three main approaches to cancer treatment:

1. Radiation therapy

Radiation therapy uses high-energy electromagnetic radiation to kill cancer cells by damaging their DNA. The radiation is carefully targeted at the tumour to minimise damage to healthy cells surrounding it. This treatment is particularly effective because cancer cells divide rapidly and are often more sensitive to radiation damage than normal cells.

2. Chemotherapy

Chemotherapy involves using special drugs that are toxic to rapidly dividing cells. Since cancer cells divide uncontrollably, they are particularly vulnerable to these drugs. However, chemotherapy also affects other rapidly dividing healthy cells in the body, such as those in hair follicles, the digestive system, and bone marrow.

3. Surgery

Surgical treatment involves physically removing tumours from the body. This might involve removing part of a tumour, the entire tumour, or sometimes whole organs or body parts if necessary. When only a small section is removed for testing, this procedure is called a biopsy. Surgery is often combined with radiation therapy or chemotherapy for the most effective treatment.

Indigenous methods

In addition to conventional treatments, some people use traditional medicines to support their immune system during cancer treatment. In South Africa, people commonly use plants such as:

• African Potato (Hypoxis hemeroallidea) - believed to boost immune system function
• Cancer bush (Sutherlandia frutescens) - traditionally used by the Khoi and Nama people for various health conditions

The cancer bush has historically been used to treat wounds, reduce fever, and address various internal health issues. Some cancer patients report that extracts from this plant may help improve appetite and general well-being during conventional treatment.

Prevention of cancer

While not all cancers can be prevented, there are many lifestyle choices that can significantly reduce your risk of developing various types of cancer. The earlier cancer is detected, the more treatable it becomes, so prevention and early detection are crucial.

Here are key strategies for reducing cancer risk:

Avoid smoking Smoking cigarettes is one of the leading preventable causes of cancer. It's also important to avoid areas where others are smoking (passive smoking) as this can also increase cancer risk.

Limit alcohol consumption Excessive alcohol intake increases the risk of several cancers, including oesophageal, liver, and breast cancers. Limiting alcohol consumption can significantly reduce these risks.

Maintain a healthy diet Eating a balanced diet rich in fruits and vegetables while avoiding heavily processed foods and burnt foods can help reduce cancer risk. Some processed foods may contain chemicals that increase cancer risk if consumed in large amounts.

Exercise regularly Regular physical activity helps maintain a healthy body weight and improves overall health, which can lower the risk of developing various cancers.

Protect yourself from sun exposure Limit time in direct sunlight, especially between 10 am and 3 pm. Use high SPF sunscreen that protects against both UVA and UVB rays, and wear protective clothing, hats, and sunglasses.

Get regular medical screenings Early detection can make cancer much more treatable. Regular screenings can identify abnormalities before they become cancerous or catch cancer in its early, most treatable stages. Examples include regular mammograms for breast cancer and pap smears for cervical cancer.

Smoking and cancer relationship

The relationship between smoking and cancer provides a clear example of how lifestyle choices affect cancer risk. Research has shown a strong correlation between cigarette consumption and lung cancer rates.

This data has been crucial in public health campaigns encouraging people to quit smoking and in implementing policies to reduce smoking rates in the population.