Introduction

This booklet is for you if you have or someone close to you has Acute Lymphoblastic Leukaemia

If you are a patient your doctor or nurse may wish to go through the booklet with you and mark sections that are particularly important for you.

What is cancer?

The organs and tissues of the body are made up of tiny building blocks called cells. Cancer is a disease of these cells.

Cells in different parts of the body may look and work differently but most reproduce themselves in the same way. Cells are constantly becoming old and dying, and new cells are produced to replace them. Normally, cells divide in an orderly and controlled manner. If for some reason the process gets out of control, the cells carry on dividing, developing into a lump which is called a tumour.

Not all tumors are cancerous. Tumors that aren't cancer are called benign. Benign tumors can cause problems -- they can grow very large and press on healthy organs and tissues. But they cannot grow into (invade) other tissues. Because they can't invade, they also can't spread to other parts of the body (metastasize – see below). These tumors are almost never life threatening.

Cancer is the name given to a malignant tumour. Doctors can tell if a tumour is benign or malignant by examining a small sample of cells under a microscope. This is called a biopsy.

A malignant tumour consists of cancer cells that have the ability to spread beyond the original area. If the tumour is left untreated, it may spread into and destroy surrounding tissue. Sometimes cells break away from the original (primary) cancer. They may spread to other organs in the body through the bloodstream or lymphatic system.

The lymphatic system is part of the immune system - the body's natural defence against infections and diseases. It is a complex system made up of organs, such as bone marrow, the thymus, the spleen, and lymph nodes. The lymph nodes (or glands) throughout the body are connected by a network of tiny lymphatic ducts.

Cancer cells often travel to other parts of the body, where they begin to grow and form new tumors that replace normal tissue. This process is called secondary cancer or metastasis. It happens when the cancer cells get into the bloodstream or lymph vessels of our body.

No matter where a cancer may spread, it is always named for the place where it started. For example, breast cancer that has spread to the liver is still called breast cancer, not liver cancer. Likewise, prostate cancer that has spread to the bone is metastatic prostate cancer, not bone cancer.

Different types of cancer can behave very differently. For example, lung cancer and breast cancer are very different diseases. They grow at different rates and respond to different treatments. That is why people with cancer need treatment that is aimed at their particular kind of cancer.

It is important to realise that cancer is not a single disease with a single type of treatment. There are more than 200 different kinds of cancer, each with its own name and treatment.

Types of cancers

Carcinomas

The majority of cancers, about 85% (85 in a 100), are carcinomas. They start in the epithelium, which is the covering (or lining) of organs and of the body (the skin). The common forms of breast, lung, prostate and bowel cancer are all carcinomas.

Carcinomas are named after the type of epithelial cell that they started in and the part of the body that is affected. There are four different types of epithelial cells:

• squamous cells - that line different parts of the body, such as the mouth, gullet (oesophagus), and the airways
• adeno cells - form the lining of all the glands in the body and can be found in organs such as the stomach, ovaries, kidneys and prostate
• transitional cells - are only found in the lining of the bladder and parts of the urinary system
• basal cells - that are found in one of the layers of the skin.

A cancer that starts in squamous cells is called a squamous cell carcinoma. A cancer that starts in glandular cells is called an adenocarcinoma. Cancers that start in transitional cells are transitional cell carcinomas, and those that start in basal cells are basal cell carcinomas.

Leukaemias and lymphomas

These occur in the tissues where white blood cells (which fight infection in the body) are formed, i.e. the bone marrow and lymphatic system. Leukaemia and lymphoma are quite rare and make up about 6.5% (6.5 in 100) of all cancers.

Sarcomas

Sarcomas are very rare. They are a group of cancers that form in the connective or supportive tissues of the body such as muscle, bone and fatty tissue. They account for less than 1% (1 in 100) of cancers.

Sarcomas are split into two main types:

• bone sarcomas - that are found in the bones
• soft tissue sarcomas - that develop in the other supportive tissues of the body.

Others forms of cancer
Brain tumours and other very rare forms of cancer make up the remainder of cancers.

Blood – Structure and Function

Blood is made up of blood cells suspended in liquid called plasma. There are three
main types of blood cells:

• red cells, which carry oxygen around the body
• platelets, which help the blood to clot and control bleeding
• white cells, which fight infection.

How blood cells are made?

Blood cells are made in the bone marrow, a spongy material inside the bones.
Normally millions of new blood cells are made every day to replace old and worn out blood cells.

All blood cells begin as a special type of cell called a stem cell. There are two types:

• Lymphoid stem cells make white blood cells called lymphocytes.
• Myeloid stem cells make all the other types of blood cells: red cells, platelets and white cells called granulocytes.

Stem cells make new blood cells by copying themselves and then dividing to form two new cells. To begin with the new blood cells made from stem cells are immature. They don't look like red cells, white cells or platelets and they can't do the jobs in the body that they can do. These immature cells are called blast cells. Normally blast cells stay in the bone marrow until they have matured into red cells, white cells or platelets.

The bone marrow

Blood is made in the bone marrow. This is a spongy material that's found in the middle of your bones, particularly in your pelvis and backbone (spine).

All your blood cells are made from special cells called stem cells. The bone marrow gives the stem cells a safe place to divide and grow to form fully developed (mature) red cells, platelets and white cells.

These are then released into your blood to carry out different functions:

• Red blood cells contain haemoglobin, which carries oxygen from your lungs to all the cells in your body.
• White blood cells fight and prevent infection. There are several types of white cell. The two most important types are neutrophils and lymphocytes.
• Platelets are very small cells that help the blood to clot and prevent bleeding and bruising.
  

The levels of these cells in your blood are measured in a blood test called a full blood count (FBC). The figures below are a guide to the levels usually found in a healthy person.

These figures can vary from hospital to hospital. Your doctor or nurse will be able to tell you what levels they use. They can also be slightly different in people of African-Caribbean and Middle Eastern origin.

The figures might look complicated when they're written down, but in practice they are used in a straightforward way. For example, you'll hear doctors or nurses saying things like 'your haemoglobin is 14' or 'your neutrophils are 4'. Many people with CML soon get used to these figures and what they mean.

Figure: The lymphatic system

White blood cells

There are two main types of white blood cell: lymphocytes and myeloid cells (also known as granulocytes). These cells work together to fight infection. Some myeloid cells and lymphocytes only live for a few days, so the bone marrow is constantly making new cells to replace the old ones in the blood.

The bone marrow normally makes millions of blood cells every day. When they're mature enough to leave the bone marrow, the white blood cells are released into the bloodstream to circulate around the body. Lymphocytes, unlike the myeloid cells, also circulate in the lymphatic system.

The lymphatic system is one of the body's natural defences against infection. It's a complex system made up of lymphatic organs such as bone marrow, tonsils, the spleen and a collection of small lymph nodes (sometimes called glands).

The lymph nodes produce lymph, a milky-looking fluid containing lymphocytes. The lymph nodes are found mainly in the neck, armpit and groin and are connected by a network of tiny lymphatic vessels.

The tonsils, liver, spleen (which breaks down old blood cells) and bone marrow also contain lymphocytes. There are two main types of lymphocyte: B-cells and T-cells.