How can cancer kill you?

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Not all cancers cause death

Firstly, it's important to remember that not all cancers cause death. Overall, 50 out of every 100 (50%) people diagnosed with cancer in England and Wales live for 10 years or more. Cancer survival is improving and has doubled in the last 40 years in the UK.

Cancer at an early stage doesn't usually kill you. A lot of effort is put into early diagnosis when treatment is likely to work best.

How does cancer cause death?

How cancer causes death depends on your cancer type and which parts of your body are affected. Some cancers start in or spread to a part of the body that does something essential for life.

Digestive system

The digestive system is also called the gastrointestinal (GI) system. It includes the:

• food pipe (oesophagus)

• stomach

• pancreas

• liver

• small and large bowel

Cancer that grows in the digestive system can block it or partly block it. So food can't go through the gut and the nutrients and calories you need can't be absorbed.

You might be able to have surgery to remove the blockage. But if this is not possible, your medical team will do all they can to control your symptoms.

If you can't eat and drink, you don't get the necessary nutrients to help your ​immune system​ to work well. So, you are less able to cope with other problems, such as infection.

Lungs

Cancer might block off part of the lung. This part then collapses and can become infected. When cancer blocks the lungs, it can affect the way that you absorb oxygen. 

If you have advanced cancer, you might not have the strength to fight off a lung infection, even with strong antibiotics. So the infection can eventually lead to death.

Bones

Cancer in the bones can cause calcium to be released into the bloodstream. This can affect the calcium balance of the body. The body has systems to correct this, but the systems don't work anymore when the imbalance becomes too great.

There is a treatment to bring calcium levels back to normal, but these only work for a limited time. Then the calcium levels can continue to rise in the blood. High calcium levels in the body can cause you to become unconscious and eventually die. 

Cancer cells can affect the bone marrow. The bone marrow is a spongy material that fills the bones. It produces very early cells called stem cells, which then develop into new blood cells. Eventually, you might not have enough healthy bone marrow to make new:

• red blood cells to carry oxygen around your body

• white blood cells to fight infection

• platelets to stop bleeding

Liver

The liver is the second largest organ in the body after your skin. It is just below your right lung and is protected by the lower ribs on the right side of your body. It does many things including:

• stores sugars and fats, so they can be used for energy

• makes different proteins that help the blood to clot, this prevents bleeding and maintains fluid balance in the body

• makes bile, which helps breaks down fats so they can be absorbed by the body

• breaks down harmful substances in the body

The liver is very important in maintaining the balance of body chemicals. Cancer that has spread to the liver can upset this chemical balance.

It can be life-threatening if the body can't correct this chemical balance.

Blood vessels

Cancers can grow into and damage blood vessels in a vital part of the body. This can cause bleeding in the brain. This bleeding can cause death if it affects certain important parts of the brain.

Treatment

Many treatments can control cancer for a long time, even if they can't cure it. But if a cancer continues to grow, it can become too much for the body to cope with.

Read more about the different treatments for cancer

Talking about dying

Talking about dying can be very difficult. So people often avoid the subject. But sharing your feelings can help everyone involved to cope better.

Dying is something most people worry about at some point. Talking about how the cancer is affecting your body can help lessen at least some of those worries.

What happens in the last days of life is different for everyone. Many people are relieved to find out that they, or their loved ones, are likely to become unconscious shortly before they die.

Read more about what might happen in the last few weeks and days of life