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Asked by anon-220178 to Ross, Lorena on 7 Jun 2019.
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Lorena Boquete Vilarino answered on 7 Jun 2019:
Great question! Firstly let me point out that not all cancers end up causing death, it varies a lot from cancer to cancer but the probability of surviving a cancer increases as we get better therapies and earlier diagnosis – that is why it is very important to follow the NHS guidelines for cancer prevention!.
There are thousands of different cancers, and they work a bit differently and may lead to death by different causes. What they do have in common is that they affect how the cells in that part of the body work.
For example, lung cancer can block part of the lung, which means the patient can’t get enough oxygen. Stomach cancer may cause your digestive system to not absorb enough nutrients, causing malnourishment.
In the late stages of cancer, patients are very weak and their immune system can’t fight infections, so many people actually die from infections rather the cancer itself.
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Comments
Emma commented on :
This is a great question, and shows a lot of understanding that often the most deadly cancers involve metastasis (This is where secondary cancers form in other parts of the body).
So how do cancers kill? The mechanism is mostly disrupting the normal function of the organ or issue they are growing in. So if you have a cancer in the brain, it can damage the tissue and put pressure on parts of the brain, this means the tissue can not function properly, and if blood flow is restricted then that tissue will die. Cancers in other parts of the body work in a similar way, so cancer in the kidneys means the kidney is less able to carry out its normal function of removing waste substances from the blood, and so this can build up and damage the kidney causing it to fail. If the cancer grows into a blood vessel and then breaks off, if can become stuck in a vessel like the heart and cause a heart attack or in the brain and cause a stroke.
Nina commented on :
The cancers I know most about are the ones affecting the brain and other parts of the nervous system. The brain and spinal cord are special cases when it comes to tumours because even ‘benign’ tumours (i.e. ones that do not invade into surrounding tissues or spread to other parts of the body) are considered ‘malignant’ because their growth and expansion can have very serious consequences and even be life threatening if left untreated. This is simply because the brain and spinal cord are enclosed in hard bony structures (skull and vertebral column) which means there is little space for extra tissue. If a tumour grows within the skull cavity (inside the brain or on the surface of the brain), over time this will lead to a build-up of pressure (known as raised ‘intracranial pressure’ or ICP which is very dangerous). This will effectively squash parts of the brain (leading to neurological deficits through pressure on specific structures, or by reducing blood supply to the brain). If not treated, the tumour will continue to grow and ultimately the pressure can become so great that an important part of the brain that is vital for life (the brainstem) is pushed towards a little hole in the back of the skull (known as the foramen magnum). The brainstem is essential for basic functions such as breathing and consciousness. Patients will generally deteriorate into a coma and then stop breathing.
Some brain tumours grow very slowly, and if they can be reached surgically they can be removed. The removal of a small benign tumour (such as a meningioma which develops from the tissue layers protecting the brain – the meninges) can achieve a long-term surgical cure. However some tumour types are not accessible by surgery or grow very quickly and spread throughout the brain in a more diffuse way such that surgery is unlikely to be of benefit (e.g. glioblastoma multiforme). Radiation therapy is another form of treatment that is sometimes applied after debulking surgery (to kill any residual tumour cells that cannot be seen by eye), or in cases where surgery is not an option. Together with chemotherapy, surgery and radiation therapy can extend life for a period, depending on the type of tumour, the stage and extent of disease.
The above has mainly referred to what we called ‘primary brain tumours’, i.e. those that start in the brain. However, there are several tumour types that can start elsewhere and then spread to the brain (e.g. lymphoma, various carcinomas) – we call these secondary or metastatic brain tumours. As above, these can ultimately lead to similar, life-threatening problems if ICP is raised.
Other types of cancer can affect the functioning of other essential organs (such as kidneys, lungs, heart, pancreas) or body systems (such as the immune system) leading to life threatening changes in blood pressure, respiratory function, key serum electrolytes (e.g. sodium, potassium), bodily fluid balance, or life-threatening infections. Some of these conditions or effects of cancer can be managed for a period of time though supportive drugs and other treatments.