When somebody dies of cancer, what exactly is the actual reason the body stops working?
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The actual physical causes of death are as varied as the cancers themselves. If you want to know how a cancer caused someone’s death you need to know the kind of cancer and what the cancerous cells original purpose was.
The cancer cells have overwhelmed some vital organ and crushed or starved it until it gets horribly infected or can no longer function.
Exactly what the failure mode is will vary case by case, depending on the type of cancer and how it has metastasized.
We typically list the root cause (cancer) on the death certificate and not whatever secondary infection or organ failure actually pushed them over the edge.
Its not the same for every case of cancer, but a generalisation would be 1 of 2 things.
Either the tumours are taking up too much nutrients/space from other organs and thus causes those organs to fail.
Or tumours block off something important like airways or arteries/veins.
Here are several options, but there are many more
Cancer might destroy the immune system so they die of infection. This happened a lot in early days of HIV, which is literally an “immunodeficiency” virus.
Cancer might invade the brain and disrupt various body control mechanisms, or create blockages in blood and spinal fluid flow that create a sudden increase in pressure in the cranial cavity and crushes parts of the brain.
Cancer could block major arteries and airways so they suffocate.
Cancer can destroy the body’s metabolism, so they basically lose their appetite and lose weight so it’s like they are starving to death.
Cancer can cause severe internal bleeding.
Cancer is a general term we use to describe any disease where cells in the body begin to divide in an uncontrolled fashion, often fast and with a very high mutation rate (so the cells begin to not look or function like those from the area of the body where they started). Cancer can be confined to a small area, or break off, travel through the blood stream, and lodge elsewhere to grow (we call that “metastasis” or “spreading”).
Cancers kill by growing a bunch of the wrong cells in the wrong place. They can physically tear up organ tissue, block blood flow, cause internal bleeding, stop usable blood cells from being made… They effectively choke out organs to the point where the organs can’t function and dies off. If the cancer has spread through the body, then many parts of the body will be failing at the same time.
Cancer death is typically due to organ failure, but the specifics of how it grows, the parts of the body affected, how it develops, etc. all depend on the particular type of cancer.
There are a couple of reasons, but the primary reason is normally that an organ system fails to function properly (so organ failure) due to a proliferation of cancer cells. You generally need the organs you have, so if you get lung cancer you die because your lungs aren’t exchanging blood gasses properly.
Imagine you have a car and in order to keep this car running you regularly need to change most of its parts out. A ship of Theseus this imaginary car is. This works great, eventually the factory sends you parts that aren’t quite to spec. They still kind of work, or if they are total failures the other working parts can keep the car running. Two things can happen, the cancer can *spread*, I start getting parts for other components that are malformed. Or, the parts for some vital function start coming to me so badly malformed that they don’t work at all. Or, some unholy combination of both. What is the exact reason for the car to stop working in these conditions? Take your pick. Sometimes it is obvious, sometimes it isn’t.
First off.. you need to understand that “cause of death” and “mechanism of death” are not the same thing.
Cause is the underlying reason why died – if it wasn’t for the cancer, they would be alive. This is what causes of the fatal chain events that leads to their death. This is why COVID was the cause of death for so many people since it ‘kicked off’ the chain of events that saw them die.
Mechanism is the actual ‘thing’ that kills them. So for cancer, this could be infection (due to compromised immune system, or by an embolism (ie: clot) shutting off flow of blood to the brain or other vital organs among a variety of causes.
Every cell in your body has a job. Every one. And all your cells, doing their job well, is what keeps you alive and healthy. Cells don’t take time off. Every moment of their existence is either doing their job or recovering, to prepare for doing a job later.
What happens when cells stop doing their job? They die. Cells have built in self destruct code, and if something goes wrong, they break themselves down, to be harvested and used for more jobs by other cells. So, if a cell finds itself somewhere it shouldn’t be, or unable to work, they self destruct.
Cancer is often a twofold break. First, the cell’s DNA (its list of instructions) tells the cell to stop doing its job and do something else instead. Second, its self destruct breaks in the DNA. Cancer cells reproduce nonstop, passing on these traits to all their offspring. If the order to self destruct when it stops working, that’s early cancer. If the order also breaks when it’s in the wrong place, then that is metastasized cancer, which is much more dangerous.
But the reason the body stops working? Enough cells stop doing their job to stop something that really needs to happen from happening.
That’s the incredibly simplified low down.
Sometimes the treatment overwhelms the patient’s immune response or organs.
Or, it can be longer term… one patient (a colleague) had been treated for breast cancer 3 times. The treatments, doctors believe, *caused* a secondary blood cancer, which killed her from lack of oxygen (too many blood cells killed).
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