While discussing on that other thread that while we may think one thing is going to kill us when in fact it's more likely that something else will, for some reason I began to wonder: just how DOES cancer kill? What is the exact physical process?
A morbid question, but a fair one. We've all heard the phrase "cancer kills" a thousand times, but what does that really mean?
By analogy, I know that running out of gas will cause my car to stop. That's the simple, immediate explanation. But thinking about
it analytically, that means that the stoppage of fuel entering the engine will cause cessation of the explosive reactions that power the moving parts that transfer energy to the wheels, thus moving the car.
In similar fashion, what is the
precise series of actions that cancer produces in the body that eventually cause the body to die?
The passage below, from a forum discussion of this very question, seems well written, informative, and seems to explain clearly what actually does happen.
And if the information I read in it is correct, the process of dieing from cancer is frankly more complicated than I had expected.
It's by a poster who claims to be a physician who treats cancer patients, and he tells us:
"I am a hospitalist (a doctor that only sees patients in the hospital), and see cancer patients die all the time. In my experience, there are two main ways that cancer causes death for the majority:
(1) Failure to thrive. This is a fancy way of saying the person isn't doing well. Cancer causes lack of appetite, fatigue, and when you combine inactivity and inadequate food and water intake, the person gets steadily weaker. Eventually the patient declines to the point that they choose to forgo things like tube feeding or IV fluids (especially after they are told that the cancer is advancing despite treatment). Essentially the person's quality of life drops below what they consider acceptable and they are ready to accept the inevitable.
These patients usually die of kidney failure due to dehydration because they don't eat or drink enough to meet their needs. This process is often accelerated by appropriate treatment of pain (because the opioid medications can suppress the drives to eat, drink and breathe), but that is ethically acceptable.
Theoretically, you could keep these patients alive for quite some time if you were to keep them hydrated and fed. We could place them on ventilators to keep them breathing, give them tube feedings and IV fluids, and do things like dialysis, and stretch the process out by months or longer. All the while their cancer would be growing merrily, but they would live until something catastrophic happened.
{2} Overwhelming infection. Due to the above, as well as the effects of chemotherapy and radiation, cancer patients do not have normal immune systems and often succumb to infection. Note, however, that this often comes after the person has made the decision that they are ready to pass away as much of the time, with aggressive treatment, we can treat severe infections.
I am sorry, but the explanations on this page (of the website where this doctor was posting) of the tumor replacing the normal organ as being the ultimate cause of death are for the most part, wrong. Lung cancer doesn't kill people by stopping the lungs from working. Breast cancer doesn't kill people because their breasts stop working. Likewise, spread of cancer to other organ(s) with subsequent shutdown of the organ(s) isn't the cause either. QuentinTNO's answer, while it sounds good, just isn't the way it is. Tumor lysis does happen, but it is rare and would only account for a tiny fraction (well less than 1%) of cancer deaths. Additionally, sudden hemorrhage is extremely rare. Bleeding from cancer is usually slow enough that we can address with transfusions.
Other less common causes of cancer death include (but by no means are limited to):
-Heart attack
-Blood clots to the lungs (pulmonary emboli)
-Brain swelling due to spread of the tumor there
-Replacement of the liver with tumor (but it is rare to get that far)
It's worthwhile to note that with medical technology, we could artificially keep people alive with widespread cancer for some time until something happened that we simply could not fix. The vast majority of the time, patients elect not to push it that far and die on their own terms.From a forum discussion at:
https://www.reddit.com/r/explainlikeimfive/comments/1nnovb/eli5_how_does_cancer_actually_kill_a_sufferer/One reason I decided to quote this passage is because it clearly states that, according to this doctor at least, many (most? all?) cancer patients die because they simply
give up, preferring to "die on their own terms," as he puts it, rather than continuing to live a life of dealing every day with cancer.
Can we believe this? If this is true, that is, if we accept what this physician is saying in the above passage, that "... the vast majority of the time, patients elect not to push it that far and die on their own terms," then do we accept that it is true that most patients with advanced cancer simply go
when they themselves feel it is "their time?"I had always been thinking that advanced cancer was a very aggressive condition that would, on its own, cause such extensive physical damage to the body that such damage alone would be sufficient to cause death.
But this doctor seems to be saying that a patient's
attitude may play a
much larger role in how long he lives with cancer than many of us may have thought.
What if one is not ready to go, even if one's quality of life is poor? Will just fighting back mentally stand a good chance of extending one's life, possibly even for a good bit, regardless of prognosis? The doctor seems to be suggesting that. Especially when he clearly suggests that just eating and drinking better, especially staying hydrated, might in themselves keep us going a good bit longer than if we don't do those things. But, again, what about
the quality of life during that time? If it has become very poor, is it worth it to most people to keep fighting to stay alive?
Maybe it all comes down to is a function of quality of life. People finally get to such a low level of quality of life, get tired of the daily struggle, not to mention likely increasing pain, that they finally just feel like calling it quits. It's possible for them to live longer, but they no longer want to. Is that what mostly happens?
And this doctor's claim might well explain a phenomenon we had all heard of, that patients with a poor attitude likely succumb to cancer sooner. That might simply be because, since they have a negative attitude to begin with, they
don't eat better,
don't stay hydrated,
don't exercise, or do the other things that might extend their lives. Thus, their deaths from cancer almost become a self-fulfilling prophecy.
But perhaps it really is true that if we become determined to keep on living, that in itself just might make us do the things that could extend our lives a good bit more than we might think it would. Something to consider.
But knowing the precise path that cancer would actually take toward causing one's demise, including the effect of the patient's own attitude, is useful, if only from the viewpoint of understanding the process.