Cancer is scary, right?

One of the reasons that cancer is so viscerally frightening is that it is so tightly associated with death.

But how does cancer actually kill a person?

This may seem like an obvious question, but the answers were not so obvious even to me a cancer biologist and cancer survivor so I've done reading and it is actually quite interesting.

I had prostate cancer, which was diagnosed 2 1/2 years ago. My doctors told me based on the histology of the cancer, that I had likely had that cancer for many years without even knowing it. They went on to tell me that even without any treatment (I opted for surgery) I might have lived many years without any symptoms of the cancer. However, they said in that scenario I would greatly increase my odds of dying of prostate cancer at some future date.

This left me can I have a potentially lethal cancer and not even know it?

How does a cancer such as prostate cancer or breast cancer, which arises in a non-essential organ, kill someone?

Of course a cancer in an organ such as the brain such as glioblastoma can literally destroy parts of the brain that are essential to life. This has important implications for other tumors with the key word here being metastasis. Cancers that sprout up in non-essential organs can travel through the body and grow like weeds in essential organs. In this scenario the cancer leaves the non-essential organ and effectively goes on to destroy an essential organ.

But how does the cancer destroy any organ? Research suggests that cancer cells are extremely good at outcompeting their neighboring normal cells, which they leave to literally starve to death. Cancer cells are hogs. In addition, some research suggests that cancer cells can act as assassins, killing neighboring cells by tricking them into self-destruction (apoptosis) or directly wiping them out.

Cancer also has broader effects on the body that ultimately can prove lethal such as destroying the immune system leading to lethal infections. It can also put great stress on the body by ramping up metabolism, producing toxins, etc.