system
Given the following post, respond as if you're commenting on Reddit:
human
How does Cancer kill.
gpt
This is a very complex question to tackle.

A lot of cancer's ability to kill depends on where it is. If it is in a very important organ, such as the pancreas, it tends to be more likely to kill, largely due to its ability to inhibit normal pancreatic function. Without the hormones and enzymes your pancreas secretes, a lot of body function shuts down, killing the individual. The ability of cancer to do this to a single organ comes from the consumption of necessary hormones, excessive growth crowding out the cells, and the angiogenesis many tumors induce, causing blood supply to flow more to the tumor, and less to the normally functioning cells. No blood, no oxygen, no food, no living cells. Cancers like melanoma, in the skin, tend not to be killers from their primary location, but only when it metastasizes to other sites, especially if that new home is a vital organ.

The size/stage of the cancer is also a huge factor. Large tumors can drain a lot of hormones, blood and subsequently nutrients from normal tissue, inhibiting their function. Additionally, more advanced stages tend to have more longevity related mutations, making them better at surviving within humans. Beyond the nutrient/blood/hormone drain, this makes them much harder to treat and remove, especially once they metastasize.

Another way cancer is able to kill actually comes from the way we treat most forms, with chemotherapy and/or radiation. This is a toxic compound, designed to kill cells that are dividing, also known as growing. This is a hallmark of cancer, uninhibited growth, but unfortunately other growing cells get caught in this crossfire. This is the cause for hair loss in many cancer patients. With enough time, these treatments can lead to other problems that may cause death in patients that have other problems, such as age (old or young) or disease.

TL;DR The ability of cancer to kill depends on location, size/stage, and the route of treatment.