When my grandmother died from leukemia I had no concept of what it was she was suffering from. For that matter, I had no concept of what any cancer was, and I would still refrain from trying to explain what it is, or more importantly what it is like to suffer from it.
From what I can tell though, cancer changes you and the people around you, it is your life as much as it can take your life.
Below is an article from the New Yorker about the perceptions and reactions in the past hundred years related to cancer, and specifically cancer treatment. I think it makes a much better stab at giving an idea of what the disease actually is.
The making of a modern disease.
This is how it starts. Carla wakes up one morning feeling that something is wrong. She has been having headaches, but not of the normal, take-a-pill-and-relax type. These headaches come with a sort of numbness, and now she notices some other things that aren’t as they should be. There are bruises on her back that she can’t explain; her gums have been going pale; and she’s very, very tired. She goes to her doctor, but he can’t tell her what’s wrong. Try some aspirin, he says; maybe it’s a migraine. The aspirin doesn’t help, so she finally asks for some blood tests and soon she winds up at Massachusetts General Hospital, in Boston, where a young and talented physician gives her the preliminary diagnosis: acute lymphoblastic leukemia (A.L.L.). Carla knows nothing about lymphoblasts, or why she’s going to have to have a bone-marrow sample taken, but she knows about leukemia. It’s cancer of the blood. She’s terrified, and she may not be in a state of mind to take in the oncologist’s reassurance that A.L.L. is “often curable.”
Carla now enters not just a cancer ward but a cancer world. The ward is what the sociologist Erving Goffman once called a “total institution,” like asylums, armies, prisons, monasteries, and Oxbridge colleges—an institution that strips you of your identity and equips you with a new one. She’s given a case number, a bracelet, a hospital gown. Some of her physicians will know her name and what she was before becoming a cancer patient, and some will not. Her chemotherapy ward is an environment made sterile in order to protect her soon to be therapeutically devastated immune system from infection, so her relations with family and friends are reconfigured along with the rhythms of her days and weeks. She’s now a case.