** This passage has some errors in it. Watch this spot for a revised/corrected version of this in the near future or check out the WEBMDwebsite for more information. ***
Leukemia is cancer of the bone morrow. Bone morrow is a special type of tissue located in the center of your bones that creates red blood cells. (Have you ever looked at a broken chicken bone and saw the red center of the bone? That is bone morrow.) Red blood cells move oxygen to, and waste (carbon-dioxide) away from your body’s cells for the process of cellular respiration (among other things). Red Blood Cells have a limited life expectancy. Without bone morrow to create the red blood cells, the body’s cells do not get the oxygen that they need and die. That is why Jamie feinted that first time at home and had oxygen tubes hooked up in the hospital.
There is no cure for Leukemia and it is fatal. Research continues into this and so far the most promising treatment is a bone morrow transplant from a close relative. The specific treatment that Jamie underwent is not specified in the movie. While Jamie also had Leukemia in the book, there was a great deal if discussion during the writing of the screenplay as to what she should have. They discussed cancer and a brain tumor, but went back to Leukemia because they needed an illness that would allow Jamie to keep her hair. [Both radiation and chemo-therapy, the treatments used in treat those other ailments, result in hair loss.]