When people first hear the word "transplant," most picture a major operation—the scene of opening the abdomen, putting something in, and sewing it up. But a hematopoietic stem cell transplant is rather different from that image. In fact the final transplant itself is a process of slowly letting cells flow in through a vein, like a transfusion, so when you actually see it, it is almost anticlimactically quiet. What is truly hard are the stages lined up before and after it: collecting, emptying the body, refilling it, and the time spent waiting for those cells to settle in. Tracing this flow through once eases the vague fear a little.
It starts with collection, gathering the hematopoietic stem cells. In an autologous transplant using your own cells, you usually receive several days of injections of a stimulant that raises the white blood cells, and the stem cells that have spilled out into the blood are filtered off with an apheresis machine. Blood leaves through one arm, circles through the machine, and returns through the other; since you have to lie still for an hour or two, many find it tedious. If calcium drops, your lips may tingle, and when that happens you can just say so. In an allogeneic transplant receiving cells from a sibling or another person, the donor goes through this process instead, or the cells are taken directly from the marrow. The collected cells are kept frozen and pulled out for use when the time comes.
Next comes the stage commonly called "conditioning," and personally I see this as the real hurdle. Over several days before the transplant, high-dose chemotherapy or radiation nearly empties out the existing marrow. You can think of it as a cleaning job that removes the diseased cells and makes room for the new ones to move in. The problem is that normal cells take a hit in this process too. The mouth becomes sore, you feel nauseated, hair falls out, and immunity drops all the way to the floor. During this period even a small infection is dangerous, so you stay in an environment close to a clean room.
Once the body has been fully emptied, it is now time to put in the new cells. The stem cells gathered earlier are thawed and infused slowly through a central venous catheter. Because of the cryopreservative there may be an odd smell like corn boiling, or brief queasiness, but it usually passes quickly. Remarkably, these cells find their own way into the marrow and settle in. No one shows them the route, yet they go as if heading home—something I always find astonishing.
The final gate is engraftment. It refers to the point when the cells that went in take root in the marrow and begin making blood again. It usually takes about two weeks after the transplant, and during that interval immunity is almost absent—a danger zone—so the white blood cell count is checked with daily blood tests. When the count rises above a certain threshold for several days in a row, it is said to have "engrafted." On hearing this news, both patient and caregiver often let out a breath they had been holding for a long time. Still, engraftment is not the end; another hurdle such as graft-versus-host disease remains, so careful management continues for a while even after discharge.
What is written here is only an attempt to sketch the broad flow; the method and schedule of treatment really do unfold very differently from person to person and from disease to disease. Be sure to decide the specifics in consultation with your medical team.
This article is intended to convey general medical information in an accessible way and does not replace individual diagnosis or treatment. Please be sure to consult your own physician about any specific decisions.