Bone Marrow Transplant

bone marrow
Bone marrow smear showing
lymphoblastic leukemia.
Image by Vashi Donsk

Bone marrow transplants (BMT) fall under the broader category of Hematopoietic (blood-forming) Stem Cell Transplants (HSCTs). Bone marrow is the spongy matter found within our bones, and it contains stem cells that grow into white blood cells, red blood cells and platelets. In a BMT, a needy patient receives these stem cells so that they can begin to produce the necessary blood components that fight infection (white cells), transport oxygen throughout the body (red cells), and clot the blood to stop bleeding (platelets).

There are two primary types of BMTs, categorized by the donor source:

  • In an autologous bone marrow transplant, the marrow recipient is also the marrow donor.
  • In an allogenic bone marrow transplant, the recipient receives marrow from a donor who is determined to be a good match by what is known as a human leukocyte-associated (HLA) type blood test

A third category, syngeneic bone marrow transplants, are very uncommon; in this case, patients receive marrow from an identical twin.

What it's effective for and why

The efficacy of bone marrow transplants is most evident in the treatment of blood cancers such as leukemia and lymphoma. BMTs also play a slightly more limited role in the treatment of neuroblastoma and multiple myeloma. The patient must first undergo extremely high-dose chemotherapy and radiation treatments, which can take months. The goal is to destroy the patient's existing stem cells and replace them with healthy ones. In the case of an autologous BMT, the patient's marrow is harvested before treatment begins; that marrow is 'purged' of any cancer cells (although not always completely), and returned to the body. As one might expect, there are fewer complications associated with an autologous BMT than with an allogenic BMT.

Risks and complications: Overview

The first 100 days following a bone marrow transplant are broken into two segments, days 0-30 and 30-100. The first, covering days 0-30, is referred to as 'Waiting for Engraftment' and since the patient is very low on all blood cell types, the risk of infection—often in the blood, mouth, lungs, or urinary tract—is the highest.

This is also a time when a serious, life-threatening complication can develop, known as Graft-Versus-Host Disease (GVHD). In a typical organ transplant, doctors worry about the patient's immune system rejecting the organ, but in bone marrow transplants the opposite is true. The patient's own immune system is extremely compromised; thus the concern is that white blood cells formed from transplanted bone marrow—the 'Graft'—will reject existing cells in the body—the 'Host'—by attacking them as foreign antigens. Since this complication is potentially lethal, the patient will receive special medication to help prevent it.

Additional risks and complications include all the many side effects of chemotherapy and radiation, as well as the long-term risks of these anti-cancer treatments, which can include cardio-pulmonary toxicity or other organ damage, and secondary cancers.

Be The Match

Allogenic bone marrow transplants can only treat a cancer patient if the right match is found. If you are interested in becoming a bone marrow donor in the United States, get more information from the National Marrow Donor Program at www.marrow.org.

Sources

  1. National Cancer Institute: Bone marrow transplants
  2. National Marrow Donor Program: Talking Transplants

 

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