Bone Marrow Transplant: A Comprehensive Guide

Bone Marrow Transplant: Types, Risks, and Outlook

A bone marrow transplant is a surgical procedure to replace damaged or diseased bone marrow, a spongy material inside the bones where the body creates and stores blood cells, with healthy marrow.

Blood cells begin as very young cells, known as hematopoietic stem cells. After they mature, they travel out of the bone marrow into the blood. A bone marrow transplant is also known as a stem cell transplant.

Damaged bone marrow creates too few blood cells and insufficient cells for the immune system. A transplant may cure some diseases or certain types of cancer. It translates to a long recovery process and a risk of serious side effects. Your doctor can talk with you about the transplant's positives and negatives.

What Is Bone Marrow?

Bone marrow is the soft and spongy tissue present inside the bones. It is where majority body's blood cells grow and are stored. The blood cells that create other blood cells are known as stem cells. 

The most primitive of stem cells is known as the pluripotent stem cell. It is different from the other blood cells in each of the following properties.

Renewal: it can regenerate another cell identical to itself.

Differentiation: It can generate one or more subsets of more mature cells.

Stem cells are required for bone marrow transplants.

Types Of Bone Marrow Transplant

Before the transplant, radiation, chemotherapy, or both may be given. This can be done in two ways.

Ablative (myeloablative) treatment: High-dose chemotherapy, radiation, or both are given to kill any cancer cells. This also kills all health bone marrow that stays and permits new stem cells to grow in the bone marrow.

Reduced intensity treatment, also known as mini transplant: Lower doses of chemotherapy & radiation are given prior to transplant. This enables older people and those with other health problems to have a transplant.

There are four types of bone marrow transplants:

Autologous bone marrow transplant: the term auto means self. Stem cells are pulled out from you before you get high-dose chemotherapy or radiation treatment. The stem cells are stored in a freezer. Post high-dose chemotherapy or radiation treatments, your stem cells are put back in your body to create normal blood cells. This is known as a rescue transplant.

Allogenic bone marrow transplant: the term allo means other. Stem cells are pulled out from another person, called a donor. Many times, the donor's genes must at least partly match your genes. Certain tests are done to see if a donor is a correct match for you. 

A sister or brother is most likely to be a good match. At times, children, parents and other relatives are good matches. Donors who are not related to you but still match can be found via national bone marrow registries.

Umbilical cord blood transplant: In is kind of allogeneic transplant stem cells are pulled out from a newborn baby's umbilical cord directly after birth. The stem cells are frozen & stored until they are required for a transplant.

Umbilical cord blood cells are very immature; hence, there is little need for perfect matching. Because of the smaller number of stem cells, blood counts take more time to recover.

Haploidentical transplant: This is a kind of allogeneic transplant in which the donor isn't fully matched with the recipient.

A haploidentical transplant may be from a family member. Children are always a half-match for their parents, & parents are a half-match for their children. Siblings are fifty per cent a half-match for each other. Special treatments are done to decrease the chance of complications due to the incomplete match.

A stem cell transplant is typically done post chemotherapy & radiation are over. The stem cells are delivered to your bloodstream, usually via a tube known as a central venous catheter. The process is similar to receiving a blood transfusion. The stem cells travel via the blood into the bone marrow.

Donor stem cells can be gathered in two ways:

Bone marrow harvest:

This is a minor surgery bone under general anaesthesia. This means the donor will be asleep & pain-free during the procedure. The bone marrow is eliminated from the back of both hip bones. The amount of marrow removed is based on the weight of the person getting it. This method is rare today.

Leukapheresis:

First, the donor is given multiple days of shots to assist stem cells move from the bone marrow into the blood. During leukapheresis, blood is pulled out from the donor via an IV line. The part of the WBCs which contains stem cells is then separated in a machine & removed to be later given to the recipient. The RBCs are returned to the donor.

Why is a bone marrow transplant needed?

A bone marrow transplant aims to cure certain diseases and types of cancer. When the doses of chemotherapy or radiation required to cure a cancer are so high that a person's bone marrow stem cells can be permanently harmed or destroyed by the treatment, a bone marrow transplant may be required. A bone marrow transplant is also required if the bone marrow has been eliminated by a disease.

l A bone marrow transplant can be used to replace non-functioning, diseased with healthy functioning bone marrow  (for conditions such as aplastic anaemia, leukaemia, and sickle cell anaemia).

l A bone marrow transplant can be used to regenerate a new immune system, which will fight existing or residual leukaemia or other cancers not killed by the radiation or chemotherapy used in the transplant.

l A bone marrow transplant can be used to replace the bone marrow & restore its usual function after high doses of chemotherapy & radiation are provided to treat a malignancy. This process is known as rescue.

l A bone marrow transplant can be used to replace bone marrow with genetically healthy functioning bone marrow to stop more Damage from a genetic disease process like adrenoleukodystrophy and Hurler's syndrome.

Before the procedure, the pros and cons must be weighed in an elaborate discussion with your doctor and specialist in bone marrow transplants.

How are a donor & recipient matched?

Matching requires typing human leukocyte antigen (HLA) tissue, which finds the genetic makeup of a person's immune system via the antigens on the surface of white blood cells. Major antigens are essential in determining donor-recipient compatibility, while minor antigens have a less defined effect on transplant success.

Medical research continues to explore the importance of all antigens in bone marrow transplants. More matching antigens result in better engraftment of donated marrow. Engraftment occurs when donated stem cells migrate to the marrow and generate new blood cells.

The genes responsible for the human immune system are primarily situated on one chromosome, with individuals inheriting two copies of each chromosome from their parents. Consequently, a full sibling of a transplant recipient has a one in four chance of being a complete match for transplantation by sharing the same set of chromosomes.

Risks of Bone marrow transplant

A bone marrow transplant may create the following symptoms:

•  Headache
•  Hives
• Chest pain
• Drop in blood pressure
• Fever, chills, flushing
• nausea
•  Pain
• Shortness of breath
• Strange taste in the mouth

Possible complications of a bone marrow transplant are based on many things, including:

• Your age
• Your overall health
• How good of a match your donor was
• The type of bone marrow transplant you received (autologous, allogeneic, or umbilical cord blood)

Complications may include:

• Anemia
• Infections, which can be very serious
• Clotting in the small veins of the liver
• Damage to the kidneys, liver, lungs, and heart
• Delayed growth in children who receive a bone marrow transplant
• Early menopause
• Bleeding in the lungs, intestines, brain, and other areas of the body
• Cataracts
•  Graft failure is when the new cells do not settle into the body and start creating stem cells
•  Graft-versus-host disease (GVHD), a condition in which the donor cells attack your own body
•  Inflammation and soreness in the mouth, throat, oesophagus, and stomach, called mucositis
• Pain
• Stomach problems, including diarrhoea, nausea, and vomiting

Bone Marrow Transplant Outlook

Prognosis greatly depends on the following:

• type of transplant
• Your age and overall health
• Your tolerance of specific medicines, procedures, or therapies
• Severity of complications
• type and extent of the disease being treated
• Disease response to treatment
•  Genetics

Prognosis and long-term survival after a bone marrow transplant can vary considerably among individuals. However, the increasing number of transplants being performed for multiple diseases and ongoing medical advancements have significantly improved the outlook for both children and adults undergoing bone marrow transplants.

Continuous post-transplant care is essential for patients. Efforts are ongoing to develop new techniques to increase treatment and lower complications and side effects associated with bone marrow transplants.