Bone marrow transplant: how it works and what it means for the donor

What bone marrow is and where it is found

Bone marrow is the soft, spongy tissue inside bones and the body's main blood-forming organ. All blood cells are constantly produced there from stem cells:

• red blood cells carry oxygen from the lungs to organs and tissues;
• platelets stop bleeding from damaged vessels;
• white blood cells protect against infection: neutrophils and monocytes destroy bacteria and fungi, while lymphocytes (T, B and NK cells) provide immunity.

There is red marrow, which makes blood, and yellow marrow, which consists of fat and does not produce blood cells. In a child, red marrow fills almost every bone. In an adult it is found in the pelvis, vertebrae, breastbone, ribs, skull and the ends of the upper arm and thigh bones. Bone marrow has nothing to do with the spinal cord or the brain.

What a bone marrow transplant is

A bone marrow transplant is the infusion of blood-forming stem cells that settle in the bones and restore blood formation and immunity. It is not a surgical operation: the cells are given into a vein, like a blood transfusion.

• Autologous transplant. The patient's own stem cells are used: they are collected in advance, frozen and returned after high-dose chemotherapy. This is most often used for myeloma and lymphomas.
• Allogeneic transplant uses cells from a healthy donor: a matched brother or sister, an unrelated donor from an international registry, or a half-matched relative (haploidentical transplant). Cord blood is another source of cells.

Which diseases require a transplant

• acute lymphoblastic leukemia and acute myeloid leukemia, at high risk of relapse or after relapse;
• chronic myeloid leukemia when targeted drugs have stopped working, and chronic lymphocytic leukemia in selected cases;
• myelodysplastic syndromes, myelofibrosis, aplastic anaemia;
• multiple myeloma;
• lymphomas, including Hodgkin lymphoma, in relapse or resistance to treatment;
• some childhood tumours: neuroblastoma, Ewing sarcoma, medulloblastoma (see paediatric oncology);
• inherited immune deficiencies and blood disorders such as thalassaemia.

How bone marrow is collected from a donor

There are two ways to obtain stem cells. The transplant centre decides which one is needed.

1. From the blood (apheresis): this is how most donations are made. For 4–5 days the donor receives a drug that moves stem cells from the marrow into the blood. Blood is then taken from a vein in one arm, passed through a cell separator that collects the stem cells, and returned to a vein in the other arm. The procedure takes 4–6 hours and needs no anaesthesia.
2. From the pelvic bone: under general anaesthesia, marrow is drawn with a syringe through punctures in the back of the pelvic bones. The operation takes 1–2 hours and the donor goes home the same or the next day. No more than 5% of the marrow is taken.

Bone marrow donor: side effects and consequences

Donating bone marrow does not harm health: the body replaces the donated cells within 2–6 weeks, the donor's immunity is not affected, and there is no evidence of a higher risk of cancer or other diseases.

• After collection from the blood: during preparation, aches in the bones and muscles, headache and tiredness are possible, as with a cold. Symptoms pass within 1–3 days after the procedure.
• After collection from the pelvic bone: pain in the lower back and pelvis and weakness for a few days, sometimes up to two weeks; bruising at the puncture sites is possible.
• Serious complications, such as a reaction to anaesthesia or damage to a nerve or muscle, occur in about 1–2% of bone marrow donors and in fewer than 1% of blood stem cell donors.

Donors return to their usual work within a few days. Before donation the donor is examined to rule out risks to their own health.

Which tests are done before a transplant

• full blood count and biochemistry (see blood test in leukemia);
• bone marrow aspiration with a cell count and histology;
• immunophenotyping, cytogenetic and molecular tests to define the disease type and prognosis;
• HLA typing of the patient and potential donors;
• assessment of the heart, lungs, kidneys and liver, and infection screening.

Bone marrow transplant: how it is done

1. Conditioning. A few days before the transplant the patient receives chemotherapy, sometimes with total body irradiation. It destroys tumour cells and suppresses the patient's own immune system so that the donor cells are not rejected.
2. Stem cell infusion. The cell suspension is given into a vein through a catheter. This takes from half an hour to several hours and needs no anaesthesia.
3. Engraftment. The cells find their own way to the bone marrow and start producing new blood cells within 2–4 weeks. During this time the patient stays in a sterile room and receives blood transfusions, antibiotics and antifungal drugs.
4. Recovery. The hospital stay is 2–3 weeks after an autologous transplant and 4–6 weeks after an allogeneic one. Immunity takes from several months to a year or more to recover.

Complications after a transplant

Graft-versus-host disease

After an allogeneic transplant, the donor's immune cells may see the patient's tissues as foreign and attack them. The acute form develops in the first months and shows as a rash, diarrhoea and jaundice; the chronic form may affect the skin, mucous membranes, eyes and lungs. Immunosuppressive drugs are given to prevent and treat it. There is also a useful side: donor cells attack remaining tumour cells (the graft-versus-leukemia effect), which lowers the risk of relapse.

Bone marrow rejection: symptoms

Rejection, or graft failure, is rare, occurring in fewer than 5% of cases. Its signs: blood counts do not recover in the expected time or fall again, and severe infections, bleeding and marked weakness persist. In this situation a second transplant is performed or an additional dose of donor cells is given.

Relapse after a transplant

The disease can return even after a successful transplant, most often in the first two years. Options then include donor lymphocyte infusions, targeted drugs, CAR-T therapy or a second transplant.

Mortality after a bone marrow transplant

The risk is mainly linked to infections while immunity has not yet recovered, graft-versus-host disease and the toxicity of chemotherapy. Procedure-related mortality is below 2–3% for autologous transplants and about 10–20% in the first year for allogeneic transplants, depending on age, the patient's condition and donor match.

Survival after a bone marrow transplant

Figures vary widely, roughly from 20% to 90%, depending on the disease, its stage, age, the type of transplant and donor match. For example, in young patients with aplastic anaemia and a matched related donor, long-term survival reaches 80–90%, while in acute myeloid leukemia transplanted in first remission it is about 50–60%. Every case is individual, and only the treating doctor can give an accurate prognosis.

Life after a transplant

For several months after discharge, regular blood tests, preventive medicines, care with food and limited contacts are needed; vaccinations are repeated later. After an allogeneic transplant people usually return to work within 6–12 months. Disability status during recovery is decided by a medical board under the rules of the country where the patient lives.

Where to have a bone marrow transplant

A comparison of countries, clinics and approximate prices is in the article Bone marrow transplant: prices and clinics, and the list of centres is in the haematology-oncology section.

Frequently asked questions

Is it painful to donate bone marrow?

Collection from the blood is painless; only the bone aches during the preparation days are unpleasant. Collection from the pelvic bone is done under anaesthesia, and the lower back aches for a few days afterwards.

Who can become a donor?

A healthy person aged 18–45 (up to 55 in some registries) without cancer, autoimmune or severe chronic diseases, HIV or viral hepatitis.

How quickly is a donor found?

Relatives are tested within 1–2 weeks. Searching for an unrelated donor in an international registry takes from a few weeks to several months.

How much does a bone marrow transplant cost?

The price depends on the type of transplant, the country and the clinic; an allogeneic transplant from an unrelated donor is the most expensive. Current prices are given in a separate article.

Clinics Direct specialists will help you choose a clinic for a bone marrow transplant and obtain an individual treatment plan with exact prices. Send a request on the website; it is free of charge.