Bone Marrow Transplant — How It Works, Benefits & Recovery — Procedure Guide, Recovery & Risks | MyMedicPlus

A bone marrow transplant (BMT), more precisely called a haematopoietic stem cell transplant (HSCT), replaces damaged, diseased, or destroyed bone marrow with healthy haematopoietic stem cells that restore the production of normal blood cells — red cells, white cells, and platelets. Transplants are classified by cell source: autologous BMT uses the patient's own stem cells collected before high-dose chemotherapy, then reinfused to reconstitute the marrow; allogeneic BMT uses stem cells donated by a matched sibling or unrelated donor identified through bone marrow registries. A third category, syngeneic BMT, uses cells from an identical twin. Stem cells are sourced from bone marrow (under general anaesthesia), peripheral blood after mobilisation with G-CSF (the most common current method), or umbilical cord blood. The procedure is used for both malignant diseases (leukaemia, lymphoma, myeloma) and non-malignant conditions (aplastic anaemia, thalassaemia, sickle cell disease) where marrow failure or replacement is the therapeutic goal. Approximately 50,000 transplants are performed worldwide each year. A bone marrow transplant (BMT), more precisely called a haematopoietic stem cell transplant (HSCT), replaces damaged, diseased, or destroyed bone marrow with healthy haematopoietic stem cells that restore the body's ability to produce normal blood cells — red cells, white cells, and platelets. The procedure is potentially curative for leukaemia, lymphoma, myeloma, aplastic anaemia, and inherited blood disorders. Autologous transplants use the patient's own stem cells collected before high-dose conditioning chemotherapy, then reinfused to rescue the marrow. Allogeneic transplants use stem cells from a matched sibling, unrelated volunteer donor, or umbilical cord blood. Matching is assessed by human leukocyte antigen (HLA) typing. BMT is performed by haematologists and transplant physicians at specialist centres, typically requiring hospital admission of 4–6 weeks.

Allogeneic BMT is indicated for acute myeloid leukaemia (AML) in first complete remission with intermediate or high-risk genetics, acute lymphoblastic leukaemia (ALL) in adults and high-risk children, chronic myeloid leukaemia (CML) failing tyrosine kinase inhibitors, myelodysplastic syndromes, aplastic anaemia unresponsive to immunosuppression, thalassaemia major, sickle cell disease with severe complications, primary immunodeficiencies (SCID), and relapsed or refractory lymphoma. Autologous BMT is indicated primarily for multiple myeloma (consolidation after induction therapy), relapsed Hodgkin and non-Hodgkin lymphoma responding to salvage chemotherapy, and selected cases of autoimmune disease. Patient selection requires assessment of disease type and stage, complete remission status, performance score (ECOG/KPS), organ function (cardiac, pulmonary, renal, hepatic), age (though reduced-intensity conditioning now allows transplant up to age 70–75), and donor availability. Contraindications include refractory disease, severe organ dysfunction, active uncontrolled infection, and poor performance status.

Bone marrow transplant proceeds in three phases. Conditioning (preparative regimen): High-dose chemotherapy — with or without total body irradiation (TBI) — is administered over 5–10 days to eliminate residual malignant cells, suppress the patient's immune system (preventing graft rejection in allogeneic BMT), and create space in the bone marrow for engraftment. Reduced-intensity conditioning (RIC or 'mini-transplant') uses lower-dose immunosuppressive regimens to allow older or less fit patients to undergo allogeneic BMT with reduced toxicity. Stem cell infusion: On 'Day 0', the donor stem cells (or the patient's own previously collected and cryopreserved cells in autologous BMT) are infused intravenously via a central venous catheter — the procedure resembles a blood transfusion and takes 1–4 hours. Engraftment: The infused stem cells home to the bone marrow cavities and begin producing new blood cells. Neutrophil engraftment (neutrophil count above 0.5 × 10⁹/L) is typically confirmed at day 14–21; platelet engraftment at day 20–28. During the aplastic phase before engraftment, patients are in strict protective isolation with prophylactic antifungal (fluconazole or voriconazole), antibacterial (fluoroquinolone), and antiviral (aciclovir) agents and receive platelet and red cell transfusions as required. Bone marrow transplant proceeds in three phases. Conditioning (preparative regimen): High-dose chemotherapy — with or without total body irradiation (TBI) — is administered over 5–10 days to eliminate the patient's existing marrow and malignant cells. Day 0 (transplant day): Harvested stem cells are infused through a central venous catheter over 30 minutes to 4 hours. For allogeneic transplants, donor stem cells are either harvested from the iliac crests under general anaesthesia (bone marrow harvest) or collected from peripheral blood after G-CSF mobilisation by apheresis. Engraftment phase (Days 1–28): The patient is profoundly immunocompromised and requires protective isolation, broad-spectrum antimicrobial prophylaxis, haematopoietic growth factors (filgrastim), and transfusion support. Engraftment is confirmed when the neutrophil count rises above 0.5 × 10⁹/L on three consecutive days. Tacrolimus-based GvHD prophylaxis continues for 6 months or longer in allogeneic transplant recipients.

For many haematological malignancies, allogeneic BMT offers the only prospect of cure. Transplanted donor immune cells also exert a graft-versus-leukaemia (GVL) effect — attacking residual leukaemic cells that may have survived conditioning — which contributes significantly to disease control beyond the conditioning regimen alone. Long-term disease-free survival (DFS) for allogeneic BMT in AML in first complete remission is 50–65% at 5 years depending on disease risk and HLA match quality. For ALL in CR1 in adults, DFS reaches 55–65%. Autologous BMT for multiple myeloma achieves complete remission in 35–50% of patients with a median progression-free survival of 3–4 years; novel triplet induction regimens followed by autologous BMT now achieve 5-year overall survival exceeding 80% in transplant-eligible myeloma. Aplastic anaemia treated with allogeneic BMT from a matched sibling donor achieves long-term survival of 85–95% in patients under 40, significantly better than immunosuppressive therapy alone. Thalassaemia major can be cured by allogeneic BMT in 80–90% of young patients in good clinical condition.

Bone marrow transplant carries significant risk, particularly with allogeneic procedures. Graft-versus-host disease (GVHD) is the principal complication unique to allogeneic transplant: donor immune T-cells recognise host tissues as foreign and attack them, commonly targeting skin (rash), gastrointestinal tract (diarrhoea, cramping), and liver (jaundice). Acute GVHD (within 100 days) occurs in 30–50% of patients receiving unmodified peripheral blood stem cells; chronic GVHD (after day 100) in 30–70%. Both are managed with immunosuppression (calcineurin inhibitors, corticosteroids), but chronic GVHD is a major cause of late morbidity and non-relapse mortality. Severe infections — bacterial, fungal (aspergillosis, candida), and viral (CMV, adenovirus, EBV-related PTLD) — during the aplastic and early post-engraftment phase carry life-threatening risk. Organ toxicity from conditioning includes hepatic sinusoidal obstruction syndrome (SOS/VOD), haemorrhagic cystitis from cyclophosphamide or BK virus, interstitial pneumonitis, and mucositis. Graft failure (primary — no engraftment; secondary — loss of engraftment) occurs in 1–5%. Treatment-related mortality (TRM) at experienced centres is 5–15% for matched sibling allogeneic BMT and 15–25% for unrelated donor transplants.

Patients remain in a positive-pressure isolation room for 3–4 weeks until neutrophil engraftment is established (neutrophils above 0.5 × 10⁹/L on 3 consecutive days) and they are clinically stable. After discharge, close outpatient monitoring continues for 100 days — the highest-risk period for infections and GVHD — with clinic visits 2–3 times weekly, blood counts, and organ function monitoring. Oral prophylactic medications (antifungal, antiviral, PCP prophylaxis with co-trimoxazole) continue for 6–12 months or longer in patients receiving ongoing immunosuppression for GVHD. Full immune reconstitution takes 6–24 months after allogeneic BMT; live vaccines must be avoided during this period. Re-vaccination schedules with killed vaccines begin at 6–12 months post-transplant. Return to normal activity and work is gradual — most patients resume full activities at 6–12 months. Psychological support, nutritional counselling, and physiotherapy are integral to comprehensive post-transplant care. Long-term surveillance includes monitoring for relapse, chronic GVHD complications, endocrine effects (hypothyroidism, premature ovarian insufficiency), secondary malignancies, and cardiovascular risk.