Bone Marrow & Stem Cell Treatment — How It Works, Benefits & Recovery — Procedure Guide, Recovery & Risks | MyMedicPlus

Bone marrow and stem cell transplantation (HSCT — haematopoietic stem cell transplantation) is a potentially curative medical procedure that replaces diseased or dysfunctional blood-forming stem cells with healthy haematopoietic progenitor cells, restoring the capacity to produce normal red blood cells, white blood cells, and platelets. There are two principal types. In autologous transplantation, the patient's own stem cells are collected before high-dose chemotherapy, cryopreserved, and reinfused after the chemotherapy to restore marrow function — used primarily in multiple myeloma and lymphoma. In allogeneic transplantation, stem cells from a compatible donor (related or unrelated) replace the patient's diseased marrow — used in leukaemia, bone marrow failure, and inherited haematological disorders. The donor stem cells also exert a graft-versus-tumour (GVT) immune effect that helps eradicate residual disease. Stem cells may be sourced from the bone marrow (under general anaesthesia), peripheral blood after mobilisation with G-CSF (most common), or umbilical cord blood. HSCT is performed at specialist haemato-oncology units with dedicated transplant facilities. Bone marrow and stem cell transplantation (HSCT — haematopoietic stem cell transplantation) is a potentially curative medical procedure that replaces diseased or dysfunctional blood-forming stem cells with healthy ones from the patient themselves (autologous) or from a matched donor (allogeneic). The transplanted stem cells engraft in the recipient's bone marrow and regenerate a fully functional haematopoietic system. Autologous HSCT uses the patient's own stem cells collected before high-dose chemotherapy, then reinfused to rescue the marrow. Allogeneic HSCT uses donor stem cells and carries both a therapeutic graft-versus-leukaemia (GvL) effect and a risk of graft-versus-host disease (GvHD). HSCT is performed by haematologists and bone marrow transplant specialists in dedicated transplant units. Over 50,000 HSCTs are performed annually in Europe alone, across more than 700 transplant centres. Stem cell sources include bone marrow, peripheral blood stem cells (most common since the 1990s), and umbilical cord blood.

Patient eligibility is determined by the underlying diagnosis, disease status, organ function, performance status, and availability of a suitable donor. Autologous HSCT is indicated for relapsed/refractory Hodgkin lymphoma, non-Hodgkin lymphoma, and multiple myeloma in first or subsequent remission where it significantly improves progression-free survival. Allogeneic HSCT is indicated for acute myeloid leukaemia (AML) and acute lymphoblastic leukaemia (ALL) in patients with high-risk or relapsed disease, chronic myeloid leukaemia (CML) refractory to tyrosine kinase inhibitors, myelodysplastic syndromes with high IPSS-R score, aplastic anaemia unresponsive to immunosuppression, sickle cell disease and beta-thalassaemia in younger patients with a matched sibling donor, and severe combined immunodeficiency (SCID). Patient eligibility for allogeneic HSCT is assessed using performance status, organ function, age, and comorbidity scores such as the HCT-CI (haematopoietic cell transplantation comorbidity index). Donor matching uses HLA (human leukocyte antigen) typing — 10/10 matched unrelated donors are standard when a sibling match is unavailable.

The transplant process occurs in several phases over 3–4 weeks. The conditioning regimen (Days -7 to -2 before transplant) delivers high-dose chemotherapy — with or without total body irradiation (TBI) — designed to eradicate residual disease, ablate the patient's haematopoietic system, and create marrow space for donor cells. Myeloablative conditioning (MAC) uses the highest doses; reduced-intensity conditioning (RIC) is used in older patients or those with comorbidities. Stem cell infusion (Day 0) delivers the graft intravenously like a blood transfusion. Infused cells home to the bone marrow niches through the CXCL12-CXCR4 axis. Engraftment — the point at which donor haematopoiesis is established, evidenced by rising neutrophil count above 0.5 × 10⁹/L — occurs at Day +14 to +21. Until engraftment, patients are profoundly immunocompromised, requiring protective isolation, prophylactic antibiotics, antifungals, and antivirals. Red cell and platelet transfusion support is provided as needed. Bone marrow harvest (for allogeneic donors using the surgical route) is performed under general anaesthesia with multiple aspirations from the posterior iliac crests, collecting 10–15 mL/kg of marrow. The transplant process occurs over 3–4 weeks in phases. The conditioning regimen (Days -7 to -2) delivers high-dose chemotherapy (with or without total body irradiation) to eradicate the patient's existing marrow and malignant cells. On Day 0, the stem cell infusion (transplant day) takes place via a central venous catheter over several hours, similar to a blood transfusion. The infused stem cells home to the bone marrow and begin engraftment over 10–21 days (marked by rising neutrophil count above 0.5 × 10⁹/L). During the aplastic nadir (Days 0–14), the patient has no functioning immune system and requires haematopoietic growth factors (G-CSF), red cell and platelet transfusions, and prophylactic antifungal (fluconazole, voriconazole), antiviral (aciclovir), and antibacterial agents. For allogeneic HSCT, GvHD prophylaxis (tacrolimus or ciclosporin with methotrexate or mycophenolate mofetil) is initiated from Day -1. Chimerism testing at 30 and 100 days post-transplant assesses donor engraftment.

Haematopoietic stem cell transplantation offers the only curative option for many haematological malignancies and bone marrow failure conditions. Autologous HSCT in eligible myeloma patients increases complete remission rates and significantly extends progression-free survival — median PFS after upfront autologous HSCT is approximately 4 years versus 2.5 years for chemotherapy alone in landmark trials. Allogeneic HSCT cures approximately 40–60% of patients with AML in first complete remission with a favourable donor, and 50–60% of adults with ALL in first CR. For aplastic anaemia, matched sibling HSCT achieves over 90% long-term event-free survival in patients under 40, outperforming immunosuppressive therapy. Sickle cell disease cure rates with matched sibling HSCT are 90–95% in children. The graft-versus-tumour (GVT) effect is a unique and powerful benefit of allogeneic transplantation: donor immune cells recognise and eliminate residual leukaemic cells, reducing relapse risk. Donor lymphocyte infusions (DLI) can harness this effect therapeutically in patients who relapse after allogeneic HSCT.

Haematopoietic stem cell transplantation carries significant morbidity and mortality, particularly with allogeneic procedures. Graft-versus-host disease (GVHD) is the most important allogeneic-specific complication: acute GVHD (Day 0–100) affects 30–50% of patients and causes skin rash, liver dysfunction, and gastrointestinal symptoms; chronic GVHD (beyond Day 100) affects 30–70% and can involve virtually any organ system. Treatment is with corticosteroids and immunosuppression. Non-relapse mortality from allogeneic HSCT is 5–20% depending on centre experience, patient age, HLA match, and conditioning intensity. Primary graft failure (failure of donor cells to engraft) occurs in 1–5%. Opportunistic infections — bacterial, viral (CMV, EBV, adenovirus), and fungal (Aspergillus, Candida) — remain a major cause of morbidity during the immunocompromised phase. Conditioning-related organ toxicity includes sinusoidal obstruction syndrome (SOS/VOD) of the liver, idiopathic pneumonia syndrome, haemorrhagic cystitis (from cyclophosphamide or BK virus), and mucositis. Long-term complications include secondary malignancies, infertility, endocrine dysfunction, and cardiovascular disease.

The initial hospitalisation lasts 3–4 weeks in a protective isolation room with HEPA air filtration and strict infection-control measures. Neutrophil engraftment at Day +14 to +21 marks a critical milestone. Following discharge, patients require frequent outpatient review (2–3 times weekly initially) for monitoring of blood counts, organ function, and infection. Prophylactic medications — antibacterials, antifungals (fluconazole or posaconazole), antivirals (aciclovir), and Pneumocystis prophylaxis (co-trimoxazole) — continue for 6–12 months post-transplant. CMV monitoring by PCR is performed weekly in seropositive patients. Full immune reconstitution after allogeneic HSCT takes 12–24 months; during this period vaccination schedules are restarted from scratch (measles, mumps, rubella, and live vaccines delayed until at least 24 months post-transplant off immunosuppression). Return to work and normal activities is highly variable — many patients return to light activity at 6 months and full activity at 12 months. Long-term follow-up includes monitoring for chronic GVHD, secondary malignancies, and cardiovascular and endocrine complications for life.