Stem Cell Transplant — Procedure Guide, Recovery & Risks | MyMedicPlus

Hematopoietic stem cell transplant (HSCT) infuses blood-forming stem cells after high-dose chemotherapy (conditioning) eliminates diseased marrow. Autologous SCT uses the patient's own cells (harvested before conditioning); allogeneic SCT uses cells from a matched sibling, unrelated donor, or umbilical cord blood. The procedure is used to treat haematological cancers and bone marrow failure syndromes. The goal is to replace a damaged or malignant haematopoietic system with healthy donor or patient-derived stem cells capable of reconstituting normal blood cell production. HSCT is performed at specialist haematology centres with dedicated transplant units.

Haematopoietic stem cell transplantation (HSCT) is broadly classified into two types: autologous transplantation, in which the patient's own stem cells are collected, cryopreserved, and reinfused after high-dose conditioning chemotherapy — eliminating relapse risk from graft rejection but offering no graft-versus-tumour (GvT) effect; and allogeneic transplantation, using stem cells from a human leukocyte antigen (HLA)-matched donor (sibling, matched unrelated donor via national registry, haploidentical parent or child, or cord blood) — which provides a potentially curative graft-versus-leukaemia (GvL) effect through donor immune cells attacking residual malignant cells, at the cost of graft-versus-host disease (GvHD) risk and the need for prolonged immunosuppression. Over 50,000 transplants are performed annually worldwide across more than 500 specialist centres.

Autologous SCT is used for multiple myeloma, Hodgkin and non-Hodgkin lymphoma, and testicular cancer. Allogeneic SCT treats acute myeloid leukemia (AML), acute lymphoblastic leukemia (ALL), chronic myeloid leukemia (CML), aplastic anemia, myelodysplastic syndrome, and thalassemia major. Patient eligibility depends on disease type, remission status, age, organ function, and availability of a suitable donor. Reduced-intensity conditioning (RIC) protocols extend eligibility to older patients (up to age 70) and those with comorbidities who cannot tolerate myeloablative chemotherapy.

Specific high-priority indications for allogeneic HSCT include: AML in first complete remission with intermediate or adverse cytogenetics; ALL in second remission or high-risk first remission; myelodysplastic syndrome with high-risk IPSS score; chronic myeloid leukaemia (CML) refractory or intolerant to two or more tyrosine kinase inhibitors; primary myelofibrosis with intermediate-2 or high IPSS risk; severe aplastic anaemia in patients under 40 with a matched sibling donor; and haemoglobinopathies (sickle cell disease, thalassaemia major) in younger patients with matched donors. Reduced-intensity conditioning (RIC) has extended transplant eligibility to patients in their 60s and 70s who would not tolerate myeloablative conditioning.

Conditioning chemotherapy (and total body irradiation in some protocols) given over 5-7 days destroys existing marrow and immunosuppresses the recipient. Stem cells harvested from peripheral blood (G-CSF mobilised), bone marrow, or cord blood are infused intravenously on day zero. Peripheral blood stem cells are collected by apheresis after 4-5 days of G-CSF injections that mobilise progenitor cells into the bloodstream. Bone marrow harvest collects 1-1.5 litres from the posterior iliac crests under general anaesthesia. Engraftment occurs in 14-28 days when donor neutrophils exceed 0.5 x 10^9/L for three consecutive days, confirming the new marrow has taken hold.

Peripheral blood stem cell collection (most common source): donor receives G-CSF (filgrastim) injections for 4–5 days to mobilise HSCs from bone marrow into peripheral blood. Apheresis — passing blood through a cell separator — collects CD34+ stem cells over 4–6 hours. Bone marrow harvest: donor undergoes general anaesthesia; 1–1.5 litres of bone marrow aspirated from posterior iliac crests through multiple small punctures. Cord blood units are cryopreserved from consenting donors at birth.

Recipient conditioning: myeloablative conditioning (MAC) uses busulfan plus cyclophosphamide or fludarabine, or total body irradiation (TBI) plus cyclophosphamide. Reduced-intensity conditioning (RIC) uses lower doses (fludarabine-based regimens) to allow transplant in patients aged 60–75 years or with significant comorbidities. The stem cell infusion resembles a blood transfusion through a central venous catheter. Neutrophil engraftment (ANC greater than 0.5 × 10^9/L) typically occurs at days 14–21 for peripheral blood stem cells and days 21–35 for cord blood.

Autologous SCT achieves 5-year overall survival of 40-60% in multiple myeloma. Allogeneic SCT cures AML in first complete remission in 40-60% of patients, exploiting a graft-versus-leukemia (GVL) effect where donor immune cells destroy residual cancer cells. Reduced-intensity conditioning (RIC) extends transplant eligibility to patients over 60 with comorbidities. For aplastic anaemia, allogeneic SCT from a matched sibling achieves long-term cure in over 80% of younger patients. The curative potential of allogeneic SCT is unmatched for many haematological malignancies, particularly those with high relapse risk after conventional chemotherapy alone.

The curative potential of allogeneic HSCT for haematological malignancies, mediated by the graft-versus-leukaemia (GvL) effect of donor immune cells, distinguishes it from all other cancer treatments. For young patients with relapsed AML who achieve second complete remission, allogeneic HSCT is the only treatment offering 30–40% cure rates. Technological advances — better HLA matching through high-resolution typing, improved GvHD prophylaxis (post-transplant cyclophosphamide for haploidentical donors), reduced-intensity conditioning, and newer antifungal and antiviral prophylaxis regimens — have progressively improved outcomes and safety over the past three decades. Patient registries (EBMT, CIBMTR) provide outcome benchmarking that drives quality improvement globally.

Allogeneic SCT carries graft-versus-host disease (GVHD) risk: acute GVHD (40-60%), chronic GVHD (30-50%). Other major risks include graft failure, veno-occlusive disease (sinusoidal obstruction syndrome), CMV and fungal infections, interstitial pneumonitis, and secondary malignancies years later. Autologous SCT avoids GVHD but has higher relapse risk due to the absence of GVL effect. Treatment-related mortality at experienced centres ranges from 5-15% for allogeneic procedures depending on donor match, patient age, and conditioning intensity.

Acute GvHD (aGvHD) — an immune attack by donor T-cells against host skin, gut, and liver — occurs in grades II–IV in 30–50% of allogeneic recipients despite prophylaxis. Severe grade III–IV aGvHD carries mortality of 20–40%. First-line treatment with high-dose steroids achieves complete response in 50–60%; refractory cases require second-line agents (ruxolitinib, extracorporeal photopheresis, infliximab). Chronic GvHD (cGvHD) is a systemic autoimmune syndrome affecting 30–50% of long-term survivors, requiring prolonged immunosuppression and causing significant morbidity including chronic respiratory disease, sicca syndrome, skin changes, and peripheral neuropathy.

The neutropenic phase lasts 2-4 weeks; patients are isolated in HEPA-filtered rooms on prophylactic antibiotics, antivirals, and antifungals. Discharge occurs after engraftment, typically 3-6 weeks post-transplant. Immune reconstitution takes 12-24 months, during which patients are vulnerable to opportunistic infections including CMV, Pneumocystis jirovecii pneumonia, and aspergillosis. Prophylactic medications, regular blood monitoring, and follow-up transfusions are required. Full return to normal activity may take 6-12 months. Lifelong surveillance monitors for relapse, late organ toxicity, and secondary malignancy.

Late effects of HSCT are a growing area of survivorship medicine. Endocrine complications include primary ovarian insufficiency (affecting most female recipients under 40) requiring hormone replacement therapy, and male hypogonadism. Cardiovascular risk is elevated from total body irradiation and long-term immunosuppression. Cataracts develop in 30–80% of TBI recipients within 5 years. Neurocognitive effects ('chemo brain') affect quality of life in many survivors. Secondary malignancies (skin cancer, solid tumours, PTLD) are a long-term surveillance priority. Long-term survivorship programmes at specialist HSCT centres provide systematic screening and monitoring.