A stem cell transplant is recommended when a disease is serious enough that standard treatments can’t cure it, but replacing the body’s blood-forming system offers a realistic chance of long-term remission or cure. The most common reason worldwide is multiple myeloma, followed by other blood cancers like leukemia and lymphoma. Increasingly, transplants are also used for severe autoimmune diseases and certain genetic blood disorders.
Blood Cancers: The Most Common Reason
The vast majority of stem cell transplants are performed for blood cancers. Multiple myeloma is the single most common indication globally. For myeloma, the standard approach uses your own stem cells (autologous transplant) collected before high-dose chemotherapy, then returned to rebuild your blood system afterward.
For acute myeloid leukemia (AML), a donor transplant (allogeneic) is the preferred option when the disease is classified as intermediate or high risk, or when it has come back after initial treatment. In AML, the transplanted donor cells don’t just replace your blood system. They actively attack remaining cancer cells through an immune effect called graft-versus-malignancy, which is one of the most powerful reasons donor transplants work for leukemia.
Lymphomas follow a slightly different pattern. For diffuse large B-cell lymphoma, the most common aggressive type, transplant isn’t a first-line treatment. It becomes the standard of care when the lymphoma relapses or doesn’t respond to initial chemotherapy. This was established by the landmark PARMA trial and remains the approach today, using your own cells rather than a donor’s.
When in Treatment a Transplant Happens
Timing matters enormously. For most blood cancers, transplant isn’t the first thing doctors try. You’ll typically go through initial chemotherapy first, and the transplant comes as a consolidation step once the disease is in remission, or as a rescue when the cancer returns.
In AML, the conventional path is to achieve remission with chemotherapy, then proceed to transplant. But for patients whose leukemia resists chemotherapy entirely, going directly to transplant without waiting for remission is emerging as a viable option. In a multicenter study, patients who went straight to transplant had a four-year overall survival of about 52%, comparable to the 46% seen in patients who achieved remission with salvage chemotherapy first and then transplanted. Patients who transplanted with active disease after failed chemotherapy fared worse, at around 37%, but still had a meaningful chance of long-term survival.
For high-risk AML in first remission, transplant is often recommended right away rather than waiting for a relapse that may be harder to treat.
Autoimmune Diseases
Stem cell transplant has moved from experimental to standard-of-care for certain severe autoimmune conditions. Multiple sclerosis and systemic sclerosis (scleroderma) account for roughly 80% of all transplants performed for autoimmune diseases in Europe. MS is the most frequent, with nearly 1,900 patients reported in the European transplant registry alone.
For MS, transplant is recommended specifically for treatment-resistant inflammatory forms of the disease, where medications have failed to control relapses and disability is progressing. It uses your own stem cells: the immune system is wiped out with chemotherapy, then rebuilt from your stored cells, essentially resetting the immune system so it stops attacking the nervous system. Crohn’s disease is another major indication, particularly when the disease is refractory to all available medications and significantly impairs quality of life.
Non-Cancerous Blood Disorders
Sickle cell disease is one of the clearest success stories for transplant outside of cancer. A study of over 1,000 sickle cell patients found a one-year survival rate of 94% and a ten-year survival of 88%. When the donor is an HLA-matched sibling, the five-year survival reaches 95%. Even with less perfectly matched donors, outcomes are strong: 87% five-year survival with a half-matched (haploidentical) family donor and 82% with a mismatched unrelated donor.
Severe aplastic anemia, where the bone marrow stops producing enough blood cells, is another well-established indication, particularly in younger patients with a matched sibling donor. Certain inherited immune deficiencies and metabolic disorders in children are also treated with transplant when no other curative option exists.
Your Own Cells vs. a Donor’s
Whether you receive your own stem cells or someone else’s depends on several factors: the type of disease, your age, whether a suitable donor exists, and whether your own bone marrow is free of disease.
Autologous transplants (your own cells) are the standard for multiple myeloma, relapsed lymphoma, and autoimmune diseases. The main advantage is no risk of the donor cells attacking your body. The main limitation is that your own cells can’t mount an immune attack against residual cancer.
Allogeneic transplants (donor cells) are preferred for leukemias, aplastic anemia, and sickle cell disease. The donor’s immune cells provide that crucial graft-versus-disease effect, but they also carry a risk of attacking your healthy tissues. The choice of donor follows a clear hierarchy. An HLA-matched sibling, requiring a 6 out of 6 match at key genetic markers, is the gold standard. When no matched sibling exists, doctors search for a matched unrelated donor through international registries, looking for an 8 out of 8 match. A half-matched family member (haploidentical donor), requiring at least a 4 out of 8 match, has become increasingly common and now accounts for about 13% of transplants for some conditions.
Who Is Eligible
There are no absolute medical contraindications that automatically disqualify someone from a stem cell transplant. Eligibility is determined case by case based on how well your major organs are functioning, particularly your heart, lungs, liver, and kidneys. Before being approved, you’ll go through a battery of tests to assess these systems.
Age is no longer a hard cutoff. While transplant was historically limited to younger patients, reduced-intensity conditioning regimens have opened the door for older adults and those with other health problems. These gentler preparatory treatments use lower doses of chemotherapy or radiation, causing less damage to the body while still allowing the transplanted cells to engraft. Major centers like Mayo Clinic now consider selected patients over 65, depending on overall fitness. Full-intensity conditioning is still used for younger, healthier patients when maximum disease eradication is the goal, particularly in aggressive leukemias.
The shift to reduced-intensity regimens has been especially important because most blood cancers are diagnosed in people between ages 65 and 70, precisely the group that couldn’t tolerate conventional transplant protocols. Studies show significantly lower treatment-related mortality with reduced-intensity conditioning compared to full-intensity regimens in older patients.
What Drives the Recommendation
Your doctor’s recommendation ultimately comes down to a risk-benefit calculation. Transplant carries real dangers, including infection, organ damage, and graft-versus-host disease. It’s recommended when the disease you’re facing carries a worse prognosis than those transplant risks. For a young person with high-risk AML in first remission, transplant offers the best shot at cure despite its risks. For someone with low-risk, early-stage disease responding well to standard chemotherapy, the risks of transplant outweigh the potential benefit.
The specific factors that tip the scale include your disease’s genetic risk profile, how well it responded to initial treatment, whether it has relapsed, your overall organ function, and whether a suitable donor is available. For cancers, the disease’s sensitivity to chemotherapy is a key predictor: cancers that respond to initial treatment tend to respond better to the transplant process as well.