B-cell acute lymphoblastic leukemia (B-ALL)

Diagnosis usually starts with a complete blood count (CBC), a routine blood test. A bone marrow sample, taken with a hollow needle, confirms the leukemia. A marker test on the cells (immunophenotyping) shows that the leukemia started in B cells rather than T cells. For children, a pediatric oncologist, a doctor who treats children with cancer, oversees care.

Chromosome tests (cytogenetics) and other gene tests on the leukemia cells come next. They look for changes that shape treatment. One example is the Philadelphia chromosome (BCR::ABL1). NCI says it is found in about 1 in 5 adults with ALL and in a small share of children. A spinal tap (lumbar puncture) checks whether leukemia is in the fluid around the brain and spinal cord. Children may also have a chest x-ray.

The full risk picture builds over the first weeks of treatment. Measurable residual disease (MRD) tests show how deeply the leukemia has responded. For children and young adults, U.S. transplant guidelines look at MRD results about 9 to 12 weeks after diagnosis. For adults 40 and older, the same guidelines advise detailed tissue typing (HLA typing) at diagnosis. That way a donor search can start early if one is needed.

Treatment commonly has several phases: inducing remission, consolidating that response and longer maintenance treatment. Chemotherapy combinations and CNS-directed treatment are tailored to the protocol. Targeted medicines are added when a relevant leukemia marker is present.

Blinatumomab, which helps T cells recognize B-lineage leukemia, and inotuzumab, which delivers a drug to CD22-positive cells, have roles in selected settings. Approved CAR-T treatments for eligible B-ALL patients use T cells modified to recognize a leukemia target. These approaches are distinct from a blood stem cell transplant.

Allogeneic transplantation is considered for selected high-risk disease, inadequate response or relapse. It is not routine for every child or adult with B-ALL. Whether a transplant should follow CAR-T treatment depends on the product, response, previous transplant and individual relapse risk; one universal sequence does not fit every patient.

When a transplant from a donor is planned, the team usually tests brothers and sisters first. Each full sibling has about a one in four chance of being a full match.

Most patients do not have a matched relative. In the words of NMDP, the U.S. registry, “75% of patients don’t have a fully matched donor in their own family.” The team then searches registries of volunteer donors around the world and banks of donated cord blood. In some transplants, a half-matched parent, child or sibling can also be the donor.

Matching depends on inherited tissue markers called HLA, so a patient is most likely to match someone who shares their ancestry. Every person who joins makes the search a little more likely to succeed, especially for patients from groups that are underrepresented on registries.

NCI says treatment gives children with ALL a good chance of cure. For adults, the outlook is not as good. For children, NCI describes risk groups. Children aged 1 to 9 with a white blood cell count under 50,000 are standard risk. Children 10 and older, or those with higher counts, are high risk. Infants, children with certain gene changes and children who respond slowly are very high risk.

How fast and how deeply the leukemia responds is an important sign. NCI notes that the drop in leukemia cells after the first month of treatment helps predict the outcome. The Philadelphia chromosome once meant a much harder course. With targeted pills called tyrosine kinase inhibitors added to chemotherapy, NCI says long-term survival is now routinely reported. For children with this change who respond well early, a transplant in first remission is no longer recommended.

When B-ALL comes back or does not respond, a donor stem cell transplant becomes a more likely part of the plan. U.S. guidelines advise a transplant consultation at first relapse. For children and young adults, the aim is a transplant once the leukemia is back in remission. For adults 40 and older, they also advise a consultation in first remission, which is not the same as a decision to transplant. Group numbers describe many people. They cannot predict how any one person will do.