Acute lymphoblastic leukemia (ALL), also known as acute lymphocytic leukemia, is a cancer of the blood and bone marrow. Treatment can cure ALL, but the cancer can sometimes return. Doctors refer to this as relapsed ALL.

ALL is most likely to develop in children under 5 years old, but the risk increases again once a person reaches the age of 50 years.

Despite the higher rate of ALL among children, a relapse is more likely in adults. Leukemia Care, a United Kingdom-based charity, notes that while nearly 10% of children who have had ALL have a relapse, the ALL relapse rate in adults is almost 50%.

This article discusses the symptoms and treatment of relapsed ALL. It also looks at the outlook for people with this condition.

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3-year-old Iker Andres Nolasco, a child diagnosed with ALL in 2021, plays with rocks near the home of his family in State of Mexico, Mexico on February 15 2022. Daniel Cardenas/Anadolu Agency via Getty Images

When a person’s initial ALL treatment has been successful, doctors refer to them as being in remission. Remission can be complete or partial. If a person is in complete remission, all signs and symptoms of the cancer are gone. This means that cancer is no longer detectable by tests, not that there is definitely no cancer left.

Partial remission indicates that the cancer is responding to treatment and that there are fewer leukemia cells in the blood.

According to the National Cancer Institute, some doctors consider a person cured once they have been in complete remission for at least 5 years.

However, if any remaining cancer cells begin to replicate, a person can develop relapsed ALL. The American Cancer Society (ACS) notes that ALL generally relapses during or shortly after treatment. A 2020 study supports this, showing that more than 90% of relapses occur within 3 years of a person achieving complete remission.

Learn more about acute lymphoblastic leukemia.

The symptoms of relapsed ALL are the same as those of the original cancer. They include:

These symptoms do not always mean that a person’s ALL has returned. However, a person who has had ALL should speak with their healthcare team if they develop any concerning symptoms.

If a doctor suspects that a person’s ALL has returned, they can perform certain diagnostic tests. These may include:

Complete blood count (CBC)

A CBC measures the number of red blood cells, white blood cells, and platelets in the blood. A person who has relapsed ALL will have lower red blood cell and platelet counts than they should.

Peripheral blood smear

A peripheral blood smear involves examining a sample of a person’s blood under a microscope to check that all the cells look normal. If a person has relapsed ALL, their blood will contain more blast cells than it should.

Bone marrow aspiration and biopsy

These tests look at samples of a person’s bone marrow. During aspiration, a doctor takes a sample of liquid bone marrow using a needle.

In a bone marrow biopsy, a doctor removes a small amount of marrow and bone. A lab technician then checks the samples for ALL cells and abnormalities.

Lumbar puncture

During a lumbar puncture, a doctor takes fluid from a person’s spinal cord. They then send the sample to a lab, where technicians will check it for ALL cells.

If doctors find ALL cells, this means that the cancer has spread to the person’s central nervous system (CNS). CNS involvement occurs in about 30–40% of people with relapsed ALL, and it is associated with less positive outcomes.


Immunophenotyping is a test that looks at the proteins on the surface of the ALL cells. It allows doctors to identify the types of cells circulating in the blood and helps them detect and classify abnormal lymphocytes or blast cells.

The two main types of lymphocytes are B cells and T cells. B cells make antibodies, which attach to pathogens and destroy them. T cells can have different roles, such as destroying pathogens or helping boost the B cells.

A doctor can use immunophenotyping to identify the type of ALL a person has. This can help them determine the best course of treatment.

Relapsed ALL can occur if cancer cells survive the initial treatment. This is possible if a person’s ALL cells become resistant to treatment.

Certain risk factors can make a person more likely to have relapsed ALL. These include:

  • being younger than 6 months or older than 60 years in age
  • being male
  • having a high white blood cell count
  • having T-cell ALL rather than B-cell ALL
  • spread of ALL to the CNS
  • certain gene mutations

The treatment options for relapsed ALL may vary depending on a person’s age. Generally, the treatment for a child with relapsed ALL can involve:

  • combination chemotherapy, which uses more than one anticancer drug
  • targeted therapy, which uses certain drugs to target specific types of cancer cells
  • transplant of blood-forming stem cells, which are cells that can develop into any type of blood cell

Other treatments for childhood relapsed ALL include chimeric antigen receptor (CAR) T-cell therapy. CAR T-cell therapy involves altering a person’s T cells to allow them to attack cancerous cells.

Research from 2018 notes that CAR T-cell therapy is an effective treatment for people who have relapsed B-cell ALL.

If relapsed ALL spreads to the CNS, doctors may prescribe different types of chemotherapy, as well as radiation therapy or stem cell transplants.

One option is systemic chemotherapy, which travels via the blood to cells all over the body. Another is intrathecal chemotherapy, which healthcare professionals inject between the layers of tissue that cover the brain and spinal cord.

In adults with relapsed ALL, doctors may recommend the following treatments:

  • combination chemotherapy and then a stem cell transplant
  • targeted therapy
  • low dose radiation therapy

Learn more about intrathecal chemotherapy.

Relapsed ALL is curable. However, the outlook can depend on:

  • a person’s age
  • the type of relapsed ALL
  • the length of time since the initial treatment
  • the site of relapse

People older than 30 years with relapsed ALL may have a less positive outlook than those under 30 years of age. Research from 2020 notes that 5-year survival rates for children with relapsed ALL are about 50%. However, survival rates are lower with future relapses. The researchers also note that the outlook is less good for people who relapse less than 3 years after initial treatment and those who have T-cell ALL.

A 2020 study found that the 5-year survival rate for adults with relapsed ALL was 5.8% when relapses occurred within 3 years of the initial treatment. However, this increased to 20% when relapses happened at a later stage.

Although treatment may cure a person of ALL, this cancer can reoccur. ALL relapses are possible when cancer cells remain after the initial treatment.

Relapsed ALL has the same symptoms as ALL. If a person notices any concerning symptoms, they should speak with a doctor.

Doctors can use various tests to diagnose a person with relapsed ALL. After receiving a diagnosis, a person can begin treatment.

The outlook for relapsed ALL is less positive than it is for initial ALL. A person’s age, the type of ALL, and the time since the initial treatment can all affect the outlook.