Prognosis and survival for acute lymphoblastic leukemia
People with acute lymphoblastic leukemia (ALL) may have questions about their prognosis and survival. Prognosis and survival depend on many factors. Only a doctor familiar with a person’s medical history, type of cancer, stage, characteristics of the cancer, treatments chosen and response to treatment can put all of this information together with survival statistics to arrive at a prognosis.
A prognosis is the doctor’s best estimate of how cancer will affect a person and how it will respond to treatment. A prognostic factor is an aspect of the cancer or a characteristic of the person that the doctor will consider when making a prognosis. A predictive factor influences how a cancer will respond to a certain treatment. Prognostic and predictive factors are often discussed together and they both play a part in deciding on a treatment plan and a prognosis.
Prognostic and predictive factors for ALL
The following are prognostic and predictive factors for ALL.
Age
Younger adults, usually those younger than 50 years of age, have a more favourable prognosis than older adults. This may be because chromosomal abnormalities can happen as a person gets older. Older people may also have other health conditions that make it difficult for them to cope with the side effects of treatments for ALL.
White blood cell count
The white blood cell (WBC) count at the time of diagnosis is a prognostic factor for ALL. People with a WBC less than 30,000/mm³ for B-cell ALL and less than 100,000/mm³ for T-cell ALL tend to have a more favourable prognosis.
ALL classification
Hyperdiploid B-ALL has a more favourable prognosis than other types of ALL, but the outcome is continuously improving with the use of targeted therapy, maintenance therapy and stem cell transplantation.
Chromosome changes
Changes to certain chromosomes are a prognostic factor for ALL.
The Philadelphia chromosome
The most common abnormality in the leukemia cells of people with ALL is the Philadelphia (Ph) chromosome. The Ph chromosome is a translocation, or rearrangement, of chromosomes 9 and 22. This translocation creates the BCR-ABL fusion gene, which leads to the development of ALL.
In the past, having leukemia cells with the Ph chromosome (referred to as Ph-positive ALL, or Ph+ ALL) used to mean a less favourable prognosis. Today targeted therapy drugs are used to treat Ph+ ALL, so the prognosis for this cancer is more favourable.
Other chromosome changes
The following chromosome abnormalities usually mean a less favourable prognosis:
- a translocation between chromosomes 4 and 11
- having an extra chromosome 8
- missing chromosome 7
- hypodiploidy (with less than the normal number of 46 chromosomes)
The following chromosome abnormalities usually mean a more favourable prognosis:
- hyperdiploidy (usually with more than 50 and less than 66 chromosomes)
- a translocation between chromosomes 10 and 14
Response to chemotherapy
The response to chemotherapy is measured as the time it takes to reach a complete remission, or complete response. When a complete remission is reached within 4 weeks of starting chemotherapy, the prognosis is more favourable. The prognosis is less favourable when it takes longer to reach complete remission. The prognosis is poorer in people who don’t reach a complete remission after chemotherapy.
Minimal residual disease (MRD) means that there are leukemia cells in the bone marrow, but they can only be seen using very sensitive tests, such as flow cytometry or polymerase chain reaction (PCR). The cancer cells can’t be seen with standard tests, such as looking at the cells under a microscope. In general, people with ALL who have MRD any time after the start of consolidation therapy (the continued treatment given to keep leukemia from coming back) have a higher risk of relapse and a poorer prognosis.
Early relapse
An early relapse means that the leukemia returns soon after treatment. It is a poor prognostic factor.
Leukemia cells in the central nervous system
Spread of ALL to the brain and spinal cord (called the central nervous system, or CNS) is a poor prognostic factor.
Prognostic risk groups
People with ALL are divided into the following prognostic risk groups:
Good risk means that the person with ALL has a more favourable prognosis. People in the good risk group:
- have no unfavourable chromosome abnormalities
- are younger than 30 years of age
- have a WBC count less than 30,000 for B-cell ALL and less than 100,000 for T-cell ALL
- reach complete remission within 4 weeks
Intermediate risk means that the person with ALL has a less favourable prognosis than good risk, but a more favourable prognosis than poor risk.
Poor risk means that the person with ALL has a less favourable prognosis. People in the poor risk group:
- have unfavourable chromosome abnormalities – t(9;22), t(4;11)
- are older than 60 years of age
- have ALL with a WBC count greater than 100,000
- do not reach a complete remission within 4 weeks