Testing procedures for APL
If signs and symptoms suggest that you have leukemia, your doctor will examine your
blood cells with a test called a
complete blood count. If the results
are abnormal, the doctor or nurse may talk to you about a
bone marrow biopsy.
Genetic testing can help track disease status, predict relapse, and improve outcomes.
For acute promyelocytic leukemia (APL) patients, one test for diagnosing APL
specifically, and
tracking disease progress, is reverse transcriptase-polymerase chain reaction testing, or
RT-PCR
testing. The RT-PCR test may be used to determine disease status and adjust
therapy if necessary. Studies have shown that a positive test may predict relapse, whereas
repeatedly negative results are associated with long-term survival in the majority of patients.
1
These studies report that patients who show a positive RT-PCR test may be given chemotherapy earlier,
which may help to improve outcome versus delaying treatment until further evidence of a relapse is present.
1,2
>> Click here to learn more about RT-PCR testing.
To learn more about the tests involved in diagnosing and treating acute myeloid leukemia (AML)
and its subtypes, such as APL, click on the links below:
Blood cell counts and blood cell examination
Changes in the numbers of different blood cell types and how the cells look under a microscope
can suggest leukemia. People with APL have too many immature blood cells, known as promyelocytes,
which cannot carry out their normal functions and which block the production of normal mature cells.
Even though presence of these immature cells may suggest leukemia, usually the disease cannot be
diagnosed without getting a sample of bone marrow cells.
3
Bone marrow aspiration and biopsy
In bone marrow aspiration, a syringe is used to suck out a small amount of liquid bone marrow
(about 1 teaspoon). The bone marrow sample is generally taken from the pelvic (hip) bone.
Sometimes the needle going into the bone is painful, but it only lasts a short time. The
sucking out of the bone marrow is often painful or at least uncomfortable for a brief time.
3
The aspiration may be followed by a bone marrow biopsy in the same area. The doctor may use the
same or a larger needle to collect a second sample called a core biopsy. This contains a small
solid piece of bone and marrow. You may feel some pressure as the doctor removes the marrow
specimen. After the biopsy needle is pulled out, this solid sample is pushed out of the needle
with a wire so that it can be examined under a microscope.
3
RT-PCR testing
RT-PCR testing analyzes the genetic abnormalities that define APL specifically. In general,
chromosome changes give us one clue to prognosis for cancer patients. APL is usually marked
by an exchange of genes between chromosomes 15 and 17. This exchange is called a translocation.
This translocation is written in a shorthand form as t(15;17), meaning a part of chromosome
15 is now located on chromosome 17, and vice versa.
4-7 When the genes trade places,
a mutant gene is formed and it is this mutant gene that prevents leukemia cells from aging in
a healthy way and causes leukemia cells to increase in number.
4-8
The presence of this mutant gene produced by the exchange of genes between chromosomes 15 and
17 is detected with the RT-PCR test.
1 The test is performed to diagnose APL and is
performed between rounds of therapy to assess a patient’s disease status.
>> Click here to learn more about the underlying causes of APL, including chromosome translocation.
Other tests
Your doctor may perform a variety of lab tests, including microscopic examinations that analyze
any samples taken (i.e., blood, bone marrow) under a microscope. Many specialized tests may be
done to determine the exact type of leukemia. Genetic testing involves looking at a cell's
chromosomes under a microscope to detect abnormalities.
3
Talk to your doctor about what tests and procedures may be involved in your treatment.
1. Lowenberg B, Griffin JD, Tallman MS. Acute myeloid leukemia and acute promyelocytic leukemia.
Hematology Am Soc Hematol Educ Program. 2003;82-101.
2. Lo Coco F, Diverio D, Avvisati G, et al. Therapy of molecular relapse in acute promyelocytic leukemia.
Blood. 1999;94:2225-2229.
3. American Cancer Society. How Is Acute Myeloid Leukemia (AML) Diagnosed? Available at:
http://www.cancer.org. Accessed September 1, 2006.
4. Grignani F, Fagioli M, Alcalay M, et al. Acute promyelocytic leukemia: from genetics to treatment.
Blood. 1994;83:10-25.
5. Douer D, Tallman MS. Arsenic trioxide: new clinical experience with an old medication in hematologic malignancies.
J Clin Oncol. 2005;23:2396-2410.
6. Miller WH Jr, Schipper HM, Lee JS, et al. Mechanisms of action of arsenic trioxide.
Cancer Res. 2002;62:3893-3903.
7. Davison K, Mann KK, Miller WH Jr. Arsenic trioxide: mechanisms of action.
Semin Hematol. 2002;39(2 Suppl 1):3-7.
8. Melnick A, Licht JD. Deconstructing a disease: RAR alpha, its fusion partners, and their roles in the pathogenesis of acute promyelocytic leukemia.
Blood. 1999;93:3167-3215.