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21

NCCN Guidelines for Patients

®

:

Acute Lymphoblastic Leukemia, Version 1.2017

2

Testing for ALL

Genetic tests

Doctors use FISH to detect certain abnormal gene

and chromosome changes in leukemia cells. This

test uses special color dyes, called probes, that

attach only to certain genes or parts of certain

chromosomes.

For example, the Philadelphia chromosome is a

common abnormal change found in adults with ALL.

This chromosome contains the

BCR-ABL

fusion

gene. To detect this, FISH uses color probes that

attach to the

BCR

gene and the

ABL

gene. The

BCR-ABL

fusion gene is shown by the overlapping

colors of the two probes.

Like cytogenetic testing, FISH is used to help plan

and monitor treatment for ALL. This test can be

performed on a sample of blood or bone marrow.

PCR/MRD

PCR (

p

olymerase

c

hain

r

eaction) is a very sensitive

test. Like FISH, it detects abnormal gene and

chromosome changes (mutations) in cells. However,

it can find mutations that are too small to be seen

with a microscope.

Doctors use this test to detect certain gene and

chromosome changes that are commonly found in

ALL. An example of this is the

BCR-ABL

fusion gene.

This gene is found on the Philadelphia chromosome.

PCR can detect gene mutations and measure the

number of cells that have them.

PCR is very helpful for checking how well treatment

is working. When the cells have certain genetic

changes, PCR can find and measure the amount of

leukemia cells left. This test can find one leukemia

cell among more than 10,000 normal cells. PCR

is the method used to find the amount of disease

present after treatment. Doctors use this to assess

for MRD (

m

inimal

r

esidual

d

isease). The presence of

MRD is a key factor used to decide if more treatment

is needed. (See page 37 for more details about

checking treatment results.)

PCR can be done on a sample of bone marrow

or blood. But, bone marrow is often preferred,

especially when checking treatment results.