Encyclopedia of Health and Medicine

leukemia 147
separately or in combination, remain the mainstay
of the therapeutic arsenal, with the objective
being to establish remission (a state in which there
is no evidence of the leukemia and all blood
counts and blood cells are normal). Oncologists
use several staging systems for leukemia to identify
the kinds of cells, cell lineage, and cell counts.
Chemotherapy is the treatment of choice, with
blood stem cell or BONE MARROW TRANSPLANTATION
sometimes an option depending on the leukemia’s
characteristics and stage at the time of diagnosis.
Research continues to produce new chemotherapy
agents and new combinations of existing agents
that appear more successful, though their ability to
sustain remission over time remains unknown. The
initial phase of chemotherapy typically involves
cycles of chemotherapy drugs administered over a
period of one to two years, with maintenance oral
chemotherapy drugs for another two and a half to
three years for ALL. Oncologists may use radiation
therapy to treat accumulations of cancerous lymphocytes
in the BRAIN, spleen, and lymph nodes
such as may occur with ALL. Many people need
supplemental BLOOD TRANSFUSION and ANTIBIOTIC
MEDICATIONS during chemotherapy.
CHEMOTHERAPY DRUGS USED TO TREAT LEUKEMIA
2-chlorodeoxyadenosine 5-azacytidine
6-thioguanine
anthracycline
arsenic trioxide
calicheamicin
carboplatin
hlorambucil
cladribine
conjugated MONOCLONAL
cyclophosphamide
ANTIBODIES (MABS)
daunorubicin
cytarabine
daunorubicin
dexamethasone
hydroxyurea
fludarabine
ifosfamide
idarubicin
interferon
imatinib
melphalan
L-asparaginase
methotrexate
mercaptopurine
pentostatin
mitoxantrone
prednisone
prednisolone
topotecan
teniposide
vincristine
vindesine
Across all types of leukemia, about 65 percent
of people achieve initial remission with treatment.
The rate of sustained remission (five years or
longer) is much higher with acute than with
chronic forms of leukemia, and in younger (under
age 14 years) than older (over age 60) people. For
children under age 14 who undergo treatment for
ALL, about 80 percent achieve long-term remission
such that doctors consider them cured of the
leukemia. About 30 percent of adults who have
ALL achieve similar long-term remission. Because
successful treatment regimens are relatively new,
however, doctors do not know what potential
health complications, if any, may arise decades
after treatment. Long-term survival rates are
higher for lymphocytic leukemias than for
myeloid leukemias.
Risk Factors and Preventive Measures
The causes of leukemia remain mostly unknown.
Doctors do know that about 60 percent of people
who have myelodysplasia syndrome eventually
develop AML. As well, people who have firstdegree
relatives (parent, sibling, or child) who
acquire ALL are about four times more likely to
develop ALL themselves. Researchers have identified
a number of potential risk factors associated
with leukemia, though the extent and nature of
the associations remains unclear. Among them are
• exposure to high-DOSE radiation, including radiation
therapy
• previous chemotherapy for other kinds of cancer
• exposure to the industrial chemicals benzene
and formaldehyde and their derivative compounds
• cigarette smoking
• infection with human T-cell leukemia virus 1
(HTLV-1)
• DOWN SYNDROME and CHROMOSOMAL DISORDERS
that run in families
Most people who develop leukemia do not
have any history of exposure to suspected risk factors,
however, making prevention recommendations
difficult. There are no known methods for
preventing leukemia.
See also B-CELL LYMPHOCYTE; CANCER TREATMENT
OPTIONS AND DECISIONS; ENVIRONMENTAL HAZARD EXPO-
SURE; ERYTHROPOIETIN (EPO); LYMPHOMA; MULTIPLE