What is acute myeloid leukemia (AML)?
Acute myeloid leukemia
(AML) goes by many names, including acute myelocytic leukemia, acute
myelogenous leukemia, acute granulocytic leukemia, and acute
non-lymphocytic leukemia. "Acute" means that the leukemia can
grow quickly, and if not treated, could be fatal in a few months.
Acute myeloid leukemia
(AML) is a disorder of the process that normally produces neutrophils, a type
of white blood cell. Neutrophils fight infections caused by bacteria. Mature
neutrophils develop from immature (undeveloped) white blood cells in a process
called differentiation. The production of mature neutrophils usually is highly
regulated. For example, the body rapidly makes more neutrophils during an
infection and returns to a regular level of production when the infection is
controlled.
AML is a cancer that
starts in the cells that are supposed to mature into different types of blood
cells. AML starts in the bone marrow (the soft inner part of the bones, where
new blood cells are made), but in most cases it quickly moves into the blood.
It can sometimes spread to other parts of the body, including the lymph nodes,
liver, spleen, central nervous system (brain and spinal cord), and testicles
(in men). In contrast, other types of cancer can start in these organs and then
spread to the bone marrow (or other places). Those cancers are not leukemia.
The American Cancer
Society's most recent estimates for acute myeloid leukemia (AML) cancer in the
United States are for 2010:
- About 12,300 new cases of AML (Most will be in
adults)
- About 8,950 deaths from AML (Almost all will be
in adults)
The average age of a
patient with AML is about 67. AML is slightly more common among men than among
women. The lifetime risk of getting AML for the average man is about 1 in 250.
For the average woman the risk is about 1 in 300.
Link between Cigarette Smoking and acute
myeloid leukemia (AML)
Multiple scientific studies found causal links between cigarette smoking
habits and risks for acute myelogenous leukemia (AML) development, mostly due
to the chemical benzene.
Benzene is a colorless and sweet smelling chemical found in numerous
modern life compounds, like gasoline, industrial solvents, or cigarettes. In
general, cigarettes release between 50 and 150 micrograms of benzene per
cigarette, thus elevating the risk of the AML development for all tobacco
smokers. It was found that the average smoker consumes just under two
milligrams of benzene every day, which is about 10 times the average daily
intake of a nonsmoker.
The benzene itself is not present in the tobacco, but is produced during
the burning process. Studies show that benzene is rapidly absorbed through the
lungs during inhalation. Overall, approximately one half of the benzene is
inhaled into the lungs, where it is then distributed to different parts of the
body, including fatty tissue and bone marrow.
Although an statistical data for the higher risks of AML development for cigarette
smokers is not uniform, based on the particular researches settings, the
majority of studies in the last 20 years have reported a statistically
significant, moderate relationship with a relative risk of about 1.4 for AML
among cigarette smokers compared to non-smokers and the relative risk
approaching 2.0 for heavy smokers.
The controversial findings in the statistically significant causal
relationship might be driven by the fact that smoking may contribute to the particular types of the leukemia, while not
affecting others.
The
French-American-British (FAB) traditional classification for describing AML
morphology, lists 9 types of AML:
M0: Myeloblastic without differentiation
M1: Myeloblastic without maturation
M2: Myeloblastic with maturation
M3: Promyelocytic
M4: Myelomonocytic
M5a: Monocytic without differentiation (monoblastic)
M5b: Monocytic with differentiation
M6: Erythroleukemic
M7: Megakaryocytic
M1: Myeloblastic without maturation
M2: Myeloblastic with maturation
M3: Promyelocytic
M4: Myelomonocytic
M5a: Monocytic without differentiation (monoblastic)
M5b: Monocytic with differentiation
M6: Erythroleukemic
M7: Megakaryocytic
Dr. Janice M. Pogoda of
the University of Southern California in Los Angeles, and colleagues performed
investigation, looking for the correlation between smoking and particular AML
subtypes. They found out that smoking plays very significant role in M2 subtype,
but not in others. Indeed, smoking may be responsible for roughly 42% of cases
of this subtype of leukemia, reported the researchers.
The results confirmed that
while smokers in general were 2.3 times more likely to develop M2 type AML,
older adults aged 60 to 75 years were at 3.3 times greater risk of developing
this illness.
Those who smoked for more
than 35 years and smoked unfiltered cigarettes showed the highest risk, but
even older adults who smoked filtered cigarettes still had a nearly threefold
higher risk compared with nonsmokers.
Other Risk Factors
There are a few known risk
factors for acute myeloid leukemia, apart from cigarette smoking.
- Chemicals. Exposure to certain chemicals has been linked
to acute leukemia. For instance, long-term exposure to high levels of
benzene from different sources is a risk factor for acute myeloid leukemia.
Benzene is a solvent used in cleaning, in some industrial processes for
drugs, plastics, dyes, gasoline, and other goods. Patients with other
cancers who are treated with certain chemotherapy drugs are more likely to
develop AML. Using these drugs along with radiation treatment further
increases the risk.
- Radiation. Exposure to a high dose of radiation exposure
is a risk factor for acute myeloid leukemia. People who survived the
atomic bomb in Japan had a greatly increased risk of getting acute
leukemia, most within six to eight years. The risk of leukemia from lower
levels of radiation, such as from radiation treatment, X-rays, or CT
scans, is not clear.
- Certain
blood problems. Patients
with certain blood problems seem to be at a higher risk for getting acute
myeloid leukemia. If your body makes too many red cells or not enough
platelets, for instance, this may raise your risk. Some people with
chronic myelogenous leukemia (CML — another type of leukemia) later
develop a form of AML. The risk of getting AML is higher if treatment for
these other blood problems includes some types of chemotherapy or
radiation.
- Congenital
(present at birth) syndromes. For the most part, AML does not appear to be an inherited disease.
It is rare for it to run in families, so a person's risk is not usually
increased if a family member has the disease. But there are some
congenital syndromes with genetic changes that seem to raise the risk of
AML. These include:
·
Down syndrome
·
Fanconi anemia
·
Bloom syndrome
·
ataxia-telangiectasia
·
Blackfan-Diamond
syndrome
- Gender. AML is more common in males than in females.
The reasons for this are not clear.
AML Symptoms
The symptoms of AML are
caused by low numbers of healthy blood cells and high numbers of leukemia
cells.
- White blood cells fight infection. Low numbers
can lead to fever and frequent infections.
- Red blood cells carry oxygen throughout the
body. Low numbers can lead to anemia — feeling tired or weak, being short
of breath and looking pale.
- Platelets control bleeding. Low numbers can
lead to easy bleeding or bruising and tiny red spots under the skin
(petechiae).
- High numbers of leukemia cells may cause pain
in the bones or joints.
A person with AML may feel
generally unwell and run-down. He or she may also have other, less common
symptoms.
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