Leukemia

Definition

Leukemia is a term for cancers of the blood cells. Leukemia starts in blood-forming tissues such as the bone marrow. Your bone marrow makes the cells that will develop into white blood cells, red blood cells, and platelets.

Each type of cell has a different job:

• White blood cells help your body fight infection
• Red blood cells deliver oxygen from your lungs to your tissues and organs
• Platelets help form clots to stop bleeding

When you have leukemia, your bone marrow makes large numbers of abnormal cells. This problem typically happens with white blood cells. These abnormal cells build up in your bone marrow and blood crowding out the healthy blood cells and making it hard for your cells and blood to do their work.

The number of new cases of leukemia diagnosed in the United States each year is about 14 per 100,000 men and women or 61,000 new cases per year. It is the tenth most common cancer according to new cases diagnosed each year. Leukemia accounts for 3% of all new cancer cases in the United States, according to 2022 estimates from the American Cancer Society.

Although leukemia is considered a disease of children, it actually affects far more adults. In fact, the likelihood of developing this cancer increases with age. Leukemia is most frequently diagnosed in people 65 to 74 years of age. Leukemia is more common in men than in women, and more common in Caucasians than in Blacks. Although leukemia is rare in children, of the children or teens who develop any type of cancer, 30% will develop some form of leukemia.

Types of leukemia

There are different types of leukemia. The type of leukemia you will depend on the type of blood cell that becomes cancer and whether it grows quickly or slowly.

The type of blood cell could be:

• Lymphocytes, a type of white blood cell
• Myeloid cells, immature cells that become white blood cells, red blood cells, or platelets

The different types can grow quickly or slowly:

• Acute leukemia is fast growing. It usually gets worse quickly if it’s not treated.
• Chronic leukemia is slow growing. It usually gets worse over a longer period of time.

The main types of leukemia are:

• Acute lymphocytic leukemia (ALL), which is the most common type of cancer in children. It can also affect adults.
• Acute myeloid leukemia (AML), which is more common in older adults but can also affect children
• Chronic lymphocytic leukemia (CLL), which is one of the most common types of leukemia in adults. It often occurs during or after middle age.
• Chronic myeloid leukemia (CML), which usually occurs in adults during or after middle age

Causes

Leukemia starts when the DNA of a single cell in the bone marrow changes (mutates) and can’t develop and function normally. All cells that arise from that initial mutated cell also have the mutated DNA.

What causes the damage to the DNA in the first place is still unknown. Scientists have been able to locate changes in certain chromosomes of patients diagnosed with different types of leukemia.

Risk factors

You cannot “catch” leukemia from someone else. It is not “transmitted” from one person to another.

Despite the fact that the exact cause of the DNA mutation that leads to leukemia not fully being known, scientists have discovered certain risk factors that may increase your risk of developing leukemia:

• Previous cancer treatment with radiation or chemotherapy.
• History of smoking or working with industrial chemicals. Benzene and formaldehyde are known cancer-causing chemicals found in tobacco smoke and building materials and household chemicals. Benzene is used in the making of plastics, rubbers, dyes, pesticides, drugs and detergents. Formaldehyde is found in building materials and many household products such as soaps, shampoos and cleaning products.
• Having a genetic disorder, such as neurofibromatosis, Klinefelter syndrome, Shwachman-Diamond syndrome or Down Syndrome.

Leukemia can happen to anyone. You may get leukemia and have none of these risk factors. Other people have one or more of these risk factors and never get leukemia. Additionally, having a family history of leukemia doesn’t necessarily mean that you will develop leukemia. Although scientists have also found other genetic mutations that can increase your risk, how much the risk is increased is not exactly known. In fact, in most cases, there’s no family history of leukemia. If you or a family member has a genetic condition, your doctor may recommend genetic testing or counseling.

Symptoms

Your symptoms depend on what type of leukemia you have.

However, the most common signs and symptoms include:

• Tire easily, little energy, weakness.
• Pale skin tone.
• Fever.
• Easy bruising and bleeding. Nosebleeds and bleeding gums. Tiny red spots in skin (called petechiae). Purplish patches in the skin.
• Bone or joint pain and/or tenderness.
• Swollen lymph nodes in the neck, underarm, groin or stomach; enlarged spleen or liver.
• Frequent infections.
• Unplanned weight loss.
• Night sweats.
• Shortness of breath.
• Pain or full feeling under the ribs on the left side.

If you have a chronic form of leukemia, you may not have any noticeable symptoms in the early stages of this cancer.

Diagnosis

Your doctor will conduct a physical exam and order blood tests. If the results are suspicious, he or she will order imaging tests and a bone marrow biopsy.

Treatments

Treatments for leukemia depend on the type of leukemia you have, your age and overall health, and if the leukemia has spread to other organs or tissues. There are five common treatment categories:

1. Chemotherapy
2. Radiation therapy
3. Immunotherapy
4. Targeted therapy
5. Hematopoietic cell transplant (also known as stem cell or bone marrow transplant)

Some leukemia treatment is delivered in three phases. Each phase has a specific goal.

• Induction therapy is the first phase. Its goal is to kill as many leukemia cells as possible in the blood and bone marrow to achieve remission. In remission, blood cell counts return to normal levels, no leukemia cells are found in the blood and all signs and symptoms of the disease are gone. Induction therapy usually lasts four to six weeks.
• Consolidation (also called intensification), the second phase, begins after leukemia is in remission. The goal of this phase is to kill any remaining undetected leukemia cells in the body so the cancer does not return. Consolidation therapy is usually given in cycles over four to six months.
• Maintenance therapy is given to kill any leukemia cells that may have survived the first two treatment phases. The goal of maintenance therapy is to prevent the return of leukemia (relapse). Treatment usually lasts for about two years.

Treatment can be also directed at the brain and spinal cord [the central nervous system] during each of these phases. This is done to kill cancer cells that hide in these areas of the body where the chemotherapy cannot reach. These “hidden” cancer cells are a reason leukemia comes back or relapses.

Other leukemia treatments do not have phases and are given indefinitely. They are continued as long as they are working to combat the leukemia and the patient is tolerating the treatment well.

Treatment is resumed or changed if leukemia comes back or relapses.

Prevention

There are a few lifestyle changes you can make to reduce your risk of leukemia. These steps can also reduce your risk of other types of cancer as well:

• Quit smoking. Smoking increases your risk of multiple types of cancer, including leukemia.
• Maintain a moderate weight. Being obese is another risk for leukemia that you can control. Taking steps to keep a moderate weight can reduce your risk of leukemia. Start by developing a balanced diet and making physical activity part of your everyday life.
• Avoid breathing in certain chemicals. The chemicals benzene and formaldehyde are known to increase your risk of leukemia. These chemicals can be found in some workplaces and buildings. If possible, avoiding these chemicals can lower your risk of leukemia.