Leukemia

 

In all types of leukemia, cancer begins in the bone marrow where leukemia cells begin to multiply. The reason that those cells change remains a mystery in most cases.

However, doctors have been able to point to some risk factors that may lead to leukemia. They know that high levels of radiation, being born with Down syndrome, having had chemotherapy or radiation for a previous cancer, and certain inherited genetic disorders can be possible causes of leukemia.

One potential risk that’s been studied is particularly worrisome: X-rays in children. However, the risk hasn’t been proven and doctors say there’s no reason to avoid necessary X-rays in children. Here’s what the research has found about X-rays and their association with certain type of leukemia, along with the role that other risk factors may play.

Causes of Leukemia: The Question of X-Rays

It’s well known that high doses of radiation can cause leukemia. Survivors of the atomic bombs that were dropped in Japan in 1945 were found to have an increased risk for leukemia, says Richard Tower II, MD, pediatric oncologist at the Children’s Hospital of Wisconsin Cancer and Blood Disorders Center in Wauwatosa. But doctors aren’t sure how low doses of radiation from X-rays may affect our risk for leukemia. One recent study by researchers at the University of California, Berkeley attempted to get an answer. The researchers studied more than 800 children who had acute lymphocytic leukemia (ALL) or acute myeloid leukemia (AML) and looked at their exposure to X-rays before diagnosis.

They found that children who had ALL were twice as likely to have had three or more X-rays compared with children who weren’t diagnosed with leukemia. Among children who had a certain type of ALL called B-cell type, having had just one X-ray increased their risk.

Does that mean parents should avoid getting X-rays for their children? Absolutely not, doctors say. It’s hard to find a cause-and-effect relationship, Dr. Tower says. The group of patients with leukemia had more exposure to X-rays, but there could be something about leukemia patients that caused them to get X-rays before being diagnosed, he adds.

The study also included other types of scans that deliver a higher amount of radiation than X-rays, such as CT scans, so it’s hard to quantify the dose of radiation that could put children at higher risk, Tower says.

The medical community in general tries to limit the number of X-rays children receive, he says, but X-rays are a valuable and necessary tool for diagnosing pneumonia, bone fractures, asthma, scoliosis, and other conditions. CT scans help doctors evaluate and make diagnoses for appendicitis and other cancers, he points out.

The bottom line is that the value of an X-ray probably outweighs the potential increase in risk for leukemia. “The vast majority of kids who get X-rays don’t get leukemia,” Tower says.

Other Leukemia Risk Factors

Researchers will continue to study the risk X-rays and other forms of radiation may carry for children, but there are other risk factors that doctors have identified for leukemia.

Down syndrome. Kids who are born with Down syndrome have a genetic mutation that may predispose them to a specific type of AML during the first three years of life. They’re also at risk for developing ALL later in childhood, Tower says.

Chemotherapy or radiation. Being treated for another cancer with chemotherapy or radiation can also put you at higher risk for leukemia later on. That’s because DNA damage in early white blood cells during chemotherapy can lead to leukemia, Tower explains. High doses of radiation during cancer treatment are also a risk factor for ALL and chronic myelogenous leukemia (CML).

Inherited genetic disorders. Some rare inherited genetic disorders such as Bloom’s syndrome can be associated with leukemia, Tower says

Smoking. Doctors believe smoking also increases risk. In one analysis of more than 24,000 people age 14 and older, researchers found that smoking cigarettes increased their risk of getting AML as adults. Another study found that being regularly exposed to secondhand smoke may be a risk factor for chronic lymphocytic leukemia (CLL).

Being exposed to benzene. People who have been chronically exposed to the chemical benzene from working at certain manufacturing jobs have been found to be at risk for leukemia.

Medication side effects after an organ transplant. The drugs taken after an organ transplant lower immunity and can put people at higher risk for leukemia.

Advanced age. Leukemia is most common among people who are older than 60 years of age.

Experts have estimated that more than 43,000 adults and 3,300 children will develop leukemia this year, but doctors are still determining the causes of leukemia in many cases. Paying attention to risk factors, getting tested, and getting treatment as early as possible once you’ve been diagnosed can give you the best prospects for reaching full remission.