Dec. 22, 2000 -- The holidays just highlight the fact that air travel is becoming more and more of a hassle. There have even been theories floating around that flying can give you cancer. And previous studies have uncovered a possible -- albeit weak -- link. New research indicates that the radiation exposure that builds up after several thousand hours in the air among airline cockpit crew members may lead to cancer -- particularly a form of leukemia -- by producing genetic changes in the body.
Acute myeloid leukemia is a cancer that causes abnormalities in the body's white blood cells. These abnormal cells reproduce uncontrollably, accumulate in the bloodstream, and ultimately take over the bone marrow.
The bone marrow is the spongy tissue inside the large bones of the body that makes vital elements for healthy circulation -- including red blood cells for carrying oxygen. Like other leukemias, treatment is very complex and may include chemotherapy and a bone marrow transplant.
Cockpit crews are exposed to a form of radiation called cosmic radiation during flights. Since cockpit crews typically spend several thousand hours a year in the air, the dose of radiation that builds up over several years can be substantial. Recently, studies have shown rates of certain types of cancer, including acute leukemia, are slightly higher among pilots and other individuals who fly for a living.
Published in 1996, the first study to raise the alert about the possible association between cancer and flying was led by Pierre R. Brand, MD, then at the BC Cancer Center in Vancouver, Canada. He and his colleagues found a higher cancer risk among pilots working for Air Canada.
Then in a study published last year, Maryanne Gundenstrup, MSc, MD, and colleagues from Copenhagen, Denmark demonstrated that Danish male jet cockpit crew members who flew more than 5,000 hours were at increased risk of getting leukemia and other types of cancer. Gundenstrup is with the National Clinic of Aviation Medicine at the University Hospital and the Institute of Cancer Epidemiology.
Now, Gundestrup and her colleagues have published a new study that may help explain how this increase in cancer occurs. They studied the genes of seven aircrew members who had leukemia and compared them to 19 patients who developed leukemia after radiation therapy as well as roughly 760 leukemia patients without a known history of exposure to radiation.
Genes make up chromosomes, which make up the body's DNA -- the blueprint for the human body, which dictates everything from hair color to sensitivity to diseases.
They found an abnormality in chromosome 7 in four of the seven aircrew members, eight of the 19 radiation-exposed leukemia sufferers, but only about 80 of the leukemia sufferers not exposed to radiation. Changes in chromosome 7 are associated with the development of leukemia. This research is published in a letter appearing in the Dec. 23, 2000 issue of the journal The Lancet.
This is a turning point in this area of research because "it has never before been reported that leukemia in aircrew is linked to chromosome changes, in fact the same changes seen in radiotherapy induced leukemia," says Gundestrup.
Brand tells WebMD that his research combined with that of Gundestrup is intriguing and may be relevant to anyone who spends several thousand hours on jets. However, the number of individuals studied in all these investigations has been small, so the link between jet flight and cancer is far from being confirmed. Even if there were a certain connection, he adds, the risk to any individual frequent flyer would be quite small. Brand is now a senior medical epidemiologist at Health Canada in Quebec.