Health
Playing for Keeps
Leukemia, a deadly cancer of the blood, can sneak up on an otherwise healthy person—even former Dallas Cowboys coach Tom Landry.
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When the bone marrow begins producing immature or useless white cells, the first damage is to the body’s immune system, where the bad cells soon crowd out the functional ones, leaving the victim more vulnerable to infection. As the number of abnormal white cells in the bone marrow mounts (like all cancer cells, they tend to reproduce much more rapidly than normal cells), the production of healthy red cells and platelets is also compromised. Fewer healthy red cells in circulation mean less oxygen being transported in the blood, resulting in the shortness of breath and the chronic fatigue that are hallmark symptoms of leukemia. A shortage of platelets causes a tendency to bleed and bruise easily. Soon vital organs are suffering from the weakened blood. Eventually, when production of the bone marrow’s stem cells—the biological precursors of the three types of blood cells—is stifled, the tyranny of the cancerous white cells becomes complete.
Medical science has identified four basic types of leukemia based on the intensity of onset and the type of white blood cells affected. There are acute and chronic varieties of leukemia that affect either lymphocytes or granulocytes, two kinds of white blood cells that help the body fight infectious bacteria and viruses and fungi. Acute leukemias occur more suddenly and with more severity; undetected or untreated, they can kill in a matter of months and require immediate treatment with large doses of chemotherapy. Victims of chronic forms of leukemia, on the other hand, can live for years in relative comfort with the disease in a stable state. They are often treated with interferon, which is milder than the drugs used in chemotherapy, unless their leukemia erupts into a more acute phase.
The type that Landry has is acute myelogenous (or granulocytic) leukemia (AML). The most common form of the cancer overall, with about 9,400 new cases annually (most of them adults over sixty), it causes 6,600 deaths a year. Remission is successfully induced in about 70 percent of patients under sixty. For people over sixty, however, the success rate is closer to 40 percent, though the relative health of the patient and how early the disease was caught can affect survival.
The preferred treatment for all types of leukemia is chemotherapy, though radiation may be used in some cases. The overall four-year, disease-free survival rate after chemo is about 40 percent. Younger patients, of course, fare better than older ones, and certain forms of leukemia are more responsive to therapy than others: Acute lymphocytic leukemia (ALL), the most common form of the disease among children, is the most responsive, chronic myelogenous (or granulocytic) leukemia the least; it can rarely be brought into complete remission by any drug or procedure other than a bone marrow transplant. Ironically, oncologists have discovered that certain substances used in chemotherapy for one cancer may actually trigger a secondary leukemia—which will probably have to be treated with more chemo.
If chemotherapy fails, a patient may be eligible for a bone marrow transplant. There are two types of bone marrow transplants: allogeneic and autologous. In the former, stem cells are usually harvested from a blood relative of the patient, generally a sibling. The patient is then given a strong dose of chemo to kill off all of the cancerous white blood cells in the system (unfortunately, it kills all of the non-cancerous blood cells as well). The healthy stem cells are then transfused into the bloodstream, where, it is hoped, they will take up residence in the bone marrow and begin producing healthy blood cells of all types. An autologous transplant works the same way, except that doctors harvest the patient’s own bone marrow and attempt to ferret out healthy stem cells for the surgery. Even if everything goes well with the procedure—and as with any transplantation, a lot can go wrong—only 45 percent of children with ALL survive disease-free when given a transplant after a first or second remission. For adults having an autologous transplant for AML, the rate goes down to between 10 and 20 percent.
Given the limitations of the current therapies for leukemia, is there any sure way to reduce your odds of getting it? Since it is not known what causes most leukemias, the answer, unfortunately, is no. But some studies have suggested that about 20 percent of leukemia cases are caused by smoking cigarettes—one more reason to quit. Exposure to toxic chemicals and to environmental radiation is also known to cause leukemia, but only a tiny percentage of cases. And some alleged causes remain impossible to prove: exposure to the electromagnetic field of large power lines, for example.
As with many cancers, hope for improved cure rates lies in a better grasp of leukemia’s genetic mechanics. Scientists now know that the cancer is promoted when a genetic mutation causes an oncogene (a gene that promotes cell division) to activate when it shouldn’t or a tumor suppressor gene (one that reins in cell division) to shut off inappropriately. In some cases such mutations are inherited, and in other cases they can be traced to a specific environmental agent. But in most cases they develop over a lifetime and appear to be related to aging as much as anything else. Such DNA mutations can occur as “copying errors,” a mistake made in the process of DNA duplication, or “translocations,” a glitch caused when DNA from one chromosome wanders off and becomes attached to another chromosome.
In either case, when and if genetic science perfects gene therapy, doctors may be able to rehabilitate such breakdowns by replacing the defective DNA with healthy DNA. Until then, however, leukemia victims must simply continue their treatment and hope that the odds are with them. Landry left Baylor medical center in early June to recuperate at home from his first round of chemotherapy. He will return to the hospital this month to continue his treatment. According to his son, he is too old to be considered for a bone marrow transplant.
“We’re very optimistic,” says the younger Landry. “But you have to be patient. We’re fortunate that he took care to get his physicals regularly. Especially for older people, that’s the lesson here.”
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