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When Bone Marrow Goes Awryby Dianne Witter
Blood cell production can be hampered by any number of causes, many of them minor and easily remedied. In myelodysplastic syndrome (MDS), however, the situation is much more complicated and difficult to treat. “It’s a disease of the bone marrow stem cells in which chromosome abnormalities compromise the ability of stem cells to mature into functional blood cells,” explained Dr. Elihu Estey. “In MDS, the marrow becomes populated by immature cells, or blasts, and cytopenias develop.” As a result, regular blood transfusions are often a necessity. Low platelet counts put patients at risk for life-threatening hemorrhage. Low white blood cell counts, particularly neutrophils, set patients up for opportunistic infections that may be resistant to treatment. The course of MDS is variable, but it is progressive. Without treatment that delays progression, about three-fourths of MDS patients die within two to three years of diagnosis; in the high-risk category, the prognosis is more like six to 12 months. But current treatments for MDS are significantly better than supportive care—the previous standard treatment—and survival curves may soon reflect that. In about 30% of patients, MDS transforms into acute myeloid leukemia (AML), said Dr. Estey, which is why it has often been referred to as “pre-leukemia.” “That’s a misnomer, though,” he said. “MDS can be, and often is, fatal before AML ever develops, and AML doesn’t develop in everyone with MDS.” Subtle signs The first clinical signs of MDS are unremarkable and thus easily missed. Pallor and excessive fatigue are the most common, sometimes accompanied by bruising, petechiae, or increased infections. Anemia is often the most salient initial finding, which scarcely narrows the diagnosis. As a result, MDS is often misdiagnosed or not diagnosed at all. It doesn’t help that MDS is largely a disease of people over 60 years old. “Many doctors feel anemia is a normal part of aging,” said Dr. Estey. He feels this belief leaves many people undiagnosed and untreated until their disease progresses. Dr. Estey suggests that the cause of a low hemoglobin level is always worth investigating. “Someone could have a very significant illness with a hemoglobin that’s just a little low,” he said. Given the complexity of MDS and the relative rarity of the disease, a definitive diagnosis usually requires referral to a cancer center or to a specialist in hematology or oncology. When a physician has determined that a patient’s anemia is not due to simpler explanations—such as iron or B12 deficiency—other findings may suggest MDS. For instance, suppression of white blood cells and/or platelets in addition to red blood cells could indicate MDS, as could abnormalities in the shape and size of the red blood cells. Ultimately, diagnosis of MDS requires a bone marrow biopsy, with cytogenetic analysis of the tissue. “As the population ages, community physicians can expect to see more patients with MDS,” said Dr. Estey. “It’s considered a rare disease, but it’s probably the most common subtype of leukemia, with about 13,000 cases diagnosed per year.” Ironically, the fact that more people are surviving cancer today than ever before has also contributed to the rising incidence of MDS—chemotherapy and radiation can damage the bone marrow and lead to therapy-related MDS in some patients.For more information on this topic or for questions about M. D. Anderson’s treatments, programs, or services, call askMDAnderson at (877) MDA-6789. Other articles in OncoLog, July/August 2006 issue:
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