Leukemia

• 1. Introduction

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  Leukemia means 'white blood', a name pathologist Rudolf Virchow built from the Greek words leukos for white and haima for blood. He coined it after looking at a blood sample under a microscope and seeing far too many white blood cells crowding the view. That single observation in the 1840s named a group of blood cancers that usually begin in the bone marrow. The cells they produce are not fully grown. Doctors call them blasts, or simply leukemia cells. Why does the body start manufacturing crowds of half-finished cells? How does a disease of the marrow turn into bruising, fevers, and a body that cannot fight off a simple infection? And how did a cancer once romanticized in fiction as a gentle, joy-ending illness become one that more than nine in ten children can survive? The answers run from the microscope to the gene, from a folic acid mimic tested on children to engineered immune cells sent to hunt tumors.

• 2. Four Families, One Disease

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  By 1900, leukemia was no longer seen as a single illness. It was understood as a family of diseases. That family splits along two axes. The first axis is speed. Acute leukemia is marked by a rapid increase in immature blood cells. They crowd the marrow until it can no longer make healthy blood, and they spill into the bloodstream and spread to other organs. Acute forms demand immediate treatment and are the most common kind in children. Chronic leukemia builds up relatively mature but still abnormal white blood cells over months or years. Because it moves slowly, doctors sometimes monitor it for a time before treating, and it mostly affects older people. The second axis is the cell of origin. Lymphocytic leukemias begin in marrow cells that would have become lymphocytes, the infection-fighting immune cells, most often the B cell. Myeloid leukemias begin in cells that would have become red blood cells, platelets, and some white cells. Cross the two axes and you get the four main types: acute lymphoblastic, acute myeloid, chronic lymphocytic, and chronic myeloid. Each carries its own odds, and those odds are the next story.

• 3. The Survival Math

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  Five-year survival for chronic myelogenous leukemia is 90 percent, and the reason is a single pill. The standard for newly diagnosed CML is imatinib, sold as Gleevec in the United States and Glivec in Europe. It has relatively few side effects and can be taken orally at home. More than 90 percent of people keep the disease in check for at least five years, turning CML into a chronic, manageable condition. Acute myelogenous leukemia tells a harsher story, with a five-year survival rate of 20 percent. It is treated with chemotherapy and strikes adults far more than children, and men more than women. Chronic lymphocytic leukemia sits at 85 percent five-year survival, yet it is incurable; treatment aims to suppress it for years rather than cure it. Hairy cell leukemia is also incurable but easily treatable, with survival of 96 to 100 percent at ten years. At the far end is T-cell prolymphocytic leukemia, a rare and aggressive disease whose median survival is measured in months. Across all types in the United States, the five-year survival rate was 69 percent from 2016 to 2022. For children under 15 in wealthy countries it climbs above 60 or even 90 percent, but for infants diagnosed under the age of one it falls to around 40 percent.

• 4. When The Marrow Fails

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  Easy bruising, pale skin, fever, and an enlarged spleen or liver are the most common symptoms in children. Each one traces back to the same failure: leukemia cells displace the normal marrow and starve the blood of healthy cells. Lost platelets break the clotting process, so people bruise easily, bleed excessively, or develop pinprick bleeds called petechiae. Suppressed or dysfunctional white blood cells leave the immune system unable to fight pathogens. The result ranges from infected tonsils and mouth sores to life-threatening pneumonia and opportunistic infections. A shortage of red blood cells produces anemia, which can cause breathlessness and pallor. Beyond the blood counts, people may feel chills, night sweats, weakness in the limbs, and flu-like fatigue. An enlarged liver and spleen can bring nausea, a feeling of fullness, and unintentional weight loss. If leukemic cells reach the central nervous system, headaches and rarer signs like seizures or coma can follow from brain stem pressure. Every one of these symptoms can belong to other diseases, which is why leukemia is always confirmed through medical tests. There is even a quieter version called aleukemia, where cancerous cells stay in the marrow instead of entering the bloodstream, so a routine blood count looks normal or low. It is particularly common in hairy cell leukemia.

• 5. Mutations And Their Triggers

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  Leukemia, like other cancers, begins with mutations in DNA. Certain mutations activate oncogenes or switch off tumor suppressor genes, disrupting how cells die, specialize, or divide. These changes can happen spontaneously or follow exposure to radiation or carcinogens. Among adults, the known causes include natural and artificial ionizing radiation, the petrochemical benzene, and alkylating chemotherapy drugs given for earlier cancers. Tobacco carries a small added risk of acute myeloid leukemia, and studies in 2009 and 2010 found a positive correlation between formaldehyde exposure and myeloid leukemia. Viruses play a role too: human T-lymphotropic virus, HTLV-1, causes adult T-cell leukemia by immortalizing infected T-cells rather than destroying them. Genetics tilt the odds as well. People with Down syndrome face a significantly increased risk of acute leukemia, especially the myeloid form, and Fanconi anemia is a risk factor for acute myeloid leukemia. A mutation in the SPRED1 gene has been linked to childhood leukemia. Chronic myelogenous leukemia carries its own genetic signature, the Philadelphia translocation, found in 95 percent of CML cases. As for the long-debated question of power lines, the International Agency for Research on Cancer found only limited evidence that high levels of extremely low frequency magnetic fields might cause some childhood cases. The World Health Organization estimates that if proven, such exposure would account for just 100 to 2400 cases worldwide each year.

• 6. Phases Of Attack

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  Periodic lumbar punctures, used to administer methotrexate directly into the spine, define how acute lymphoblastic leukemia is fought, because the treatment must keep cancer out of the central nervous system. ALL therapy unfolds in distinct phases. Induction chemotherapy brings the marrow into remission; for children with low-risk disease this usually means prednisone, L-asparaginase, and vincristine in the first month. Consolidation then clears any leukemia cells that remain, often with antimetabolites like methotrexate and 6-mercaptopurine. CNS prophylaxis uses radiation of the head or drugs delivered into the spine to block spread to the brain. Maintenance treatment follows with lower drug doses and can continue for up to three years. Chronic lymphocytic leukemia takes a different path, because much of it is low-grade disease that does not benefit from treatment at all. Doctors act when hemoglobin or platelet counts fall, when the disease advances, or when lymph nodes and spleen overgrow painfully. Hairy cell leukemia is often left alone until symptoms appear, then treated with one week of cladribine or six months of pentostatin, which usually produces a prolonged remission from a single round. Bone marrow transplantation offers a possible cure for harder cases, but it carries real danger. In chronic myelogenous leukemia, roughly 30 percent of people die from the transplant procedure itself.

• 7. From Velpeau To Engineered Cells

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  Alfred-Armand-Louis-Marie Velpeau, an anatomist and surgeon, first described leukemia in 1827, nearly two decades before Virchow gave the fuller account in 1845. About ten years after Virchow, the pathologist Franz Ernst Christian Neumann examined the marrow of a deceased patient and found it colored a dirty green-yellow instead of red. That clue let him pin the abnormal blood on a problem in the bone marrow itself. The push toward cure came later. By 1947, Boston pathologist Sidney Farber believed aminopterin, a folic acid mimic, might cure leukemia in children. Most children with ALL who were tested showed improvement in their marrow, though none were truly cured, and the work opened the door to further experiments. In 1962, researchers Emil J. Freireich Jr. and Emil Frei III tried combination chemotherapy, and some patients survived long after the tests. Today the frontier is gene therapy. One approach uses genetically modified T cells, called CAR-T cells, to attack cancer. In 2011, a year after treatment, two of three people with advanced chronic lymphocytic leukemia were reported cancer-free. By 2013, three of five people with acute lymphocytic leukemia were in remission. As of 2018, two CAR-T therapies had been approved by the Food and Drug Administration, though the treatment carries significant side effects and loss of the targeted antigen is a common cause of relapse.

• 8. Numbers And Meanings

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  In 2015, leukemia was present in 2.3 million people worldwide and caused 353,500 deaths. It is the most common cancer in children, with three-quarters of childhood cases being the acute lymphoblastic type, yet over 90 percent of all leukemias are diagnosed in adults, where CLL and AML lead. In the United States, about 245,000 people live with some form of the disease, and around 5.4 billion dollars is spent on treatment each year. Around 30 percent more men than women have leukemia, and white American children are almost twice as likely to develop it as black American children. The disease also carries cultural weight. According to Susan Sontag, leukemia was often romanticized in 20th-century fiction as a clean, joy-ending illness whose fair and gentle victims die young, making it the cultural successor to tuberculosis. The 1970 romance novel Love Story is one example of that romanticizing. Among real patients, the gap between fiction and detection remains wide. The American Cancer Society estimates that at least one-fifth of people with leukemia have not yet been diagnosed, because the symptoms are vague enough to be mistaken for almost anything else.