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Leukemia

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Template:Short description Template:Cs1 config Template:For multi Template:Use dmy dates Template:Use American English Template:Infobox medical condition (new)

Leukemia (also spelled leukaemia; pronounced Template:IPAc-en<ref name=pronunciation/> Template:Respell) is a group of blood cancers that usually begin in the bone marrow and produce high numbers of abnormal blood cells.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> These blood cells are not fully developed and are called blasts or leukemia cells.<ref name=NCIBook2013>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Symptoms may include bleeding and bruising, bone pain, fatigue, fever, and an increased risk of infections.<ref name=NCIBook2013 /> These symptoms occur due to a lack of normal blood cells.<ref name=NCIBook2013 /> Diagnosis is typically made by blood tests or bone marrow biopsy.<ref name=NCIBook2013 />

The exact cause of leukemia is unknown.<ref name=Hut2010/> A combination of genetic factors and environmental (non-inherited) factors are believed to play a role.<ref name=Hut2010>Template:Cite journal</ref> Risk factors include smoking, ionizing radiation, petrochemicals (such as benzene), prior chemotherapy, and Down syndrome.<ref name=Hut2010 /><ref name=NCISnap /> People with a family history of leukemia are also at higher risk.<ref name=NCISnap /> There are four main types of leukemia—acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL) and chronic myeloid leukemia (CML)—and a number of less common types.<ref name=NCISnap>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name=WCR2014/> Leukemias and lymphomas both belong to a broader group of tumors that affect the blood, bone marrow, and lymphoid system, known as tumors of the hematopoietic and lymphoid tissues.<ref>Template:Cite journal</ref><ref>Template:Cite book</ref>

Treatment may involve some combination of chemotherapy, radiation therapy, targeted therapy, and bone marrow transplant, with supportive and palliative care provided as needed.<ref name=NCISnap/><ref name="BCDtargetedTherapy">Template:Cite journal</ref> Certain types of leukemia may be managed with watchful waiting.<ref name=NCISnap/> The success of treatment depends on the type of leukemia and the age of the person. Outcomes have improved in the developed world.<ref name=WCR2014/> Five-year survival rate was 67% in the United States in the period from 2014 to 2020.<ref name=SEER>{{#invoke:citation/CS1|citation |CitationClass=web }} Updated as required.</ref> In children under 15 in first-world countries, the five-year survival rate is greater than 60% or even 90%, depending on the type of leukemia. For infants (those diagnosed under the age of 1), the survival rate is around 40%.<ref name=ACS2014/> In children who are cancer-free five years after diagnosis of acute leukemia, the cancer is unlikely to return.<ref name=ACS2014>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

In 2015, leukemia was present in 2.3 million people worldwide and caused 353,500 deaths.<ref name=GBD2015Pre>Template:Cite journal</ref><ref name=GBD2015De>Template:Cite journal</ref> In 2012, it had newly developed in 352,000 people.<ref name=WCR2014>Template:Cite book</ref> It is the most common type of cancer in children, with three-quarters of leukemia cases in children being the acute lymphoblastic type.<ref name=NCISnap/> However, over 90% of all leukemias are diagnosed in adults, CLL and AML being most common.<ref name=NCISnap/><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It occurs more commonly in the developed world.<ref name=WCR2014/> Template:TOC limit

ClassificationEdit

Four major kinds of leukemia
Cell type Acute Chronic
Lymphocytic leukemia
(or "lymphoblastic")		 Acute lymphoblastic leukemia
(ALL)		 Chronic lymphocytic leukemia
(CLL)
Myelogenous leukemia
("myeloid" or "nonlymphocytic")		 Acute myelogenous leukemia
(AML or myeloblastic)		 Chronic myelogenous leukemia
(CML)
File:Acute leukemia 1.webm
An explanation of acute leukemia

General classificationEdit

Clinically and pathologically, leukemia is subdivided into a variety of large groups. The first division is between its acute and chronic forms:<ref name=":1">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

  • Acute leukemia is characterized by a rapid increase in the number of immature blood cells. The crowding that results from such cells makes the bone marrow unable to produce healthy blood cells resulting in low hemoglobin and low platelets. Immediate treatment is required in acute leukemia because of the rapid progression and accumulation of the malignant cells, which then spill over into the bloodstream and spread to other organs of the body. Acute forms of leukemia are the most common forms of leukemia in children.
  • Chronic leukemia is characterized by the excessive buildup of relatively mature, but still abnormal, white blood cells (or, more rarely, red blood cells). Typically taking months or years to progress, the cells are produced at a much higher rate than normal, resulting in many abnormal white blood cells. Whereas acute leukemia must be treated immediately, chronic forms are sometimes monitored for some time before treatment to ensure maximum effectiveness of therapy. Chronic leukemia mostly occurs in older people but can occur in any age group.

Additionally, the diseases are subdivided according to which kind of blood cell is affected. This divides leukemias into lymphoblastic or lymphocytic leukemias and myeloid or myelogenous leukemias:<ref name=":1" />

Combining these two classifications provides a total of four main categories. Within each of these main categories, there are typically several subcategories. Finally, some rarer types are usually considered to be outside of this classification scheme.<ref name=":1" /><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Specific typesEdit

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  • Chronic lymphocytic leukemia (CLL) most often affects adults over the age of 55. It sometimes occurs in younger adults, but it almost never affects children. Two-thirds of affected people are men. The five-year survival rate is 85%.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref> It is incurable, but there are many effective treatments. One subtype is B-cell prolymphocytic leukemia, a more aggressive disease.

  • Acute myelogenous leukemia (AML) occurs far more commonly in adults than in children, and more commonly in men than women. It is treated with chemotherapy. The five-year survival rate is 20%.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref> Subtypes of AML include acute promyelocytic leukemia, acute myeloblastic leukemia, and acute megakaryoblastic leukemia.

  • Chronic myelogenous leukemia (CML) occurs mainly in adults; a very small number of children also develop this disease. It is treated with imatinib (Gleevec in United States, Glivec in Europe) or other drugs.<ref>{{#invoke:citation/CS1|citation

|CitationClass=web }}</ref> The five-year survival rate is 90%.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> One subtype is chronic myelomonocytic leukemia.

Pre-leukemiaEdit

Signs and symptomsEdit

File:Symptoms of leukemia.png
Common symptoms of chronic or acute leukemia<ref>Reference list is found at image description page in Wikimedia Commons</ref>

The most common symptoms in children are easy bruising, pale skin, fever, and an enlarged spleen or liver.<ref>Template:Cite journal</ref>

Damage to the bone marrow, by way of displacing the normal bone marrow cells with higher numbers of immature white blood cells, results in a lack of blood platelets, which are important in the blood clotting process. This means people with leukemia may easily become bruised, bleed excessively, or develop pinprick bleeds (petechiae).<ref>Template:Cite journal</ref>

White blood cells, which are involved in fighting pathogens, may be suppressed or dysfunctional. This could cause the person's immune system to be unable to fight off a simple infection or to start attacking other body cells. Because leukemia prevents the immune system from working normally, some people experience frequent infection, ranging from infected tonsils, sores in the mouth, or diarrhea to life-threatening pneumonia or opportunistic infections.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Finally, the red blood cell deficiency leads to anemia, which may cause dyspnea and pallor.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Some people experience other symptoms, such as fevers, chills, night sweats, weakness in the limbs, feeling fatigued and other common flu-like symptoms. Some people experience nausea or a feeling of fullness due to an enlarged liver and spleen; this can result in unintentional weight loss. Blasts affected by the disease may come together and become swollen in the liver or in the lymph nodes causing pain and leading to nausea.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

If the leukemic cells invade the central nervous system, then neurological symptoms (notably headaches) can occur. Uncommon neurological symptoms like migraines, seizures, or coma can occur as a result of brain stem pressure. All symptoms associated with leukemia can be attributed to other diseases. Consequently, leukemia is always diagnosed through medical tests.

The word leukemia, which means 'white blood', is derived from the characteristic high white blood cell count that presents in most affected people before treatment. The high number of white blood cells is apparent when a blood sample is viewed under a microscope, with the extra white blood cells frequently being immature or dysfunctional. The excessive number of cells can also interfere with the level of other cells, causing further harmful imbalance in the blood count.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Some people diagnosed with leukemia do not have high white blood cell counts visible during a regular blood count. This less-common condition is called aleukemia. The bone marrow still contains cancerous white blood cells that disrupt the normal production of blood cells, but they remain in the marrow instead of entering the bloodstream, where they would be visible in a blood test. For a person with aleukemia, the white blood cell counts in the bloodstream can be normal or low. Aleukemia can occur in any of the four major types of leukemia, and is particularly common in hairy cell leukemia.<ref name=ACS1/>

CausesEdit

Studies in 2009 and 2010 have shown a positive correlation between exposure to formaldehyde and the development of leukemia, particularly myeloid leukemia.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref> The different leukemias likely have different causes.<ref>Template:Cite book</ref>

Leukemia, like other cancers, results from mutations in the DNA. Certain mutations can trigger leukemia by activating oncogenes or deactivating tumor suppressor genes, and thereby disrupting the regulation of cell death, differentiation or division. These mutations may occur spontaneously or as a result of exposure to radiation or carcinogenic substances.<ref>Template:Cite journal</ref>

Among adults, the known causes are natural and artificial ionizing radiation and petrochemicals, notably benzene and alkylating chemotherapy agents for previous malignancies.<ref name="isbn1-55009-111-5">Template:Cite book</ref><ref name="isbn1-893441-36-9">Template:Cite book</ref><ref name="isbn0-8247-0170-4">Template:Cite book</ref> Use of tobacco is associated with a small increase in the risk of developing acute myeloid leukemia in adults.<ref name="isbn1-55009-111-5" /> Cohort and case-control studies have linked exposure to some petrochemicals and hair dyes to the development of some forms of leukemia. Diet has very limited or no effect, although eating more vegetables may confer a small protective benefit.<ref name="pmid12163333">Template:Cite journal</ref>

Viruses have also been linked to some forms of leukemia. For example, human T-lymphotropic virus (HTLV-1) causes adult T-cell leukemia.<ref>Template:Cite book</ref>

A few cases of maternal-fetal transmission (a baby acquires leukemia because its mother had leukemia during the pregnancy) have been reported.<ref name="isbn1-55009-111-5" /> Children born to mothers who use fertility drugs to induce ovulation are more than twice as likely to develop leukemia during their childhoods than other children.<ref name="Rudant2012">Template:Cite journal</ref>

In a recent systematic review and meta-analysis of any type of leukemia in neonates using phototherapy, typically to treat neonatal jaundice, a statistically significant association was detected between using phototherapy and myeloid leukemia. However, it is still questionable whether phototherapy is genuinely the cause of cancer or simply a result of the same underlying factors that gave rise to cancer.<ref>Template:Cite journal</ref>

RadiationEdit

Large doses of Sr-90 (called a bone seeking radioisotope) from nuclear reactor accidents, increases the risk of bone cancer and leukemia in animals and is presumed to do so in people.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Genetic conditionsEdit

Some people have a genetic predisposition towards developing leukemia. This predisposition is demonstrated by family histories and twin studies.<ref name="isbn1-55009-111-5" /> The affected people may have a single gene or multiple genes in common. In some cases, families tend to develop the same kinds of leukemia as other members; in other families, affected people may develop different forms of leukemia or related blood cancers.<ref name="isbn1-55009-111-5" />

In addition to these genetic issues, people with chromosomal abnormalities or certain other genetic conditions have a greater risk of leukemia.<ref name="isbn1-893441-36-9" /> For example, people with Down syndrome have a significantly increased risk of developing forms of acute leukemia (especially acute myeloid leukemia), and Fanconi anemia is a risk factor for developing acute myeloid leukemia.<ref name="isbn1-55009-111-5" /> Mutation in SPRED1 gene has been associated with a predisposition to childhood leukemia.<ref>Template:Cite journal</ref>

Inherited bone marrow failure syndromes represent a kind of premature aging of the bone marrow. In people with these syndromes and in older adults, mutations associated with clonal hematopoiesis may arise as an adaptive response to a progressively deteriorating hematopoietic niche, i.e., a depleting pool of Hematopoietic stem cells. The mutated stem cells then acquire a self-renewal advantage.<ref>Template:Cite journal</ref>

Chronic myelogenous leukemia is associated with a genetic abnormality called the Philadelphia translocation; 95% of people with CML carry the Philadelphia mutation, although this is not exclusive to CML and can be observed in people with other types of leukemia.<ref>Template:Cite journal</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Non-ionizing radiationEdit

Whether or not non-ionizing radiation causes leukemia has been studied for several decades. The International Agency for Research on Cancer expert working group undertook a detailed review of all data on static and extremely low frequency electromagnetic energy, which occurs naturally and in association with the generation, transmission, and use of electrical power.<ref name="isbn92-832-1280-0">Template:Cite book</ref> They concluded that there is limited evidence that high levels of ELF magnetic (but not electric) fields might cause some cases of childhood leukemia.<ref name="isbn92-832-1280-0" /> No evidence for a relationship to leukemia or another form of malignancy in adults has been demonstrated.<ref name="isbn92-832-1280-0" /> Since exposure to such levels of ELFs is relatively uncommon, the World Health Organization concludes that ELF exposure, if later proven to be causative, would account for just 100 to 2400 cases worldwide each year, representing 0.2 to 4.9% of the total incidence of childhood leukemia for that year (about 0.03 to 0.9% of all leukemias).<ref name="urlWHO | Electromagnetic fields and public health">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

DiagnosisEdit

File:Leukemia- SAG.jpg
The increase in white blood cells in leukemia

Diagnosis is usually based on repeated complete blood counts and a bone marrow examination following observations of the symptoms. Sometimes, blood tests may not show that a person has leukemia, especially in the early stages of the disease or during remission. A lymph node biopsy can be performed to diagnose certain types of leukemia in certain situations.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Following diagnosis, blood chemistry tests can be used to determine the degree of liver and kidney damage or the effects of chemotherapy on the person. When concerns arise about other damages due to leukemia, doctors may use an X-ray, MRI, or ultrasound. These can potentially show leukemia's effects on such body parts as bones (X-ray), the brain (MRI), or the kidneys, spleen, and liver (ultrasound). CT scans can be used to check lymph nodes in the chest, though this is uncommon.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Despite the use of these methods to diagnose whether or not a person has leukemia, many people have not been diagnosed because many of the symptoms are vague, non-specific, and can refer to other diseases. For this reason, the American Cancer Society estimates that at least one-fifth of the people with leukemia have not yet been diagnosed.<ref name=ACS1>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

TreatmentEdit

Most forms of leukemia are treated with pharmaceutical medication, typically combined into a multi-drug chemotherapy regimen. Some are also treated with radiation therapy. In some cases, a bone marrow transplant is effective.

Acute lymphoblasticEdit

Template:Further Management of ALL is directed towards control of bone marrow and systemic (whole-body) disease. Additionally, treatment must prevent leukemic cells from spreading to other sites, particularly the central nervous system (CNS); periodic lumbar punctures are used for diagnostic purposes and to administer intrathecal prophylactic methotrexate.<ref>Template:Cite journal</ref> In general, ALL treatment is divided into several phases:

  • Induction chemotherapy to bring about bone marrow remission. For adults, standard induction plans include prednisone, vincristine, and an anthracycline drug; other drug plans may include L-asparaginase or cyclophosphamide. For children with low-risk ALL, standard therapy usually consists of three drugs (prednisone, L-asparaginase, and vincristine) for the first month of treatment.
  • Consolidation therapy or intensification therapy to eliminate any remaining leukemia cells. There are many different approaches to consolidation, but it is typically a high-dose, multi-drug treatment that is undertaken for a few months. People with low- to average-risk ALL receive therapy with antimetabolite drugs such as methotrexate and 6-mercaptopurine (6-MP). People who are high-risk receive higher drug doses of these drugs, plus additional drugs.
  • CNS prophylaxis (preventive therapy) to stop cancer from spreading to the brain and nervous system in high-risk people. Standard prophylaxis may include radiation of the head and/or drugs delivered directly into the spine.
  • Maintenance treatments with chemotherapeutic drugs to prevent disease recurrence once remission has been achieved. Maintenance therapy usually involves lower drug doses and may continue for up to three years.
  • Alternatively, allogeneic bone marrow transplantation may be appropriate for high-risk or relapsed people.<ref>Template:Cite book</ref>

Chronic lymphocyticEdit

Template:Further

Decision to treatEdit

Hematologists base CLL treatment on both the stage and symptoms of the individual person. A large group of people with CLL have low-grade disease, which does not benefit from treatment. Individuals with CLL-related complications or more advanced disease often benefit from treatment. In general, the indications for treatment are:

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Treatment approachEdit

Most CLL cases are incurable by present treatments, so treatment is directed towards suppressing the disease for many years, rather than curing it. The primary chemotherapeutic plan is combination chemotherapy with chlorambucil or cyclophosphamide, plus a corticosteroid such as prednisone or prednisolone. The use of a corticosteroid has the additional benefit of suppressing some related autoimmune diseases, such as immunohemolytic anemia or immune-mediated thrombocytopenia. In resistant cases, single-agent treatments with nucleoside drugs such as fludarabine,<ref>Template:Cite journal</ref> pentostatin, or cladribine may be successful. Younger and healthier people may choose allogeneic or autologous bone marrow transplantation in the hope of a permanent cure.<ref>Template:Cite journal</ref>

Acute myelogenousEdit

Template:Further

Many different anti-cancer drugs are effective for the treatment of AML. Treatments vary somewhat according to the age of the person and according to the specific subtype of AML. Overall, the strategy is to control bone marrow and systemic (whole-body) disease, while offering specific treatment for the central nervous system (CNS), if involved.<ref>Template:Cite book</ref>

In general, most oncologists rely on combinations of drugs for the initial, induction phase of chemotherapy. Such combination chemotherapy usually offers the benefits of early remission and a lower risk of disease resistance. Consolidation and maintenance treatments are intended to prevent disease recurrence. Consolidation treatment often entails a repetition of induction chemotherapy or the intensification of chemotherapy with additional drugs. By contrast, maintenance treatment involves drug doses that are lower than those administered during the induction phase.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Chronic myelogenousEdit

Template:Further

There are many possible treatments for CML, but the standard of care for newly diagnosed people is imatinib (Gleevec) therapy.<ref name="pmid17970609">Template:Cite journal</ref> Compared to most anti-cancer drugs, it has relatively few side effects and can be taken orally at home. With this drug, more than 90% of people will be able to keep the disease in check for at least five years,<ref name="pmid17970609"/> so that CML becomes a chronic, manageable condition.

In a more advanced, uncontrolled state, when the person cannot tolerate imatinib, or if the person wishes to attempt a permanent cure, then an allogeneic bone marrow transplantation may be performed. This procedure involves high-dose chemotherapy and radiation followed by infusion of bone marrow from a compatible donor. Approximately 30% of people die from this procedure.<ref name="pmid17970609"/>

Hairy cellEdit

Template:Further

Decision to treat
People with hairy cell leukemia who are symptom-free typically do not receive immediate treatment. Treatment is generally considered necessary when the person shows signs and symptoms such as low blood cell counts (e.g., infection-fighting neutrophil count below 1.0 K/μL), frequent infections, unexplained bruises, anemia, or fatigue that is significant enough to disrupt the person's everyday life.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Typical treatment approach
People who need treatment usually receive either one week of cladribine, given daily by intravenous infusion or a simple injection under the skin, or six months of pentostatin, given every four weeks by intravenous infusion. In most cases, one round of treatment will produce a prolonged remission.<ref>Template:Cite journal</ref>

Other treatments include rituximab infusion or self-injection with Interferon-alpha. In limited cases, the person may benefit from splenectomy (removal of the spleen). These treatments are not typically given as the first treatment because their success rates are lower than cladribine or pentostatin.<ref>Template:Cite journal</ref>

T-cell prolymphocyticEdit

Template:Further

Most people with T-cell prolymphocytic leukemia, a rare and aggressive leukemia with a median survival of less than one year, require immediate treatment.<ref name="pmid11535503">Template:Cite journal</ref>

T-cell prolymphocytic leukemia is difficult to treat, and it does not respond to most available chemotherapeutic drugs.<ref name="pmid11535503" /> Many different treatments have been attempted, with limited success in certain people: purine analogues (pentostatin, fludarabine, cladribine), chlorambucil, and various forms of combination chemotherapy (cyclophosphamide, doxorubicin, vincristine, prednisone CHOP, cyclophosphamide, vincristine, prednisone [COP], vincristine, doxorubicin, prednisone, etoposide, cyclophosphamide, bleomycin VAPEC-B). Alemtuzumab (Campath), a monoclonal antibody that attacks white blood cells, has been used in treatment with greater success than previous options.<ref name="pmid11535503" />

Some people who successfully respond to treatment also undergo stem cell transplantation to consolidate the response.<ref name="pmid11535503" />

Juvenile myelomonocyticEdit

Treatment for juvenile myelomonocytic leukemia can include splenectomy, chemotherapy, and bone marrow transplantation.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

PrognosisEdit

The success of treatment depends on the type of leukemia and the age of the person. Outcomes have improved in the developed world.<ref name=WCR2014/> The average five-year survival rate is 65% in the United States.<ref name=SEER/> In children under 15, the five-year survival rate is greater (60 to 85%), depending on the type of leukemia.<ref name=ACS2014/> In children with acute leukemia who are cancer-free after five years, the cancer is unlikely to return.<ref name=ACS2014/>

Outcomes depend on whether it is acute or chronic, the specific abnormal white blood cell type, the presence and severity of anemia or thrombocytopenia, the degree of tissue abnormality, the presence of metastasis and lymph node and bone marrow infiltration, the availability of therapies and the skills of the health care team. Treatment outcomes may be better when people are treated at larger centers with greater experience.<ref>Template:Cite journal</ref>

EpidemiologyEdit

File:Leukaemia world map-Deaths per million persons-WHO2012.svg
Deaths due to leukemia per million persons in 2012: Template:Div colTemplate:LegendTemplate:LegendTemplate:LegendTemplate:LegendTemplate:LegendTemplate:LegendTemplate:LegendTemplate:LegendTemplate:LegendTemplate:LegendTemplate:Div col end

In 2010, globally, approximately 281,500 people died of leukemia.<ref name=Loz2012>Template:Cite journal</ref> In 2000, approximately 256,000 children and adults around the world developed a form of leukemia, and 209,000 died from it.<ref name=Numbers>Template:Cite journal</ref> This represents about 3% of the almost seven million deaths due to cancer that year, and about 0.35% of all deaths from any cause.<ref name=Numbers /> Of the sixteen separate sites the body compared, leukemia was the 12th most common class of neoplastic disease and the 11th most common cause of cancer-related death.<ref name=Numbers /> Leukemia occurs more commonly in the developed world.<ref name=WCR2014/>

United StatesEdit

About 245,000 people in the United States are affected with some form of leukemia, including those that have achieved remission or cure. Rates from 1975 to 2011 have increased by 0.7% per year among children.<ref>Template:Cite journal</ref> Approximately 44,270 new cases of leukemia were diagnosed in the year 2008 in the US.<ref name=LLS>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> This represents 2.9% of all cancers (excluding simple basal cell and squamous cell skin cancers) in the United States, and 30.4% of all blood cancers.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Among children with some form of cancer, about a third have a type of leukemia, most commonly acute lymphoblastic leukemia.<ref name=LLS /> A type of leukemia is the second most common form of cancer in infants (under the age of 12 months) and the most common form of cancer in older children.<ref name="SEER1999">Template:Cite book</ref> Boys are somewhat more likely to develop leukemia than girls, and white American children are almost twice as likely to develop leukemia than black American children.<ref name="SEER1999" /> Only about 3% cancer diagnoses among adults are for leukemias, but because cancer is much more common among adults, more than 90% of all leukemias are diagnosed in adults.<ref name=LLS />

Race is a risk factor in the United States. Hispanics, especially those under the age of 20, are at the highest risk for leukemia, while whites, Native Americans, Asian Americans, and Alaska Natives are at higher risk than African Americans.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

More men than women are diagnosed with leukemia and die from the disease. Around 30 percent more men than women have leukemia.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

AustraliaEdit

In Australia, leukemia is the eleventh most common cancer.<ref name="CancerAustralia">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> In 2014–2018, Australians diagnosed with leukemia had a 64% chance (65% for males and 64% for females) of surviving for five years compared to the rest of the Australian population–there was a 21% increase in survival rates between 1989–1993.<ref name="CancerAustralia" />

UKEdit

Overall, leukemia is the eleventh most common cancer in the UK (around 8,600 people were diagnosed with the disease in 2011), and it is the ninth most common cause of cancer death (around 4,800 people died in 2012).<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

HistoryEdit

File:Rudolf Virchow.jpg
Rudolf Virchow

Leukemia was first described by anatomist and surgeon Alfred-Armand-Louis-Marie Velpeau in 1827. A more complete description was given by pathologist Rudolf Virchow in 1845. Around ten years after Virchow's findings, pathologist Franz Ernst Christian Neumann found that the bone marrow of a deceased person with leukemia was colored "dirty green-yellow" as opposed to the normal red. This finding allowed Neumann to conclude that a bone marrow problem was responsible for the abnormal blood of people with leukemia.<ref>Template:Cite journal</ref>

By 1900, leukemia was viewed as a family of diseases as opposed to a single disease. By 1947, Boston pathologist Sidney Farber believed from past experiments that aminopterin, a folic acid mimic, could potentially cure leukemia in children. The majority of the children with ALL who were tested showed signs of improvement in their bone marrow, but none of them were actually cured. Nevertheless, this result did lead to further experiments.<ref>Template:Cite journal</ref>

In 1962, researchers Emil J. Freireich, Jr. and Emil Frei III used combination chemotherapy to attempt to cure leukemia. The tests were successful with some people surviving long after the tests.<ref>Template:Cite journal</ref>

EtymologyEdit

Observing an abnormally large number of white blood cells in a blood sample from a person, Virchow called the condition Leukämie in German, which he formed from the two Greek words leukos (λευκός), meaning 'white', and haima (αἷμα), meaning 'blood'.<ref name="MedlinePlus 2019">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It was formerly also called leucemia.<ref name="etymology">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Society and cultureEdit

According to Susan Sontag, leukemia was often romanticized in 20th-century fiction, portrayed as a joy-ending, clean disease whose fair, innocent and gentle victims die young or at the wrong time. As such, it was the cultural successor to tuberculosis, which held this cultural position until it was discovered to be an infectious disease.<ref>Template:Cite book</ref> The 1970 romance novel Love Story is an example of this romanticization of leukemia.<ref>Template:Cite thesis</ref>

In the United States, around $5.4 billion is spent on treatment a year.<ref name="NCISnap2">{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Research directionsEdit

Significant research into the causes, prevalence, diagnosis, treatment, and prognosis of leukemia is being performed. Hundreds of clinical trials are being planned or conducted at any given time.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Studies may focus on effective means of treatment, better ways of treating the disease, improving the quality of life for people, or appropriate care in remission or after cures.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

In general, there are two types of leukemia research: clinical or translational research and basic research. Clinical/translational research focuses on studying the disease in a defined and generally immediately applicable way, such as testing a new drug in people. By contrast, basic science research studies the disease process at a distance, such as seeing whether a suspected carcinogen can cause leukemic changes in isolated cells in the laboratory or how the DNA changes inside leukemia cells as the disease progresses. The results from basic research studies are generally less immediately useful to people with the disease.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

Treatment through gene therapy is currently being pursued. One such approach used genetically modified T cells, known as chimeric antigen receptor T cells (CAR-T cells), to attack cancer cells. In 2011, a year after treatment, two of the three people with advanced chronic lymphocytic leukemia were reported to be cancer-free<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> and in 2013, three of five subjects who had acute lymphocytic leukemia were reported to be in remission for five months to two years.<ref name=SloanKettering>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> Subsequent studies with a variety of CAR-T types continue to be promising.<ref name=":0">Template:Cite journal</ref> As of 2018, two CAR-T therapies have been approved by the Food and Drug Administration. CAR-T treatment has significant side effects,<ref>Template:Cite journal</ref> and loss of the antigen targeted by the CAR-T cells is a common mechanism for relapse.<ref name=":0" /> The stem cells that cause different types of leukemia are also being researched.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

PregnancyEdit

Leukemia is rarely associated with pregnancy, affecting only about 1 in 10,000 pregnant women.<ref name=Shapira /> How it is handled depends primarily on the type of leukemia. Nearly all leukemias appearing in pregnant women are acute leukemias.<ref name=Koren>Template:Cite journal</ref> Acute leukemias normally require prompt, aggressive treatment, despite significant risks of pregnancy loss and birth defects, especially if chemotherapy is given during the developmentally sensitive first trimester.<ref name=Shapira/> Chronic myelogenous leukemia can be treated with relative safety at any time during pregnancy with Interferon-alpha hormones.<ref name=Shapira /> Treatment for chronic lymphocytic leukemias, which are rare in pregnant women, can often be postponed until after the end of the pregnancy.<ref name=Shapira>Template:Cite journal</ref><ref name=Koren />

See alsoEdit

ReferencesEdit

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External linksEdit

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