Leukemia
Leukemia (also spelled leukaemia and pronounced /luːˈkiːmiːə/[1] loo-KEE-mee-ə) is a group of blood cancers that usually begin in the bone marrow and result in high numbers of abnormal blood cells.[9] These blood cells are not fully developed and are called blasts or leukemia cells.[2] Symptoms may include bleeding and bruising, bone pain, fatigue, fever, and an increased risk of infections.[2] These symptoms occur due to a lack of normal blood cells.[2] Diagnosis is typically made by blood tests or bone marrow biopsy.[2]
For the journal, see Leukemia (journal). For animal diseases, see Leucosis.Leukemia
Leukaemia
Hematology and oncology
Smoking, family history, ionizing radiation, some chemicals such as trichloroethylene, prior chemotherapy, Down syndrome.[3][5]
Five-year survival rate 57% (U.S.)[4]
2.3 million (2015)[7]
353,500 (2015)[8]
The exact cause of leukemia is unknown.[5] A combination of genetic factors and environmental (non-inherited) factors are believed to play a role.[5] Risk factors include smoking, ionizing radiation, petrochemicals (such as benzene), prior chemotherapy, and Down syndrome.[5][3] People with a family history of leukemia are also at higher risk.[3] There are four main types of leukemia—acute lymphoblastic leukemia (ALL), acute myeloid leukemia (AML), chronic lymphocytic leukemia (CLL) and chronic myeloid leukemia (CML)—as well as a number of less common types.[3][10] 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.[11][12]
Treatment may involve some combination of chemotherapy, radiation therapy, targeted therapy, and bone marrow transplant, in addition to supportive care and palliative care as needed.[3][6] Certain types of leukemia may be managed with watchful waiting.[3] The success of treatment depends on the type of leukemia and the age of the person. Outcomes have improved in the developed world.[10] Five-year survival rate is 65% in the United States.[4] 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.[13] In children with acute leukemia who are cancer-free after five years, the cancer is unlikely to return.[13]
In 2015, leukemia was present in 2.3 million people worldwide and caused 353,500 deaths.[7][8] In 2012, it had newly developed in 352,000 people.[10] It is the most common type of cancer in children, with three-quarters of leukemia cases in children being the acute lymphoblastic type.[3] However, over 90% of all leukemias are diagnosed in adults, with CLL and AML being most common in adults.[3][14] It occurs more commonly in the developed world.[10]
Prognosis[edit]
The success of treatment depends on the type of leukemia and the age of the person. Outcomes have improved in the developed world.[10] The average five-year survival rate is 65% in the United States.[4] In children under 15, the five-year survival rate is greater (60 to 85%), depending on the type of leukemia.[13] In children with acute leukemia who are cancer-free after five years, the cancer is unlikely to return.[13]
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.[74]
Society and culture[edit]
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.[91] The 1970 romance novel Love Story is an example of this romanticization of leukemia.[92]
In the United States, around $5.4 billion is spent on treatment a year.[93]
Research directions[edit]
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.[94] 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.[95]
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.[96]
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[97] and in 2013, three of five subjects who had acute lymphocytic leukemia were reported to be in remission for five months to two years.[98] Subsequent studies with a variety of CAR-T types continue to be promising.[99] As of 2018, two CAR-T therapies have been approved by the Food and Drug Administration. CAR-T treatment has significant side effects,[100] and loss of the antigen targeted by the CAR-T cells is a common mechanism for relapse.[99] The stem cells that cause different types of leukemia are also being researched.[101]
Pregnancy[edit]
Leukemia is rarely associated with pregnancy, affecting only about 1 in 10,000 pregnant women.[102] How it is handled depends primarily on the type of leukemia. Nearly all leukemias appearing in pregnant women are acute leukemias.[103] 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.[102] Chronic myelogenous leukemia can be treated with relative safety at any time during pregnancy with Interferon-alpha hormones.[102] Treatment for chronic lymphocytic leukemias, which are rare in pregnant women, can often be postponed until after the end of the pregnancy.[102][103]