It is common knowledge that cancer can start in any part of the body and spread to other parts. Leukemia is widely referred to as a group of blood cancers and is classified by the type of white blood cells and by the rate of disease progression over time (“Cancer Treatment Centers of America”, n.d.). In the framework of this paper, seven types of leukemia will be examined, providing the characteristics and genetics involved, signs and symptoms.
Generally, leukemia is classified according to how quickly it progresses, thus, it can be either acute (fast-growing) or chronic (slow-growing) (“Cancer Treatment Centers of America”, n.d.). Acute leukemia develops rapidly and leads to accumulation of functionless blood cells in the bone marrow, with chronic leukemia the cells are abnormal, but relatively mature, and accumulated at a slower pace (“Cancer Treatment Centers of America”, n.d.). The general survival rate for individuals diagnosed with leukemia is 62.7%, as for the new cases and deaths, the figure below illustrates the trend (see Figure 1).
Thus, the number of new cases and deaths is slowly decreasing in the recent years, so the overall prognosis is quite positive. While this is the broad categorization, there are more specific types of leukemia that will be analyzed below.
Acute lymphocytic leukemia (ALL) develops rapidly, replacing cells that produce lymphocytes with immature leukemia cells (“Cancer Treatment Centers of America”, n.d.). These cells are carried to other organs and tissues in the body, causing several symptoms (“Cancer Treatment Centers of America”, n.d.). Those are quite similar to the typical flu and include, for instance, weakness, fever, pale skin, loss of appetite, vomiting and body aches (“Cancer Treatment Centers of America”, n.d.).
Sometimes people also experience nosebleeds, swollen lymph nodes, shortness of breath and more (“Cancer Treatment Centers of America”, n.d.). ALL is usually tied to the fact that people have more B lymphatic cells, responsible for preventing the body from infections, than T-cells, responsible for destroying the infected cells (“Cancer Treatment Centers of America”, n.d.). As for genetics, ALL, like any other type of cancer, cannot be inherited.
Still, some risk factors might or might not increase one’s chances of getting it. For example, due to errors in the processes of cells’ division, mutations can occur and change the chromosome, the most common type found in ALL cells are translocations, but there are more (“American Cancer Society”, n.d.). This type of cancer is mostly spread among children and young people under the age of 20 (“National Cancer Institute”, n.d.). While the number of new cases of ALL has been gradually increasing, the percentage of people who survived it also grows steadily and as of 2016 equals 68.6% (“National Cancer Institute”, n.d.).
Chronic lymphocytic leukemia (CLL) is a slow-growing type, beginning in the bone marrow and extending into the blood, lymph nodes, liver or spleen (“Cancer Treatment Centers of America”, n.d.). The symptoms of CLL take time to develop, as the disease itself might go unnoticed for years, its symptoms happen to be vague (“Cancer Treatment Centers of America”, n.d.). Over its development CLL might include anemia, leukopenia, enlarged liver or spleen and more (“Cancer Treatment Centers of America”, n.d.).
The genetics behind CLL is similar to ALL, although the exact cause of it is not discovered, the DNA mutations and differences between normal lymphocytes and CLL cells are one of the possible options (“American Cancer Society”, n.d.). According to scientists, CLL starts when lymphocytes continue dividing without restraint after their reaction to an antigen, but the reason why that happens is unknown (“American Cancer Society”, n.d.).
Acute myeloid leukemia (AML) is the most common type of fast-growing leukemia which starts when the bone marrow forms abnormal red blood cells, platelets or blasts (immature cells) (“Cancer Treatment Centers of America”, n.d.). As these blasts are not developed, they cannot function to protect the body from infections (“Cancer Treatment Centers of America”, n.d.). Unlike other types of leukemia, AML can be divided into eight subtypes, defining the cell cancer developed from infections (“Cancer Treatment Centers of America”, n.d.). AML symptoms are frequent infections and fever, easy bleeding or bruising, anemia, bone pain (“Cancer Treatment Centers of America”, n.d.).
The genetic mutations that forestall AML are often the outcome of turning on oncogenes or turning off tumor suppressor genes (“American Cancer Society”, n.d.). The data on this type of cancer is concerning, as although new cases emerge at a slower pace, the survival rate is around 23% (“National Cancer Institute”, n.d.). In 2019, with 21000 new cases of AML in the US, around 11000 people died (“National Cancer Institute”, n.d.). The median age at diagnosis is 68, while the target group extends to people in their 60s – 80s (“National Cancer Institute”, n.d.).
Chronic myeloid leukemia (CML) begins in specific blood-forming cells of the bone marrow (“American Cancer Society”, n.d.). The symptoms include fever, weight loss, pale skin, night sweats and easy bleeding (“Cancer Treatment Centers of America”, n.d.). CML proved to be associated with the Philadelphia chromosome, that emerges when a piece of chromosome 22 attaches to chromosome 9 and vice versa (“Cancer Treatment Centers of America”, n.d.).
A genetic change happens in an immature version of myeloid cells (responsible for red blood cells, platelets and white blood cells, except for lymphocytes). This change creates a BCR-ABL gene, which turns normal cells into CML cells, that form in the bone marrow and then spill over into the blood (“American Cancer Society”, n.d.). Moreover, CML can transform into ALL, a fast-growing type of cancer (“American Cancer Society”, n.d.). According to the latest data, the new cases of CML appear almost at the same rate over the years, and the survival rates are generally optimistic – more than 69% (“National Cancer Institute”, n.d.). The age group most vulnerable to CML are people in their 60s and 70s with a slightly lesser risk in late 70s or 80s (“National Cancer Institute”, n.d.).
Hairy cell leukemia (HCL) is a subtype of CLL that is rare and slowly progressing, while also not fully curable (“Cancer Treatment Centers of America”, n.d.). It is caused by the creation of too many lymphocytes by the bone marrow, so with the accumulation of leukemia cells, less red blood cells and platelets are produced (“Cancer Treatment Centers of America”, n.d.). HCL symptoms represent the same set, mentioned above, but also painless lumps in the neck, stomach, underarm or groin and pains below the ribs (“Cancer Treatment Centers of America”, n.d.).
Statistically, HCL affects males four times more often than females with around 600 new cases appearing yearly in the US (“National Organization for Rare Disorders”, n.d.). While most of the diagnosed people are males above 50 years old, it is possible to get HCL at any age from 20 to 80 (“National Organization for Rare Disorders”, n.d.).
T-cell prolymphocytic leukemia (T-PLL) represents a sporadic and aggressive type of cancer, identified by the extensive growth of T-lymphocytes (“Leukemia & Lymphoma Society”, n.d.). The genetic mutations transform a healthy T-cell into a cancer cell that keeps dividing and accumulating more leukemia cells with the mutated DNA (“Leukemia & Lymphoma Society”, n.d.). It usually concerns the chromosome 14 and causes abnormal changes to the proto-oncogene TCL-1 that deals with the cell growth, but after mutations loses control over the cells, which, in turn, leads to cancer (“Leukemia & Lymphoma Society”, n.d.).
Besides the typical symptoms, T-PPL involves skin lesions and rash. According to the existing data, T-PPL is diagnosed at a median age of 61 and is more common among males (“Leukemia & Lymphoma Society”, n.d.).
Finally, adult T-cell leukemia (ATL) is an “aggressive T-cell malignancy caused by human T-cell lymphotropic virus type 1 (HTLV-1)” (Hermine, Ramos & Tobinai, 2018, para 1). “HTLV-1 provokes transformation and clonal expansion of T-cells”, sometimes leading to ATL (Hermine et al., 2018, para 3). It is believed that a variety of factors contribute to ATL, including epigenetic, viral, constitutional and acquired genetic features (Hermine et al., 2018).
The symptoms include skin and lung lesions, hepatomegaly, splenomegaly, hypercalcemia and more (Hermine et al., 2018). According to estimations, from five to ten millions of people worldwide are infected with HTLV-1, and the risk of it transforming into ATL is around 3-5% (Hermine et al., 2018). Most importantly, the virus is endemic in several regions, for example, in Japan, South and Central America, or Africa (Hermine et al., 2018). Commonly, individuals diagnosed with it in the US or Europe have been contacting or having sexual relations with people from those regions (Hermine et al., 2018).
References
American Cancer Society. (n.d.). Web.
Cancer Treatment Centers of America. (n.d.). Web.
Hermine, O., Ramos, J. C., & Tobinai. (2018). A review of new findings in adult T-cell leukemia-lymphoma: A focus on current and emerging treatment strategies. Advances in Therapy, 35(2), 135-152.
Leukemia & Lymphoma Society. (n.d.). Web.
National Cancer Institute: Surveillance, Epidemiology, and End Results Program. (n.d.). Web.
National Organization for Rare Disorders. (n.d.). Web.