Leukemia: Perbedaan antara revisi

Caption = Sediaan sumsum tulang dengan pewarnaan Wright. Sediaan menujukkanmenunjukkan leukemia limfoblastik akut prekurisrprekursor sel-B.|

'''LeukemuaLeukemia'''; dalam bahasa Yunani leukos ''[[wikt:λευκός|λευκός]]'', "putih"; aima ''[[wikt:αίμα|αίμα]]'', "darah"), atau lebih dikenal sebagai '''kanker darah''' adalah sekelompokmerupakan penyakit dalam klasifikasi [[kanker]] (istilah medis: [[neoplasma|neoplastik]]) yangpada beragam,[[darah]] atau [[sumsum tulang]] yang ditandai oleh perbanyakan secara tak normal atau transformasi maligna dari sel-sel pemebntukpembentuk darah di [[sumsum tulang]] dan [[jaringan limfoid]]., Sel-selumumnya normalterjadi dipada dalam sumsum tulang digantikan olehleukosit ([[sel tak normal atau abnormal. Sel abnormal ini keluar dari sumsum dan dapat ditemukan di dalam darah perifer atau darah tepiputih]]).<ref Selname=sumber>{{cite leukemia mempengaruhi hematopoiesis atau proses pemebentukan sel darah normal dan imunitas tubuh penderita.book

Kata ''leukemia'' berarti "[[darah putih"]], karena pada peneritapenderita ditemukan banyak sel darah putih sebelum diberi terapi. Sel darah putih yang tampak banyak merupakan [[sel]] yang muda, misalnya [[promielosit]]. Jumlah yang semakinmakin meninggi ini dapat mengganggu fungsi normal dari sel lainnya.

=== Perjalanan alamiah penyakit: akut dan kronis ===

Leukemia akut ditandai dengan suatu perjalanan penyakit yang sangat cepat, mematikan, dan memburuk. Apabila tidak diobati segera, maka penderita dapat meninggal dalam hitungan minggu hingga garihari. Sedangkan leukemia kronis memiliki perjalanan penyakit yang tidak begitu cepat sehingga memiliki harapan hidup yang lebih lama, hingga lebih dari 1 tahun bahkan ada yang mencapai 5 tahun.

=== Tipe sel predominan yang terlibat: limfoid dan mieloid ===

* Ketika leukemia mempengaruhimemengaruhi [[limfosit]] atau sel limfoid, maka disebut [[leukemia limfositik]].

* Ketika leukemia mempengaruhimemengaruhi sel mieloid seperti [[neutrofil]], [[basofil]], dan [[eosinofil]], maka disebut [[leukemia mielositik]].

=== Jumlah leukosit dalam darah ===

* Leukemia leukemik, bila jumlah leukosit di dalam darah lebih dari normal, terdapat sel-sel abnormal.

* Leukemia subleukemik, bila jumlah leukosit di dalam darah kurang dari normal, terdapat sel-sel abnormal.

* Leukemia aleukemik, bila jumlah leukosit di dalam darah kurang dari normal, tidak terdapat sel-sel abnormal.

=== Prevalensi empat tipe utama ===

* [[Leukemia limfositik akut]] (LLA) merupakan tipe leukemia paling sering terjadi pada anak-anak. Penyakit ini juga terdapat pada dewasa yang terutama telah berumur 65 tahun atau lebih.

* [[Leukemia mielositik akut]] (LMA) lebih sering terjadi pada dewasa daripada anak-anak. Tipe ini dahulunya disebut leukemia nonlimfositik akut.

* [[Leukemia limfositik korniskronis]] (LLK) sering diderita oleh orang dewasa yang berumur lebih dari 55 tahun. Kadang-kadang juga diderita oleh dewasa muda, dan hampir tidak ada pada anak-anak.

* [[Leukemia mielositik kronis]] (LMK) sering terjadi pada orang dewasa. Dapat juga terjadi pada anak-anak, namuntetapi sangat sedikit.

== Patogenesis ==

leukemiaLeukemia akut dan kronis merupakan suatu bentuk keganasan atau maligna yang muncul dari perbanyakan klonal sel-sel pembentuk [[sel]] darah yang tidak terkontrol. Mekanisme kontrol seluler normal mungkin tidak bekerja dengan baik akibat adanya perubahan pada kode [[genetika|genetik]] yang seharusnya bertanggung jawab atas pengaturan pertubuhan sel dan diferensiasi.

Sel-sel leukemia menjalani waktu daur ulang yang lebih lambat dibandingkan sel normal. Proses pematangan atau maturasi berjalan tidak lengkap dan lanbarlambat dan bertahan hidup lebih lama dibandingkan sel sejenis yang normal.

== Etiologi ==

Penyebab leukemia belum diketahui secara pasti, namuntetapi diketahui beberapa faktor yang dapat mempengaruhimemengaruhi frekuensi leukemia, seperti:

=== Radiasi ===

* PeneritaPenderita dengan radioterapi lebih sering menderita leukemia

=== Faktor leukemogenik ===

Terdapat beberapa zat [[kimia]] yang telah diidentifikasi dapat mempengaruhimemengaruhi frekuensi leukemia:

* Bahan kimia inustriindustri seperti [[insektisida]]

=== Epidemiologi ===

* Di [[Afrika]], 10-2010–20% pwnsweitapenderita LMA memiliki kloroma di sekitar [[orbita]] [[mata]]

* Di [[Kenya]], [[Tiongkok]], dan [[India]], LMK mengenai peneritapenderita berumur 20-4020–40 tahun

=== Herediter ===

Penderita [[sindrom Down|sindrom down]] memiliki insidensi leukemia akut 20 kali lebih besar dari orang normal.

=== Virus ===

[[Virus]] dapat menyebabkan leukemia seperti [[retrovirus]], virus leukemia feline, HTLV-1 pada [[dewasa]].

Many different chemotherapeutic plans are available for the treatment 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. 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 (lessening of the disease) and a lower risk of disease resistance. Consolidation or "maintenance" treatments may be given to prevent disease recurrence once remission has been achieved. Consolidation treatment often entails a repetition of induction chemotherapy or the intensification chemotherapy with added drugs. By contrast, maintenance treatment involves drug doses that are lower than those administered during the induction phase.

In addition, specific treatment plans may be used, depending on the type of leukemia that has been diagnosed. Whatever the plan, it is important for the patient to understand the treatment that is being given and the decision-making process behind the choice.

Follow-up therapy for such patients may involve:

Patients with newly diagnosed disease also may be considered for stem cell transplantation (SCT), either from the bone marrow or other sources. Allogeneic bone marrow transplant (alloBMT) is reserved primarily for patients under 55 years of age who have a compatible family donor. Approximately half of newly diagnosed AML patients are in this age group, with 75% achieving a complete remission (CR) after induction and consolidation therapy. Allogeneic bone marrow transplant is available for about 15% of all patients with AML. Unfortunately, it is estimated that only 7% of all AML patients will be cured using this procedure.

People who receive stem cell transplantation (SCT, alloBMT) require protective isolation in the hospital, including filtered air, sterile food, and sterilization of the microorganisms in the gut, until their total white blood cell (WBC) count is above 500.

Once the patient is in remission, he or she will receive consolidation or maintenance therapy, for example, consolidation therapy with high-dose ara-C (HDAC) with/without anthracycline drugs).

If, however, the AML patient has resistant disease (about 15%) or relapses (about 70%), second remissions sometimes are achieved by treating them with:

Elderly AML patients have special treatment concerns. They may be less able to tolerate the septicemia (blood poisoning) associated with granulocytopenia, and they often have higher rates of myelodysplastic ('preleukemia') syndrome (MDS). Individuals who are over age 75 or who have significant medical conditions can be treated effectively with low-dose ara-C. High-dose post-induction chemotherapy is unlikely to be tolerated by elderly patients.

Until recently, the treatment plans and responses of children with AML did not differ much from those of adults. Yet new, more intensive induction and consolidation treatments have resulted in higher remission rates and prolonged survivals. Many induction trials have produced good results using combinations of cytarabine (ara-C) plus an anthracycline (e.g., daunorubicin, doxorubicin). In children under 3 years of age, the anthracycline used for induction should be chosen with care, since doxorubicin produces more toxicity and related deaths than daunorubicin.

The challenge of treating newly diagnosed CML is to determine the best overall strategy to control the disease. General strategies for management include a variety of options:

'''Leukapheresis''', also known as a peripheral blood stem cell transplant, with stem cell cryopreservation (frozen storage) prior to any other treatment. The patient's blood is passed through a machine that removes the stem cells and then returns the blood to the patient. Leukapheresis usually takes 3 or 4 hours to complete. The stem cells may or may not be treated with drugs to kill any cancer cells. The stem cells then are stored until they are transplanted back into the patient.

'''HLA (human leukocyte antigen) typing''' of all patients under age 60, as well as typing of siblings, parents, and children, if available. This procedure will determine whether a compatible donor is available for stem cell transplantation.

'''Pre-treatment fertility measures''' (e.g., cryopreservation of semen prior to treatment; completion of a pregnancy prior to treatment) in young patients who have not completed their families.

''Interferon-alpha (INF-a) therapy'''.

'''Chemotherapy''' with drugs such as hydroxyurea (Hydrea®), busulfan (Myleran®) or imatinib mesylate (Gleevec(tm)).

In general, CML treatment options are divided into two groups: those that do not increase survival and those that do. Chemotherapeutic drugs such as hydroxyurea (Hydrea®) and busulfan (Myleran®) can normalize the blood count for a period of time, but they do not increase survival. They often are used to control blood counts in patients who cannot undergo SCT or who do not respond to interferon therapy because of age or medical considerations.

Gleevec, is one of a new class of cancer drugs that disables an abnormal enzyme in the cancerous cell, kills it, but leaves healthy cells virtually untouched. Other cancer therapies, such as chemotherapy, attack healthy cells as well as cancer cells, leaving patients with unpleasant and often severe side effects.

In June of 2006, the Food and Drug Administration (FDA) approved the oral tyrosine kinase inhibitor dasatinib (Sprycel(tm)) to treat CML that does not respond to other therapy.

One treatment that does impact on CML survival is allogeneic bone marrow transplantation, the use of high dose chemotherapy and radiation followed by infusion of a donor bone marrow. This procedure removes the chromosomal abnormality in a large percentage of patients and for them is curative. In addition, there is treatment with interferon (INF). About 20% to 30% of patients taking interferon show elimination of the abnormal chromosome and improved survival. Recent findings also suggest that low-dose cytarabine (ara-C), in combination with interferon, may be more beneficial than interferon alone. For patients who do not respond to interferon, autologous or allogeneic stem cell transplantation is the only alternative.

Proper management of ALL focuses on control of bone marrow and systemic (whole-body) disease as well as prevention of cancer at other sites, particularly the central nervous system (CNS). In general, ALL treatment is divided into several phases:

'''Induction chemotherapy''' to bring about remission - that is, leukemic cells are no longer found in bone marrow samples. For adult ALL, 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. High-risk children may receive these drugs plus an anthracycline such as daunorubicin.

'''Consolidation therapy''' (1-3 months in adults; 4-8 months in children) to eliminate any leukemia cells that are still "hiding" within the body. A combination of chemotherapeutic drugs is used to keep the remaining leukemia cells from developing resistance. Patients with low- to average-risk ALL receive therapy with antimetabolite drugs such as methotrexate and 6-mercaptopurine (6-MP). High-risk patients receive higher drug doses plus treatment with extra chemotherapeutic agents.

'''Maintenance treatments''' with chemotherapeutic drugs (e.g., prednisone + vincristine + cyclophosphamide + doxorubicin; methotrexate + 6-MP) to prevent disease recurrence once remission has been achieved. Maintenance therapy usually involves drug doses that are lower than those administered during the induction phase. In children, an intensive 6-month treatment program is needed after induction, followed by 2 years of maintenance chemotherapy.

A laboratory test known as [[polymerase chain reaction]] (PCR) is advisable for ALL patients, since it may help to identify specific genetic abnormalities. Such abnormalities have a large impact upon prognosis and, consequently, treatment plans. PCR testing is especially important for patients whose disease is B-cell in type. B-cell ALL usually is not cured by standard ALL therapy. Instead, higher response rates are achieved with the aggressive, cyclophosphamide-based regimens that are used for non-Hodgkin's lymphoma.

Among ALL patients, 3-5% children and 25-50% of adults are positive for the Philadelphia chromosome (Ph1){{Fact|date=February 2007}}. Because these patients have a worse prognosis than other individuals with ALL, many oncologists recommend allogeneic bone marrow transplantation (alloBMT), since remission may be brief following conventional ALL chemotherapy.

People who receive bone marrow transplantation will require protective isolation in the hospital, including filtered air, sterile food, and sterilization of the microorganisms in the gut, until their total white blood cell (WBC) count is above 500.

Recurrent ALL patients usually do not benefit from additional chemotherapy alone. If possible, they should receive re-induction chemotherapy, followed by allogeneic bone marrow transplant (alloBMT).

The unpleasant truth is that CLL is probably "incurable" by present treatments. But, fortunately, a large group of CLL patients do not require therapy. Studies suggest that people with Stage A CLL (that is, individuals who have fewer than three areas of enlarged lymphoid tissue) do not benefit from early treatment. They may, in fact, suffer drawbacks because of it. Therefore, most oncologists base CLL treatment upon both the stage and symptoms of the patient.

For example, in older patients (60+ years) who have low-risk early stage disease (Rai Stage 0) a conservative "watch and wait" approach may be taken.

Corticosteroids are first-line agents for people in whom the immune systems has been altered by CLL. CLL may cause autoimmune syndromes in which the patient's immune system attacks and destroys his or her own blood cells. When the red blood cells are affected, the condition is known as immunohemolytic anemia, characterized by decreased numbers of red blood cells, which may cause fatigue, dizziness, and shortness of breath. When the blood platelets are affected, it is called immune-mediated thrombocytopenia, in which a decreased numbers of platelets may lead to bleeding.

For younger patients who are experiencing symptoms, the physician may consider early chemotherapy, plus allogeneic or autologous bone marrow transplantation (alloBMT; autoBMT).

In general, the indications for treatment are:

Symptoms that are related to enlargement of the lymph nodes in one area or an overgrown spleen may be treated by localized, low-dose radiotherapy, or surgical management by splenectomy (removal of the spleen). But if leukemia has invaded the lymph nodes at many different sites, total body irradiation (TBI) may be needed.

The chemotherapeutic plans that are used most often for CLL are:

* single-agent treatments with nucleoside drugs such as fludarabine, pentostatin, or cladribine (2-chlorodeoxyadenisine; 2-CDA). However, such drugs usually are reserved for cases in which CLL is resistant (unresponsive to treatment) or returns after chemotherapy with chlorambucil or cyclophosphamide.

Treatment is generally considered necessary when the patient shows signs and symptoms such as low blood cell counts (e.g., infection-fighting neutrophil count below 1.0 K/ul), frequent infections, unexplained bruises, anemia, or fatigue that is significant enough to disrupt the patient's everyday life.

==Pranala luarLihat pula ==

* {{en}} [http://leukemia.acor.org Association of Cancer Online Resources (ACOR) Leukemia Links] {{Webarchive|url=https://web.archive.org/web/20070224145506/http://leukemia.acor.org/ |date=2007-02-24 }}

* {{en}} [http://www.leukemia-research.org Leukemia Research Foundation] {{Webarchive|url=https://web.archive.org/web/20210325072740/http://www.leukemia-research.org/ |date=2021-03-25 }}

== Referensi ==