General Considerations regarding Leukemia
Leukemia is a malignant disease of the blood, where the uncontrolled proliferation of immature blood cells that originate from hematopoietic stem cell mutation occurs. Eventually these aberrant cells compete with normal cells for space in the bone marrow, causing bone marrow failure and death.
Classification of leukemia
The most common leukemias are generally classified as
- Acute lymphocytic
- Acute myeloid
- Chronic lymphocytic
- Chronic myeloid
The classification criteria of leukemia is histological and is based on
- The similarity between the leukemic cells and normal cells (myeloid versus lymphoid) and
- The clinical course of the disease (acute versus chronic).
The acute forms of leukemia result from the accumulation of immature and functionless cells in the bone marrow, with rapid progression, rapidly fatal in untreated patients. Chronic leukemias, in turn, begin slowly with uncontrolled proliferation of more mature and differentiated cells.
Treatment of leukemia
The treatment of leukemia depends on factors such as type and subtype of the disease, risk factors, and age of the patient.
Generally, the recommended treatment is chemotherapy with or without adjuvant treatments.
Hematopoietic stem cell transplantation (HSCT) is also done as mentioned below:
1. Acute lymphoblastic leukemia (ALL):
- Prophase (initial reduction of leukemic cells),
- Induction (achieve complete remission),
- Consolidation (increase the quality of remission),
- Intensification (post-remission further reduction), and
- Maintenance therapy (maintenance of consolidation)
- Prophylactic central nervous system (CNS) therapeutic irradiation or irradiation if CNS is involved;
- The HSCT can be done in some cases
2. Acute myeloid leukemia (AML):
- Induction (until complete remission)
3. Chronic myeloid leukemia (CML):
- Remission of leukemic cells and Philadelphia chromosome-positive with high doses of chemotherapy, monitoring of therapy, and HSCT
4. Chronic lymphocytic leukemia (CLL):
- Conventional treatment is not curative; chemotherapy is performed as a control.
Special Considerations about HSCT
Treatment with HSCT aims to repopulate the marrow with normal healthy cells which were earlier destroyed with high doses of chemotherapy with or without radiation.
The HSCT can be of the autologous type (patient's own hematopoietic stem cells) or allogeneic (hematopoietic cells obtained from a donor) and consists of five phases:
- Neutropenic phase conditioning
- Engraftment to hematopoietic recovery
- Immune reconstitution/recovery from systemic toxicity
- Long-term survival.
The main complications of HSCT are graft rejection (for failure in the patient's immunosuppression) and the graft-versus-host disease (GVHD), where immunocompetent donor cells attack the patient's antigens, which may lead to the depletion of T lymphocytes. Potentially fatal, GVHD can occur soon after HSCT (acute GVHD) or after a few months (chronic GVHD or cGVHD). With deep and long immunosuppression, the patient becomes susceptible to fungal and viral infections.
Referrence: Caroline Zimmermann, Maria Inês Meurer, Liliane Janete Grando, Joanita Ângela Gonzaga Del Moral, Inês Beatriz da Silva Rath, and Silvia Schaefer Tavares Journal of Oncology Volume 2015 (2015), Article ID 571739, 14 pages http://dx.doi.org/10.1155/2015/571739