The blood and lymph cancers, also called hematologic malignancies (hema is Greek for blood), are a complicated group of diseases that are related by their common origin in cells that comprise the blood and lymph systems of the body. All blood and lymph cells are born in the bone marrow. Some remain there, some circulate in the bloodstream, and others populate the lymph tissues found throughout the body, most prominently the lymph nodes and spleen.
There are three major categories of hematologic malignancies:
1. Leukemia
2. Lymphoma
3. Multiple myeloma
Because these cancers grow in the bone marrow and/or the lymph nodes and spleen, they cause alterations of blood counts, enlargement of lymph nodes, or defects in the body’s immune defenses, resulting in infections. Any one of these changes may prompt an evaluation that leads to the diagnosis of leukemia, lymphoma, or myeloma. Unlike many carcinomas, these cancers cannot be screened for or caught at a preventable stage because their natural growth patterns lead them to be present in many locations in the body at the time of detection. For example, leukemia and myeloma affect the bone marrow (throughout the body), and lymphomas often affect different lymph node regions in the body. Because of this, they nearly always require treatments that travel throughout the body-namely, drug therapies.
Surgery plays a minor role in managing blood and lymph cancers.
Radiation therapy may be used in conjunction with drug therapies, depending on the clinical situation: a patient with a large mass of Hodgkin or non-Hodgkin’s lymphoma in the chest, for example, is usually treated with chemotherapy followed by radiation therapy, resulting in a very high cure rate. Isolated tumors of multiple myeloma (called plasmacytomas) may be treated with radiation.
Leukemia is not treated with radiation except as part of a stem cell transplant procedure, when it is given to the whole body in an effort to eradicate the disease. These examples do not encompass the full spectrum of radiation use in these cancers.
The care of a patient with a hematologic malignancy is usually managed by a physician trained in both oncology and hematology. Advances in treating these cancers are occurring rapidly, and many new promising drugs are being developed each year that require testing in clinical trials. Hematologists/oncologists in the community and those in large cancer centers often work together to plan a treatment strategy for their patients, which may include a stem cell transplant or participation in a research trial testing new medicines.
Despite their similarities, each of these three disorders is distinct. Each arises from a different type of bone marrow cell, grows differently in the body, causes different symptoms, requires specific treatments, and has varied rates of curability. In order to gain an appreciation for the blood cancers, it is helpful to have a working knowledge of how normal blood and lymph cells are produced in the body.
