Lymphoma, a cancer originating in the lymphatic system, directly affects the body’s immune defense system. The disease is characterized by the uncontrolled growth of abnormal white blood cells called lymphocytes, which typically form tumors in the lymph nodes. Lymphoma can cause low white blood cell (WBC) counts, a condition known as leukopenia. This relationship is complex, as the low counts can result from the cancer itself or from the treatments used to fight the disease. Understanding this dual nature is important for managing the overall health of a person with lymphoma.
Understanding White Blood Cells and Leukopenia
White blood cells (leukocytes) are the body’s primary defense against infection and foreign invaders. Produced in the bone marrow, these cells circulate throughout the bloodstream and lymphatic tissues. The total WBC count measures five different cell types: neutrophils, lymphocytes, monocytes, eosinophils, and basophils.
Neutrophils are the most numerous, acting as first responders to destroy bacteria and fungi. Lymphocytes, the cells that become cancerous in lymphoma, identify viruses and produce antibodies.
Leukopenia describes an overall low WBC count, generally below 3,000 to 4,000 cells per microliter of blood. The most clinically relevant type is neutropenia, which refers specifically to a low neutrophil count. A significant drop in neutrophils dramatically raises the risk of serious bacterial infection. Severe neutropenia occurs when the absolute neutrophil count (ANC) drops below 500 cells per microliter.
Lymphoma’s Direct Impact on Blood Cell Production
Lymphoma causes low blood counts when cancerous cells spread beyond the lymph nodes and infiltrate the bone marrow. The bone marrow is where all blood cells are manufactured from hematopoietic stem cells. When lymphoma is advanced, abnormal lymphocytes colonize this space.
This infiltration leads to a “crowding out” effect within the marrow cavity. The rapidly dividing lymphoma cells displace or suppress normal stem cells. This impairs the stem cells’ ability to produce adequate numbers of all blood components, resulting in pancytopenia (low counts of red cells, platelets, and white cells).
The presence of cancer cells can also alter the bone marrow’s microenvironment, disrupting signaling pathways required for healthy blood cell development. These disruptions prevent the proper maturation and release of functional white blood cells into the bloodstream. This direct suppression of hematopoiesis means low counts can manifest as disease progression, often preceding treatment.
Treatment-Related Causes of Low Counts
Therapies used to treat lymphoma are a frequent and expected cause of leukopenia. The primary cause is chemotherapy, a systemic treatment designed to kill rapidly dividing cells. Because the bone marrow is highly proliferative, its healthy cells are susceptible to chemotherapy’s cytotoxic effects, a side effect known as myelosuppression.
Chemotherapy temporarily suppresses the bone marrow’s ability to produce all blood cells, leading to a predictable drop in counts. The lowest point of the WBC count, called the nadir, typically occurs 7 to 14 days after a dose. This period marks the peak risk of infection, though counts usually recover before the next treatment cycle.
Radiation therapy also contributes to low counts, especially when large blood-forming sites like the pelvis or chest are within the treatment field. Radiation slows blood cell production in the targeted area. Combining radiation with chemotherapy can worsen the overall impact on the bone marrow.
Clinical Significance and Management of Low Counts
The most significant consequence of a low white blood cell count, particularly neutropenia, is a heightened susceptibility to infection. Without sufficient mature neutrophils, the body cannot mount an effective initial defense against bacteria. An infection that is minor for a healthy person can quickly become life-threatening when WBC counts are low.
Low counts are monitored closely throughout treatment using a Complete Blood Count (CBC) test. If counts drop too low, especially the ANC, healthcare providers implement supportive measures. Management often involves growth factors, such as Granulocyte Colony-Stimulating Factor (G-CSF, e.g., filgrastim or pegfilgrastim).
These growth factors are administered as injections to stimulate the bone marrow to accelerate the production and release of new white blood cells. They are often given the day after chemotherapy to prevent severe drops. If fever or other signs of infection occur while counts are low, immediate medical attention and rapid administration of broad-spectrum antibiotics are necessary.