Anemia is a medical condition where the blood lacks sufficient healthy red blood cells. These cells carry oxygen from the lungs to tissues throughout the body. When red blood cell count or hemoglobin levels are low, the body’s tissues may not receive enough oxygen, leading to symptoms like fatigue, weakness, shortness of breath, and pale skin. Anemia is a common complication for individuals with cancer, stemming from various mechanisms related to the disease itself or its treatments.
Cancers Directly Affecting Blood Production
Certain cancers impair red blood cell production by interfering with the bone marrow, the tissue where blood cells are formed. Cancers originating in the bone marrow, such as leukemias, lymphomas, and multiple myeloma, often lead to anemia. In leukemia, abnormal white blood cells rapidly multiply and crowd out healthy red blood cell production. Lymphoma cells can also infiltrate the bone marrow, disrupting red blood cell formation.
Multiple myeloma, a cancer of plasma cells in the bone marrow, also causes anemia by this mechanism. The cancerous plasma cells proliferate uncontrollably, leaving less space for healthy blood cells to develop. This crowding reduces the bone marrow’s capacity to produce red blood cells. Solid tumor cancers, such as breast or prostate cancer, can also spread to the bone marrow, similarly disrupting red blood cell production.
Cancers Leading to Blood Loss
Some cancers can cause anemia through chronic or acute blood loss. This occurs when tumors are in organs prone to bleeding. Colorectal cancer frequently leads to anemia because tumors in the gastrointestinal tract can bleed, often subtly and continuously. Even small amounts of ongoing blood loss can deplete iron stores, necessary for producing new red blood cells, resulting in iron-deficiency anemia.
Stomach cancer can also cause anemia due to slow, persistent bleeding from the tumor into the stomach. This internal bleeding reduces red blood cell count. Cancers affecting the urinary tract, such as bladder or kidney cancer, may also cause blood loss through hematuria (blood in the urine). While visible blood is a clear sign, chronic microscopic bleeding contributes to anemia by depleting iron.
Cancers Causing Anemia Through Systemic Effects
Anemia in cancer patients can also arise from systemic effects, distinct from direct bone marrow involvement or blood loss. One common mechanism is “anemia of chronic disease” or “anemia of inflammation.” The inflammatory response triggered by cancer interferes with iron utilization and suppresses red blood cell production. Inflammatory mediators, such as cytokines, can inhibit erythropoiesis, the process of red blood cell formation, and shorten the lifespan of red blood cells.
Some cancers can also affect kidney function, important for red blood cell production. The kidneys produce erythropoietin (EPO), a hormone that signals the bone marrow to produce red blood cells. Cancers involving or impacting the kidneys, such as kidney cancer or multiple myeloma, can reduce EPO production. Decreased EPO levels reduce bone marrow stimulation, resulting in fewer red blood cells and contributing to anemia.
Anemia as a Consequence of Cancer Treatment
Beyond the disease itself, cancer treatments often contribute to or directly cause anemia. Chemotherapy is a primary cause of treatment-induced anemia because it targets rapidly dividing cells, including healthy cells in the bone marrow responsible for producing red blood cells. This suppression of bone marrow activity, known as myelosuppression, reduces red blood cell production. Chemotherapy drugs can also induce eryptosis, a process of red blood cell destruction.
Radiation therapy, especially when it targets areas with significant bone marrow like the pelvis, can also suppress red blood cell production. The extent of this effect depends on the treated area and the radiation dosage. While these treatments are effective against cancer cells, their impact on the bone marrow’s ability to produce blood cells is a common side effect contributing to anemia in cancer patients.