Cancer and cancer treatment causes low white blood cell count in the body, states MedlinePlus. Cancer can develop in the bone marrow, leading to low production of neutrophils. Some cancer treatments, such as radiation therapy and chemotherapy, usually cause low blood cells, says Mayo Clinic. Cancers that come off from a tumor and spread to other parts of the body can cause low white blood cell count.
Medically known as leukopenia, a low white blood cell count makes the body vulnerable to infections, explains Mayo Clinic. Certain drugs used in chemotherapy destroy the bone marrow, which is responsible for making white blood cells. The drugs also kill cells, but they can recover over time. The doctor may advise the patient on the effects of a particular chemotherapy drug and dose.
Patients who receive radiation therapy to a large part of the body, have a high risk of suffering from a low white blood cell count, notes Mayo Clinic. Cancers, such as leukemia, develop in the bone marrow, limiting the growth of normal cells. For cancers that spread to the bone marrow, the cancerous cells displace the healthy body cells, limiting the production of the cells. It is necessary to monitor the blood cell count to prevent infections.