Platelets (thrombocytes) are small cell fragments manufactured in the bone marrow. Their primary function is hemostasis—the process of stopping bleeding—by rushing to damaged blood vessels and forming a plug or clot. A low platelet count, medically termed thrombocytopenia, is a common and serious complication in cancer care. This condition increases the risk of bleeding and bruising, potentially disrupting treatment schedules, making understanding its causes and management essential.
Understanding Why Platelets Drop During Cancer Treatment
Thrombocytopenia in cancer patients is often a result of treatment, most commonly chemotherapy, which targets rapidly dividing cells throughout the body. Since the cells that produce platelets, called megakaryocytes, are constantly dividing in the bone marrow, chemotherapy drugs inadvertently damage them. This suppression of the bone marrow’s ability to create new platelets is known as myelosuppression, and it is a typical side effect of many cancer regimens.
Radiation therapy can also contribute to a low platelet count, especially when large areas of active bone marrow, such as the pelvis, are included in the treatment field. The damage is usually temporary, but recovery can take several weeks. The lowest point, or nadir, often occurs about 10 to 14 days after a chemotherapy session.
Beyond treatment-related causes, the cancer itself can directly interfere with platelet production. Certain cancers, especially blood cancers like leukemia and lymphoma, can crowd the bone marrow with malignant cells, physically leaving less space for healthy blood cell formation. This infiltration prevents the megakaryocytes from manufacturing an adequate supply of platelets.
Other factors can also cause a reduction in circulating platelets, such as tumor metastasis to the bone marrow from solid tumors like breast or lung cancer. Furthermore, a condition called hypersplenism can occur, where an enlarged spleen sequesters and removes too many platelets from the bloodstream. The spleen normally stores about one-third of the body’s platelets, but a larger spleen can hold onto an excessive amount, leading to fewer platelets available for clotting.
Recognizing Signs and Severity of Low Platelet Counts
Observable physical symptoms include easy or excessive bruising (ecchymosis), often appearing as large, discolored patches. Patients may also notice small, pinprick-sized red or purple spots on the skin, typically on the lower legs, which are called petechiae. More significant bleeding manifestations include frequent nosebleeds, prolonged bleeding from minor cuts, or bleeding gums, especially during tooth brushing.
Internal bleeding, which is more serious, may be indicated by blood in the urine, giving it a pink or red color, or blood in the stool, which can appear black and tarry. Severe headaches or changes in vision can signal potentially life-threatening bleeding within the brain, requiring immediate medical attention.
Thrombocytopenia is categorized by severity based on the measured platelet count. A normal count ranges from 150,000 to 450,000 platelets per microliter of blood; counts below 150,000 are defined as thrombocytopenia.
- Mild severity: 100,000 to 149,000.
- Moderate thrombocytopenia: 50,000 to 99,000, carrying an increased risk of bleeding with injury.
- Severe thrombocytopenia: 20,000 to 49,000, making minor bleeding likely even without injury.
- Very severe: Below 10,000, presenting a high risk for spontaneous, life-threatening internal hemorrhage.
Management and Monitoring Strategies
Monitoring platelet levels is a part of cancer treatment, primarily accomplished through a complete blood count (CBC) test. The CBC is performed frequently during chemotherapy cycles to track the patient’s platelet count and anticipate when the nadir might occur. The results guide the healthcare team in deciding whether intervention is necessary to prevent severe bleeding complications.
For patients with very low counts, typically below 10,000, or those actively bleeding, the primary intervention is a platelet transfusion. Transfusions involve administering donor platelets intravenously to quickly raise the circulating count and are often given prophylactically to prevent spontaneous bleeding. Since transfused platelets only last about three days, some patients may require multiple transfusions to maintain a safe level.
Another management strategy involves pharmacological support using thrombopoietin (TPO) receptor agonists, such as romiplostim or eltrombopag. TPO is the natural regulator of platelet production, and these agonist drugs mimic its effect, binding to receptors on megakaryocytes in the bone marrow to stimulate platelet generation. These medications are studied for their potential to reduce the need for transfusions and allow cancer treatment to continue without delay.
In cases where chemotherapy is the clear cause, the treatment plan may need to be modified to allow the bone marrow time to recover. This may involve adjusting the chemotherapy schedule, such as lengthening the time between cycles, or reducing the dose of the cytotoxic drugs. This adjustment is a careful balance between managing the bleeding risk and maintaining the effectiveness of the anti-cancer therapy.
Self-Care to Minimize Bleeding Risk
Patients can take self-care steps to minimize their risk of bleeding while their counts are low. These actions help protect against trauma-induced bleeding:
- Avoid non-steroidal anti-inflammatory drugs (NSAIDs) like aspirin and ibuprofen, as these inhibit platelet function.
- Use a soft-bristle toothbrush.
- Avoid dental flossing.
- Take precautions to prevent falls or injury.