Thrombocytopenia in cancer

Dr Garrick Laudin sheds light on why thrombocytopenia can develop during cancer and its impact on treatment.

Thrombocytopenia is the medical term for a low platelet count. It’s common in patients with both solid organ cancers (breast, lung, prostate, and colon cancer) and blood or lymph node cancers (leukaemia, lymphoma, and multiple myeloma). 

What are platelets?

Platelets are microscopic blood cells whose normal number and function are important for the formation of blood clots at sites where blood vessels become injured. They are produced in the bone marrow, the major site of adult blood cell production, before making their way into the circulatory system. 

In healthy people, up to one-third of circulating platelets may be found in the spleen. The spleen is a specialised organ that plays a key immune function by removing dying or aged blood cells. Normal adult platelet counts range between 150 and 450 billion platelets per litre of blood (150 – 450 × 10⁹/L). A full blood count can diagnose thrombocytopenia. 

Symptoms 

Bleeding usually occurs when platelet counts become significantly low. However, somewhat counterintuitively, the exact correlation between platelet count and bleeding risk is relatively weak. Bleeding risk depends on platelet number, platelet function as well as any additional bleeding risk factors. 

The World Health Organization grades the severity of bleeding symptoms from grade 1 to grade 4. Grade 1 is mild bleeding, such as petechiae (pinpoint red or purple spots on the skin) or mild epistaxis (nosebleeds). Grade 2 is moderate bleeding, such as mild blood loss or bruising, and is managed with local interventions and typically doesn’t require blood transfusions. Grade 3 refers to severe bleeding, requiring red blood cell transfusions or causing a significant drop in blood pressure. Grade 4 bleeding is potentially fatal bleeding into the central nervous system (brain or eye) or severe blood loss, leading to shock.

What processes lead to thrombocytopenia?

Thrombocytopenia can be understood through three mechanisms: decreased platelet production, increased platelet destruction, or platelet sequestration.

Reduced platelet production occurs when a cancer primarily involves or spreads to the bone marrow, interrupting normal platelet numbers. It may also occur when chemotherapy temporarily suppresses the bone marrow’s ability to make platelets. Apart from traditional chemotherapy, immunotherapies and radiotherapy (involving large areas of bone marrow) may also affect platelet production.

In some patients, platelets are destroyed or cleared by the immune system faster than they can be produced. This occurs when the immune system mistakenly attacks platelets, a condition known as immune thrombocytopenia. Some cancers, particularly lymphomas, can trigger this immune response. 

The spleen, when enlarged, can also sequester (trap) excessive numbers of platelets, resulting in a reduced circulating platelet count.

How is thrombocytopenia diagnosed?

Your doctor may request additional investigations to determine why the platelet count is low. These may include microscopic examination of a blood smear, a bone marrow biopsy, imaging studies assessing spleen size, or a review of your medications and cancer treatments.

How is thrombocytopenia treated?

In many cases, treating the underlying cancer allows the bone marrow to recover, and platelet counts to increase. 

Sometimes your oncology team may need to delay chemotherapy, reduce treatment doses, or adjust treatment schedules to give the bone marrow time to recover. 

If platelet counts become dangerously low or if bleeding occurs, platelet transfusions may be administered. These are temporary supportive measures while the underlying cause is being identified and treated.

Living with thrombocytopenia

If you have been diagnosed with thrombocytopenia, you should avoid contact sports or medications that may increase your risk of bleeding. 

Simple measures, like using a soft toothbrush, may help prevent gum bleeding, while avoiding razor blades may reduce the risk of skin cuts. Discuss any medications you are taking with your oncology team, particularly anti-inflammatory drugs and anticoagulants as these may increase bleeding risk. 

Take-home message

Hearing that you have a low platelet count can be worrying, especially when you are already coping with a cancer diagnosis. Thrombocytopenia is a well-recognised complication of both cancer and its treatment. Regular blood tests, awareness of warning signs, and communication with your oncology team are key to staying safe. If you notice new bruising, bleeding, or any other worrying symptoms, seek medical advice without delay. 

Dr Garrick Laudin is a specialist physician and clinical haematologist affiliated with the University of the Witwatersrand, who currently practices at Chris Hani Baragwanath Academic Hospital. His special interests are the hyperinflammatory syndromes associated with haematological malignancies, the haemolytic anaemias, and bone marrow failure syndromes.

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