Thrombopoietin Is a Platelet Growth Factor That May Lessen the Need for Platelet Transfusions after Chemotherapy for Cancer

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The summary below is from the full report titled "Recombinant Human Thrombopoietin Attenuates Carboplatin-Induced Severe Thrombocytopenia and the Need for Platelet Transfusions in Patients with Gynecologic Cancer.". It is in the 7 March 2000 issue of Annals of Internal Medicine (volume 132, pages 364-368). The authors are S. Vadhan-Raj, C.F. Verschraegen, C. Bueso-Ramos, H.E. Broxmeyer, A.P. Kudelka, R.S. Freedman, C.L. Edwards, D. Gershenson, D. Jones, M. Ashby, and J.J. Kavanagh.

What is the problem and what is known about it so far?

Platelets are tiny cells produced in the bone marrow and released into the bloodstream, where they help the blood to clot. The risk for bleeding is therefore increased in patients with low platelet counts. Many cancer chemotherapies interfere with platelet production; a low platelet count (thrombocytopenia) is therefore a common side effect of chemotherapy. Platelet transfusions are used to treat dangerously low platelet counts. Unfortunately, such transfusions can result in transfusion reactions or infection; they are also quite expensive. Moreover, some patients stop responding to platelet transfusions after a while. Carboplatin is a drug that can be effective as chemotherapy for cancers of the ovaries and uterus. However, low platelet counts often complicate treatment with carboplatin. Thrombopoietin is a naturally occurring hormonal growth factor that stimulates the bone marrow to make platelets. Genetically engineered thrombopoietin (recombinant human thrombopoietin, or rhTPO) recently became available.

Why did the researchers do this particular study?

The researchers wanted to see whether giving patients thrombopoietin after they received carboplatin chemotherapy would minimize the occurrence of low platelet counts.

Who was studied?

Twenty-nine women with gynecologic cancer who received two cycles of chemotherapy with carboplatin.

How was the study done?

The women received no thrombopoietin after a first cycle of chemotherapy. On the second, fourth, sixth, and eighth day after their second cycle of chemotherapy, they were given injections of thrombopoietin. The researchers measured platelet counts and the need for platelet transfusions after each chemotherapy cycle.

What did the researchers find?

Platelet counts decreased less after chemotherapy when women received thrombopoietin than when they did not receive it. Platelet counts also returned to normal more quickly with thrombopoietin therapy than without it. After the first cycle of chemotherapy, 75% of women needed platelet transfusions; only 25% needed them after the second cycle of chemotherapy.

What were the limitations of the study?

This study included only 29 women, all of whom received carboplatin-containing chemotherapy for a limited number of cancer types. Further studies are being done to see whether these findings would apply to people with other types of cancer or to those who receive other forms of chemotherapy.

What are the implications of the study?

This study suggests that thrombopoietin may help prevent low platelet counts that often occur after certain kinds of chemotherapy. This could possibly reduce the risk for bleeding and the need for platelet transfusions.