IMPAIRED HEMOSTASIS is a common cause of morbidity and mortality in patients with malignancy. The numerous and oftentimes unique complications of each neoplasm, and the many medications to which the patient is exposed, complicate the interpretation and therapy of this problem. This chapter will stress acquired disorders, remembering that these patients can also suffer from congenital disorders of hemostasis.
QUANTITATIVE PLATELET DISORDERS
Thrombocytopenia represents the most common cause of bleeding in the cancer patient. Almost all drugs used in the treatment of malignancy have some myelosuppressive effects and may cause profound thrombocytopenia. Exceptions to this include corticosteroids, vincristine, and asparaginase. Withdrawal of the myelosuppressive drug is often followed by platelet recovery, but persistent thrombocytopenia may occur (i.e., busulfan). In a malnourished, marrow-compromised host, even relatively modest dosages of radiation can result in significant and prolonged thrombocytopenia, especially when given in combination with myelosuppressive drugs.
Marrow infiltration by metastatic disease (i.e., breast, prostate) or intrinsic neoplastic proliferations (i.e., leukemia) result in decreased marrow reserve. The presence of nucleated red blood cells, thrombocytopenia and early myeloid precursors in the blood smear is often the first sign of myelophthisic disease. Infections are common and are often associated with thrombocytopenia. Marrow suppression, direct interaction between platelets and bacteria or viruses, immune complex reactions and disseminated intravascular coagulation (DIC) all play a role.
Defibrination syndromes and microangiopathic hemolytic anemia are common causes ofthrombocytopenia and are discussed later in this chapter. Hemangiomas by sequestration and activation of the clotting me.chanism can result in peripheral utilization of platelets. The exposed vascular subendothelium represents a fertile field for platelet-tissue interactions and subsequent thrombocytopenia. These denuded areas result from cancer surgery, mucositis secondary to chemotherapeutic drugs and/or infections and necrotic tumor masses.
Idiopathic thrombocytopenic purpura (ITP) and immunohemolyric anemia are usually observed in the setting of a lymphopro-