To evaluate the effectiveness of intravenous rhTPO vs. placebo as primary prophylaxis in reducing the cumulative proportion of patients requiring platelet transfusion for severe chemotherapy-induced thrombocytopenia (platelet count <15,000) during the first four study cycles. To evaluate the severity and duration of thrombocytopenia and neutropenia associated with rhTPO prophylaxis, the impact of rhTPO prophylaxis on health economics/cost effectiveness, and patient quality of life. To assess the safety of multiple IV doses of rhTPO.