In Cycle 1, all patients will receive chemotherapy by itself. Three (3) weeks later, in Cycle 2, the same dose of chemotherapy will be given followed by AMG 531. AMG 531 will be given on one of 3 schedules. AMG 531 will be given as an injection under the skin on the day after chemotherapy and 2 days later; it will be given 5 days before and the day after chemotherapy; or it will be given 5 and 3 days before chemotherapy and on the day after chemotherapy and 2 days later. The schedule you receive will depend on when you enroll on the study. After 2 cycles of treatment, based on response of the disease and tolerance to the treatment, all participants may be able to receive up to 4 more cycles of chemotherapy followed by AMG 531. All participants will continue on the same schedule you were receiving before. The dose of AMG 531 may be increased at one time point during the study based on the response of the platelet counts.