The purpose of the study is to see how effective the combination of chemotherapy drugs VP-16, chlorambucil, dexamethasone, and vincristine is for patients who have blood cancers that have returned or not responded to prior treatment. Some patients may also receive a medication called rituximab if their doctor thinks it is appropriate. This drug combination will be given to study participants in a low dose continuous basis. The study will also collect information about the side effects of the above drug combination on patients with these types of cancers. Previous studies on patients with non-Hodgkin's lymphoma indicate that some patients treated with this drug combination achieved a high response. The aim of this study is to test this drug combination in a controlled setting.