Progress in CLL, chemotherapy, antibodies and transplantation

Abstract

Over the last decade, major advancements in our understanding of chronic lymphocytic leukemia (CLL) and its variants have occurred. It has become apparent that there is diversity in types of CLL including those patients that do or do not have hyper-mutation of their immunoglobulin genes. Mutated genes confer a favorable prognosis. One of the major advances in our therapy has been the discovery of the activity of purine analogs, which have been demonstrated to be more active than conventional therapy in achieving complete remission, prolonged remission duration, and a suggestion of improved survival. More recently, based on information that purine analogs inhibit DNA repair, rational combinations have been developed. In particular, fludarabine plus cyclophosphamide appeared to have added activity compared to either drug given alone or in sequence. This has led to a higher response rate, longer time to progression, and an improvement in survival in patients treated following prior alkylating agents. Two monoclonal antibodies, Rituximab and Campath-1H, have become available for clinical use and research. Rituximab has modest activity as a single agent, with higher response rates being noted in patients who receive more intensive regimens. Rituximab has been successfully combined with chemotherapy, and in association with fludarabine plus cyclophosphamide (FCR) has a very high response rate and the ability to obtain polymerase chain reaction (PCR) negativity for the immunoglobulin heavy chain region. Campath-1H is very active as a single agent and is being recommended for treatment for patients with fludarabine refractory disease and will receive increased attention as a research agent in earlier-stage patients. Autologous and allogeneic bone marrow transplantation have emerged as significant treatments in CLL. The ability to achieve responses in bone marrow and peripheral blood with newer regimens has given the opportunity to collect stem cells from patients. There is a suggestion that intensification of remissions with autologous transplant can lead to PCR negativity and prolonged remissions. Allogeneic transplantation has been demonstrated to be effective with a strong suggestion of graph versus leukemia effect. This has been utilized in the development of non-ablative marrow allogenaic bone marrow transplant programs. Non-ablative transplants appear to be as effective as ablative transplants in the most recent analysis. Thus, multiple modalities have been brought together to achieve high-quality complete remissions in CLL, giving the prospect of improved survival.