Acute lymphoblastic leukaemia in elderly patients: biological characteristics and therapeutic approaches

Acute lymphoblastic leukaemia (ALL) is a rare disease in the elderly. The prevalence of ALL in patients >60 years of age is reported to be between 16% and 31% of all adult cases. The biology of ALL in older patients seems to be significantly different from that in younger patients and may, at least in part, explain poor treatment outcome. Immunophenotyping and cytogenetic characteristics are among the most important biological differences in comparison with younger adults. The frequency of pre B-cell ALL and common ALL is higher and T-cell ALL subtype is under-represented in elderly populations compared with younger patients. The frequency of the Philadelphia chromosome also seems to increase with age and adversely influences complete remission rate and survival. Few reports on the effectiveness and toxicity of therapeutic programmes concerning exclusively older patients with ALL have been published so far and only some of them were prospective studies. In some of the studies age-adapted approaches have been applied in which protocols processed earlier for younger patients have been adopted for older patients. In such modified protocols chemotherapy was usually less aggressive, especially if it was given for patients with comorbidities and poor performance status. Consequently, in several studies elderly patients received suboptimal treatment. Death during induction chemotherapy was observed in 7-42% of the patients in particular reports. The overall response rate varied from 12% to 85%. The median overall survival (OS) durations in patients who received a curative approach ranged from 3 to 14 months and from 1 to 14 months in patients treated palliatively. Poor performance status, comorbidities and high early mortality during intensive chemotherapy are the main reasons for poor treatment results and short OS time. New therapeutic approaches are necessary to improve the outcome in this age group of patients with ALL.