Long-term follow-up and potential for cure in acute promyelocytic leukaemia
Acute promyelocytic leukaemia (APL) may be characterized simultaneously as the most potentially rapidly fatal human acute leukaemia if untreated, yet the most frequently cured acute leukaemia if promptly diagnosed and treated without delay. Co-operative group and single-institution studies which include large numbers of patients with relatively long follow-up demonstrate that, with all-trans retinoic acid (ATRA) plus anthracycline-based chemotherapy, the majority of newly-diagnosed patients appear cured of their disease. The 5-year disease-free survival rates range from 75 to 85%. Early death is still observed in approximately 10% of patients and remains a difficult obstacle to increasing the cure rate. Prognostic factors which identify patients at high risk for recurrence are becoming increasingly recognized. Older age (over age 55-60 years), elevated white blood cell count at presentation (higher than 5,000-10,000/microl), and expression of CD56 unfavourably influence outcome. The treatment of such patients remains a challenge, although it is important to note that APL is the only type of AML in which a significant proportion of older patients may be cured. Because more patients are cured of their disease, potential long-term consequences may become increasingly recognized. These include the emergence of extramedullary disease, the development of secondary myelodysplasia or acute myeloid leukaemia and the potential for late-onset cardiac toxicity.