Extramedullary relapse after all-trans retinoic acid treatment in acute promyelocytic leukemia--the occurrence of retinoic acid syndrome is a risk factor

Acute promyelocytic leukemia: evolving therapeutic strategies

Acute promyelocytic leukemia (APL) is now the most curable subtype of acute myeloid leukemia in adults. All-trans retinoic acid (ATRA), which induces differentiation of the leukemic cells into mature granulocytes, represents the important advance. The incorporation of ATRA in induction results in a high complete remission rate, leads to rapid resolution of the characteristic life-threatening coagulopathy, and, most importantly, decreases the relapse rate compared with treatment with chemotherapy alone. However, ATRA is associated with unique toxicities not observed with conventional cytotoxic chemotherapy. A number of clinical trials have been performed to define the optimal role of ATRA in the treatment of patients. The therapeutic strategies have rapidly evolved as a result of both single institution and large cooperative group trials. Arsenic trioxide and stem cell transplantation are effective treatments for patients with APL who relapse after or are refractory to ATRA-based therapy. As experience with ATRA and arsenic trioxide in patients with APL accumulates, a number of important questions arise that need to be addressed.

Orchestration of multiple arrays of signal cross-talk and combinatorial interactions for maturation and cell death: another vision of t(15;17) preleukemic blast and APL-cell maturation

Despite intensive molecular biology investigations over the past 10 years, and an important breakthrough on how PML-RARalpha, the fusion protein resulting from t(15;17), can alter RARalpha and PML functions, no definitive views on how leukemia is generated and by what mechanism(s) the normal phenotype is restored, are yet available. 'Resistances' to pharmacological levels of all-trans-retinoic acid (ATRA) have been observed in experimental in vivo and in vitro models. In this review, we emphasize the key role played by signal cross-talk for both normal and neoplastic hemopoiesis. After an overview of reported experimental data on APL-cell maturation and apoptosis, we apply our current knowledge on signaling pathways to underline those which might generate signal cross-talks. The design of biological models suitable to decipher the integration of signal cross-talks at the transcriptional level should be our first priority today, to generate some realistic therapeutic approaches After 'Ten Years of Molecular APL', we still know very little about how the disease develops and how effective medicines work.

Extramedullary involvement at relapse in acute promyelocytic leukemia patients treated or not with all-trans retinoic acid: a report by the Gruppo Italiano Malattie Ematologiche dell'Adulto

PURPOSE

Recent reports of extramedullary disease (EMD) at recurrence in acute promyelocytic leukemia (APL) have raised increasing concern about a possible role of retinoic acid (RA) therapy.

PATIENTS AND METHODS

We analyzed the risk of developing EMD localization at relapse in APL patients enrolled onto two consecutive studies of the Gruppo Italiano Malattie Ematologiche dell'Adulto. The studies investigated chemotherapy alone (LAP0389) versus RA plus chemotherapy (AIDA).

RESULTS

When all relapse types were taken into account, 94 (51%) of 184 patients and 131 (18%) of 740 patients who attained hematologic remission underwent relapse in the LAP0389 and AIDA studies, respectively (P < .0001). EMD localization was documented in five (5%) of 94 and 16 (12%) of 131 patients (P = .08). Hematologic and/or molecular relapse was diagnosed concomitantly in all but two patients with EMD in the AIDA study. For patients in the LAP0389 and AIDA series, the probability of EMD localization of any type at relapse was 3% and 4.5%, respectively (P = .79), while the probability of CNS involvement was 0.6% and 2% (P = .28). No significant differences were found with regard to mean WBC count and promyelocytic leukemia/retinoic acid receptor-alpha junction type in comparisons of patients with EMD and hematologic relapse.

CONCLUSION

APL patients receiving all-trans retinoic acid in addition to chemotherapy have no increased risk of developing EMD at relapse as compared with those treated with chemotherapy alone.

Treatment of acute promyelocytic leukaemia

We review improvements achieved in the treatment of acute promyelocytic leukaemia (APL) over the last ten years. The combination of all- trans retinoic acid (ATRA) and conventional anthracycline-ARA-C chemotherapy (CT) has clearly demonstrated its superiority over CT alone (in terms of relapse and survival) in newly diagnosed APL. Combination treatment probably also reduces the incidence of initial failures, and complete remission (CR) rates greater than 90% are now regularly reported in large multicentre trials. Some randomized studies strongly suggest than prolonged maintenance treatment (for 1 or 2 years) with ATRA and low dose CT, and possibly very early introduction of anthracycline CT during induction treatment (i.e. not after ATRA) may reduce the incidence of relapse. With those treatments, the risk of relapse appears to be only 10-15%, although it remains greater in patients who initially have white blood cell counts (often associated with variant M(3)morphology, short bcr(3)isoform etc.) and patients with residual disease detectable by RT-PCR at the end of consolidation courses.ATRA syndrome remains the major side effect of ATRA treatment. It occurs in 10-15% of patients and is currently fatal in at least 10% of them. Rapid onset of CT and/or high dose steroids should improve its outcome.A sizeable proportion of APL patients who relapse after ATRA and CT can be durably salvaged by the same treatment followed by allogeneic or autologous stem cell transplantation, provided the transplant (in the autologous setting) is RT-PCR negative. Arsenic trioxide can induce CR in most APL patients refractory to ATRA and CT. It acts mainly by inducing apoptosis of APL cells. A place for arsenic trioxide earlier in the treatment of APL must currently be more precisely defined. Another issue in the treatment of APL is reducing the toxicity of first line treatment without increasing the relapse risk. Preliminary findings suggest that this could be achieved by consolidation CT using an anthracycline alone, without cytarabine.

Acute progranulocytic leukemia

Acute progranulocytic leukemia (APL) is characterized by unique biologic and clinical features. Understanding of these unique features has resulted in dramatic improvements in therapy for patients with APL. Current therapy with all-trans-retinoic acid (ATRA) plus an anthracycline with or without cytosine-arabinoside has yielded complete response rates of 85% or greater and long-term disease-free survival rates of 70% or greater. Arsenic trioxide has also surfaced as an effective induction therapy for relapsed APL. Further progress in the care of patients with APL awaits better definition of optimal schedules for ATRA plus chemotherapy, the role of arsenic trioxide, the use of current molecular monitoring for minimal residual disease, optimal therapy for minimal residual disease, and improved methods to address complications of APL including early hemorrhagic deaths and ATRA toxicities.

All-trans retinoic acid and chemotherapy in the treatment of acute promyelocytic leukemia

All-trans retinoic acid (ATRA) can induce complete remission (CR) in most patients with acute promyelocytic leukemia (APL) through in vivo differentiation of APL-blasts. However, it cannot eliminate the leukemic clone and must be used in combination with anthracycline-based chemotherapy. Experience accumulated over the last 10 years has clearly shown that the combination of ATRA and chemotherapy gave better survival than chemotherapy alone in newly diagnosed APL because of fewer relapses and a slightly higher CR rate. It is also strongly suggested that maintenance treatment with ATRA, and possibly with low-dose chemotherapy, can further reduce the incidence of relapse. Overall, more than 90% of patients with newly diagnosed APL can achieved CR, and about 75% can be cured by the combination of ATRA and chemotherapy. ATRA syndrome remains the major side effect of ATRA treatment, which should be prevented by addition of chemotherapy and/or dexamethasone in case of increasing white blood cell (WBC) counts. Current issues in the treatment of newly diagnosed APL include the role of early addition of chemotherapy to ATRA, whether or not ara-C is useful in combination with anthracycline, and a possible interest of arsenic trioxide during consolidation in patients remaining at relatively high risk of relapse.