Secondary acute promyelocytic leukemia. Characteristics and prognosis of 14 patients from a single institution.

The aims of this study were to analyze the characteristics and outcome of patients with secondary acute promyelocytic leukemia (APL) and compare them to those with primary APL. One hundred and thirteen patients referred to our service with a diagnosis of APL were reviewed. Fourteen were classified as secondary APL. Nine were induced with chemotherapy, and five with all-trans retinoic acid plus chemotherapy. Pretreatment characteristics, response to therapy and outcome of primary vs secondary APL were compared by standard statistical methods. Secondary APL constituted 12% of all APL cases. Patients with secondary APL were significantly older (median age 56 vs 36 years; P < 0.01) and had a lower incidence of hypofibrinogenemia (P < 0.01) than those with primary APL. The complete response (CR) rates were similar with secondary vs primary APL (CR rates 79 vs 69%), as were CR duration and survival. The CR rates at 5 years were 57 and 45%, respectively(P not significant), and the survival rates 37 and 35%, respectively (P not significant). The incidence of secondary APL within APL disease (12%) was similar to the incidence of secondary acute myeloid leukemia (AML) in karyotypes not known to be therapy-related (diploid, t(8;21), inversion 16: incidences 9 to 12%), but was significantly lower than in karyotypes known to be therapy-related (chromosome 5 or 7 abnormalities, 11q; incidences 30 and 33%). We conclude that secondary APL has general characteristics and outcome similar to primary APL. it is more likely a second primary rather than therapy-related AML, and should be treated in a manner similar to primary APL.