A Comparison of Outcomes in Patients with Secondary Acute Promyelocytic Leukemia (APL) and De Novo APL-A Case-Matched Retrospective Analysis of the Polish Adult Leukemia Group (PALG).

BACKGROUND: Secondary acute promyelocytic leukemia (sAPL) is a very rare subtype of acute myeloid leukemia that develops following exposure to chemotherapy, radiotherapy, or immunosuppressive agents. The treatment results and survival outcomes of sAPL patients are still not precisely defined. METHODS: A search of the Polish Adult Leukemia Group (PALG) database identified 29 cases of sAPL (median age 57 years; 62.1% female) among 437 APL patients (6.7%) diagnosed between 2006 and 2024. Each sAPL case was matched to a de novo APL patient by sex, age, year of diagnosis, and treatment protocol (LPA (Leucemia Promielocítica Aguda) 2005, LPA 2012, or LPA 2017). RESULTS: All sAPL cases occurred following chemo- and/or radiotherapy, most commonly for breast cancer. The sAPL cases demonstrated higher CD15 expression than the de novo APL cases (median 27.6% vs. 7%, p = 0.04). The two groups exhibited comparable complete remission rates (82.8% sAPL vs. 75.9% de novo; p = 0.75) and early mortality rates (17.2% vs. 20.7%, p = 1.0). However, relapse-free survival was significantly shorter in sAPL (median 94.7 months vs. not reached; HR 7.23, 95% CI 1.63-32.02, p = 0.030), whereas overall survival did not differ significantly between groups. Multivariate analysis identified Eastern Cooperative Oncology Group performance status ≥3 and CD15 expression > 20% as independent predictors of inferior survival. CONCLUSIONS: These findings suggest that sAPL shares many clinical features with de novo APL but carries a higher risk of relapse, highlighting the need for further prospective studies and the potential implementation of tailored therapeutic strategies.